2015 Vol. 21, No. 3
2015, 21(3): 211-221.
doi: doi:10.16555/j.1006-8775.2015.03.001
Abstract:
Based on intensive automatic weather station data, satellite cloud imagery, NCEP reanalyzed data, and the simulation results from mesoscale numerical models, this study analyzes the characteristics and formation mechanisms of the mesoscale convection system (MCS) during the extreme precipitation event that was triggered by a weakened low-pressure inverted trough of Typhoon Haikui on August 10/2012. The results of this study show that cold air at the rear of a northeastern cold vortex creates thermodynamic conditions favorable to the development of extreme precipitation. The main body of the cold air is northward located so that the cold air invades only the middle layer of the periphery of the inverted trough. Thus, the cold air minimally affects the lower layer, which results in a vertically distributed structure of the temperature advection that augments the formation and development of convective instability stratification. In the middle troposphere, the cold air encounters the convergent, ascending, warm moist air from the low-pressure inverted trough, leading to frontogenesis. The frontogenesis enhances wind convergence which, in turn, further enhances the frontogenesis, and the positive feedback between these two forces augments the development of meso- and small-scale convection systems in the rainstorm region and its vicinity, which strengthens the upward transportation of water vapor from low layers and thickening of water vapor convergence and results in local heavy rains.
Based on intensive automatic weather station data, satellite cloud imagery, NCEP reanalyzed data, and the simulation results from mesoscale numerical models, this study analyzes the characteristics and formation mechanisms of the mesoscale convection system (MCS) during the extreme precipitation event that was triggered by a weakened low-pressure inverted trough of Typhoon Haikui on August 10/2012. The results of this study show that cold air at the rear of a northeastern cold vortex creates thermodynamic conditions favorable to the development of extreme precipitation. The main body of the cold air is northward located so that the cold air invades only the middle layer of the periphery of the inverted trough. Thus, the cold air minimally affects the lower layer, which results in a vertically distributed structure of the temperature advection that augments the formation and development of convective instability stratification. In the middle troposphere, the cold air encounters the convergent, ascending, warm moist air from the low-pressure inverted trough, leading to frontogenesis. The frontogenesis enhances wind convergence which, in turn, further enhances the frontogenesis, and the positive feedback between these two forces augments the development of meso- and small-scale convection systems in the rainstorm region and its vicinity, which strengthens the upward transportation of water vapor from low layers and thickening of water vapor convergence and results in local heavy rains.
2015, 21(3): 222-231.
doi: doi: 10.16555/j.1006-8775.2015.03.002
Abstract:
An objective analysis of tropical cyclone tracks is performed, with which the tracks of 131 tropical storms (TSs) in 1972-2011 are separated into three types that move west-, north- and northwestward, denoted as Types A, B and C, respectively. Type A (21 TSs and 16% of total) has the origin in the southwestern Bay of Bengal, with the TS in a unimodal distribution as its seasonal feature, occurring mainly in autumn; 18 of the 21 TSs (taking up 90%) land mostly on the western Bay coast (west of 85°E); 5% of Type-A TSs attains the wind speed of >42.7 to 48.9 m/s. Type A has little or no effect on Tibet. Type B (74 TSs, 56.6% of the total) has its preferable origin in the central Bay of Bengal, with the TS in a bimodal distribution as its seasonal pattern. This type denotes the travel in the north in spring, with the landfall of 67 of the 74 TSs (accounting for 91%) mainly on the middle coast of the Bay (85° to 95°E), and 19% of the TSs reaching the wind velocity of >42.7 to 48.9 m/s, which exert great effect on Tibet and it is this TS track that gives strong precipitation on its way through this region. Type C (36 TSs, 27.5% of the total) has its main origin in the southern part of the bay, and these TSs are formed largely in autumn, moving in the northwest direction, and 23 of the 36 TSs (64%) land mostly on the western Bay coast, lasting for a longer time, with almost no impact upon Tibet.
