Abstract:

Haidong is an important grain production base in Qinghai, and drought directly affects the orderly development of agriculture. Based on the daily precipitation data of 5 meteorological stations in Haidong from 1961 to 2015, we analyzed the variation trend of rain days and precipitation of different grades and Z index, and studied the effects of rain days and precipitation of different grades on drought and flood. The results showed that: (1) half-year precipitation in summer (winter) was dominated by light rain (snow) and moderate rain (snow), the precipitation and rain days of light rain and heavy rain (moderate rain) in summer half year were decreasing (increasing) and the precipitation and rain days at all grades in winter half year were decreasing; (2) the Z index in summer, winter half year showed an insignificant trend of decrease; (3) according to the analysis of partial correlation coefficient and relative contribution rate, the precipitation and rain days of medium rain and heavy rain in summer half year had significant influence on Z index, while the precipitation and rain days of light snow in winter half year had the greatest influence on Z index change; (4) the synthetic analysis showed that the precipitation and rain days of different grades were basically positive in flood years, the differences of precipitation and rain days of different grades was mainly shown in the heavy rain and moderate rain in summer half year, and the differences in winter half year was mainly reflected in the precipitation and rain days of light snow; in the dry year, the precipitation and rain days at all grades were basically negative, the differences in summer half year was mainly reflected in precipitation and rain days of moderate rain, while the differences in winter half years was mainly reflected in the precipitation and rain days of light snow and moderate snow.

Key words: different grades of precipitation, variation trend, partial correlation, relative contribution rate, synthesis analysis, Haidong