Quantifying the Differences of Clouds Observed By Radar and Lidar from Three Platforms over the Southern Ocean

This study investigates total cloud fractions (CFs) and their vertical distributions using data collected by radars and combined radar-lidar systems during the SOCRATES and MARCUS campaigns, and spaceborne CloudSat and CALIPSO over the Southern Ocean. We found that radars with higher sensitivity (-50 dBZ reflectivity for HCR during SOCRATES and M-WACR during MARCUS) detected more clouds compared to the CloudSat CPR which has a lower sensitivity of -26 dBZ. The total CFs observed by HCR closely resemble those detected by CPR when aircraft flew above the cloud top. However, when both HCR and M-WACR used zenith-pointing views, the CF differences became minimal, indicating that the viewing angle significantly impacts cloud observation accuracy across different platforms. Incorporating lidar observations increased the detection of clouds, where the total CFs increased to 0.794, 0.851, and 0.907 compared to those observed with radar alone (0.511 for CPR, 0.686 for HCR, and 0.765 for M-WACR).