An objective analysis of tropical cyclone tracks is performed, with which the tracks of 131 tropical storms (TSs) in 1972-2011 are separated into three types that move west-, north- and northwestward, denoted as Types A, B and C, respectively. Type A (21 TSs and 16% of total) has the origin in the southwestern Bay of Bengal, with the TS in a unimodal distribution as its seasonal feature, occurring mainly in autumn; 18 of the 21 TSs (taking up 90%) land mostly on the western Bay coast (west of 85°E); 5% of Type-A TSs attains the wind speed of >42.7 to 48.9 m/s. Type A has little or no effect on Tibet. Type B (74 TSs, 56.6% of the total) has its preferable origin in the central Bay of Bengal, with the TS in a bimodal distribution as its seasonal pattern. This type denotes the travel in the north in spring, with the landfall of 67 of the 74 TSs (accounting for 91%) mainly on the middle coast of the Bay (85° to 95°E), and 19% of the TSs reaching the wind velocity of >42.7 to 48.9 m/s, which exert great effect on Tibet and it is this TS track that gives strong precipitation on its way through this region. Type C (36 TSs, 27.5% of the total) has its main origin in the southern part of the bay, and these TSs are formed largely in autumn, moving in the northwest direction, and 23 of the 36 TSs (64%) land mostly on the western Bay coast, lasting for a longer time, with almost no impact upon Tibet.
2015, 21(3): 232-245.
doi: doi: 10.16555/j.1006-8775.2015.03.003
Abstract:
In this study a coupled air–Csea–Cwave model system, containing the model components of GRAPES-TCM, ECOM-si and WAVEWATCH III, is established based on an air–Csea coupled model. The changes of wave state and the effects of sea spray are both considered. Using the complex air–Csea–Cwave model, a set of idealized simulations was applied to investigate the effects of air–Csea–Cwave interaction in the upper ocean. Results show that air–Cwave coupling can strengthen tropical cyclones while air–Csea coupling can weaken them; and air–Csea–Cwave coupling is comparable to that of air–Csea coupling, as the intensity is almost unchanged with the wave model coupled to the air–Csea coupled model. The mixing by vertical advection is strengthened if the wave effect is considered, and causes much more obvious sea surface temperature (SST) decreases in the upper ocean in the air–Csea coupled model. Air–Cwave coupling strengthens the air–Csea heat exchange, while the thermodynamic coupling between the atmosphere and ocean weakens the air–Csea heat exchange: the air–Csea–Cwave coupling is the result of their balance. The wave field distribution characteristic is determined by the wind field. Experiments are also conducted to simulate ocean responses to different mixed layer depths. With increasing depth of the initial mixed layer, the decrease of SST weakens, but the temperature decrease of deeper layers is enhanced and the loss of heat in the upper ocean is increased. The significant wave height is larger when the initial mixed layer depth increases.
In this study a coupled air–Csea–Cwave model system, containing the model components of GRAPES-TCM, ECOM-si and WAVEWATCH III, is established based on an air–Csea coupled model. The changes of wave state and the effects of sea spray are both considered. Using the complex air–Csea–Cwave model, a set of idealized simulations was applied to investigate the effects of air–Csea–Cwave interaction in the upper ocean. Results show that air–Cwave coupling can strengthen tropical cyclones while air–Csea coupling can weaken them; and air–Csea–Cwave coupling is comparable to that of air–Csea coupling, as the intensity is almost unchanged with the wave model coupled to the air–Csea coupled model. The mixing by vertical advection is strengthened if the wave effect is considered, and causes much more obvious sea surface temperature (SST) decreases in the upper ocean in the air–Csea coupled model. Air–Cwave coupling strengthens the air–Csea heat exchange, while the thermodynamic coupling between the atmosphere and ocean weakens the air–Csea heat exchange: the air–Csea–Cwave coupling is the result of their balance. The wave field distribution characteristic is determined by the wind field. Experiments are also conducted to simulate ocean responses to different mixed layer depths. With increasing depth of the initial mixed layer, the decrease of SST weakens, but the temperature decrease of deeper layers is enhanced and the loss of heat in the upper ocean is increased. The significant wave height is larger when the initial mixed layer depth increases.
