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Urban impacts on precipitation
Article  in  Asia-Pacific Journal of the Atmospheric Sciences · January 2014
DOI: 10.1007/s13143-014-0016-7
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Asia-Pacific J. Atmos. Sci.
DOI:10.1007/s13143-014-0016-7
REVIEW
Urban Impacts on Precipitation
Ji-Young Han1
, Jong-Jin Baik2
, and Hyunho Lee2
1
Korea Institute of Atmospheric Prediction Systems, Seoul, Korea
2
School of Earth and Environmental Sciences, Seoul National University, Seoul, Korea
(Manuscript received 27 August 2013; accepted 4 November 2013)
© The Korean Meteorological Society and Springer 2013
Abstract: Weather and climate changes caused by human activities
(e.g., greenhouse gas emissions, deforestation, and urbanization)
have received much attention because of their impacts on human
lives as well as scientific interests. The detection, understanding, and
future projection of weather and climate changes due to urbanization
are important subjects in the discipline of urban meteorology and
climatology. This article reviews urban impacts on precipitation.
Observational studies of changes in convective phenomena over and
around cities are reviewed, with focus on precipitation enhancement
downwind of cities. The proposed causative factors (urban heat
island, large surface roughness, and higher aerosol concentration) and
mechanisms of urban-induced and/or urban-modified precipitation
are then reviewed and discussed, with focus on downwind precipitation
enhancement. A universal mechanism of urban-induced
precipitation is made through a thorough literature review and is as
follows. The urban heat island produces updrafts on the leeward or
downwind side of cities, and the urban heat island-induced updrafts
initiate moist convection under favorable thermodynamic conditions,
thus leading to surface precipitation. Surface precipitation is likely to
further increase under higher aerosol concentrations if the air
humidity is high and deep and strong convection occurs. It is not
likely that larger urban surface roughness plays a major role in urbaninduced
precipitation. Larger urban surface roughness can, however,
disrupt or bifurcate precipitating convective systems formed outside
cities while passing over the cities. Such urban-modified precipitating
systems can either increase or decrease precipitation over and/or
downwind of cities. Much effort is needed for in-depth or new
understanding of urban precipitation anomalies, which includes local
and regional modeling studies using advanced numerical models and
analysis studies of long-term radar data.
Key words: Urban impacts, precipitation, urban heat island, surface
roughness, aerosols, urbanization
1. Introduction
The global population has become concentrated in cities
(UN, 2012). Urbanization is accompanied by artificial changes
in land use/land cover, creating substantial contrasts in land
surface characteristics between urban areas and surrounding
rural areas. Urban areas have features different from surrounding
rural areas. Urban areas are composed of numerous manmade
structures, so the urban surface is generally rougher than
its surrounding rural surface. The urban surface covered with
materials such as concrete and asphalt has large thermal inertia
and accordingly stores great amounts of heat. In built-up urban
areas, the sky-view factor is small. Hence, incoming shortwave
radiation and outgoing longwave radiation are trapped in street
canyons. Anthropogenic heat is released into the urban atmosphere.
In addition, the urban atmosphere is more polluted than
the rural atmosphere mainly because of pollutants emitted from
automobiles. A considerable number of observational studies
show that urban areas cause changes in temperature, wind,
humidity, and rainfall, produce peculiar circulations, and affect
local or even regional weather and climate (Landsberg, 1970;
Oke, 1987; Cotton and Pielke, 1995).
The most well-known and highly-documented phenomenon
appearing in cities is the urban heat island, that is, higher nearsurface
air temperature in the urban area than in its surrounding
rural area. The urban heat island is most pronounced on
calm, clear nights (e.g., Jauregui, 1997; Klysik and Fortuniak,
1999). The intensity of the urban heat island exhibits diurnal
and seasonal variations (e.g., Kim and Baik, 2002; Lee and
Baik, 2010) and is influenced or modulated by mesoscale or
synoptic weather conditions (e.g., Morris and Simmonds, 2000;
Gedzelman et al., 2003). Causative factors of the urban heat
island are well known and include impervious surfaces, anthropogenic
heat, air pollution, and three-dimensional urban
geometry (encompassing additional heat stored in walls, radiation
trapping, and wind speed reduction) (Oke, 1982; Ryu and
Baik, 2012). The urban heat island can induce or modify local
flow/circulation. Reviews of the urban heat island are given,
for example, in Arnfield (2003).
Anthropogenic aerosols released into the urban atmosphere
are of various sizes and chemical compositions. Anthropogenic
aerosols, together with gaseous pollutants, lead to deterioration
in the urban air quality and are harmful to human health. In
particular, aerosols smaller than 100 nm in diameter, called
ultrafine aerosols, are known to be very harmful. Aerosols can
serve as cloud condensation nuclei, and their sizes and
chemical compositions greatly influence the size distribution
of drops nucleated in a cloud (Houze, 1993; Pruppacher and
Klett, 1997), affecting the subsequent evolution of clouds and
precipitation. Aerosol-cloud-precipitation interactions have been
extensively investigated because of the importance of aerosols
Corresponding Author: Jong-Jin Baik, School of Earth and Environmental
Sciences, Seoul National University, Seoul 151-742,
Korea.
E-mail: jjbaik@snu.ac.kr
ASIA-PACIFIC JOURNAL OF ATMOSPHERIC SCIENCES
in weather and climate (Khain, 2009). However, the roles of
aerosols in clouds and precipitation in urban areas with higher
aerosol number concentrations have not been extensively
investigated.
Many observational studies have indicated that cities affect
precipitation and specifically that precipitation tends to increase
over and/or downwind of urban areas. Theoretical studies have
been attempted to gain an understanding of the essential dynamics
responsible for the precipitation enhancement. Numerical
modeling studies have been made to find causes and
mechanisms of the precipitation enhancement. Precipitation is
one of the key elements of the water and energy cycles of the
atmosphere, and understanding precipitation processes under a
wide range of environmental conditions is an important problem
in meteorology. This study conducts a literature review
of urban impacts on precipitation. In section 2, observational
studies of urban-related changes in convective phenomena,
especially precipitation enhancement over and/or downwind of
urban areas, are reviewed. In section 3, causes and mechanisms
of the precipitation enhancement are reviewed and discussed.
In section 4, a summary and conclusions are given.
2. Observational evidence
During the past several decades, abundant observational
evidence of urban-related changes in convective phenomena
has been reported. In 1968, Changnon presented an interesting
finding, an anomalous behavior of precipitation in the La Porte
area downwind of Chicago, that is, an observational evidence
for precipitation enhancement downwind of Chicago (Changnon,
1968). This anomaly is known as the La Porte anomaly (Fig.
1). Changnon’s pioneering work initiated many studies aimed
at detecting precipitation anomalies over and/or downwind of
major global cities and at finding causes and mechanisms of
such precipitation anomalies.
An intensive field campaign of inadvertent weather modification,
the Metropolitan Meteorological Experiment (METROMEX),
was conducted in the St. Louis area from 1971 to 1975
to dimensionalize urban-related anomalies in precipitation and
severe weather and to find possible causes of these anomalies
(Changnon et al., 1977; Ackerman et al., 1978). Analyses of
Fig. 1. Average warm season (April-September) rainfall pattern (cm)
in the La Porte-Chicago area during 1954-63. [after Changnon
(1980a).]
Fig. 2. Mean annual distribution of the Tropical Rainfall Measuring Mission (TRMM)-derived rainfall rates from January 1998
to May 2002 (excluding August 2001). The oval is the approximate Houston urban zone. The vector indicates the mean annual
700-hPa wind direction over the Houston area. The pentagon-shaped box is the downwind urban-impacted region, and the
rectangular box is the upwind control region. [after Shepherd and Burian (2003).]
Ji-Young Han et al.
the METROMEX data indicate increased cloudiness (up to
10%), increased total rainfall (up to 30%), and increased
severe storm activity (up to 100%) over and 15 to 40 km
downwind of St. Louis in summer. The main focus of the
METROMEX effort was summer season precipitation, but
some studies (e.g., Huff and Changnon, 1986; Changnon et al.,
1991) analyzed the METROMEX data for other seasons to
ascertain the presence of urban effects on the transition seasons
(spring and fall) and winter precipitation. Using a statistical
approach, Changnon et al. (1991) revealed that an urban effect
in the St. Louis area, leading to increased downwind precipitation,
exists in fall (+17%) but is negligible in spring (+4%)
and not present in winter.
Shepherd et al. (2002) and Shepherd and Burian (2003)
established the possibility of utilizing satellite-based rainfall
estimates to identify the modification of rainfall by urban areas
on a global scale and over longer time periods. Their results
corroborate early METROMEX findings and other groundbased
observational and modeling studies that show rainfall
maxima over and/or downwind of major cities (see the example
of Houston in Fig. 2).
