Author

Ian Y. Chang

Date of Award

2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Atmospheric Science

Committee Chair

Sundar A. Christopher

Committee Member

Qingyuan Han

Committee Member

Udaysankar S. Nair

Committee Member

John R. Christy

Committee Member

Ping Yang

Subject(s)

Atmospheric aerosols--Remote sensing., Radiative transfer.

Abstract

The representation of aerosols, clouds, and aerosol-cloud radiative effects remains highly uncertain, restricting the reconstruction of past climate and the prediction of future climate change. The above-cloud absorbing aerosol direct radiative effects generally result in a positive sign at top-of-atmosphere (TOA) over the ocean. This sign results from a reduction of scattered radiation at TOA due to absorbing aerosol’s SW absorption. Geostationary satellite data from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) in conjunction with NASA A-Train data are used to develop an algorithm for detecting biomass burning smoke aerosols above clouds. The detection relies on spectral signatures, textural characteristics, and time-dependent spectral variation of SEVIRI data. The user accuracy of this algorithm is ~65% and the producer accuracy is over ~77%. Above-cloud AOD retrievals from SEVIRI and Moderate Resolution Imaging Spectroradiometer (MODIS) are compared against the Spectrometers for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) data set for September 2016. MODIS and SEVIRI AODs have a good agreement compared with 4STAR AODs when simultaneously retrieved above-cloud AODs and underlying cloud properties assuming a single scattering albedo (SSA) of 0.84 at 470 nm and 0.76 at 860 nm. Above-cloud AOD retrieval generally agrees to within 0.2 above homogeneous clouds with a cloud optical depth (COD) greater than 8. However, above-cloud AOD retrievals are biased high when retrieving above thin clouds since the radiance separation between aerosols and clouds becomes complex. Results indicate that the assumed SSA play a significant role in the retrieved above-cloud AODs.

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