科研之友
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摘要
Regional climate model precipitation makes up for the deficiency of scarce meteorological stations in the alpine and cold mountains, which is an important variable of hydrological simulation. However, there is great uncertainty of model outputs in alpine region, both in the total amount and frequency. In view of this, we have improved the existing quantile mapping method(QM)for precipitation frequency correction, and corrected the daily precipitation simulated by WRF model of the upper reaches of Heihe river. Precipitation at the 95th and 98th percentiles were selected as the threshold, and 2004-2009 as the modeling period and 2010-2013 as the validation period. The transfer function was established by piecewise fitting method, focusing on correct the simulated extreme precipitation separately. The results show that the method not only has a significant improvement on the spatial distribution of precipitation, but also has a great correction effect on extreme precipitation. Before the correction, the RMSE between the sinulated and the stations precipitation was 3.41 mm·d-1, and the absolute deviation was 115.67 mm·y-1. After correction, the RMSE was reduced to 3.11 mm·d-1, and the absolute deviation was significantly improved to 60.3 mm·y-1. The spatial distribution of annual precipitation in the basin improved obviously, and the annual precipitation amount is closer to the precipitation interpolated, the spation correlation coefficient increased from 0.74 to 0.94. The correction effect in spring and summer is better than that in autumn and winter, among which the correction effect in summer is the most obvious. Before the correction, precipitation deviation during -0.1~0.1 only accounts for 28% of the total area of the basin, while after the correction the proportion increased to 66%. At the same time, this method performs well in extreme precipitation correction, reduces the simulation deviation of simple daily intensity index(SDII)and very extremely precipitation (R99p), the correlation coefficient of simulated and interpolated precipitation at the 95th percentiles was improved from 0.15 to 0.48. This study provides a more effective bias correction method for the upper Heihe river with scarce stations, which is conducive to obtaining more accurate precipitation data for the hydrological research of the cold regions.
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