On factors controlling marine boundary-layer aerosol optical depth based on ARM Azores measurements and satellite measurements

 
Poster PDF

Authors

Tao Luo — University of Wyoming
Zhien Wang — University of Colorado

Category

Aerosol Properties

Description

Sea spray aerosol is one of the largest natural contributors to the global aerosol loading and thus plays an important role in the global radiative budget through both direct and indirect effects. Many previous studies have shown either strong or weak relationships between marine boundary-layer (MBL) aerosol optical depth (AOD) and near-surface wind speed because marine aerosol is influenced by a wide range of factors.

This study attempts to examine extra contributing factors beyond wind to better characterize MBL AOD variations by using multiple satellite data and ARM surface data from the Azores. MBL AOD and aerosol layer structure were retrieved from CALIPSO and CloudSat satellite data, and only cloud-free and single aerosol layer conditions were considered. Daily surface wind speed data and sea surface temperature were obtained from the AMSR-E. Large-scale meteorological conditions were obtained from ECMWF. Detailed data analyses were carried out over nine regions representing different areas of the global oceans based on the two-year (2007–2008) satellite measurements. The results show that among the selected factors, surface wind speed and MBL depth are found to be the two most important factors determining MBL AOD. This suggests that not only mechanical production of sea-spray particles driven by near-surface wind processes but also vertical re-distribution driven by turbulent and shallow convective mixing in the MBL controls MBL AOD variations. A new relationship of between AOD and those two factors was derived based on satellite results and was further evaluated with ARM measurements from the Azores. Numerical simulations using WRF model and ARM data from the Azores are conducted to show the potential improvements in radiation computation.