Improvement of Land Surface Microwave Emissivity Model (LandEM) and its preliminary application in the Qingzang Plateau region

Physical models have been developed in the past for simulations of microwave land surface emissivity (MLSE) but the application using physical models are very limited. This paper focuses on the Land Microwave Emissivity (LandEM) model in the Advanced Radiation Transfer Simulation System (ARMS), improves the soil dielectric constant and rough surface reflectance models, and conducts corresponding MLSE simulation and evaluation combined with ground observation MLSE data. Also, the main input parameters to LandEM are optimized. Taking the Qingzang Plateau region as an example, three semi-empirical models of rough surface reflectance and one empirical model of emissivity are selected to form nine MLSE simulation schemes. Using three sets of MLSE products retrieved from satellite observations, nine different simulation schemes are evaluated, and the optimal scheme is selected to simulate the MLSE in the Qingzang Plateau region. The research results show that the introduction of Mironov"s room temperature soil dielectric constant model in the LandEM model can improv the simulated MLSE. The introduction of the Zhang frozen soil dielectric constant model further compensates for the shortcomings of the original frozen soil dielectric constant estimation. The MLSE simulated by introducing the Chen-Weng rough surface reflectance model has also been effectively improved. For MLSE simulation in the Qingzang Plateau region, the Qp model is more suitable for bare soil rough surfaces, while the Chen-Weng model is more suitable for vegetation rough surfaces; The improved LandEM model and optimized simulation scheme can effectively simulate the horizontal polarization MLSE values and spatial distribution in the Qingzang Plateau region with a spatial resolution of 0.10 °, as well as the vertical polarization MLSE values. However, it cannot effectively simulate the spatial differences in vertical polarization MLSE.