Numerical Simulation Of The Effect Of Urban Underlying Surface Heterogeneity On Summer Regional Heat Island Effect In The Yangtze River Delta

The high-resolution mesoscale numerical model WRF3.9.1 coupled urban canopy model UCM was used to simulate the impact of urban heterogeneity on the regional heat island effect in the Yangtze River Delta for five years'summer?2011-2015,Jun.Jul.Aug.?.The land cover data is updated with the MODIS data of 500m resolution in 2013,and the urban underlying surface is divided into high,medium and low Intensity Residential according to the proportion of urban,sensitivity test is designed to study the direct urban heterogeneity of the city's own development.Using the ChinaLC land cover data,the land use type of a large number of newly added farmland and natural vegetation in the suburbs of the 1981 and 2010 suburbs was set as the unique variable design sensitivity test to study the indirect urban heterogeneity caused by suburban farmland degradation.The test results show that:?1?After considering the urban direct heterogeneity,the heat island intensity,surface heat island intensity,dry island intensity and wind speed attenuation are reduced by0.12?,0.67?,0.96%,0.04 m s^-1,respectively,and the percentage is 16.2%,21.7%,18.0%,6.1%,with large reduction and strong daytime weak night;The difference between sensible heat flux and latent heat flux is the main cause of the weakening of heat island efficiency;the surface of low and medium density cities is colder,drier,and high density urban surface is warmer and drier,and the temperature in the entire Yangtze River Delta region is lower and the humidity is higher.?2?the intensity of the high-altitude heat island and the heat island circulation are weakened,but the multi-heat island circulation between cities can be strengthened,and the high-density large city can suppress the low surrounding area.The heat island circulation of a small density city.?3?The 2010 ChinaLC Data can significantly improve the model's simulation capability compared to the WRF's own USGS data;the indirect urban heterogeneity performance increases the temperature in the Yangtze River Delta,the heat island weakens,and the effect is enhanced with increasing temperature;The diurnal average temperature of urban reaches above 35?,and the heat island intensity,surface heat island intensity,dry island strength,and wind speed attenuation can be reduced by 0.32?,0.53?,1.51%,0.18 m s^-1,respectively;The area of high temperature increased by 29.5%,2.3%,13.6%respectively in NingZhenYang agglomeration,Big Shanghai agglomeration,Hangzhou Bay agglomeration,and the high temperature area and heat stress level in the Yangtze River Delta increased as a whole.