积雪面积与雪水当量时空关系及其在寒区水文中的同化应用

Simulation of cold region hydrological processes has larger uncertainties due to the imperfect parameterization of snow and the error of atmosphere driving data. Although remote sensed snow data can improve the understanding, their applications in cold region hydrology model are not efficient yet. In this study, the airborne remote sensing observations by simultaneously mounting the optical camera and microwave radiometers on unmanned aerial vehicle (UAV) will provide a large amount of spatiotemporal data of snow cover area (SCA) and snow water equivalent (SWE) in the study area. These SCA and SWE data with high spatial resolution will be used to develop a snow depletion curve (SDC) in the mountainous region. Then, the SDC will transfer the fraction of SCA data derived from the middle resolution satellite remote sensing data (such as MODIS and MERSI) to SWE data. Finally, these SWE data will be assimilated into cold region distributed hydrologic model to improve the accuracy of cold regional hydrologic simulation, specially the snow melting runoff in spring. This study will be expected to provide a solution to fuse the remote sensing data into cold region hydrological model.

遥感数据在寒区水文模型中的应用缺乏有效的手段，其作用并没有得到充分发挥。本研究将以航空遥感为桥梁，同时获取遥感像元尺度内积雪面积和雪水当量的空间数据，发展适合研究区的积雪衰减曲线，将中分辨率卫星遥感数据获取的积雪面积比例数据转换为雪水当量，同化应用到寒区分布式水文模型中，提高寒区水文模拟精度，尤其是春季融雪径流。为水文模型中有效利用遥感数据提供方法研究，同时促进遥感技术在水文领域的应用水平。

雪深与雪水当量是重要的寒区水文模拟与预报变量，由于被动微波遥感分辨率低，其反演得到的雪深与雪水当量无论是精度还是空间分辨率都难以满足复杂地形下寒区水文过程模拟与预报。通过积雪衰减曲线建立光学遥感获取的中高分辨率积雪面积与雪深/雪水当量转换关系，可以将具有较高精度的中高分辨率积雪面积数据应用于寒区水文过程研究中。本项目以祁连山八宝河子流域和冰沟小流域为研究区，建立了寒区分布式水文气象观测网和积雪、冻土综合观测场，获取了水文气象以及积雪和冻土连续的分布式观测数据。通过地面与遥感积雪同步观测，获取了大量雪深与雪水当量地面观测数据，发展了基于SAR遥感数据的雪深与雪水当量反演算法，获取了30米分辨率像元尺度上的雪深与雪水当量的空间分布数据，结合地形等辅助信息建立了山区复杂地形条件下的积雪衰减曲线。利用GBHM和CRHM模型开展冰沟小流域以及八宝河子流域融雪径流模拟与率定，在此基础上以积雪衰减曲线作为同化算子，将光学遥感获取的积雪面积比例产品同化到寒区分布式水文模型中，显著提高了寒区水文径流模拟精度，尤其是春季融雪径流模拟精度，为寒区水文模拟与短期预报提供了新思路。