Comparisons of urban-related warming in Beijing using different methods to calculate the daily mean temperature  

作　　者：Deming ZHAO Jian WU 

机构地区：[1]CAS Key Laboratory of Regional Climate-Environment for Temperate East Asia, Institute of Atmospheric Physics,Chinese Academy of Sciences [2]Department of Atmospheric Science, Yunnan University

出　　处：《Science China Earth Sciences》2019年第4期693-702,共10页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.41775087&41675149);the National Key R&D Program of China(Grant No.2016YFA0600403);the Chinese Academy of Sciences Strategic Priority Program(Grant No.XDA05090206);the National Key Basic Research Program on Global Change(Grant No.2011CB952003);the Jiangsu Collaborative Innovation Center for Climatic Change

摘　　要：To evaluate the contribution of urban surface expansion to regional warming using different methods to calculate the daily mean surface air temperature(SAT), satellite-based images displaying urban surface expansion over the past 37 years(1980–2016) across China were collected for use in nested numerical experiments using the weather research and forecasting(WRF) regional climate model. The contribution of urban surface expansion to urban-related warming was determined using the daily mean SAT averages based on four time records each day(00, 06, 12, and 18 h UTC, T_4) and averages of the SAT maximum(Tmax) and minimum(Tmin)(Txn). The contribution of urban surface expansion to urban-related warming(relative value) in Beijing was 0.110°C per decade(22.8% of total warming) for T_4 and 0.094°C per decade(20.2%) for Txn. The values obtained when using T_4 were larger than those obtained when using Txn. Differences in the urban-related warming calculated using T_4 and Txncould be attributed to the smaller changing trends in Txnin the urban-surface expansion experiment, which resulted from a large changing trend in Tminand a much smaller changing trend in Tmax. The changes in the diurnal cycle of the energy budget due to urban surface expansion induced changes in the diurnal cycle of SAT, as evidenced by the four time records each day, as well as Tmaxand Tmin. This was especially true for periods of intense urban surface expansion, although the annual mean SAT calculated using Txnwas larger than that calculated using T_4. The increase in impervious area(walls, streets, etc.) due to urban surface expansion, as well as the widespread use of building materials with a large heat capacity resulted in a marked increase in ground heat flux in the daytime. This restricted the increase in SAT in the daytime, but promoted it at night. The increases in SAT due to urban surface expansion were not symmetrical, being smaller in the daytime and larger at night.To evaluate the contribution of urban surface expansion to regional warming using different methods to calculate the daily mean surface air temperature(SAT), satellite-based images displaying urban surface expansion over the past 37 years(1980–2016) across China were collected for use in nested numerical experiments using the weather research and forecasting(WRF) regional climate model. The contribution of urban surface expansion to urban-related warming was determined using the daily mean SAT averages based on four time records each day(00, 06, 12, and 18 h UTC, T_4) and averages of the SAT maximum(Tmax) and minimum(Tmin)(Txn). The contribution of urban surface expansion to urban-related warming(relative value) in Beijing was 0.110°C per decade(22.8% of total warming) for T_4 and 0.094°C per decade(20.2%) for Txn. The values obtained when using T_4 were larger than those obtained when using Txn. Differences in the urban-related warming calculated using T_4 and Txncould be attributed to the smaller changing trends in Txnin the urban-surface expansion experiment, which resulted from a large changing trend in Tminand a much smaller changing trend in Tmax. The changes in the diurnal cycle of the energy budget due to urban surface expansion induced changes in the diurnal cycle of SAT, as evidenced by the four time records each day, as well as Tmaxand Tmin. This was especially true for periods of intense urban surface expansion, although the annual mean SAT calculated using Txnwas larger than that calculated using T_4. The increase in impervious area(walls, streets, etc.) due to urban surface expansion, as well as the widespread use of building materials with a large heat capacity resulted in a marked increase in ground heat flux in the daytime. This restricted the increase in SAT in the daytime, but promoted it at night. The increases in SAT due to urban surface expansion were not symmetrical, being smaller in the daytime and larger at night.

关 键 词：Urban SURFACE expansion SURFACE air TEMPERATURE DAILY mean TEMPERATURE Changing trend Urban-related WARMING 

分 类 号：P[天文地球]