Urban-related changes in convective phenomena have been
detected over and around major cities in the United States and
globally, as listed in Table 1. For example, observational
studies show an increase in the cloud-to-ground flash density
(lightning activity) and a decrease in the percentage of positive
flashes over and/or downwind of Houston (Orville et al., 2001;
Steiger et al., 2002), three large metropolitan areas in southeastern
Brazil (São Paulo, Campinas, and São José dos
Campos) (Naccarato et al., 2003; see Fig. 3), and Seoul (Kar et
al., 2007). Several case studies show that the structure and
movement of cloud systems can be influenced by urban areas.
A radar observation study of cloud systems crossing the city of
Bucharest shows the disruption of a frontal system passing
over the city and the reshaping of the frontal system after
crossing it (Tumanov et al., 1999). Bornstein and LeRoy
(1990) found that moving thunderstorms with strong regional
flows tend to bifurcate and move around the city due to the
urban barrier effect in the New York City area. By analyzing
surface meteorological data in the Atlanta area, Bornstein and
Lin (2000) documented convective thunderstorms that were
initiated in urban heat island-induced convergence zones. The
rapid growth of moving storms passing over cities was
observed in some major urban areas, such as in the London
area (Atkinson, 1971) and the Chicago area (Changnon and
Westcott, 2002). Recent studies by Kug and Ahn (2013) and
Pinto et al. (2013), respectively, show that precipitation enhancement
in Korean cities and a significant increase in
Table 1. Observational studies of urban-related changes in convective phenomena over and around cities.
City References
Asia
Pearl River Delta, China Li et al. (2011)
Shanghai, China Chow and Chang (1984)
Kolkata, India De and Rao (2004), Rao et al. (2004), Mitra et al. (2012)
Mumbai, India Khemani and Ramana Murty (1973), De and Rao (2004), Rao et al. (2004), Kishtawal et al. (2010)
Tel Aviv, Israel Goldreich and Manes (1979), Goldreich (1987), Halfon et al. (2009)
Tokyo, Japan Yonetani (1982), Inoue and Kimura (2004), Fujibe et al. (2009)
Seoul, Korea Kar et al. (2007), Kim et al. (2011), Kim et al. (2012), Kug and Ahn (2013)
Taipei, Taiwan Chen et al. (2007)
Europe
London, England Atkinson (1968, 1969, 1971), Hand (2005)
Hamburg, Germany Schlünzen et al. (2010)
Bucharest, Romania Tumanov et al. (1999)
Moscow, Russia Romanov (1999)
North America
Windsor, Canada Sanderson and Gorski (1978)
Mexico City, Mexico Jauregui and Romales (1996)
Atlanta, United States
Bornstein and Lin (2000), Shepherd et al. (2002), Dixon and Mote (2003), Diem and Mote (2005),
Mote et al. (2007), Rose et al. (2008)
Chicago, United States Changnon (1968, 1980b, 2001), Huff and Changnon (1973), Westcott (1995), Changnon and Westcott (2002)
Houston, United States
Huff and Changnon (1973), Orville et al. (2001), Steiger et al. (2002), Shepherd and Burian (2003),
Burian and Shepherd (2005)
St. Louis, United States
Huff and Changnon (1973, 1986), Changnon et al. (1977, 1991), Ackerman et al. (1978), Changnon (1981),
Westcott (1995)
South America
São Paulo, Brazil Naccarato et al. (2003), Farias et al. (2009), Pinto et al. (2013)
ASIA-PACIFIC JOURNAL OF ATMOSPHERIC SCIENCES
thunderstorm days in large cities in southeastern Brazil are
related to the population growth of the cities. More extensive
reviews of the observational studies of urban-induced and/or
urban-modified precipitation are given in Garstang et al.
(1975), Lowry (1998), and Shepherd (2005).
3. Causes and mechanisms
Three causative factors (urban heat island, large surface
roughness, and higher aerosol concentration) and a number of
mechanisms have been proposed to explain observed urban
precipitation anomalies. This section reviews the proposed
causes and mechanisms.
a. Urban heat island
Heat sources (e.g., latent heating due to cumulus convection)
or sinks (e.g., evaporative cooling of falling raindrops) in the
atmosphere dynamically induce flow/circulation. The urban heat
island, which is regarded as a low-level heat source, induces
flow. The urban heat island-induced flow can be theoretically
investigated in the context of the response of a stably stratified
atmosphere to specified surface or low-level heating. A number
of linear, theoretical studies have been performed following
this line of research. Olfe and Lee (1971) carried out twodimensional,
steady-state flow calculations in a uniform basicstate
flow. In their study, the urban heat island is represented
by various surface temperature distributions and for turbulent
heat transfer the turbulent diffusion term is added in the
thermodynamic energy equation. They showed downward motion
directly over the upwind portion of the urban heat island
and upward motion on the downwind side (Fig. 4). They also
showed positive temperature perturbations near the ground and
negative temperature perturbations aloft. The three-dimensional
solution for temperature perturbations was also analyzed, which
was obtained by the superposition of the two-dimensional
solutions at varying angles to the uniform basic-state flow
direction. A two-dimensional, time-dependent problem was
solved by Lin and Smith (1986) to examine the transient
dynamics of airflow near a heat source in a uniform basic-state
flow, with applications to several problems including the heat
island problem. It was found that air parcels descend over a
heat island and ascend on the downwind side. Importantly,
through an analysis of the time-dependent solution, they provided
an explanation for the curious negative phase relationship
between heating and induced vertical displacement in the
vicinity of the heat source.
Baik (1992) analytically solved a two-dimensional, steadystate
problem to investigate the characteristics of airflow past
an urban heat island in a basic-state flow with shear. The urban
heat island is specified as low-level heating that has a bell shape
in the horizontal and decreases linearly with height, roughly
imitating real urban heat islands. The turbulent diffusion term
was not considered because the low-level heating can be to
some or a large extent regarded as a consequence of the
turbulent heat transfer from near the surface where the heat
source is located. He found that there exists upward motion
downwind of the urban heat island and that the magnitude of
the perturbation vertical velocity is larger in the shear flow
case than in the uniform flow case. Han and Baik (2008) solved
a three-dimensional, time-dependent problem for airflow past
an urban heat island in a uniform basic-state flow. The urban
heat island is specified as steady-state low-level heating in
three dimensions. They also confirmed upward motion downwind
of the heating center. The dispersion of gravity wave
Fig. 3. (a) Cloud-to-ground flash density (flashes per km2
) averaged
over three summer seasons from 2000 to 2002 and (b) percentage of
positive cloud-to-ground flashes in southeastern Brazil. The outlined
area in both figures is located between latitude 22.19o
S and 24.25o
S,
and longitude 44.62o
W and 47.62o
W. [after Naccarato et al. (2003).]
Fig. 4. Field of the urban heat island-induced vertical velocity calculated
using a linear theory. The vertical velocity is normalized by the
basic-state flow. [after Olfe and Lee (1971).]
Ji-Young Han et al.
energy into an additional dimension was shown to result in a
faster approach to a quasi-steady state and a weaker quasisteady
flow in three dimensions.
The linear, theoretical studies mentioned above highlight
that upward motion is induced on the downwind side in the
presence of an urban heat island. Lin and Smith (1986), Baik
(1992), and Han and Baik (2008) suggested that the urban heat
island-induced upward motion on the downwind side is
responsible for the precipitation enhancement observed downwind
of urban areas. It is noteworthy that gravity waves are
generated by heating in a stably stratified atmosphere, so the
velocity perturbations induced by an urban heat island in the
linear, theoretical studies are essentially gravity waves.
Baik and Chun (1997) extended the previous linear, theoretical
studies by solving a weakly nonlinear problem in two
dimensions using the perturbation method. They showed that
the linear solution part exhibits upward motion downwind,
while the weakly nonlinear solution part exhibits downward or
upward motion downwind depending on the inverse Froude
number that is proportional to the buoyancy frequency and
heating depth and inversely proportional to the basic-state
wind speed. When the inverse Froude number is large within a
valid range of the perturbation expansion, the linear and
weakly nonlinear effects constructively work together to produce
enhanced upward motion downwind. They proposed that
this explains to a greater extent precipitation enhancement
downwind of urban areas than is possible from the linear effect
alone.
Nonlinear numerical models have been used to investigate
urban heat island-induced flow and convection, with specified
low-level heating representing an urban heat island under
idealized environmental conditions. Using a simple two-dimensional
model, Baik (1992) examined nonlinear effects on
the flow field. He found that for small heating amplitude
(hence, small nonlinearity factor) the flow field is similar to
that in the previous linear studies, while for large heating
amplitude (thus, large nonlinearity factor) two distinct flow
features are observed: a linear gravity-wave-type response field
on the upwind side and a strong updraft cell on the downwind
side. The strong updraft cell was suggested to be responsible
for the observed downwind precipitation enhancement. Atmospheric
stability plays an important role in enhancing or suppressing
updrafts or convection. Baik et al. (2007) examined
the effects of atmospheric boundary-layer stability on urban
heat island-induced circulation using a two-dimensional, dry
mesoscale model. They showed that as the boundary layer
becomes less stable, the downwind updraft cell induced by an
urban heat island strengthens and the vertical extent of the
downwind updraft cell increases. This result implies that in the
daytime, with a nearly neutral or less stable boundary layer, the
urban heat island-induced circulation can become strong. They
suggested that the finding explains urban-induced thunderstorms
observed in the late afternoon or evening with a nearly
neutral or less stable boundary layer.
