Cloud phase classification using SLSTR measured brightness temperatures at 3.74, 10.85, 12.00 um

Abstract

This study investigates the sensitivity of brightness temperatures at 3.74, 10.8, and 12 um in identifying water, ice, and mixed-phase clouds (MPC). Radiative transfer simulations with SCIATRAN reveal that the directional brightness temperature difference at 3.74 um (DBT3.74) distinguishes water and MPC from ice clouds due to scattering differences. To separate potential MPC from water clouds, we introduce the Liquid Cloud Probability Index (LCPI) based on cloud top temperature and absorption differences between water and ice at 10.8 and 12 um. The combined DBT 3.74-LCPI framework is validated using the Sea and Land Surface Temperature Radiometer (SLSTR) dual-view data collocated with CLDCLASS-LIDAR cloud phase product, showing over 90% accuracy in water and ice phase classification, and approximately 60% for mixed phase clouds. This dual-view, multi-channel method enhances the detection of cloud phases, offering improved results for passive satellite sensors.