Aerosol environment of tropical MCSs using CALIPSO observations

Aerosol-cloud interactions have been difficult to quantify using satellite data due to artifacts and cloud contamination of the aerosol concentration observations. The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite provides high resolution profiles of cloud and aerosol layers. By carefully selecting CALIPSO profiles unlikely to be contaminated by clouds, it is possible to examine the large-scale aerosol environments of tropical mesoscale convective systems (MCSs) identified by other satellites in NASA's afternoon (A-Train) constellation.

A contrast is observed between MCSs in a region of high (the Indian subcontinent and surrounding seas) and low background aerosol concentration (the western and eastern equatorial Pacific). Over the Arabian Sea and the Bay of Bengal, and to a lesser degree over India itself, MCSs are most frequently observed when aerosol optical depths are lower than their climatological monthly-means. This observation is consistent with the prevalence of MCSs during active monsoon periods, when the monsoon flow advects cleaner oceanic air into the region. In contrast, MCSs in the western and eastern Pacific intertropical convergence zone (ITCZ) are associated with slightly elevated aerosol concentrations. Aerosol anomalies near MCSs are generally larger in magnitude at night, when lidar measurements are less noisy due to the lack of solar radiation.