基于NCEP风向数据的中国夏季降水估算研究

提出一个基于NCEP风向数据估算全国夏季降水的模型。根据NCEP地面气压、经纬向风数据计算得到全国1971—2000年夏季各月盛行风向;并将盛行风向与宏观坡向夹角的余弦值作为降水的坡向因子,以此区分山体迎风坡和背风坡降水的空间分布。利用站点观测资料、数字高程模型数据、坡向、坡度因子,采用逐步回归分析法,建立估算夏季降水的回归方程,得到全国1971—2000年夏季各月及总降水量的空间分布图,并对模型结果进行检验与对比分析。结果表明,此方法估算夏季总降水量的平均绝对误差为27 mm,平均相对误差为11.8%。模型结果能体现迎风坡与背风坡的雨量差,符合客观规律,能够定性、定量地再现中国夏季降水的实际空间分布特征。

Estimation of summer precipitation in China based on wind data from NCEP

Based on the wind data from NCEP, an estimation model for calculating the summer precipitation in China is presented. The required monthly prevailing wind data is obtained through surface pressure, zonal and meridional wind data from NCEP during 1971-2000. The cosine value of the separation angle between the prevailing wind direction and the macro-topographic orientation is taken as slope factor to identify the windward slopes and leeward slopes. Then a multiple stepwise regression equation is developed to estimate summer precipitation in China according to precipitation data from observation gauges, digital elevation model(DEM), topographic orientation, etc, and the spatial distribution of the monthly and total summer precipitation from 1971 to 2000 in China is available. Results produced by validation and comparative analysis indicate that in summer the mean absolute error is 27 mm and the mean relative error is about 11.8%. The estimated precipitation distribution is reasonable because the difference in precipitation between the windward slope and the leeward is obvious. It is also able to qualitatively and quantitatively describe the real distribution of summer precipitation in China.