Characteristics of Precipitation and Air Temperature Variation during 1951-2009 in North China

Annual and monthly observed temperature and precipitation data at 64 weather stations in five provinces of North China are used to estimate the areal temperature and precipitation using the Thiessen polygon method.The regression equations between the observed temperature/precipitation at seven stations with long time-series records and areal magnitude from 1961 to 2009 were then built.The areal temperature/precipitation time series was extended back to 1951 through the seven stations with long time-series records.With this extended dataset,the temperature/precipitation trend for 1951-2009 was investigated with Mann-Kendall,Mann-Whitney and the moving average method.The results indicate that: 1) the temperature increased by 1.5 ℃ during the past 59 years and showed a statistically significant increasing trend with the magnitude of about 2.2% per decade;the time series of annual temperature appeared step change around 1993 and the temperature anomalies changed from negative periods to positive periods from 1989.2) The annual precipitation did not present a statistically significant trend and showed a decline of 1.3% per decade;the precipitation anomaly showed that the year 1976 is the turning point from wet to dry.The result of this paper can be used as a reference for further analysis of climate change and its impacts as well as the responses of water resources to climate change in North China.