Modification of Saharan air layer and environmental shear over the eastern Atlantic Ocean by dust-radiation effects

NCUIR > College of Earth Sciences > Department of Atmospheric Sciences and Graduate Institute of Atmospheric Physics > journal & Dissertation > Item 987654321/50328

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Title:	Modification of Saharan air layer and environmental shear over the eastern Atlantic Ocean by dust-radiation effects
Authors:	Chen,SH;Wang,SH;Waylonis,M
Contributors:	大氣物理研究所
Keywords:	TROPICAL CYCLOGENESIS;NUMERICAL SIMULATIONS;OPTICAL-PROPERTIES;MINERAL DUST;AEROSOL;MODEL;INTENSITY;DISTURBANCES;VALIDATION;HURRICANES
Date:	2010
Issue Date:	2012-03-27 17:29:30 (UTC+8)
Publisher:	國立中央大學
Abstract:	[1] This study investigates the influence of dust-radiation effects on the modification of the Saharan air layer (SAL) and environmental shear. A tracer model based on the Weather Research and Forecast model was developed to examine the influence using a dust outbreak event. Two numerical experiments were conducted with (ON) and without (OFF) the dust-radiation effects. Both simulations reasonably reproduced SAL's features. However, the 700 hPa maximum temperature within SAL was slightly underestimated and shifted northwestward from OFF. These were improved from ON, but the maximum temperature became slightly overestimated, which might be due to inaccurate optical properties. The dust-radiation interactions mainly warmed the dusty air between 750 and 550 hPa because dust shortwave absorption dominated dust longwave cooling. Another major warming area was found near the surface over the ocean due to longwave radiative heating by dust aloft. The modification of temperature resulted in an adjustment of the vertical wind shear. To the south of SAL, where easterly wave disturbances and tropical storms usually occur, the vertical zonal wind shear increased by about 1 similar to 2.5 m s(-1) km(-1) from 750 to 550 hPa, resulting in a maximum wind change of 3 similar to 5 m s(-1), a 30 similar to 40% increase, around the top of this layer. The enhancement of the vertical shear in this layer could potentially have an impact on TC genesis and development. The dust-radiation effects also modified the moisture and dust distribution, which can have a feedback (i.e., a secondary effect) on the heating profile and the vertical shear.
Relation:	JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Appears in Collections:	[Department of Atmospheric Sciences and Graduate Institute of Atmospheric Physics ] journal & Dissertation

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