Dissertations, Theses, and Capstone Projects

Date of Degree

9-2015

Document Type

Dissertation

Degree Name

Ph.D.

Program

Earth & Environmental Sciences

Advisor

Reza Khanbilvardi

Committee Members

Shayesteh E. Mahani

Fred Moshary

Nir Krauker

Brian Vant-Hull

Robert Rabin

Subject Categories

Geology

Keywords

Aerosol optical Depth; Cloud Water Path; Correlations; Physical mechanisms

Abstract

Divergence between correlative studies involving aerosol and cloud proxies has been thought of in the past as the results of varying physical mechanisms. Although models have supported the existence of variable correlations, from an observational standpoint it is difficult to attribute with confidence the correlations to specific physical mechanisms. We explore a methodology to assess the correlation between cloud water path (CWP) and aerosol optical depth (AOD) using MODIS Aqua retrieved aerosol and cloud properties for regions dominated by different types of aerosol: Non Absorbing Aerosol Dominated Region over land (NAADR_Land), Non Absorbing Aerosol Dominated Region over Ocean (NAADR_Marine), Absorbing Aerosol Dominated Region over Sahara (AADR_Sahara), Absorbing Aerosol Dominated Region in biomass burning Subtropical African region( AADR_ SubTrop) and Absorbing Aerosol Dominated Region in urban areas (AADR_Urban). Along with these properties, meteorological conditions were catalogued as well. The data covers three months period, June through August 2005, during which each aerosol type is predominant in specific latitude belt. The proposed approach sorts the data into AOD bins; the mean AOD value for each bin and the corresponding mean CWP value are determined. The mean CWP is plotted against the mean AOD. The response curve of CWP to aerosol loading is non-monotonic and shows for all aerosol types, a peak CWP value corresponding to a threshold aerosol loading value (AODpeak). The peak is used to divide the total range of aerosol loading into two sub ranges. For AOD value below the threshold aerosol loading value, mean CWP and mean AOD are positively correlated. The correlation between mean CWP and mean AOD is negative for aerosol loading above the threshold value (AODpeak). Irrespective of the regional variations in aerosol type and AOD which are strongly connected to both the atmospheric water vapor content and the lower tropospheric static stability, the CWP peak observed for each aerosol type seems to describe a universal feature that may be useful for organizing future investigations of aerosol-cloud interactions in different regions.

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