2015, 21(3): 246-254.
doi: doi: 10.16555/j.1006-8775.2015.03.004
Abstract:
Using the 1980-2010 winter GODAS oceanic assimilations, study is conducted of the winter heat content (HC) established in the subsurface layer (5 to 366 m in depth) over the western Pacific warm pool (WP), followed by investigating the HC spatiotemporal characteristics, persistence and the impacts on the climate anomalies of neighboring regions. Results are as follows: 1) the pattern of integral consistency is uncovered by the leading EOF1 (PC1) mode of HC interannual variability, the year-to-year fluctuation of the time coefficients being well indicative of the interannual anomaly of the WP winter subsurface-layer thermal regime. The HC variation is bound up with ENSO, keeping pronounced autocorrelation during the following two seasons and more, with the persistence being more stable in comparison to SSTA in the equatorial middle eastern Pacific; 2) the winter HC anomalies produce lasting effect on the WP thermal state in the following spring and summer and corresponding changes in the warm water volume lead to the meridional transport and vertical exchange of warm water, which exerts greater impacts upon the sea surface temperature/heat flux over the warm pool per se and neighboring regions, especially in the Philippine Sea during the posterior spring and summer; 3) the increase in the winter HC corresponds to the spring OLR decrease and richer precipitation over the waters east to the Philippine Sea and the resultant convective heating anomalies are responsible for the rise of geopotential isobaric surfaces over tropical and subtropical western North Pacific, thereby producing effect on the western Pacific subtropical high (anomaly). Subsequently, the sea-surface heat flux exchange is intensified in the warm pool, a robust anomalous cyclone shows up at lower levels, air-sea interactions are enhanced and abnormal convective heating occurs, together making the winter HC anomalies even more closely associated with the variation in the summer subtropical high. As a result, the WP winter HC can be used as an effective predictor of the variation in spring/summer western Pacific subtropical high and the strength of summer monsoon over the northwestern Pacific.
Using the 1980-2010 winter GODAS oceanic assimilations, study is conducted of the winter heat content (HC) established in the subsurface layer (5 to 366 m in depth) over the western Pacific warm pool (WP), followed by investigating the HC spatiotemporal characteristics, persistence and the impacts on the climate anomalies of neighboring regions. Results are as follows: 1) the pattern of integral consistency is uncovered by the leading EOF1 (PC1) mode of HC interannual variability, the year-to-year fluctuation of the time coefficients being well indicative of the interannual anomaly of the WP winter subsurface-layer thermal regime. The HC variation is bound up with ENSO, keeping pronounced autocorrelation during the following two seasons and more, with the persistence being more stable in comparison to SSTA in the equatorial middle eastern Pacific; 2) the winter HC anomalies produce lasting effect on the WP thermal state in the following spring and summer and corresponding changes in the warm water volume lead to the meridional transport and vertical exchange of warm water, which exerts greater impacts upon the sea surface temperature/heat flux over the warm pool per se and neighboring regions, especially in the Philippine Sea during the posterior spring and summer; 3) the increase in the winter HC corresponds to the spring OLR decrease and richer precipitation over the waters east to the Philippine Sea and the resultant convective heating anomalies are responsible for the rise of geopotential isobaric surfaces over tropical and subtropical western North Pacific, thereby producing effect on the western Pacific subtropical high (anomaly). Subsequently, the sea-surface heat flux exchange is intensified in the warm pool, a robust anomalous cyclone shows up at lower levels, air-sea interactions are enhanced and abnormal convective heating occurs, together making the winter HC anomalies even more closely associated with the variation in the summer subtropical high. As a result, the WP winter HC can be used as an effective predictor of the variation in spring/summer western Pacific subtropical high and the strength of summer monsoon over the northwestern Pacific.
