Aerosol Optical Depth Climatology Derived from Micropulse Lidar Data at Various ARM Sites World-wide

Micropulse Lidar (MPL) systems have been running at all US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) sites including 5 permanent and 2 mobile facilities. The locations of the sites represent a broad range of climate conditions around the world [http://www.arm.gov/sites]. Aerosol optical depth (AOD) is a measure of the extinction of solar radiation due to aerosols; liquid and solid particles suspended in the air from natural or man-made sources. In the absence of clouds, the MPL, operating at 532 nm, produces profiles of atmospheric scattering that result from aerosols (Mie-scattering) and molecules (Rayleigh-scattering). In combination with AOD data from the nearly co-located multifilter rotating shadowband radiometer (MFRSR), these data can be used to calculate profiles of AOD. The raw data used in this study are averaged in time for 30 seconds and 30 meters in altitude. MPL backscatter observations at the DOE ARM sites from 2007 through 2010 have been examined and used in this AOD climatology. The AOD values at Southern Great Plains (SGP) site are also compared with the corresponding values obtained from a nearly co-located Raman Lidar (RL) operating at 355 nm. The comparison shows good agreement. A multi-year vertical profile of AOD climatology at different ARM sites, including diurnal and seasonal variability will be presented. These results are expected to be of significant importance to the scientific community to understand the aerosol properties and the boundary layer dynamics better as well as to improve global climate models by better incorporating the aerosol radiative effects.