Three Cluster Methods in Regionalization of Temperature Zones in China

A scheme for regionalization of temperature zones was established on the basis of daily surface air temperature observations from 512 stations in China during 1961-2010. Days with daily surface air temperature ≥10 ℃ were used as indicators for zoning the temperature distribution. After REOF (Rotated Empirical Orthogonal Function) analysis, areas with similar temperature changes in the time evolution were classified as one zone. The temperature zones were classified by three types of clustering analysis methods. The national area was divided into ten temperature zones by using the K-means method, nine temperature zones by using the Ward method, and 13 temperature zones by using the CAST (Cluster Analysis with Statistical Test) method. The boundaries of the various regions show a good consistency with the Chinese topography. Calculation by using the K-means method is considered to be simple and quick because, the results are revised until the best results are achieved. Moreover, the clustering process of the Ward method is clear; any number of categories may be selected. Finally, the results of the CAST method pass the significance test; therefore, this method is meaningful for zoning.