2015, 21(3): 255-264.
doi: doi: 10.16555/j.1006-8775.2015.03.005
Abstract:
Based on the reanalysis data of monthly mean global SST and wind from the NCEP/NCAR and the observation data of rain seasons in 124 stations of Yunnan province from 1961 to 2006, we applied the analytical methods of correlation analysis and composite analysis and a significance testing method to two sets of samples of average differences. The goal is to investigate into the influence of the Southern Hemispheric (SH) SST on the summer precipitation in Yunnan from January to May so as to identify the key time and marine regions. Physical mechanisms are obtained by analyzing the influence of sea level wind and the key marine regions on the precipitation during Yunnan’s rain season. Results show that there is indeed significant relationship between the SST in SH and summer precipitation in Yunnan. The key areas for influencing the summer precipitation are mainly distributed in a region called “West Wind Drift” in the SH, including the Southeast Indian, southern Australia, west coast of eastern Pacific off Chile, Peru and the southwest Atlantic Magellan. Besides, the most significant marine region is the west coast of Chile and Peru (cold-current areas of the eastern Pacific). Diagnostic analysis results also showed that monsoons in the Bay of Bengal, a cross-equatorial flow in the Indian Ocean near the equator and southwest monsoon in India weaken during the warm phase of the Peruvian cold current in the eastern Pacific. Otherwise, they strengthen.
Based on the reanalysis data of monthly mean global SST and wind from the NCEP/NCAR and the observation data of rain seasons in 124 stations of Yunnan province from 1961 to 2006, we applied the analytical methods of correlation analysis and composite analysis and a significance testing method to two sets of samples of average differences. The goal is to investigate into the influence of the Southern Hemispheric (SH) SST on the summer precipitation in Yunnan from January to May so as to identify the key time and marine regions. Physical mechanisms are obtained by analyzing the influence of sea level wind and the key marine regions on the precipitation during Yunnan’s rain season. Results show that there is indeed significant relationship between the SST in SH and summer precipitation in Yunnan. The key areas for influencing the summer precipitation are mainly distributed in a region called “West Wind Drift” in the SH, including the Southeast Indian, southern Australia, west coast of eastern Pacific off Chile, Peru and the southwest Atlantic Magellan. Besides, the most significant marine region is the west coast of Chile and Peru (cold-current areas of the eastern Pacific). Diagnostic analysis results also showed that monsoons in the Bay of Bengal, a cross-equatorial flow in the Indian Ocean near the equator and southwest monsoon in India weaken during the warm phase of the Peruvian cold current in the eastern Pacific. Otherwise, they strengthen.
2015, 21(3): 265-275.
doi: doi: 10.16555/j.1006-8775.2015.03.006
Abstract:
The consistency of global atmospheric mass and water budget performance in 20 state-of-the-art ocean–Catmosphere Coupled Model Intercomparison Project Phase 5 (CMIP5) coupled models has been assessed in a historical experiment. All the models realistically reproduce a climatological annual mean of global air mass (AM) close to the ERA-Interim AM during 1989–C2005. Surprisingly, the global AM in half of the models shows nearly no seasonal variation, which does not agree with the seasonal processes of global precipitable water or water vapor, given the mass conservation constraint. To better understand the inconsistencies, we evaluated the seasonal cycles of global AM tendency and water vapor source (evaporation minus precipitation). The results suggest that the inconsistencies result from the poor balance between global AM tendency and water vapor source based on the global AM budget equation. Moreover, the cross-equatorial dry air mass ?ux, or hemispheric dry mass divergence, is not well represented in any of the 20 CMIP5 models, which show a poorly matched seasonal cycle and notably larger amplitude, compared with the hemispheric tendencies of dry AM in both the Northern Hemisphere and Southern Hemisphere. Pronounced erroneous estimations of tropical precipitation also occur in these models. We speculate that the large inaccuracy of precipitation and possibly evaporation in the tropics is one of the key factors for the inconsistent cross-equatorial mass ?ux. A reasonable cross-equatorial mass ?ux in well-balanced hemispheric air mass and moisture budgets remains a challenge for both reanalysis assimilation systems and climate modeling.
