Description and Demonstration of the Multilayer Emission Model "2S L-MEM" for Passive L-Band Satellite Observations on Land

Abstract. This paper presents and reviews the modeling of satellite-observed L-band brightness temperature (BT) over land using the two-stream multi-layer microwave emission model (2S-MEM). While the 2S-MEM has been applied in several earlier studies, a comprehensive description tailored to the interpretation of satellite based passive L-band observations has been lacking. Here, we consolidate and clarify the different components of the model formulation in the context of satellite-based L-band radiometry and demonstrate its practical application across various scenarios. Three case studies from different in situ sites and corresponding L-band BT datasets from ESA’s SMOS and NASA’s SMAP satellites are presented. In each case study, BTs are simulated from in situ measurements and compared with corresponding satellite observations. We discuss the challenges of modeling coarse-resolution L-band BTs measured by satellite using in situ point data, and the resulting uncertainties in BT simulations that must be considered in both forward and inverse applications, including geophysical parameter retrievals.