Using a two-dimensional mesoscale model with bulk cloud
microphysics, Baik et al. (2001) demonstrated that the downwind
updraft cell induced by an urban heat island can
dynamically initiate moist convection and result in surface
precipitation in the downwind region under favorable thermodynamic
conditions. It was shown that for the same basicstate
wind speed and heat island intensity a stronger dynamic
forcing (that is, a stronger downwind updraft) is required to
trigger moist convection under less favorable thermodynamic
conditions. The two-dimensional numerical study of Baik et
al. (2001) was extended to a three-dimensional numerical study
by Han and Baik (2008). In addition to demonstrating in three
dimensions the initiation of moist convection by the downwind
updraft cell induced by an urban heat island and the subsequent
downwind surface precipitation (Fig. 5), they showed
that the intensity and horizontal structure of an urban heat
island affect the amount and distribution of surface precipitation
downwind of the urban heat island.
The above idealized, nonlinear numerical studies propose the
urban heat island as a cause and mechanism of the observed
downwind precipitation enhancement by showing that the
urban heat island induces a downwind updraft cell under the
conditions of strong urban heat island, weak atmospheric
stability or weak basic-state wind and that the downwind updraft
cell initiates moist convection downwind under favorable
thermodynamic conditions, thus producing surface precipitation
downwind. It is noted that the nonlinearity factor for
thermally induced finite-amplitude waves is proportional to the
heating amplitude and inversely proportional to the buoyancy
frequency and the square of the basic-state wind speed (Chun,
1991; Lin and Chun, 1991). Therefore, the conditions of strong
urban heat island, weak atmospheric stability or weak basicstate
wind correspond to relatively large nonlinearity factors
(relatively high nonlinear flow systems).
There are case modeling studies that emphasize the key role
of the urban heat island in enhancing precipitation over and/or
downwind of cities. Using a three-dimensional mesoscale
model, Craig and Bornstein (2002) simulated summertime
convective precipitation over Atlanta. In their study, the urban
area is roughly represented using the flat-sandbox urbanization
approach. By comparing simulations with and without the city
of Atlanta, they demonstrated that the urban heat island produces
a confluence region, which then leads to convergence,
upward motion, and cumulus convection, resulting in precipitation
around the eastern boundaries of the city. Their case
modeling study provides a link of urban heat island forcing to
precipitation. Rozoff et al. (2003) conducted numerical experiments
of summertime thunderstorms over St. Louis using a
three-dimensional mesoscale model that includes an urban
canopy model [TEB: Town Energy Budget, Masson (2000)]
and examined urban-enhanced precipitation, with focus on
surface-driven low-level convergence mechanisms. The inclusion
of an urban canopy model in a mesoscale model is
necessary to better represent various physical processes
occurring at and near the urban surface. Their sensitivity
experiments show that the urban heat island plays the largest
ASIA-PACIFIC JOURNAL OF ATMOSPHERIC SCIENCES
role in initiating deep, moist convection downwind of the city.
Shem and Shepherd (2009) performed two case studies on
summertime thunderstorms over Atlanta using a three-dimensional
mesoscale model. The simple urban land-cover parameterization
is utilized. Precipitation amounts downwind of the
city were found to be higher by 10-13% in the simulations
with the city of Atlanta than in the simulations in which the
city is removed and replaced by the dominant land-cover type
of the surrounding rural area. They stated that the increase in
precipitation amount is possibly attributed to intensified
activity within the planetary boundary layer resulting from the
urban heat island effect. The urban heat island effect on summertime
precipitation over a complex geographic environment
in northern Taiwan including the city of Taipei was examined
through a case modeling study by Lin et al. (2011). They
employed a three-dimensional mesoscale model that includes
the urban canopy model of Kusaka et al. (2001). The simulation
results show that not only the rainfall system is enhanced
downwind of the city over the mountainous area, but
also it occurs in the upwind plain area. In the above case
modeling studies, convection is explicitly resolved using bulk
cloud microphysics.
The work of Thielen et al. (2000) is of note, as it addresses
the question of the extent of influence of urban surfaces on the
development of precipitation using a two-dimensional mesoscale
model with bulk cloud microphysics. The model is
initialized with a single profile of temperature, dew point
temperature, and wind speed based on the summertime midday
sounding observed upwind of Paris. Among spatially varying
surface sensible heat flux, surface latent heat flux, and roughness
length, on a time scale of less than 4 h the surface sensible
heat flux variations were found to have the most significant
impact on the development of precipitation. This result implies
that the urban heat island is the most influential factor because
the (much) larger surface sensible heat flux in urban areas than
in surrounding rural areas greatly contributes to increasing nearsurface
air temperature in urban areas, thus exhibiting enhanced
urban heat island. The inclusion of urban heat islands was
found to result in increased precipitation over the urban heat
island and at a certain distance downwind of it.
In observational studies, it is inherently difficult to isolate
and understand the effects of the individual factors that
influence a phenomenon and also find the relative importance
of each individual factor. However, in numerical modeling
studies, isolation is possible and relative importance can be
found through a series of well-designed simulations. The above
idealized and case modeling studies confirm that the urban heat
island-induced strong updrafts can produce clouds/thunderstorms
on the downwind side, resulting in downwind precipitation
enhancement. This mechanism works, particularly
well when the urban surface sensible heat flux is large and the
atmospheric boundary layer is almost neutral. The urban heat
island and the mechanism largely explain observations of thunderstorms
often occurring downwind of cities in the afternoon
or in the early evening in summer.
b. Large surface roughness
Spatial changes in surface roughness can lead to changes in
airflow. Larger surface roughness in a city than in its surrounding
rural area causes air approaching the city to slow
Fig. 5. Fields of the (a) cloud water mixing ratio (g kg−1
), (b) rainwater
mixing ratio (g kg−1
), (c) vertical velocity (m s−1
), and (d) temperature
(o
C) in a three-dimensional, moist simulation. The center of the urban
heat island is located at x = 50 km, and the concentrated heating region
is outlined by dashed line between x = 40 and 60 km. [after Han and
Baik (2008).]
Ji-Young Han et al.
down near the upwind city boundary and/or over the city. In
addition, the air approaching a city tends to divert around it
and the diverted air can converge on the downwind side of the
city, yielding upward motion there (Cotton and Pielke, 1995).
These two features that can appear due to rougher urban surface
are schematically depicted in Fig. 6.
The question arises as to whether the upward motion near
the upwind urban boundary and/or over an urban area that
results from rougher urban surface is strong enough to initiate
moist convection in that area. Some studies have produced
relevant answers to this question. A two-dimensional modeling
study of Thielen et al. (2000) indicates that precipitation is
enhanced with increased roughness. They speculated that the
effect of roughness changes on the precipitation intensity could
be substantially reduced because the airflow can go around the
urban area. A case modeling study for St. Louis indicates that
the increased urban momentum drag induces convergence on
the windward side of the city, but this convergence is not
strong enough to initiate storms (Rozoff et al., 2003). If the
results of Thielen et al. (2000) and Rozoff et al. (2003) are
considered together, two inferences can be made. First, the
upward motion induced by rougher urban surface will be
stronger in two dimensions than in three dimensions. In terms
of dimensions, this is similar to the result of Han and Baik
(2008) that shows that the urban heat island-induced upward
motion is stronger in two dimensions than in three dimensions.
Second, in three dimensions, the upward motion will become
strong with increasing urban roughness. Due to the lack of
extensive previous studies, it is not confirmed that roughness
alone can initiate moist convection (or the roughness can play
an important role in initiating moist convection) in reality and
thus can explain to some extent observed precipitation enhancement
over and/or downwind of cities. There is, of course,
a possibility that updrafts produced by high-rise buildings in
highly built-up urban areas can initiate moist convection,
although not studied yet. To make any conclusions related to
the problem in question, case modeling studies for many cities,
together with idealized modeling studies, are needed in three
dimensions. We add here that there are no existing systematic
studies that investigate a possible connection between the
convergence of the diverted airflow on the downwind side of a
city and the initiation of moist convection. This is an
interesting research topic, necessitating investigation.
