Estimation Of Areal Precipitation In The Qilian Mountains Based On Two Different Gridded Precipitation Datasets

As the total volume of precipitation within a domain, areal precipitation, is an important parameter in hydrological studies. In quantization of hydrological process,precipitation is usually expressed as water volume for a region, and areal precipitation is also an important input in numerical modeling of meteorological and hydrological studies. To accurately estimate areal precipitation in a specific region, many approaches have been yielded in the past years, including spatial interpolation,multiple linear regression and remote sensing. Due to complex terrain in the Qilian Mountains, the existing in-situ meteorological observation network is still too limited to cover the entire vertical landscape of the alpine regions, and areal precipitation directly estimated using measured data may underestimate precipitation to some degree. In this study, the gridded daily precipitation dataset based on 0.5°×0.5°gridded dataset and 0.1°×0.1°gridded dataset in precipitation released by NMIC are applied to the Qilian Mountains, and the long-term changes and seasonal variation of areal precipitation for this region are assessed. The results are given as follows:(1) According to the bias of gridded data, The 0.5°×0.5°gridded dataset mostly concentrates between 0% and 20%, which mostly locate at lower elevation. The0.1°×0.1°gridded dataset mostly concentrates between-20% and 0%. From the bias of correlation coefficients between observed and interpolated precipitation can based on different gridded dataset, correlation coefficients based on 0.5°×0.5°gridded dataset are all above 0.85, in which correlation coefficients more than 0.95 include 25 observed stations. The correlation coefficients based on 0.1°×0.1°gridded dataset are all above 0.80.(2) The spatial distribution of annual precipitation based on the two datasets show significant difference. Precipitation in summer and winter shows the most and the least, respectively. And precipitation at east shows more than at west. The variation trends at west based on two different datasets all show increasing trend, in which east parts based on 0.5°×0.5° gridded dataset shows the least increasing trend and south parts based on 0.1°×0.1° gridded dataset shows significant increasing trend.(3) The annual precipitation based on the two datasets show significant difference. The annual precipitation based on 0.5°×0.5°gridded dataset in summer,autumn and winter all show increasing trend, in which the variation trend in summer shows the largest and the least in winter. The annual precipitation based on 0.1°×0.1°gridded dataset in spring and summer show increasing trend, but decreasing trend show in autumn and winter.(4) The principal component analysis is applied to the gridded precipitation in the study region, and the results show that the first principal component of annual precipitation has the very similar value in whole region, in which the bias only exists in the northwestern corner. The negative value region of the second principal component is consistent with the spatial domain of the high-altitude Tibetan plateau.The third principal component exhibits negative value in southeast and positive value in northwest, in which the negative value show in the Qilian Mountains.(5) Based on different gridded precipitation dataset, there is different in four seasons of areal precipitation in the Qilian Mountains. The annual mean value of areal precipitation based on 0.5°×0.5° gridded dataset in the Qilian Mountains indicate that The tendency of areal precipitation in summer is the largest among the four seasons,and the lowest trend magnitude is seen in spring. The tendency of areal precipitation based on 0.1°×0.1°gridded dataset in the Qilian Mountainsin summer is the largest among the four seasons, and the lowest trend magnitude is seen in spring. The annual mean value of areal precipitation based on different two datasets all show the largest in summer and the least in winter.(6) The mutation test of precipitation in each seasons based on 0.5°×0.5°gridded dataset in the Qilian Mountains after 1970 s shows the intersection existed in UF and UB curves in each seasons. Some mutation years in spring, summer and winter are significant past 0.05 levels.(7) The area of annual precipitation based on 0.5°×0.5°gridded dataset is larger than 0.1°×0.1°gridded dataset by 1.19×104 km2. The precipitation based on0.5°×0.5°gridded dataset between 500-600 mm shows the largest by 24.7%. However,The precipitation based on 0.1°×0.1°gridded dataset between 100-200 mm shows the largest.