A Comparison Study of Research Methods for Urban Heat Island of Megacity:with Special Regards on Shanghai

The development of international megacity is usually characterized by multi-center.Based on temperature data with four times a day(2:00,8:00,14:00,20:00) provided by 33 stations in 2007,the characters of the UHI(Urban Heat Island) in Shanghai were studied,a new method to calculate UHI was developed.The new method adds the stations located in the center of urbanized suburban into urban stations.The comparison between traditional method and new method shows that:(1) The frequency differences between UHIs calculated by new method and traditional method is significant,while the differences between accumulated UHIs is not significant.(2) About the daily variations,the patterns of UHI frequency and accumulated UHI by two methods are similar;the differences of UHI frequency and accumulated UHI by two methods are significant in 14:00,while in 2:00 the differences are not significant.(3) About the seasonal variations,the results calculated by two methods significantly differs from each other.In summer and spring,the UHI is more significant when calculated by new method.(4) In time and season when the solar radiation is strong,the difference between results calculated by two methods is significant.Using the new method could reveal some characters neglected by traditional method.(5) The secondary UHI in Shanghai is significant.The station located in the center of Songjiang district monitored a significantly higher temperature than other rural stations.It's more reasonable to calculate UHI with the method referred in megacity like Shanghai.