The study of division, according to the annual and interannual variations, is separately carried out by using the cluster analysis and REOF analysis methods based on the monthly precipitation data at 243 stations in Northern China during 1958-2009. According to the correspondence of changes of monthly precipitation, Northern China can be divided into seven regions.The study result shows that except for a few stations where there are two peaks of precipitation within one year, the characteristics of annual precipitation around the most areasof Northern China are similar, which precipitation in summer is much more than that in other seasons. With the same methods, the four-level divisionsof annual precipitation are obtained: 2, 4, 9 and 12 regions. In recent 52 years, the precipitation trend appeared downward in the eastern and central part of Northern China, while it increased in the westone. The division pattern of annual precipitation experienced a change in the 1980′s. From 1960′s to 1970′s, there are three regions. The east region and the west are more likely, distinguished from the central region. However, there weretwo regions since 1980′s, which represented the remarkable differences between the east region and the west.
Introduction