As described in section 2, observational studies show that
precipitating convective systems can be disrupted or bifurcated
while passing over cities (Bornstein and LeRoy, 1990; Tumanov
et al., 1999). These observed phenomena are attributed to
larger urban roughness. Miao et al. (2011) conducted a case
study of the effects of urban processes on summer precipitation
over Beijing using a three-dimensional mesoscale model
that includes the urban canopy model of Kusaka et al. (2001).
They indicated that the presence of the city leads to the
breaking of the squall line into convective cells over the urban
area. Previous observational and case modeling studies demonstrate
that cities affect precipitating convective systems that
pass over them. However, it is not clear whether disrupted or
bifurcated convective systems produce more precipitation over
and/or downwind of cities. Precipitation can either increase or
decrease depending on factors such as water vapor supply and
the degree of urban roughness. Idealized and further case
modeling studies would help understand the mechanism
involved in the impacts of rougher urban surface on precipitating
convective systems passing over the urban area and
find under what conditions precipitation can increase/decrease.
c. Higher aerosol concentration
Aerosols can significantly affect the development of clouds
and precipitation by acting as cloud condensation nuclei
(CCN) or ice nuclei as well as by absorbing and scattering
solar radiation. There is a general agreement that an increased
aerosol (number) concentration suppresses precipitation from
warm shallow clouds by producing a narrow drop size distribution
that is inefficient in the collision-coalescence process
(e.g., Rosenfeld, 1999). However, the role of aerosols in suppressing
or enhancing precipitation from mixed-phase clouds
and the mechanism involved are still under debate.
From observations taken from the Tropical Rainfall Measuring
Mission (TRMM) satellite, Rosenfeld (2000) found
evidence that both warm-rain and cold-rain processes are
inhibited in polluted clouds. He suggested that the lack of
primary and secondary ice production resulting from reduced
cloud droplet size could be the reason for the suppression of
ice precipitation formation. Combining remote sensing and insitu
mountaintop measurements, Borys et al. (2003) showed
that a pollution-induced decrease in cloud droplet size causes a
decrease in snowfall rate from mixed-phase clouds in mountainous
regions by inhibiting the riming process. Givati and
Rosenfeld (2004) observed a downwind shift of precipitation
from relatively short-lived orographic clouds in polluted urban
areas in the United States and Israel, and suggested that this is
Fig. 6. Schematic of low-level airflow over and around an urban area
due to changes in surface roughness. [after Cotton and Pielke (1995).]
ASIA-PACIFIC JOURNAL OF ATMOSPHERIC SCIENCES
due to the effect of aerosols that slow down the conversion of
cloud water to precipitation. This observation is supported by
Lynn et al. (2007), who investigated the effects of aerosols on
orographic precipitation in the Sierra Nevada of California by
performing simulations under maritime and continental aerosol
conditions using a two-dimensional mesoscale model with bin
cloud microphysics. They showed that a downwind shift of
precipitation results from the fact that anthropogenic aerosols
suppress the warm rain process and therefore produce more
cloud ice and snow, which can be advected farther downwind
because of their lower sedimentation velocities. By analyzing
the weekly cycles of pollution and precipitation, Svoma and
Balling (2009) found that the aerosol concentration is inversely
related to the winter precipitation frequency in the Phoenix
metropolitan area. Based on this observation, they suggested
that human activity influences precipitation primarily by the
suppressing effect of aerosols.
On the other hand, some observational studies that analyze
the relation between the weekly cycles of air pollutants and
summertime precipitation show evidence of enhanced rainfall
on high aerosol concentration days in the southeast United
States (e.g., Bell et al., 2008; Lacke et al., 2009). A positive
correlation between the aerosol concentration and the cloud-toground
lightning activity is found in many urban areas, for
example, in Spain (Soriano and Pablo, 2002), Brazil (Naccarato
et al., 2003; Farias et al., 2009), the United States (Steiger and
Orville, 2003), and Korea (Kar et al., 2007, 2009). By analyzing
both surface and satellite observations, Choi et al.
(2008) found that higher aerosol concentrations are significantly
correlated with an increase in moderate rainfall events
and with an increase in mid-level ice or mixed clouds in China.
They suggested that on the time scale of a few days the
increase in aerosol concentration results in an increase of
summer rainfall frequency via enhanced ice nucleation in the
mid-troposphere. Several studies explain the observed precipitation
enhancement in polluted areas by a mechanism that the
delayed onset of precipitation in deep convection allows
updrafts to accelerate and transport more cloud water to upper
levels where it can release the additional latent heat of freezing
(e.g., Andreae et al., 2004; Rosenfeld et al., 2008; Carrió et al.,
2010; Carrió and Cotton, 2011). A more detailed explanation
of how increased aerosol concentration in urban areas affects
convection induced by the urban heat island is provided in a
recent numerical study of Han et al. (2012) using a twodimensional
cloud model with bin microphysics. The simulation
results show that the development of stronger convective
cloud under higher aerosol concentrations is mainly due to the
release of an increased amount of latent heat resulting from the
enhanced condensation process. The low collision efficiency
of smaller cloud droplets and the resulting stronger updraft
under higher aerosol concentrations result in larger liquid
water content (LWC) at higher levels, leading to the enhanced
riming process, which produces large ice particles. The melting
of a larger amount of hail leads to precipitation enhancement
downwind of the urban area with increasing urban aerosol
concentration. These urban aerosol impacts on deep convective
cloud and precipitation are summarized in a schematic
diagram (Fig. 7).
Several observational and numerical studies indicate that
anthropogenic air pollution can inhibit or enhance convective
activity depending on cloud type (as discussed above), environmental
conditions, and size and concentration of aerosol
particles. For example, Khain et al. (2008) and Khain (2009)
indicated that aerosols usually decrease precipitation in stratocumulus
clouds or in isolated cumulus clouds developing in a
dry environment, while aerosols usually increase precipitation
in cloud ensembles or in clouds developing in a moist environment
(Fig. 8). By analyzing the trends of orographic winter
precipitation and aerosols in the western United States,
Rosenfeld and Givati (2006) suggested that a decreasing trend
in orographic precipitation during the last two decades is likely
to be the result of decreasing concentrations of coarse aerosols
which may enhance precipitation by acting as giant CCN, in
conjunction with the stable or increasing concentrations of fine
aerosols which may suppress precipitation.
Using a three-dimensional mesoscale model that incorporates
sophisticated surface and bulk microphysics processes, van
den Heever and Cotton (2007) examined the impacts of urbanenhanced
aerosols on convective storms that develop over and
downwind of St. Louis, focusing on the dependence of cloudaerosol
interactions on the size and concentration of background
aerosols. Their sensitivity experiments show that when
giant CCN are enhanced, the rapid formation of liquid water
and ice species leads initially to stronger updrafts, which in
Fig. 7. Schematic diagram that shows how increased aerosol concentration
in the urban area affects deep convective cloud and
precipitation. [after Han et al. (2012).]
Ji-Young Han et al.
turn enhances surface precipitation. However, this generates
stronger downdrafts and more intense cold pools earlier,
causing the earlier demise of the storm and the absence of new
storm development. On the contrary, when CCN alone
(without giant CCN) are enhanced, although the updrafts
develop later in association with the delayed hydrometeor
formation, they are eventually stronger. The storms last longer
and new storm development occurs. They stated that complex,
nonlinear relationships between the microphysics and dynamics
make it difficult to make definitive statements about the
impacts of urban aerosols on downwind convection and precipitation.
They also showed that urban aerosol effects decrease
with increasing background aerosol concentration. Different
cloud-aerosol interactions with varying aerosol concentrations
are indicated in case modeling studies of Carrió et al. (2010)
and Carrió and Cotton (2011), which examine the effects of
urban growth and associated aerosols sources on convection
over Houston using a three-dimensional cloud-resolving model
with detailed treatments of land surface processes and aerosol
microphysics. In their simulations, precipitation first increases
and then decreases with increasing aerosol concentration. With
the highest aerosol concentration, riming of ice particles
becomes so inefficient that a greater fraction of condensate is
transported into the storm anvil, causing a decrease in precipitation
efficiency. They also showed that higher pollution
levels are required to reach maximum precipitation efficiency
for more unstable environments. By analyzing the cloud-toground
lightning data and pollution data over the metropolitan
area of São Paulo, Farias et al. (2014) also found that lightning
activity first tends to increase and then to decrease with increasing
pollutant concentration.
Previous modeling studies seem to suggest that surface precipitation
can increase further under higher aerosol concentrations
if the air humidity is high and deep and strong convection
occurs. However, the relation between the aerosol concentration
and surface precipitation amount is, as indicated by many
observational and modeling studies, varies depending on many
factors. For example, a three-dimensional mesoscale modeling
study for the northeastern United States including New York
City (Ntelekos et al., 2009) shows that increasing aerosol concentration
can lead to either enhancement or suppression of
precipitation in intense convective storms, which depends on
convective available potential energy (CAPE), relative humidity,
and wind shear. High CAPE, high relative humidity, and
strong wind shear were found to result in precipitation enhancement
with increasing aerosol concentration. Systematic
modeling studies are required to find under what conditions the
surface precipitation increases/decreases with increasing urban
aerosol concentration and understand mechanisms involved.
