Spatial-temporal Variation of Precipitation Concentration Degree and Precipitation Concentration Period in Gansu Province in Recent 50 Years

Abstract

Inhomogeneity is the inherent attribute of precipitation and is usually an important factor affecting the occurrence of hydrological disasters such as floods and debris flows. Based on the monthly precipitation data of 27 national meteorological stations in the past 50 years, the spatial and temporal distribution characteristics of precipitation concentration degree (PCD) and precipitation concentration period (PCP) in Gansu Province were assessed in this study. The results indicated that: (a) the annual precipitation had distinct regional differences (annual average values were between 43.3-605.4 mm) and strong inter-annual fluctuations (coefficient of variation was usually above 0.20, some up to 0.40-0.45); (b) the main range of PCD was from 0.52 to 0.67, with significantly reduced inter-annual fluctuation and a long-term trend of gradual decrease; (c) the spatial-temporal variation of PCP was generally small, mainly concentrated in 192.8°-205.0°(mid-late July), and showed a slightly advanced variation tendency. Under the overall background of warming and wetting, Gansu Province presents evolution characteristics of PCD weakening and PCP advancing, and the formation mechanism and potential effects of this phenomenon require further attention.