1965-2008年华北北部日降水相关性变化特征

his paper was based on 63 meteorological stations with daily rainfall data during 1965-2008 in the northern part of North China. The 44 years' series were divided into two 22 years' periods which were 1987-2008 and 1965-1986. Correlation coefficients of daily rainfall between each pair of stations were calculated and compared for two periods. Comparing with period 1965-1986, correlation coefficients for period 1987-2008 for most stations were significantly decreased. Similarly, the whole period was divided into four 11 years' series which were 1965-1975，1976-1986，1987-1997 and 1998-2008. When correlation coefficients for the second 11 years' period were compared with those for the first period, stations with decreasing trends were mainly distributed in the northwestern part of the study area and those with increasing trends were mainly distributed in the southeastern part. When correlation coefficients for the third 11 years' period were compared with those for the second period, stations with decreasing trends were mainly distributed in the southeastern part and those with increasing trends were mainly distributed in the southwestern part. When correlation coefficients for the fourth 11 years' period were compared with those for the third period, there were 558 pairs of stations with significantly decreasing trends and one pair with increasing trend. In a word, correlation coeffients of daily rainfall in the northern part of North China were generally decreasing, especially for the period 1998-2008.