Also, the effects of the size distribution of aerosols need to be
investigated. Comprehensive reviews of the complexity of
cloud-aerosol interactions, which do not focus on the impacts
of urban aerosols, are given in Levin and Cotton (2009), Khain
(2009), and Tao et al. (2012).
d. Urban vs. no-urban simulation studies
A simple approach that is used to examine the bulk effect of
urban areas or urbanization on precipitation using numerical
models is to perform two simulations (an urban simulation and
a no-urban simulation) and compare the simulation results. In
the no-urban simulation, the urban area is replaced by the land
use/land cover of the surrounding rural area or before urbanization.
Both simulations utilize the same initial and boundary
conditions. In addition, simulations using a variety of urbanization
scenarios can be performed. Numerous modeling studies
have taken this line of research using mesoscale models or
regional climate models. In the models used, the increase in
aerosol concentration due to urban air pollution and its effects
on cloud and precipitation processes are not treated, so
precipitation changes are caused by the combined effect of the
urban heat island and the larger urban surface roughness.
A large number of modeling studies indicate precipitation
enhancement over and/or downwind of cities (e.g., Rozoff et
al., 2003; Shem and Shepherd, 2009; Shepherd et al., 2010;
Lin et al., 2011; Wan et al., 2013). Interestingly, some
modeling studies indicate that cities can decrease precipitation
(e.g., Trusilova et al., 2008; Zhang et al., 2009). A modeling
study of Trusilova et al. (2008) shows that summer precipitation
increases in the eastern region of Europe, but decreases
in the central and southern regions of Europe and that the
reduction in summer precipitation is distinct downwind of
cities in the central and southern regions of Europe. They
explained these regional differences in summer precipitation
with the climatic differences of the regions. For example, the
central region of Europe has a mild climate and precipitation in
the region is frequent in summers. Thus, the summer precipitation
reduction is explained by the reduction in surface
Fig. 8. A schematic diagram of the aerosol effects on clouds and cloud
systems of different types under different environmental conditions.
The zone above (below) the diagonal corresponds to a decrease (an
increase) in precipitation with an increase in the aerosol concentration.
[after Khain (2009).]
ASIA-PACIFIC JOURNAL OF ATMOSPHERIC SCIENCES
water availability in the extensive urban areas of the region.
Through numerical simulations, Zhang et al. (2009) suggested
that the observed reduction in summer precipitation in the
northeast area of Beijing is due to the urban expansion and
showed that the reduction in evaporation in the urban area and
the subsequent decrease in CAPE are responsible for the
summer precipitation reduction. Previous studies show that in
many regions of the world urbanization acts to increase precipitation
over and/or downwind of cities, but in some regions
the precipitation reduction occurs. Further in-depth modeling
studies are necessary to find the causes and processes that lead
to such differences.
Table 2 lists three-dimensional numerical modeling studies
of urban-related changes in precipitation over and around cities.
4. Summary and conclusions
In this article, we have reviewed urban impacts on precipitation.
Observational studies show that cities do affect the
spatial distribution and amount of precipitation and that precipitation
tends to increase over and/or downwind of cities.
Causative factors and mechanisms involved have been proposed
to explain, in particular, the observed downwind precipitation
enhancement. Here, we present a universal mechanism
of urban-induced precipitation based on the results of
previous studies. The urban heat island can lead to a nearsurface
convergence zone and consequently updrafts on the
leeward or downwind side of cities. Under thermodynamic
conditions that are conducive to moist convection, the urban
heat island-induced updrafts act as dynamic forcing to initiate
moist convection and produce surface precipitation. Surface
precipitation is likely to further increase under higher aerosol
concentrations if the air humidity is high and deep and strong
convection occurs. Larger surface roughness does not appear
to play a major role in urban-induced precipitation. Observational
studies indicate that precipitating convective systems
Table 2. Three-dimensional numerical modeling studies of urban-related changes in precipitation over and around cities.
City References
Asia
Beijing, China Guo et al. (2006), Jiang and Liu (2007), Zhang et al. (2009), Miao et al. (2011)
Eastern and Southern China Shao et al. (2013)
Nanjing, China Yang et al. (2012)
Pearl River Delta, China Lin et al. (2009)
Yangtze River Delta, China Wan et al. (2013)
Mumbai, Bangalore, and Chennai, India Goswami et al. (2010)
Jerusalem, Israel Shafir and Alpert (1990)
Kanto area, Japan Yang et al. (2000)
Seoul and surrounding area, Korea Eun et al. (2011)
Taipei, Taiwan Lin et al. (2011)
Western Plain, Taiwan Lin et al. (2008)
Europe
Brussels, Begium Hamdi et al. (2012)
Vilnius, Lithuania Mažeikis (2013)
Whole Europe Trusilova et al. (2008)
North America
San Juan, Puerto Rico Comarazamy et al. (2006)
Atlanta, United States Craig and Bornstein (2002), Shem and Shepherd (2009)
Baltimore-Washington, United States Ntelekos et al. (2008), Li et al. (2013)
Fairbanks, United States Mölders and Olson (2004)
Houston, United States Li et al. (2008), Carrió et al. (2010), Shepherd et al. (2010), Carrió and Cotton (2011)
Indianapolis, United States Niyogi et al. (2011)
New York City, United States Ntelekos et al. (2009)
St. Louis, United States Rozoff et al. (2003), van den Heever and Cotton (2007)
Oceania
Sydney, Australia Gero and Pitman (2006)
Ji-Young Han et al.
are influenced (disrupted or bifurcated) by cities while passing
over them. This is attributed to the larger urban surface roughness.
The urban-modified precipitating systems can, however,
either increase or decrease precipitation over and/or downwind
of cities depending on many factors such as topography and
local/regional water vapor supply. It cannot be definitely stated
that urban-modified precipitation systems produce more precipitation
downwind of cities than upwind of cities.
As reviewed in this study, numerical models have been
extensively used for studying urban impacts on precipitation.
To better simulate and predict urban-related weather and
climate, numerical models need to be further developed, with
focus on the interactions of urban surfaces with the overlying
atmosphere (urban parameterization: e.g., Masson, 2000; Kusaka
et al., 2001; Martilli et al., 2002) and cloud microphysics. To
more reliably and intensively study the effects of urban air
pollution on precipitation and aerosol-cloud-precipitation interactions,
it is necessary to couple meteorological models
with aerosol/chemistry models. In addition, the bin cloud
microphysics would be better to be included in cloud-resolving
mesoscale models because it relaxes some constraints imposed
on bulk cloud microphysics and contains higher-level cloud
microphysical processes, although it requires much longer
computing times. Such advanced coupled models would offer
the possibility of in-depth or new understandings of individual
physical processes and complex interactions among the processes.
Together with model development and modeling
studies, a greater number of observational studies for major
global cities using all available data are necessary. In particular,
the analyses of long-term radar data would be greatly
beneficial because of its high spatiotemporal resolution and
wide spatial coverage. Such research would lead to a better
understanding of urban impacts on precipitation.
If urbanization continues in the future, cities are likely to
exert greater influences on local and regional weather and
climate. It would be interesting to conduct research on how the
spatial pattern and amount of precipitation change with future
urbanization. Intensive studies are required to further understand
and reliably predict urban precipitation anomalies.
Acknowledgments. This work was funded by the National
Research Foundation of Korea (NRF) grant funded by the
Korea Ministry of Education, Science and Technology (MEST)
(No. 2012-0005674) and also by the Korea Meteorological
Administration Research and Development Program under
Grant CATER 2012-6030.
Edited by:
REFERENCES
Ackerman, B., and Coauthors, 1978: Summary of METROMEX, Volume 2:
Causes of Precipitation Anomalies, Bull. 63, Illinois State Water
Survey, 395 pp.
Andreae, M. O., D. Rosenfeld, P. Artaxo, A. A. Costa, G. P. Frank, K. M.
Longo, and M. A. F. Silva-Dias, 2004: Smoking rain clouds over the
Amazon. Science, 303, 1337-1342.
Arnfield, A. J., 2003: Two decades of urban climate research: A review of
turbulence, exchanges of energy and water, and the urban heat island.
Int. J. Climatol., 23, 1-26.
Atkinson, B. W., 1968: A preliminary examination of the possible effect of
London’s urban area on the distribution of thunder rainfall 1951-60. T. I.
Brit. Geogr., 44, 97-118.
______, 1969: A further examination of the urban maximum of thunder
rainfall in London, 1951-60. T. I. Brit. Geogr., 48, 97-119.
______, 1971: The effect of an urban area on the precipitation from a
moving thunderstorm. J. Appl. Meteorol., 10, 47-55.
