A global view on stratospheric ice clouds: assessment of processes related to their occurrence based on satellite observations

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Zou, Ling, Griessbach, Sabine, Hoffmann, Lars, Spang, Reinhold
• Format: Article in Journal/Newspaper
• Language: English
• Published: EGU 2022
• Subjects: info:eu-repo/classification/ddc/550; Drake Passage; Patagonia
• Online Access: https://juser.fz-juelich.de/record/907854; https://juser.fz-juelich.de/search?p=id:%22FZJ-2022-02252%22

Ice clouds play an important role in regulating water vapor and influencing the radiative budget in the atmosphere. This study investigates stratospheric ice clouds (SICs) in the latitude range betweenbased on the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). As polar stratospheric clouds include other particles, they are not discussed in this work. Tropopause temperature, double tropopauses, clouds in the upper troposphere and lower stratosphere (UTLS), gravity waves, and stratospheric aerosols are analyzed to investigate their relationships with the occurrence of and variability in SICs in the tropics and at midlatitudes.We found that SICs with cloud-top heights of 250 m above the first lapse rate tropopause are mainly detected in the tropics. Monthly time series of SICs from 2007 to 2019 show that high occurrence frequencies of SICs follow the Intertropical Convergence Zone (ITCZ) over time in the tropics and that SICs vary interannually at different latitudes. Results show that SICs associated with double tropopauses, which are related to poleward isentropic transport, are mostly found at midlatitudes. More than 80 % of the SICs around 30∘ N/S are associated with double tropopauses.Correlation coefficients of SICs and all the other abovementioned processes confirm that the occurrence of and variability in SICs are mainly associated with the tropopause temperature in the tropics and at midlatitudes. UTLS clouds, which are retrieved from the Atmospheric Infrared Sounder (AIRS) and used as a proxy for deep convection in the tropics and high-altitude ice cloud sources at midlatitudes, have the highest correlations with SICs in the monsoon regions and the central United States. Gravity waves are mostly related to SICs at midlatitudes, especially over Patagonia and the Drake Passage. However, the second-highest correlation coefficients show that the cold tropopause temperature, the occurrence of double tropopauses, high stratospheric aerosol loading, frequent UTLS clouds, and ...