The impacts of three periods of urban land expansion during 1990–2010 on near-surface air temperature in summer in Beijing were simulated in this study, and then the interrelation between heat waves and urban warming...The impacts of three periods of urban land expansion during 1990–2010 on near-surface air temperature in summer in Beijing were simulated in this study, and then the interrelation between heat waves and urban warming was assessed. We ran the sensitivity tests using the mesoscale Weather Research and Forecasting model coupled with a single urban canopy model,as well as high-resolution land cover data. The warming area expanded approximately at the same scale as the urban land expansion. The average regional warming induced by urban expansion increased but the warming speed declined slightly during 2000–2010. The smallest warming occurred at noon and then increased gradually in the afternoon before peaking at around 2000 LST—the time of sunset. In the daytime, urban warming was primarily caused by the decrease in latent heat flux at the urban surface. Urbanization led to more ground heat flux during the day and then more release at night, which resulted in nocturnal warming. Urban warming at night was higher than that in the day, although the nighttime increment in sensible heat flux was smaller. This was because the shallower planetary boundary layer at night reduced the release efficiency of near-surface heat. The simulated results also suggested that heat waves or high temperature weather enhanced urban warming intensity at night. Heat waves caused more heat to be stored in the surface during the day, greater heat released at night, and thus higher nighttime warming. Our results demonstrate a positive feedback effect between urban warming and heat waves in urban areas.展开更多
This paper evaluated the performance of a coupled modeling system,Weather Research and Forecasting(WRF)/Urban Canopy Model(UCM),in the simulation of a heat wave event which occurred around Guangzhou during late June t...This paper evaluated the performance of a coupled modeling system,Weather Research and Forecasting(WRF)/Urban Canopy Model(UCM),in the simulation of a heat wave event which occurred around Guangzhou during late June through early July,2004.Results from three experiments reveal that the UCM with new land data(hereafter referred to as E-UCM)reproduces the best 2-m temperature evolution and the smallest minimum absolute average error as compared with the other two experiments,the BPA-Bulk Parameterization Approach with new land data(E-BPA)and the UCM with original U.S. Geological Survey land data(E-NOU).The E-UCM is more useful in capturing the temporal and spatial distribution of the nighttime Urban Heat Island(UHI).Differences in surface energy balance between the urban and suburban areas show that low daytime albedo causes more absorption of solar radiation by urban areas.Due to the lack of vegetation which inhibits cooling by evapotranspiration,most of the incoming energy over urban areas is partitioned into sensible heat flux and therefore heats the surface and enhances the heat wave.During nighttime,the energy in the urban area is mainly from soil heat flux.Although some energy is partitioned as outgoing long wave radiation,most of the soil heat flux is partitioned into sensible heat flux due to the small latent heat flux at night.This leads to the development of nighttime UHI and the increase of the magnitude and duration of heat waves within the municipality.展开更多
Fog may continue to inhibit industry in the future.Here,we focused on a specific advection fog event in Shanghai,China,and applied a pseudo global warming method to examine advection fog under the RCP8.5 highemission ...Fog may continue to inhibit industry in the future.Here,we focused on a specific advection fog event in Shanghai,China,and applied a pseudo global warming method to examine advection fog under the RCP8.5 highemission scenario.The method involved downscaling the future atmospheric conditions over the ensemble average of 19 global climate models from the fifth phase of the Coupled Model Intercomparison Project(CMIP5).We used the Weather Research and Forecasting Model coupled with a single-layer urban canopy model(WRF‒UCM)to run four sensitivity experiments and examined the advection fog and its relationship to changes in meteorological conditions.The results showed that:1)The advection fog event tended to remain in Shanghai despite global warming;2)advection fog will not change greatly in the future;however,the onset and dissipation times will change slightly;3)relative humidity(RH)locally increases prior to the onset of the advection fog,and decreases at the dissipating stage,despite the current and future experiments having the same RH initial and boundary conditions;4)a small increase in surface air temperature and an increase in RH contribute to the early advection fog onset,and vice versa.Windspeed facilitates the early onset and dissipation of advection fog.展开更多
