The larger and highly variable microwave emissivity over land results in more difficulties to retrieve the precipitation and other atmospheric parameters over land. The research about microwave emissivity over land is still weak due to the complicated terrains in China. In the paper, the synchronous observation of infrared and visible scanner (VIRS) and microwave imager (TMI) on the Tropical Rainfall Measuring Mission (TRMM) satellite and one microwave radiation transfer model to retrieve the microwave emissivity over land of China were utilized in Jianghuai-Huanghuai region. Then, combining with the land cover type data derived from MODIS observations, the variation characteristics of microwave emissivity over different types of land cover in the middle region of China was further analyzed.
Results show that the microwave emissivity of crop land surface is smallest and its polarization difference is largest while forest emissivity is largest and its polarization difference is smallest among mainly 5 types of land cover in this region. In addition, the microwave emissivity over different types of land cover shows more significant variation in day and night time while less variation in seasons. For the error estimation of emissivity, the influences of land surface temperature (LST), microwave brightness temperature (TB) and relative humidity (RH) on microwave 22 and 85 GHz channels are quite obvious. For those channels with frequencies less than 85GHz, the influence of TB on estimation of emissivity is most obvious, then LST and RH. For high frequency 85GHz, the influence of RH on estimation of emissivity is most obvious, then TB and LST.