The Simulation of L-Band Microwave Emission of Frozen Soil during the Thawing Period with the Community Microwave Emission Model (CMEM)

One-third of the Earth’s land surface experiences seasonal freezing and thawing. Freezing-thawing transitions strongly impact land-atmosphere interactions and, thus, also lower atmosphere above such areas. Observations two L-band satellites, Soil Moisture Active Passive (SMAP) Ocean Salinity (SMOS) missions, provide flags that characterize surfaces as either frozen or not frozen. However, both state transitions—freezing thawing (FT)—are continuous complex processes in space time. Especially L-band, which has penetration depths up to tens centimeters, brightness temperature ( T B ) may be generated by a vertically-mixed profile different FT states, cannot described current version Community Microwave Emission Model (CMEM). To model transitions, we extended CMEM Fresnel mode with an component allowing for (1) varying fraction open water on top soil, (2) implementing temporal phase transition delay based difference between soil at 2.5 cm depth. The (CMEM-FT) can capture progression from completely thawed contributing layer observed microwave radiometer ELBARA-III installed Maqu station northeastern margin Tibetan Plateau. improves correlation observations simulations 0.53/0.45 0.85/0.85 its root-mean-square-error 32/25 K 20/15 H/V-polarization during conditions. Yet, CMEM-FT does still simulate sufficiently.