An Assessment of the Surface Longwave Direct Radiative Effect of Airborne Saharan Dust during the NAMMA Field Campaign

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Title:	An Assessment of the Surface Longwave Direct Radiative Effect of Airborne Saharan Dust during the NAMMA Field Campaign
Authors:	Hansell,RA;Tsay,SC;Ji,Q;Hsu,NC;Jeong,MJ;Wang,SH;Reid,JS;Liou,KN;Ou,SC
Contributors:	大氣物理研究所
Keywords:	EMITTED RADIANCE INTERFEROMETER;OPTICAL-CONSTANTS;MINERAL AEROSOLS;EXPERIMENT SHADE;C-130 AIRCRAFT;AFRICAN DUST;PUERTO-RICO;ATMOSPHERE;IMPACT;CLOUD
Date:	2010
Issue Date:	2012-03-27 17:29:08 (UTC+8)
Publisher:	國立中央大學
Abstract:	In September 2006, NASA Goddard's mobile ground-based laboratories were deployed to Sal Island in Cape Verde (16.73 degrees N. 22.93 degrees W) to support the NASA African Monsoon Multidisciplinary Analysis (NAMMA) field study. The Atmospheric Emitted Radiance Interferometer (AERI), a key instrument for spectrally characterizing the thermal IR, was used to retrieve the dust IR aerosol optical depths (AOTs) in order to examine the diurnal variability of airborne dust with emphasis on three separate dust events. AERI retrievals of dust AOT are compared with those from the coincident/collocated multifilter rotating shadowband radiometer (MFRSR), micropulse lidar (MPL), and NASA Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) sensors. The retrieved AOTs are then inputted into the Fu-Liou 1D radiative transfer model to evaluate local instantaneous direct longwave radiative effects (DRE(LW)) of dust at the surface in cloud-free atmospheres and its sensitivity to dust microphysical parameters. The top-of-atmosphere DRE(LW) and longwave heating rate profiles are also evaluated. Instantaneous surface DRE(LW) ranges from 2 to 10 W m(-2) and exhibits a strong linear dependence with dust AOT yielding a DRE(LW) of 16 W m(-2) per unit dust AOT. The DRE(LW) is estimated to be similar to 42% of the diurnally averaged direct shortwave radiative effect at the surface but of opposite sign, partly compensating for the shortwave losses. Certainly nonnegligible, the authors conclude that DRE(LW) can significantly impact the atmospheric energetics, representing an important component in the study of regional climate variation.
Relation:	JOURNAL OF THE ATMOSPHERIC SCIENCES
Appears in Collections:	[Department of Atmospheric Sciences and Graduate Institute of Atmospheric Physics ] journal & Dissertation

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