Baik, J.-J., 1992: Response of a stably stratified atmosphere to low-level
heating-An application to the heat island problem. J. Appl. Meteorol.,
31, 291-303.
______, and H.-Y. Chun, 1997: A dynamical model for urban heat islands.
Bound.-Layer Meteor., 83, 463-477.
______, Y.-H. Kim, and H.-Y. Chun, 2001: Dry and moist convection
forced by an urban heat island. J. Appl. Meteorol., 40, 1462-1475.
______, ______, J.-J. Kim, and J.-Y. Han, 2007: Effects of boundary-layer
stability on urban heat island-induced circulation. Theor. Appl.
Climatol., 89, 73-81.
Bell, T. L., D. Rosenfeld, K.-M. Kim, J.-M. Yoo, M.-I. Lee, and M.
Hahneberger, 2008: Midweek increase in U.S. summer rain and storm
heights suggests air pollution invigorates rainstorms. J. Geophys. Res.,
113, D02209, doi:10.1029/2007JD008623.
Bornstein, R., and M. LeRoy, 1990: Urban barrier effects on convective
and frontal thunderstorms. Extended Abstracts, Fourth Conf. Mesoscale
Processes, Boulder, CO, Amer. Meteor. Soc., 120-121.
______, and Q. Lin, 2000: Urban heat islands and summertime convective
thunderstorms in Atlanta: three case studies. Atmos. Environ., 34, 507-
516.
Borys, R. D., D. H. Lowenthal, S. A. Cohn, and W. O. J. Brown, 2003:
Mountaintop and radar measurements of anthropogenic aerosol effects
on snow growth and snowfall rate. Geophys. Res. Lett., 30, 1538,
doi:10.1029/2002GL016855.
Burian, S. J., and J. M. Shepherd, 2005: Effect of urbanization on the
diurnal rainfall pattern in Houston. Hydrol. Process., 19, 1089-1103.
Carrió, G. G., and W. R. Cotton, 2011: Urban growth and aerosol effects on
convection over Houston. Part II: Dependence of aerosol effects on
instability. Atmos. Res., 102, 167-174.
______, ______, and W. Y. Y. Cheng, 2010: Urban growth and aerosol
effects on convection over Houston. Part I: The August 2000 case.
Atmos. Res., 96, 560-574.
Changnon, S. A., Jr., 1968: The La Porte weather anomaly-Fact or fiction?
Bull. Amer. Meteor. Soc., 49, 4-11.
______, 1980a: More on the La Porte anomaly: A review. Bull. Amer.
Meteor. Soc., 61, 702-717.
______, 1980b: Evidence of urban and lake influences on precipitation in
the Chicago area. J. Appl. Meteorol., 19, 1137-1159.
______, 1981: METROMEX: A Review and Summary. Meteor. Monogr.,
No. 40, Amer. Meteor. Soc., 181 pp.
______, 2001: Assessment of historical thunderstorm data for urban
effects: The Chicago case. Climatic Change, 49, 161-169.
______, and N. E. Westcott, 2002: Heavy rainstorms in Chicago:
Increasing frequency, altered impacts, and future implications. J. Amer.
Water Resour. Assoc., 38, 1467-1475.
______, F. A. Huff, P. T. Schickerdanz, and J. L. Vogel, 1977: Summary of
METROMEX, Volume 1: Weather Anomalies and Impacts. Bull. 62,
Illinois State Water Survey, 260 pp.
______, R. T. Shealy, and R. W. Scott, 1991: Precipitation changes in fall,
winter, and spring caused by St. Louis. J. Appl. Meteorol., 30, 126-134.
Chen, T.-C., S.-Y. Wang, and M.-C. Yen, 2007: Enhancement of afternoon
thunderstorm activity by urbanization in a valley: Taipei. J. Appl.
ASIA-PACIFIC JOURNAL OF ATMOSPHERIC SCIENCES
Meteor. Climatol., 46, 1324-1340.
Choi, Y.-S., C.-H. Ho, J. Kim, D.-Y. Gong, and R. J. Park, 2008: The
impacts of aerosols on the summer rainfall frequency in China. J. Appl.
Meteor. Climatol., 47, 1802-1813.
Chow, S. D., and C. Chang, 1984: Shanghai urban influences on humidity
and precipitation distribution. GeoJournal, 8, 201-204.
Chun, H.-Y., 1991: Role of a critical level in a shear flow with diabatic
forcing. Ph. D. dissertation, North Carolina State University, 159 pp.
Comarazamy, D. E., J. E. González, J. Luvall, D. Rickman, and A. Picón,
2006: A validation study of the urban heat island in the tropical coastal
city of San Juan, Puerto Rico. Extended Abstracts, Sixth Symp. on the
Urban Environment, Atlanta, GA, Amer. Meteor. Soc., 7 pp.
Cotton, W. R., and R. A. Pielke, 1995: Human Impacts on Weather and
Climate. Cambridge University Press, 288 pp.
Craig, K. J., and R. D. Bornstein, 2002: MM5 simulations of urban
induced convective precipitation over Atlanta. Preprints. Fourth Symp.
on the Urban Environment, Norfolk, VA, Amer. Meteor. Soc., 5-6.
De, U. S., and G. S. P. Rao, 2004: Urban climate trends - The Indian
scenario. J. Ind. Geophys. Union, 8, 199-203.
Diem, J. E., and T. L. Mote, 2005: Interepochal changes in summer
precipitation in the southeastern United States: Evidence of possible
urban effects near Atlanta, Georgia. J. Appl. Meteorol., 44, 717-730.
Dixon, P. G., and T. L. Mote, 2003: Patterns and causes of Atlanta’s urban
heat island-initiated precipitation. J. Appl. Meteorol., 42, 1273-1284.
Eun, S.-H., S.-H. Chae, B.-G. Kim, and K.-H. Chang, 2011: Effect of
urbanization on the light precipitation in the mid-Korean peninsula.
Atmosphere, 21, 229-241. (in Korean with English abstract)
Farias, W. R. G., O. Pinto, K. P. Naccarato, and I. R. C. A. Pinto, 2009:
Anomalous lightning activity over the metropolitan region of São Paulo
due to urban effects. Atmos. Res., 91, 485-490.
______, ______, I. R. C. A. Pinto, and K. P. Naccarato, 2014: The
influence of urban effect on lightning activity: Evidence of weekly
cycle. Atmos. Res., 135-136, 370-373.
Fujibe, F., H. Togawa, and M. Sakata, 2009: Long-term change and spatial
anomaly of warm season afternoon precipitation in Tokyo. Sci. Online
Lett. Atmos., 5, 17-20.
Garstang, J., P. D. Tyson, and G. D. Emmitt, 1975: The structure of heat
islands. Rev. Geophys. Space Phys., 13, 139-165.
Gedzelman, S. D., S. Austin, R. Cermak, N. Stefano, S. Partridge, S.
Quesenberry, and D. A. Robinson, 2003: Mesoscale aspects of the
urban heat island around New York City. Theor. Appl. Climatol., 75, 29-
42.
Gero, A. F., and A. J. Pitman, 2006: The impact of land cover change on a
simulated storm event in the Sydney basin. J. Appl. Meteor. Climatol.,
45, 283-300.
Givati, A., and D. Rosenfeld, 2004: Quantifying precipitation suppression
due to air pollution. J. Appl. Meteorol., 43, 1038-1056.
Goldreich, Y., 1987: Advertent/inadvertent changes in the spatial
distribution of rainfall in the central coastal plain of Israel. Climatic
Change, 11, 361-373.
______, and A. Manes, 1979: Urban effects on precipitation patterns in the
greater Tel-Aviv area. Arch. Meteor. Geophys. B, 27, 213-224.
Goswami, P., H. Shivappa, and B. S. Goud, 2010: Impact of urbanization
on tropical mesoscale events: Investigation of three heavy rainfall
events. Meteorol. Z., 19, 385-397.
Guo, X., F. Danhong, and W. Jing, 2006: Mesoscale convective
precipitation system modified by urbanization in Beijing City. Atmos.
Res., 82, 112-126.
Halfon, N., Z. Levin, and P. Alpert, 2009: Temporal rainfall fluctuations in
Israel and their possible link to urban and air pollution effects. Environ.
Res. Lett., 4, 025001, doi:10.1088/1748-9326/4/2/025001.
Hamdi, R., D. Degrauwe, and P. Termonia, 2012: Coupling the Town
Energy Balance (TEB) scheme to an operational limited-area NWP
model: Evaluation for a highly urbanized area in Belgium. Wea.
Forecasting, 27, 323-344.
Han, J.-Y., and J.-J. Baik, 2008: A theoretical and numerical study of urban
heat island-induced circulation and convection. J. Atmos. Sci., 65, 1859-
1877.
