Quantitative methods for identifying meteorological conditions conducive to the development of urban heat islands

Abstract

Meteorological conditions significantly influence the development of urban heat islands (UHIs); hence, a reliable assessment and understanding of UHIs depends primarily on the days selected for observation and analysis. Numerous studies were conducted on the characteristics and causes of UHIs; however, few studies focused on the methods and criteria for identifying meteorological conditions conducive to UHI development. The objective of this study is to investigate the performances of four quantitative methods for identifying meteorological conditions conducive to UHI development based on three years of observations in Nanjing, China. The methods include the widely used method based on cloud cover and wind speed and three methods that combine the effects of multiple meteorological variables on UHIs into a single indicator. Correlations analysis between the daily maximum urban heat island intensity (UHIImax) and the meteorological variables indicates that it is inadequate to identify meteorological conditions conducive to UHI development using a single variable, such as solar radiation, cloud cover, or wind speed. The correlations between the daily UHIImax and the indicators are significant (r > 0.60, P < 0.001). The observations are split into calibration and validation sets. Then, the performances of the four methods are evaluated, and the appropriate thresholds for identifying meteorological conditions conducive to UHI development in Nanjing are determined. The results demonstrate that all four methods can be used for identifying meteorological conditions conducive to UHI development in Nanjing. The features and limitations of the four methods and the potential applications are discussed.