Climatology temperature mapping for California urban heat island study site selection

Existing climate data sources can be used in two general types of analysis for the detection of urban heat islands, local historical trends and current spatial variations. Historical analyses use long-term data records,—preferentially from several locations in and around an urban area,—to trace the gradual influence of urban development on its climate. This paper uses existing temperature climatology data from 300 cooperative weather stations to analyze the spatial distribution in temperature during 60 year period in California. Temperature maps of long-term mean monthly temperature and recent monthly mean were produced for all months of the year. During the summer months, there is an increase of 1-3 oF in average monthly temperature for Sacramento, Modesto and San Jose relative 50 years ago. In addition, a long term summer time average monthly temperature for San Jose, Sacramento, and Modesto was done to show the temperature trends in the past 60 years. The summer time temperature trends in San Jose, Modesto and Sacramento showed a statistically significant increase of 0.65, 0.46, and 0.49 oF per decade respectively. The historical temperature trend is compared to the localization of the temperature increase and the population growth and urban expansion. These observed increases in temperatures may be due to long-term climate changes, micro-climate influences, or local-scale heat islands. This information will be used to select a site for mesoscale model simulations of urban heat islands in the central San Joaquin valley cities.