Existing Climate Data Sources and Their Use in Heat Island Research

Existing climate data sources can be used in two general types of analysis for the detection of urban heat islands. 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. Primary sources of such data include the cooperative network, first-order National Weather Service stations, and military weather stations. Short-term analyses use information from a dense urban weather station network to discern the location, extent, and magnitude of urban heat islands. Such analyses may use the aforementioned national networks or regional networks such as agricultural, air quality monitoring, or utility networks.

We demonstrate the use of existing data sources with a historical analysis of temperature trends in Los Angeles, California, and short-term analysis of the urban temperature profile for Phoenix, Arizona. The Los Angeles climate was examined with eleven long-term data records from the cooperative network. Statistically significant trends of rising temperature were detected at Los Angeles Civic Center and other stations over some parts of the year, although timing of the increase varied from station to station. Observed increases in temperatures may be due to long-term climate changes, micro-climate influences, or local-scale heat islands. A short-term analysis was made for Phoenix using the PRISMS station network. Mean diurnal temperature profiles for a month were examined and compared with those for adjacent rural areas. Data from stations in the center of Phoenix showed clear and significant night-time and daytime temperature differences of 3 - 4°F. These temperature increases may be attributable to a local-scale heat island.

Chapter I: Introduction

Ongoing research by the Heat Island Project at Berkeley Lab has shown that the use of high-albedo building materials and urban vegetation can substantially conserve cooling energy (Taha 1988; Akbari et al. 1993, 1997). These savings result from the direct effects of such actions in reducing the heat flow into conditioned spaces in buildings. Yet large additional savings may indirectly accrue from the reduced air temperatures on the scale of a neighborhood or city (Taha 1988) as both high-albedo surfaces and vegetation reduce the amount of incident solar radiation channeled into sensible heat (Oke 1978). Reduced air temperatures will consequently lower requirements for air-conditioning.

In this paper, we summarize the status of our research on the urban climate data. We describe two different methods for urban climate analysis--historical and short-term--and describe the various bodies of existing data appropriate for each method. These include the national networks of climate data as well as smaller networks particular to specific states or cities. We also present analyses of the urban climates of Los Angeles, California, and Phoenix, Arizona, using these data sources. These analyses reveal some of the advantages and shortcomings of the data sources and point to promising avenues of analysis that should be pursued further. Continue to: Chapter II. Historical Analysis