The consistency of global atmospheric mass and water budget performance in 20 state-of-the-art ocean–Catmosphere Coupled Model Intercomparison Project Phase 5 (CMIP5) coupled models has been assessed in a historical experiment. All the models realistically reproduce a climatological annual mean of global air mass (AM) close to the ERA-Interim AM during 1989–C2005. Surprisingly, the global AM in half of the models shows nearly no seasonal variation, which does not agree with the seasonal processes of global precipitable water or water vapor, given the mass conservation constraint. To better understand the inconsistencies, we evaluated the seasonal cycles of global AM tendency and water vapor source (evaporation minus precipitation). The results suggest that the inconsistencies result from the poor balance between global AM tendency and water vapor source based on the global AM budget equation. Moreover, the cross-equatorial dry air mass ?ux, or hemispheric dry mass divergence, is not well represented in any of the 20 CMIP5 models, which show a poorly matched seasonal cycle and notably larger amplitude, compared with the hemispheric tendencies of dry AM in both the Northern Hemisphere and Southern Hemisphere. Pronounced erroneous estimations of tropical precipitation also occur in these models. We speculate that the large inaccuracy of precipitation and possibly evaporation in the tropics is one of the key factors for the inconsistent cross-equatorial mass ?ux. A reasonable cross-equatorial mass ?ux in well-balanced hemispheric air mass and moisture budgets remains a challenge for both reanalysis assimilation systems and climate modeling.
2015, 21(3): 276-284.
doi: doi: 10.16555/j.1006-8775.2015.03.007
Abstract:
Using hourly rainfall intensity, daily surface air temperature, humidity and low-level dew point depressions at 55 stations in the southeast coast of China, and sea surface temperature from reanalysis in the coastal region, this paper analyzes the connection between peak intensity of extreme afternoon short-duration rainfall (EASR) and humidity as well as surface air temperature. The dependency of extreme peak intensity of EASR on temperature has a significant transition. When daily highest surface temperature is below (above) 29°C, the peak rainfall intensity shows an ascending (descending) tendency with rising temperature. Having investigated the role of moisture condition in the variation of EASR and temperature, this paper discovered that the decrease of peak rainfall intensity with temperature rising is connected with the variation of relative humidity. At higher temperatures, the land surface relative humidity decreases dramatically as temperature further increases. During this process, the sea surface temperature maintains basically unchanged, resulting in indistinct variations of water vapor content at seas. As water vapor over land is mainly contributed by the quantitative moisture transport from adjacent seas, the decline of relative humidity over land will be consequently caused by the further rise of surface air temperature.
Using hourly rainfall intensity, daily surface air temperature, humidity and low-level dew point depressions at 55 stations in the southeast coast of China, and sea surface temperature from reanalysis in the coastal region, this paper analyzes the connection between peak intensity of extreme afternoon short-duration rainfall (EASR) and humidity as well as surface air temperature. The dependency of extreme peak intensity of EASR on temperature has a significant transition. When daily highest surface temperature is below (above) 29°C, the peak rainfall intensity shows an ascending (descending) tendency with rising temperature. Having investigated the role of moisture condition in the variation of EASR and temperature, this paper discovered that the decrease of peak rainfall intensity with temperature rising is connected with the variation of relative humidity. At higher temperatures, the land surface relative humidity decreases dramatically as temperature further increases. During this process, the sea surface temperature maintains basically unchanged, resulting in indistinct variations of water vapor content at seas. As water vapor over land is mainly contributed by the quantitative moisture transport from adjacent seas, the decline of relative humidity over land will be consequently caused by the further rise of surface air temperature.
