Effect of high-level clouds on the polarization of scattered solar radiation at the zenith based on passive polarimetric and polarization lidar measurements

Subject of study. The polarization characteristics of scattered solar radiation in the presence and absence of high-level clouds (HLCs) are investigated. Aim of study. The aim is to develop a technique for detecting and identifying HLCs containing horizontally oriented ice particles based on passive measurements of the polarization characteristics of scattered solar radiation at the zenith. Method. The polarization characteristics of scattered solar radiation obtained from passive (polarimetric) measurements are analyzed in conjunction with the optical and geometric characteristics of HLCs determined simultaneously from active polarization (lidar) observations. Main results. Polarimetric measurements of scattered solar radiation at the zenith, performed with simultaneous monitoring of the atmospheric aerosol state, including HLCs, using a matrix polarization lidar, are presented. Under clear-sky conditions, the expected consistency between the polarization degree of scattered solar radiation and the solar zenith angle is observed. In the presence of HLCs, deviations from a smooth diurnal variation caused by the multilayer cloud structure are revealed. Practical significance. The results confirm the feasibility of using passive polarimetry for diagnosing the state of cloud cover and atmospheric aerosol layers. They also demonstrate the need for the further development of polarimetric methods and their integration with active atmospheric sensing techniques. Improvement of these methods will contribute to increased accuracy in climate research.