The API Spatial and Temporal Change Analysis of Key Environmental Protection Cities in China Based on EOF

In this paper, monthly averaged API index data from August 2006 to September 2009 of the 86 key environmental protection cities in China were broken down into several fields and their time functions by the Empirical Orthogonal Function (EOF) method, and the temporal and spatial distribution characteristics of API were analyzed. It was shown that the regional differences of API were significant among major Chinese environmental protection cities, and the 86 key cities may be divided into 8 areas. The analysis by the EOF could effectually reflect the spatial-temporal distinctly differences of API distributions, which may provide new methods and ideas to study regional situations of air pollution.