2015, 21(3): 285-294.
doi: doi: 10.16555/j.1006-8775.2015.03.008
Abstract:
In this study, the vertical profiles of radar refractive factor (Z) observed with an X-band Doppler radar in Jurong on July 13, 2012 in different periods of a stratiform cloud precipitation process were simulated using the SimRAD software, and the contributions of each impact resulting in the bright band were analyzed quantitatively. In the simulation, the parameters inputted into SimRAD were updated until the output Z profile was nearly consistent with the observation. The input parameters were then deemed to reflect real conditions of the cloud and precipitation. The results showed that a wider (narrower) and brighter (darker) bright band corresponded to a larger (smaller) amount, wider (narrower) vertical distribution, and larger (smaller) mean diameter of melting particles in the melting layer. Besides this, radar reflectivity factors under the wider (narrower) melting layer were lager (smaller). This may be contributed to the adequate growth of larger rain drops in the upper melting layer. Sensitivity experiments of the generation of the radar bright band showed that a drastic increasing of the complex refractive index due to melting led to the largest impact, making the radar reflectivity factor increase by about 15 dBZ. Fragmentation of large particles was the second most important influence, making the value decrease by 10 dBZ. The collision–Ccoalescence between melting particles, volumetric shrinking due to melting, and the falling speed of raindrops made the radar reflectivity factor change by about 3–C7 dBZ. Shape transformation from spheres to oblate ellipsoids resulted in only a slight increase in the radar reflectivity factors (about 0.2 dBZ), which might be due to the fact that there are few large particles in stratiform cloud.
In this study, the vertical profiles of radar refractive factor (Z) observed with an X-band Doppler radar in Jurong on July 13, 2012 in different periods of a stratiform cloud precipitation process were simulated using the SimRAD software, and the contributions of each impact resulting in the bright band were analyzed quantitatively. In the simulation, the parameters inputted into SimRAD were updated until the output Z profile was nearly consistent with the observation. The input parameters were then deemed to reflect real conditions of the cloud and precipitation. The results showed that a wider (narrower) and brighter (darker) bright band corresponded to a larger (smaller) amount, wider (narrower) vertical distribution, and larger (smaller) mean diameter of melting particles in the melting layer. Besides this, radar reflectivity factors under the wider (narrower) melting layer were lager (smaller). This may be contributed to the adequate growth of larger rain drops in the upper melting layer. Sensitivity experiments of the generation of the radar bright band showed that a drastic increasing of the complex refractive index due to melting led to the largest impact, making the radar reflectivity factor increase by about 15 dBZ. Fragmentation of large particles was the second most important influence, making the value decrease by 10 dBZ. The collision–Ccoalescence between melting particles, volumetric shrinking due to melting, and the falling speed of raindrops made the radar reflectivity factor change by about 3–C7 dBZ. Shape transformation from spheres to oblate ellipsoids resulted in only a slight increase in the radar reflectivity factors (about 0.2 dBZ), which might be due to the fact that there are few large particles in stratiform cloud.
2015, 21(3): 295-302.
doi: doi: 10.16555/j.1006-8775.2015.03.009
Abstract:
Although the urban heat island (UHI) is a well-documented phenomenon, relatively little information in the literature is available about its impact on summer extreme heat event (EHE). As UHI is characterized by increased temperature, it can potentially increase the magnitude and duration of EHEs within cities. Based on daily maximum temperature records from 62 observation stations in Zhejiang province from the period 1971-2011 and satellite-measured nighttime light imagery from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) during 1992-2010, we analyzed the long-term change of summer EHEs and its association with the rapid urbanization process. The results could be concluded as follows: (1) Zhejiang has experienced rapid urbanization and dramatic growth in urban areas in the past two decades, especially after 2000. (2) The summer mean maximum temperature and the 95th percentile of summer daily maximum temperature in most of its stations have increased, with the most significant increase occurring in the highly urbanized areas including the city belt around Hangzhou Bay, Taizhou–CWenzhou and Jinghua–CYiwu city belts. (3) The hot days and hot-day degrees, defined by both daily 95th percentile and the threshold of 35℃, show that the UHI effect causes additional hot days and heat stress in urban stations compared to rural stations. The results in this study suggest that the UHI effect should be determined and incorporated in preparing high temperature forecasts in cities.
