A Global and Regional Trend Study of the Vertical Distribution of Aerosols As Observed By Caliop

Abstract:

Trends in atmospheric aerosol particle loading have gained increased attention in recent years due to their impact on Earth’s radiation budget and global climate change. Past studies have examined this topic through aerosol optical depth (AOD) observations derived from passive satellite sensors such as Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging Spectroradiometer (MISR). However, such passive sensors acquire only column-integrated measurements and thus can provide no insight into the vertical distribution of any AOD trends they might detect. Yet knowledge of aerosol vertical distribution and trends are critical for studies involving aerosol climate impacts and air quality. Using seven and a half years (June 2006 – December 2013) of aerosol profile data from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), we investigate trends in CALIOP-derived AOD at various altitudes throughout the atmospheric column. This differs from existing CALIOP-based climatological studies that focus solely on the mean state of aerosol vertical distribution. Daytime and nighttime analyses are decoupled to account for differences in the vertical structure of the troposphere, and detection sensitivity of CALIOP, between the two regimes. The results of this study are presented globally and for selected regions. Of particular interest are North Africa and Asia, as these are areas with frequently high AOD and have also exhibited trends from passive sensor observations.