基金supported by the National Basic Research Program of China(Grant No.2015CB953602)the National Social Science Fund of China(Grant No.17BGL256)
文摘The impacts of three periods of urban land expansion during 1990–2010 on near-surface air temperature in summer in Beijing were simulated in this study, and then the interrelation between heat waves and urban warming was assessed. We ran the sensitivity tests using the mesoscale Weather Research and Forecasting model coupled with a single urban canopy model,as well as high-resolution land cover data. The warming area expanded approximately at the same scale as the urban land expansion. The average regional warming induced by urban expansion increased but the warming speed declined slightly during 2000–2010. The smallest warming occurred at noon and then increased gradually in the afternoon before peaking at around 2000 LST—the time of sunset. In the daytime, urban warming was primarily caused by the decrease in latent heat flux at the urban surface. Urbanization led to more ground heat flux during the day and then more release at night, which resulted in nocturnal warming. Urban warming at night was higher than that in the day, although the nighttime increment in sensible heat flux was smaller. This was because the shallower planetary boundary layer at night reduced the release efficiency of near-surface heat. The simulated results also suggested that heat waves or high temperature weather enhanced urban warming intensity at night. Heat waves caused more heat to be stored in the surface during the day, greater heat released at night, and thus higher nighttime warming. Our results demonstrate a positive feedback effect between urban warming and heat waves in urban areas.
基金Natural Science Foundation of China(40775068)Specialized Projects of Scientific Research for Public Welfare Industry(Meteorology)+3 种基金Open Projects of Key National Laboratories for Disasters-causing Weather(GYHY200706014GYHY200906026)Science Foundation of China(2009LASW-B03)Foundation for Scientific Research on Tropical and Marine Meteorology
文摘This paper evaluated the performance of a coupled modeling system,Weather Research and Forecasting(WRF)/Urban Canopy Model(UCM),in the simulation of a heat wave event which occurred around Guangzhou during late June through early July,2004.Results from three experiments reveal that the UCM with new land data(hereafter referred to as E-UCM)reproduces the best 2-m temperature evolution and the smallest minimum absolute average error as compared with the other two experiments,the BPA-Bulk Parameterization Approach with new land data(E-BPA)and the UCM with original U.S. Geological Survey land data(E-NOU).The E-UCM is more useful in capturing the temporal and spatial distribution of the nighttime Urban Heat Island(UHI).Differences in surface energy balance between the urban and suburban areas show that low daytime albedo causes more absorption of solar radiation by urban areas.Due to the lack of vegetation which inhibits cooling by evapotranspiration,most of the incoming energy over urban areas is partitioned into sensible heat flux and therefore heats the surface and enhances the heat wave.During nighttime,the energy in the urban area is mainly from soil heat flux.Although some energy is partitioned as outgoing long wave radiation,most of the soil heat flux is partitioned into sensible heat flux due to the small latent heat flux at night.This leads to the development of nighttime UHI and the increase of the magnitude and duration of heat waves within the municipality.
基金supported by the National Natural Science Foundation of China(Grant No.52175103).
文摘Fog may continue to inhibit industry in the future.Here,we focused on a specific advection fog event in Shanghai,China,and applied a pseudo global warming method to examine advection fog under the RCP8.5 highemission scenario.The method involved downscaling the future atmospheric conditions over the ensemble average of 19 global climate models from the fifth phase of the Coupled Model Intercomparison Project(CMIP5).We used the Weather Research and Forecasting Model coupled with a single-layer urban canopy model(WRF‒UCM)to run four sensitivity experiments and examined the advection fog and its relationship to changes in meteorological conditions.The results showed that:1)The advection fog event tended to remain in Shanghai despite global warming;2)advection fog will not change greatly in the future;however,the onset and dissipation times will change slightly;3)relative humidity(RH)locally increases prior to the onset of the advection fog,and decreases at the dissipating stage,despite the current and future experiments having the same RH initial and boundary conditions;4)a small increase in surface air temperature and an increase in RH contribute to the early advection fog onset,and vice versa.Windspeed facilitates the early onset and dissipation of advection fog.
