Analysis Of Urban Heat Island In Shanghai

With economy development and urban's expanding, urban heat island, as a main character of modern urban climate, is increasingly severe and seriously effect peoples life. It is important for study urban heat island, and it can help city planning and weather forecast of precision and particularity. In the paper, the characteristics of the intensity of the urban heat island and the air temperature change in Shanghai and its suburb are analyzed based on historic monthly meteorological data from 1981 to 2003 at 11 stations in Shanghai and its adjacent areas. The data include average air temperature,extreme highest air temperature and extreme lowest air temperature. Values of meteorological elements observed 4 times each day(air pressure, air temperature, dew point, cloud cover, wind speed and wind orientation)in Shanghai were processed by Principal Component Analysis and Cluster Analysis,and weather on each day was classified to 6 weather types for winter and 5 for summer. Then correlation analysis was performed within the intensity of UHI and frequency of weather types in winter and summer. The result indicate the urban heat island intensiy was stronggest in 1995 in Shanghai. In the four seasons,the urban heat island intensity is strongest at autumn and winter, weakest at summer. The difference of average air temperature between urban and suburb is biggest at summer, subsequently is spring and autumn,lowest at winter.The difference of the average of lowest air temperature between urban and suburb is bigger at autumn and winter, lowest at summer which is negative indicate that the extreme lowest air temperature in suburb higher than urban. The monthly change of urban heat island intensity is strongest in October, weakest in June. And the monthly change of the difference of extreme highest air temperature and extreme lowest air temperature between city and its adjacent area is just reverse,the monthly difference of extreme highest air temperature is strongest in July at summer,weakest in January at winter;The difference of extreme lowest air temperature between urban and suburb is strongest in April,May and October,weakest in July. Urban heat island intensity and the frequency of weather types are analyzed,urban heat island intensity is stronger with the frequency of WCD increase;And urban heat island intensity also become stronger with the frequency of CM decrease.The frequency of other four weater types is very little,and its effect on urban heat island intensity is small.Weather of Shanghai is controlled by the weather type of HMGW at summer, and urban heat island intensity can become stronger with the frequency of HMGW decrease.Although the frequency of the weather type of HMW increasing can made urban heat island intensity decrease,the frequency of HMW far less than the HMGW, and the effect on urban heat island intensity by HMW also less than the HMGW's.