______, ______, and A. P. Khain, 2012: A numerical study of urban
aerosol impacts on clouds and precipitation. J. Atmos. Sci., 69, 504-520.
Hand, W. H., 2005: Climatology of shower frequency in the British Isles at
5 km resolution. Weather, 60, 153-158.
Houze, R. A., Jr., 1993: Cloud Dynamics. Academic Press, 573 pp.
Huff, F. A., and S. A. Changnon, Jr., 1973: Precipitation modification by
major urban areas. Bull. Amer. Meteor. Soc., 54, 1220-1232.
______, and ______, 1986: Potential urban effects on precipitation in the
winter and transition seasons at St. Louis, Missouri. J. Climate Appl.
Meteor., 25, 1887-1907.
Inoue, T., and F. Kimura, 2004: Urban effects on low-level clouds around
the Tokyo metropolitan area on clear summer days. Geophys. Res. Lett.,
31, L05103, doi:10.1029/2003GL018908.
Jauregui, E., 1997: Heat island development in Mexico City. Atmos.
Environ., 31, 3821-3831.
______, and E. Romales, 1996: Urban effects on convective precipitation
in Mexico City. Atmos. Environ., 30, 3383-3389.
Jiang, X., and W. Liu, 2007: Numerical simulations of impacts of
urbanization on heavy rainfall in Beijing using different land-use data.
Acta Meteorol. Sin., 21, 245-255.
Kar, S. K., Y.-A. Liou, and K.-J. Ha, 2007: Characteristics of cloud-toground
lightning activity over Seoul, South Korea in relation to an
urban effect. Ann. Geophys., 25, 2113-2118.
______, ______, and ______, 2009: Aerosol effects on the enhancement
of cloud-to-ground lightning over major urban areas of South Korea.
Atmos. Res., 92, 80-87.
Khain, A. P., 2009: Notes on state-of-the-art investigations of aerosol
effects on precipitation: A critical review. Environ. Res. Lett., 4,
015004, doi:10.1088/1748-9326/4/1/015004.
______, N. BenMoshe, and A. Pokrovsky, 2008: Factors determining the
impact of aerosols on surface precipitation from clouds: An attempt at
classification. J. Atmos. Sci., 65, 1721-1748.
Khemani, L. T., and Bh. V. Ramana Murty, 1973: Rainfall variations in an
urban industrial region. J. Appl. Meteorol., 12, 187-194.
Kim, D.-W., Y.-H. Kim, K.-H. Kim, S.-S. Shin, D.-K. Kim, Y.-J. Hwang,
J.-I. Park, D.-Y. Choi, and Y.-H. Lee, 2012: Effect of urbanization on
rainfall events during the 2010 summer intensive observation period
over Seoul metropolitan area. J. Korean Earth Sci. Soc., 33, 219-232.
(in Korean with English abstract)
Kim, Y.-H., and J.-J. Baik, 2002: Maximum urban heat island intensity in
Seoul. J. Appl. Meteorol., 41, 651-659.
______, D.-Y. Choi, and D.-E. Chang, 2011: Characteristics of urban
meteorology in Seoul metropolitan area of Korea. Atmosphere, 21, 257-
271. (in Korean with English abstract)
Kishtawal, C. M., D. Niyogi, M. Tewari, R. A. Pielke, Sr., and J. M.
Shepherd, 2010: Urbanization signature in the observed heavy rainfall
climatology over India. Int. J. Climatol., 30, 1908-1916.
Klysik, K., and K. Fortuniak, 1999: Temporal and spatial characteristics of
the urban heat island of Lodz, Poland. Atmos. Environ., 33, 3885-3895.
Kug, J.-S., and M. S. Ahn, 2013: Impact of urbanization on recent
temperature and precipitation trends in the Korean peninsula. Asia-Pac.
J. Atmos. Sci., 49, 151-159.
Kusaka, H., H. Kondo, Y. Kikegawa, and F. Kimura, 2001: A simple
single-layer urban canopy model for atmospheric models: Comparison
with multi-layer and slab models. Bound.-Layer Meteor., 101, 329-358.
Lacke, M. C., T. L. Mote, and J. M. Shepherd, 2009: Aerosols and
associated precipitation patterns in Atlanta. Atmos. Environ., 43, 4359-
4373.
Ji-Young Han et al.
Landsberg, H. E., 1970: Man-made climatic changes. Science, 170, 1265-
1274.
Lee, S.-H., and J.-J. Baik, 2010: Statistical and dynamical characteristics of
the urban heat island intensity in Seoul. Theor. Appl. Climatol., 100,
227-237.
Levin, Z., and W. R. Cotton, 2009: Aerosol Pollution Impact on
Precipitation: A Scientific Review. Springer, 386 pp.
Li, D., E. Bou-Zeid, M. L. Baeck, S. Jessup, and J. A. Smith, 2013:
Modeling land surface processes and heavy rainfall in urban
environments: Sensitivity to urban surface representations. J.
Hydrometeor., 14, 1098-1118.
Li, G., Y. Wang, and R. Zhang, 2008: Implementation of a two-moment
bulk microphysics scheme to the WRF model to investigate aerosolcloud
interaction. J. Geophys. Res., 113, D15211, doi:10.1029/
2007JD009361.
Li, W., S. Chen, G. Chen, W. Sha, C. Luo, Y. Feng, Z. Wen, and B. Wang,
2011: Urbanization signatures in strong versus weak precipitation over
the Pearl River Delta metropolitan regions of China. Environ. Res. Lett.,
6, 034020, doi:10.1088/1748-9326/6/3/034020.
Lin, C.-Y., W.-C. Chen, S. C. Liu, Y. A. Liou, G. R. Liu, and T. H. Lin,
2008: Numerical study of the impact of urbanization on the
precipitation over Taiwan. Atmos. Environ., 42, 2934-2947.
______, ______, P.-L. Chang, and Y.-F. Sheng, 2011: Impact of the urban
heat island effect on precipitation over a complex geographic
environment in northern Taiwan. J. Appl. Meteor. Climatol., 50, 339-
353.
Lin, W., L. Zhang, D. Du, L. Yang, H. Lin, Y. Zhang, and J. Li, 2009:
Quantification of land use/land cover changes in Pearl River Delta and
its impact on regional climate in summer using numerical modeling.
Reg. Environ. Change, 9, 75-82.
Lin, Y. L., and R. B. Smith, 1986: Transient dynamics of airflow near a
local heat source. J. Atmos. Sci., 43, 40-49.
______, and H.-Y. Chun, 1991: Effects of diabatic cooling in a shear flow
with a critical level. J. Atmos. Sci., 48, 2476-2491.
Lowry, W. P., 1998: Urban effects on precipitation amount. Prog. Phys.
Geography, 22, 477-520.
Lynn, B., A. Khain, D. Rosenfeld, and W. L. Woodley, 2007: Effects of
aerosols on precipitation from orographic clouds. J. Geophys. Res., 112,
D10225, doi:10.1029/2006JD007537.
Martilli, A., A. Clappier, and M. W. Rotach, 2002: An urban surface
exchange parameterization for mesoscale models. Bound.-Layer
Meteor., 104, 261-304.
Masson, V., 2000: A physically-based scheme for the urban energy budget
in atmospheric models. Bound.-Layer Meteor., 94, 357-397.
Mažeikis, A., 2013: Urbanization influence on meteorological parameters
of air pollution: Vilnius case study. Baltica, 26, 51-56.
Miao, S., F. Chen, Q. Li, and S. Fan, 2011: Impacts of urban processes and
urbanization on summer precipitation: A case study of heavy rainfall in
Beijing on 1 August 2006. J. Appl. Meteor. Climatol., 50, 806-825.
Mitra, C., J. M. Shepherd, and T. Jordan, 2012: On the relationship
between the premonsoonal rainfall climatology and urban land cover
dynamics in Kolkata city, India. Int. J. Climatol., 32, 1443-1454.
Mölders, N., and M. A. Olson, 2004: Impact of urban effects on
precipitation in high latitudes. J. Hydrometeor., 5, 409-429.
Morris, C. J. G., and I. Simmonds, 2000: Associations between varying
magnitudes of the urban heat island and the synoptic climatology in
Melbourne, Australia. Int. J. Climatol., 20, 1931-1954.
Mote, T. L., M. C. Lacke, and J. M. Shepherd, 2007: Radar signatures of
the urban effect on precipitation distribution: A case study for Atlanta,
Georgia. Geophys. Res. Lett., 34, L20710, doi:10.1029/2007GL031903.
Naccarato, K. P., O. Pinto, and I. R. C. A. Pinto, 2003: Evidence of thermal
and aerosol effects on the cloud-to-ground lightning density and
polarity over large urban areas of Southeastern Brazil. Geophys. Res.
Lett., 30, 1674, doi:10.1029/2003GL017496.
Niyogi, D., P. Pyle, M. Lei, S. P. Arya, C. M. Kishtawal, M. Shepherd, F.
