华北积雪冻融循环微波辐射特征研究

摘要

积雪冻融循环监测是陆表水文过程和冰雪自然灾害研究的重要方面。被动微波遥感由于具有对水分敏感、高时间分辨率的特点，尤其适合大尺度的积雪冻融监测及相关参数的反演。该研究于2012年11月6日～27日在河北怀来遥感综合实验站使用车载多频率微波辐射计 TMMR 观测了积雪冻融循环微波辐射特征。研究发现，36．5GHz 的观测亮温对积雪的冻融循环最敏感，18．7GHz 次之，融化和冻结的时亮温差别可分别约达80K和60K；HUT 单层和多层积雪微波辐射模型对18．7GHz 和36．5GHz 的模拟亮温能够基本反映冻融循环过程中的亮温变化；多层模型更适合模拟冻融循环的过程，18．7GHz 和36．5GHz 在 V 极化的相关系数均为0．97；冻融循环研究中，冰壳、冰层粒径的观测、雪湿度的观测和湿雪介电常数模型仍有待进一步改善。%Monitoring snow melting/refreezing plays an important role in studying hydrological process of land surface and ice/snow natural disaster.With the characteristics of sensitivity to liquid water and high temporary resolution,passive remote sensing is especially suitable for monitoring snow melting/refreezing and retrieval of related parameters at large scales.An experiment based on TMMR (Truck-Mounted Multi-frequency Radiometer)was carried out to observe microwave emission characteristics of snow melting/refreezing cycles,from 6 th to 27 th ,November,2012,at Integrated Experiment Station of Remote Sensing in Huailai,Hebei province.The brightness temperature of 37GHz is the most sensitive to snow melting/refreezing cycles,and 18.7GHz follows,with 80K and 60K difference of brightness temperature at V polarization separately.Simulations at 18.7GHz and 36.5GHz by both HUT (Helsinki University of Technology)and multilayer HUT microwave snow emission model can mainly reflect the variations of brightness temperature in melting/refreezing cycles.Multilayer HUT model is more accurate to simulate the process of the cycles,whose correlation coefficients are both 0.97 at V polarization of 18.7GHz and 36. 5GHz.The measurements of snow grain size of ice crust or ice layer and liquid water content in melting/refreezing cycles, together with dielectric model of wet snow,need further improvement.