羌塘高原卫星降水产品校正与降水量估算

The spatial distribution of the precipitation determines the spatial pattern of the cryospheric hydrology elements and the ecological environment over the Qiangtang plateau. Only based on the data from four CMA stations, which are located on the southern edge of Qiangtang plateau, it is difficult to obtain the spatial distribution of precipitation, and it is also difficult to evaluate and correct the satellite precipitation products. This project aims to establish a rain gauge network in the Qiangtang plateau, to evaluate and correct the satellite precipitation products based on the spatial up-scaled gauge data, and to improve the accuracy of precipitation estimation by remote sensing in the Qiangtang plateau. The research contents include (1) the establishment of the rain gauge network in the Qiangtang plateau, the analysis of the temporal characteristic of precipitation days and frequency; (2) with the help of MODIS products to obtain the gauge data with satellite pixel scale through up-scaling method; (3) evaluation the amount of precipitation of two new generation satellite products against the scale-matched gauge data, and evaluation the precipitation days and frequency of those two products against hourly gauge data; (4) development of correction method to obtain corrected satellite precipitation data since 2014 in the Qiangtang plateau, and analysis of the precipitation spatial characteristics in the Qiangtang plateau. The highlights of this study lie in the development of up-scaling method for gauge data with the aid of the remote sensing data, the development of correction method for satellite products based on the up-scaled gauge data, the improvement of accuracy of satellite precipitation data in the Qiangtang plateau.

降水量空间特征决定了羌塘高原冰冻圈水文要素和生态环境的空间格局。仅凭羌塘高原南缘4个国家基准站观测数据，很难获得降水量的空间分布，也难以完成卫星降水产品的评估和校正。本项目拟建立羌塘高原雨量计观测网，基于空间升尺度后的观测网数据评估和校正卫星降水产品，提高羌塘高原降水量遥感估算精度。研究内容包括（1）建立羌塘高原雨量计观测网，分析降水量和降水频率的时间特征；（2）借助MODIS遥感产品，升尺度获得卫星像元尺度雨量计观测数据；（3）用升尺度观测网数据验证两种新一代卫星降水产品，用小时分辨率观测网数据验证两种卫星产品的降水日数和降水频率；（4）发展羌塘高原卫星降水产品校正方法，获得2014年以来经过校正的卫星数据，分析羌塘高原降水量的空间特征。本研究亮点在于借助遥感数据发展了站点观测升尺度方法，基于尺度匹配的雨量计观测网数据发展了羌塘高原卫星降水校正方法，提高了羌塘高原卫星降水数据的精度。

在项目资助下，课题组维护和拓展了新建的两个高原中西部降水观测断面。积累并共享了56个雨量计的观测数据。利用观测数据开展了以下研究：1）揭示了青藏高原中西部降水特征的独特性。高原中西部暖季降水自西向东缓慢增加，但自色林错西岸开始迅速增加，说明色林错以西地区可能是季风和中纬度西风的一个过渡区。暖季降水从南到北的空间变化十分剧烈，有明显的降水量“双峰”和“双谷”。“双峰”出现在喜马拉雅南坡和冈底斯南坡，而“双谷”则出现在喜马拉雅山北侧和羌塘高原。2）揭示GPM时代卫星降水产品存在的问题。发现遥感不仅不能反映高原降水日变化特征，也不能反映复杂山区降水的海拔梯度特征。项目成果为降水卫星遥感反演算法的改进提供了依据。项目成果有望在青藏高原中西部，特别是羌塘高原内流区，水资源潜力估算、以及水量平衡研究方面具有应用潜力。项目资助共发表了 7 篇 SCI 论文，被广泛引用，其中 1 篇成为 ESI 高被引论文。