Chen, and B. Wolfe, 2011: Urban modification of thunderstorms: An
observational storm climatology and model case study for the
Indianapolis urban region. J. Appl. Meteor. Climatol., 50, 1129-1144.
Ntelekos, A. A., J. A. Smith, M. L. Baeck, W. F. Krajewski, A. J. Miller,
and R. Goska, 2008: Extreme hydrometeorological events and the
urban environment: Dissecting the 7 July 2004 thunderstorm over the
Baltimore MD Metropolitan Region. Water Resour. Res., 44, W08446,
doi:10.1029/2007WR006346.
______, ______, L. Donner, J. D. Fast, W. I. Gustafson, E. G. Chapman,
and W. F. Krajewski, 2009: The effects of aerosols on intense
convective precipitation in the northeastern United States. Quart. J.
Roy. Meteor. Soc., 135, 1367-1391.
Oke, T. R., 1982: The energetic basis of the urban heat island. Quart. J.
Roy. Meteor. Soc., 108, 1-24.
______, 1987: Boundary Layer Climates. 2nd ed. Routledge, 435 pp.
Olfe, D. B., and R. L. Lee, 1971: Linearized calculations of urban heat
island convection effects. J. Atmos. Sci., 28, 1374-1388.
Orville, R. E., and Coauthors, 2001: Enhancement of cloud-to-ground
lightning over Houston, Texas. Geophys. Res. Lett., 28, 2597-2600.
Pinto, O., I. R. C. A. Pinto, and M. A. S. Ferro, 2013: A study of the longterm
variability of thunderstorm days in southeast Brazil. J. Geophys.
Res.-Atmos., 118, 5231-5246.
Pruppacher, H. R., and J. D. Klett, 1997: Microphysics of Clouds and
Precipitation. 2nd ed. Kluwer Academic Publishers, 954 pp.
Rao, G. S. P., A. K. Jaswal, and M. S. Kumar, 2004: Effects of urbanization
on meteorological parameters. MAUSAM, 55, 429-440.
Romanov, P., 1999: Urban influence on cloud cover estimated from
satellite data. Atmos. Environ., 33, 4163-4172.
Rose, L. S., J. A. Stallins, and M. L. Bentley, 2008: Concurrent cloud-toground
lightning and precipitation enhancement in the Atlanta, Georgia
(United States), urban region. Earth Interact., 12. [Available online at
http://EarthInteractions.org.]
Rosenfeld, D., 1999: TRMM observed first direct evidence of smoke from
forest fires inhibiting rainfall. Geophys. Res. Lett., 26, 3105-3108.
______, 2000: Suppression of rain and snow by urban and industrial air
pollution. Science, 287, 1793-1796.
______, and A. Givati, 2006: Evidence of orographic precipitation
suppression by air pollution-induced aerosols in the western United
States. J. Appl. Meteor. Climatol., 45, 893-911.
______, U. Lohmann, G. B. Raga, C. D. O’Dowd, M. Kulmala, S. Fuzzi,
A. Reissell, and M. O. Andreae, 2008: Flood or drought: How do
aerosols affect precipitation? Science, 321, 1309-1313.
Rozoff, C. M., W. R. Cotton, and J. O. Adegoke, 2003: Simulation of St.
Louis, Missouri, land use impacts on thunderstorms. J. Appl. Meteorol.,
42, 716-738.
Ryu, Y.-H., and J.-J. Baik, 2012: Quantitative analysis of factors
contributing to urban heat island intensity. J. Appl. Meteor. Climatol.,
51, 842-854.
Sanderson, M., and R. Gorski, 1978: The effect of metropolitan DetroitWindsor
on precipitation. J. Appl. Meteorol., 17, 423-427.
Schlünzen, K. H., P. Hoffmann, G. Rosenhagen, and W. Riecke, 2010:
Long-term changes and regional differences in temperature and
precipitation in the metropolitan area of Hamburg. Int. J. Climatol., 30,
1121-1136.
Shafir, H., and P. Alpert, 1990: On the urban orographic rainfall anomaly
in Jerusalem-A numerical study. Atmos. Environ., 24B, 365-375.
Shao, H., J. Song, and H. Ma, 2013: Sensitivity of the East Asian summer
monsoon circulation and precipitation to an idealized large-scale urban
expansion. J. Meteor. Soc. Japan, 91, 163-177.
Shem, W., and M. Shepherd, 2009: On the impact of urbanization on
summertime thunderstorms in Atlanta: Two numerical model case
ASIA-PACIFIC JOURNAL OF ATMOSPHERIC SCIENCES
studies. Atmos. Res., 92, 172-189.
Shepherd, J. M., 2005: A review of current investigations of urban-induced
rainfall and recommendations for the future. Earth Interact., 9.
[Available online at http://EarthInteractions.org.]
______, and S. J. Burian, 2003: Detection of urban-induced rainfall
anomalies in a major coastal city. Earth Interact., 7. [Available online at
http://EarthInteractions.org.]
______, H. Pierce, and A. J. Negri, 2002: Rainfall modification by major
urban areas: Observations from spaceborne rain radar on the TRMM
satellite. J. Appl. Meteorol., 41, 689-701.
______, M. Carter, M. Manyin, D. Messen, and S. Burian, 2010: The
impact of urbanization on current and future coastal precipitation: A
case study for Houston. Environ. Plann. B, 37, 284-304.
Soriano, L. R., and F. Pablo, 2002: Effect of small urban areas in central
Spain on the enhancement of cloud-to-ground lightning activity. Atmos.
Environ., 36, 2809-2816.
Steiger, S. M., and R. E. Orville, 2003: Cloud-to-ground lightning
enhancement over Southern Louisiana. Geophys. Res. Lett., 30, 1975,
doi:10.1029/2003GL017923.
______, ______, and G. Huffines, 2002: Cloud-to-ground lightning
characteristics over Houston, Texas: 1989-2000. J. Geophys. Res., 107,
4117, doi:10.1029/ 2001JD001142.
Svoma, B. M., and R. C. Balling, Jr., 2009: An anthropogenic signal in
Phoenix, Arizona winter precipitation. Theor. Appl. Climatol., 98, 315-
321.
Tao, W.-K., J.-P. Chen, Z. Li, C. Wang, and C. Zhang, 2012: Impact of
aerosols on convective clouds and precipitation. Rev. Geophys., 50,
RG2001, doi:10.1029/ 2011RG000369.
Thielen, J., W. Wobrock, A. Gadian, P. G. Mestayer, and J.-D. Creutin,
2000: The possible influence of urban surfaces on rainfall development:
a sensitivity study in 2D in the meso-γ-scale. Atmos. Res., 54, 15-39.
Trusilova, K., M. Jung, G. Churkian, U. Karstens, M. Heimann, and M.
Claussen, 2008: Urbanization impacts on the climate in Europe:
Numerical experiments by the PSU-NCAR mesoscale model (MM5). J.
Appl. Meteor. Climatol., 47, 1442-1455.
Tumanov, S., A. Stan-Sion, A. Lupu, C. Soci, and C. Oprea, 1999:
Influences of the city of Bucharest on weather and climate parameters.
Atmos. Environ., 33, 4173-4183.
UN, cited 2012: World Urbanization Prospects, The 2011 Revision.
[Available online at http://esa.un.org/unup/.]
van den Heever, S. C., and W. R. Cotton, 2007: Urban aerosol impacts on
downwind convective storms. J. Appl. Meteor. Climatol., 46, 828-850.
Wan, H., Z. Zhong, X. Yang, and X. Li, 2013: Impact of city belt in
Yangtze River Delta in China on a precipitation process in summer: A
case study. Atmos. Res., 125-126, 63-75.
Westcott, N. E., 1995: Summertime cloud-to-ground lightning activity
around major Midwestern urban areas. J. Appl. Meteorol., 34, 1633-
1642.
Yang, B., Y. Zhang, and Y. Qian, 2012: Simulation of urban climate with
high-resolution WRF model: A case study in Nanjing, China. Asia-Pac.
J. Atmos. Sci., 48, 227-241.
Yang, K., G. Huang, and N. Tamai, 2000: Surface process and topographic
effect on the weather development in Kanto region. Proc., Joint Conf.
on Water Resource Engineering and Water Resources Planning and
Management 2000, Minneapolis, MN, Environmental and Water
Resources Institute of ASCE, 10 pp.
Yonetani, T., 1982: Increase in number of days with heavy precipitation in
Tokyo urban area. J. Appl. Meteorol., 21, 1466-1471.
Zhang, C. L., F. Chen, S. G. Miao, Q. C. Li, X. A. Xia, and C. Y. Xuan,
2009: Impacts of urban expansion and future green planting on summer
precipitation in the Beijing metropolitan area. J. Geophys. Res., 114,
D02116, doi:10.1029/2008JD010328.
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