Open AccessAerosol's optical and physical characteristics and direct radiative forcing during a shamal dust storm, a case study
Author(s) -
Thuraya Saeed,
Hassan AlDashti,
Christos Spyrou
Publication year - 2014
Publication title -
atmospheric chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.622
H-Index - 206
eISSN - 1680-7324
pISSN - 1680-7316
DOI - 10.5194/acp-14-3751-2014
Subject(s) - dust storm , aerosol , total ozone mapping spectrometer , atmospheric sciences , environmental science , atmosphere (unit) , albedo (alchemy) , storm , radiative forcing , shortwave , radiative transfer , moderate resolution imaging spectroradiometer , longwave , longitude , latitude , meteorology , physics , stratosphere , satellite , ozone layer , art , quantum mechanics , astronomy , performance art , art history
Dust aerosols are analyzed for their optical and physical properties duringan episode of a dust storm that blew over Kuwait on 26 March 2003 when the military Operation IraqiFreedom was in full swing. The intensity of the duststorm was such that it left a thick suspension of dust throughout thefollowing day, 27 March. The synoptic sequence leading to the dust storm andthe associated wind fields are discussed. Ground-based measurements ofaerosol optical thickness reached 3.617 and 4.17 on 26 and 27 March respectivelywhile the Ångstrom coefficient, α870/440, dropped to −0.0234and −0.0318. Particulate matter concentration of 10 μm diameter orless, PM10, peaked at 4800 μg m−3 during dust storm hours of 26March. Moderate Resolution Imaging Spectroradiometer (MODIS) retrievedaerosol optical depth (AOD) by Deep Blue algorithm and Total Ozone MappingSpectrometer (TOMS) aerosol index (AI) exhibited high values.Latitude–longitude maps of AOD and AI were used to deduce source regions ofdust transport over Kuwait. The vertical profile of the dust layer wassimulated using the SKIRON atmospheric model. Instantaneous net direct radiativeforcing is calculated at top of atmosphere (TOA) and surface level. Thethick dust layer of 26 March resulted in cooling the TOA by −60 Wm−2and surface level by −175 Wm−2 for a surface albedo of 0.35. Slightlyhigher values were obtained for 27 March due to the increase in aerosoloptical thickness. Radiative heating/cooling rates in the shortwave andlongwave bands were also examined. Shortwave heating rate reached a maximumvalue of 2 K day−1 between 3 and 5 km, dropped to1.5 K day−1 at 6 km and diminished at 8 km. Longwaveradiation initially heated the lower atmosphere by a maximum value of0.2 K day−1 at surface level, declined sharply atincreasing altitude and diminished at 4 km. Above 4 km longwave radiationstarted to cool the atmosphere slightly reaching a maximum rate of−0.1 K day−1 at 6 km