Spaceborne Far‐Infrared Signal Simulations Over the Antarctic Plateau With Temperature‐Dependent Ice Cloud Optical Properties

Abstract Longwave cloud radiative effects significantly influence variability in global and regional Earth systems. However, there have been very few, if any, measurements of the far‐infrared (FIR) radiation over the polar regions, where about half of the outgoing longwave radiation is in the FIR spectrum. This motivated the Polar Radiant Energy in the Far Infrared Experiment (PREFIRE) and was part of the motivation for the Far‐infrared‐Outgoing‐Radiation Understanding and Monitoring (FORUM) mission. The absorption properties of ice in the FIR varies with temperature and should be considered when prescribing the radiative properties of ice particles. This study tests the ability of recently developed temperature‐dependent aggregate and column ice particle optical models to represent the radiative signatures of ice clouds in the FIR, and their potential to support applications of PREFIRE and FORUM observations. Using a radiative transfer code, these models are used to simulate Thermal InfraRed Spectrometer (TIRS) measurements from the two PREFIRE CubeSats for all overpasses at the Concordia (DOME‐C) station in January 2025, a polar day month when shortwave passive cloud retrievals are most accurate. The Clouds and Earth's Radiant Energy System (CERES) SYN1deg Level 3 hourly cloud retrievals are used as cloud inputs in the radiative transfer simulations. Temperature and humidity vertical profiles are taken from radiosonde data. The results show that both the aggregate and column ice optical models simulate the TIRS signals to within a brightness temperature of 4 K.