Although the urban heat island (UHI) is a well-documented phenomenon, relatively little information in the literature is available about its impact on summer extreme heat event (EHE). As UHI is characterized by increased temperature, it can potentially increase the magnitude and duration of EHEs within cities. Based on daily maximum temperature records from 62 observation stations in Zhejiang province from the period 1971-2011 and satellite-measured nighttime light imagery from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) during 1992-2010, we analyzed the long-term change of summer EHEs and its association with the rapid urbanization process. The results could be concluded as follows: (1) Zhejiang has experienced rapid urbanization and dramatic growth in urban areas in the past two decades, especially after 2000. (2) The summer mean maximum temperature and the 95th percentile of summer daily maximum temperature in most of its stations have increased, with the most significant increase occurring in the highly urbanized areas including the city belt around Hangzhou Bay, Taizhou–CWenzhou and Jinghua–CYiwu city belts. (3) The hot days and hot-day degrees, defined by both daily 95th percentile and the threshold of 35℃, show that the UHI effect causes additional hot days and heat stress in urban stations compared to rural stations. The results in this study suggest that the UHI effect should be determined and incorporated in preparing high temperature forecasts in cities.
2015, 21(3): 303-310.
doi: doi: 10.16555/j.1006-8775.2015.03.010
Abstract:
Analyzing the thermal distribution on plane conditions objectively is difficult due to lack of enough meteorological observation stations within urban residential areas. In this paper satellite observations synchronous or quasi-synchronous with ground observations are adopted, and a teleconnection model is built between the satellite spectral and surface temperature for quantitative retrieval of temperature. Furthermore, by combining the satellite data with other multiple factors, a GIS comprehensive analysis model and a functional evaluation method for urban residential districts are established, which are used to study the relation between the air temperature and media characteristics on ground as well as the greening cooling effect in recent years in Shanghai. The results show that the air temperature in greened urban residential districts is generally lower than the average temperature and much less than the highest one. In general, the average air temperature in the greened area is at most 1.19℃ lower than the maximum temperature in the districts, which is 0.67℃ and 0.55℃ lower than that of the highest for buildings and roads respectively. The temperature is inversely proportional with greening fraction but is directly proportional with the ratio of roads and buildings. The higher the greening fraction in internal residential districts, the lower the temperature, and the higher the ratio of road and building is, the higher the temperature.
Analyzing the thermal distribution on plane conditions objectively is difficult due to lack of enough meteorological observation stations within urban residential areas. In this paper satellite observations synchronous or quasi-synchronous with ground observations are adopted, and a teleconnection model is built between the satellite spectral and surface temperature for quantitative retrieval of temperature. Furthermore, by combining the satellite data with other multiple factors, a GIS comprehensive analysis model and a functional evaluation method for urban residential districts are established, which are used to study the relation between the air temperature and media characteristics on ground as well as the greening cooling effect in recent years in Shanghai. The results show that the air temperature in greened urban residential districts is generally lower than the average temperature and much less than the highest one. In general, the average air temperature in the greened area is at most 1.19℃ lower than the maximum temperature in the districts, which is 0.67℃ and 0.55℃ lower than that of the highest for buildings and roads respectively. The temperature is inversely proportional with greening fraction but is directly proportional with the ratio of roads and buildings. The higher the greening fraction in internal residential districts, the lower the temperature, and the higher the ratio of road and building is, the higher the temperature.
粤公网安备 4401069904700002号