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Shortwave Direct Radiative Effects of Above-Cloud Aerosols Over Global Oceans Derived From 8 Years of CALIOP and MODIS ObservationsIn this paper, we studied the frequency of occurrence and shortwave direct radiative effects (DREs) of above-cloud aerosols (ACAs) over global oceans using 8 years (2007-2014) of collocated CALIOP and MODIS observations. Similar to previous work, we found high ACA occurrence in four regions: southeastern (SE) Atlantic region, where ACAs are mostly light-absorbing aerosols, i.e., smoke and polluted dust according to CALIOP classification, originating from biomass burning over the African Savanna; tropical northeastern (TNE) Atlantic and the Arabian Sea, where ACAs are predominantly windblown dust from the Sahara and Arabian deserts, respectively; and the northwestern (NW) Pacific, where ACAs are mostly transported smoke and polluted dusts from Asia. From radiative transfer simulations based on CALIOP-MODIS observations and a set of the preselected aerosol optical models, we found the DREs of ACAs at the top of atmosphere (TOA) to be positive (i.e., warming) in the SE Atlantic and NW Pacific regions, but negative (i.e., cooling) in the TNE Atlantic Ocean and the Arabian Sea. The cancellation of positive and negative regional DREs results in a global ocean annual mean diurnally averaged cloudy-sky DRE of 0.015 W m(exp. -2) [range of -0.03 to 0.06 W m (exp. -2)] at TOA. The DREs at surface and within the atmosphere are -0.015 W m(exp. -2) [range of -0.09 to -0.21 W m(exp. -2)], and 0.17 W m(exp. -2) [range of 0.11 to 0.24 W m(exp. -2)], respectively. The regional and seasonal mean DREs are much stronger. For example, in the SE Atlantic region, the JJA (July-August) seasonal mean cloudy-sky DRE is about 0.7 W m(exp. -2) [range of 0.2 to 1.2 W m(exp. -2)] at TOA. All our DRE computations are publicly available. The uncertainty in our DRE computations is mainly caused by the uncertainties in the aerosol optical properties, in particular aerosol absorption, the uncertainties in the CALIOP operational aerosol optical thickness retrieval, and the ignorance of cloud and potential aerosol diurnal cycle. In situ and remotely sensed measurements of ACA from future field campaigns and satellite missions and improved lidar retrieval algorithm, in particular vertical feature masking, would help reduce the uncertainty.
Document ID
20170003725
Document Type
Reprint (Version printed in journal)
Authors
Zhang, Zhibo (Maryland Univ. Baltimore County Baltimore, MD, United States)
Meyer, Kerry (NASA Goddard Space Flight Center Greenbelt, MD United States)
Yu, Hongbin (Maryland Univ. Baltimore County Baltimore, MD, United States)
Platnick, Steven (NASA Goddard Space Flight Center Greenbelt, MD United States)
Colarco, Peter (NASA Goddard Space Flight Center Greenbelt, MD United States)
Liu, Zhaoyan (NASA Langley Research Center Hampton, VA United States)
Oraiopoulos, Lazaros (NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
April 20, 2017
Publication Date
March 4, 2016
Publication Information
Publication: Atmospheric Chemistry and Physics
Volume: 16
Issue: 5
ISSN: 1680-7316
Subject Category
Statistics and Probability
Earth Resources and Remote Sensing
Meteorology and Climatology
Report/Patent Number
GSFC-E-DAA-TN41888
Funding Number(s)
CONTRACT_GRANT: NSF CNS-0821258
CONTRACT_GRANT: NNX15AT34A
CONTRACT_GRANT: NSF CNS-1228778
CONTRACT_GRANT: NNH14CK44C
CONTRACT_GRANT: NSF DMS-0821311
CONTRACT_GRANT: NNX14AI35G
CONTRACT_GRANT: NNX14AB21G
Distribution Limits
Public
Copyright
Other
Keywords
direct radiative effects
MODIS
CALIOP