Remote Sensing Data Analysis And Numerical Simulation Of The Urban Heat Island Effects In Lake Tai Basin

Lake Tai Basin is one of the most highly developed and urbanized areas in China. It is very important and valuable to study the urbanization effects on boundary layer structure and local climate processes to improve the quality of urban meteorological service and provide development planning and decision-making for the government. Observation data and WRF simulation are used to study the urban heat island (UHI) effects on regional climate in Lake Tai Basin and the heat wave influences on the urban heat island is discussed.Firstly, the urban heat island intensity and warming rate are analyzed using the temperature data from 2003 to 2013. The results show that the selection of reference station has a direct impact on the UHI studies. The atmospheric UHI (AUHI) intensity is high at night and low during the day which assumes a "concave" structure if taking Changshu and Zhangjiagang as reference stations. While the results of using Dongshan as the reference station present a low AUHI intensity duiring the daytime and a high AUHI intensity at night. Although there is no apparent warming trend of urban in four seasons, the AUHI intensity increases over the past decade.The results of the atmospheric stability research tell us that the number of unstable class is about 50 percent in the study area at noon. The number of unstable class increases but the number of days of neutral stability decreases over the past decade. The UHI intensity is strongest under the unstable condition, and weakest under the neutral condition. While it is highly influenced by reference stations when studying the nighttime surface UHI(SUHI) effects. The SUHI intensity is very weak when taking Dongshan and Changshu as reference stations due to the special geography and economic development which contributes to their high surface temperature. If taking Zhangjiagang and the outskirt chosen in the upwind direction of Lake Tai as reference stations, it shows a seasonal variation SUHI that performs strong SUHI intensity in spring and summer in the day but weak SUHI intensity in summer at night.At last, when studying the hot days in summer of 2013, observation results show a wide range impact of high temperature caused by large-scale synoptic background which could lead to significant warming impact both on urban and rural area. The temperature difference between urban and suburban decreases and the AUHI is very weak or even disappeared during the day. But it is stronger than normal at night. However, unlike the AUHI, the SUHI intensity is strong in the heat wave.The model results turn out that the YSU boundary layer scheme has better simulation results of temperature and relative humidity, while the MYJ boundary layer scheme is slightly better at simulating wind and special humidity.In general, the model can simulate the 2m temperature trends well, but underestimate the 2m temperature. It will overestimate the skin temperature of urban area and undervalue the relative humidity in the day. The ability of simulating wind and moisture is poor due to urban complex three-dimensional structure and the imperfect simulation capabilities of model.