Abstract
Abstract. Dust aerosols are analyzed for their optical and physical properties during an episode of a dust storm that blew over Kuwait on 26 March 2003 when the military Operation Iraqi Freedom was in full swing. The intensity of the dust storm was such that it left a thick suspension of dust throughout the following day, 27 March. The synoptic sequence leading to the dust storm and the associated wind fields are discussed. Ground-based measurements of aerosol optical thickness reached 3.617 and 4.17 on 26 and 27 March respectively while the Ångstrom coefficient, α870/440, dropped to −0.0234 and −0.0318. Particulate matter concentration of 10 μm diameter or less, PM10, peaked at 4800 μg m−3 during dust storm hours of 26 March. Moderate Resolution Imaging Spectroradiometer (MODIS) retrieved aerosol optical depth (AOD) by Deep Blue algorithm and Total Ozone Mapping Spectrometer (TOMS) aerosol index (AI) exhibited high values. Latitude–longitude maps of AOD and AI were used to deduce source regions of dust transport over Kuwait. The vertical profile of the dust layer was simulated using the SKIRON atmospheric model. Instantaneous net direct radiative forcing is calculated at top of atmosphere (TOA) and surface level. The thick dust layer of 26 March resulted in cooling the TOA by −60 Wm−2 and surface level by −175 Wm−2 for a surface albedo of 0.35. Slightly higher values were obtained for 27 March due to the increase in aerosol optical thickness. Radiative heating/cooling rates in the shortwave and longwave bands were also examined. Shortwave heating rate reached a maximum value of 2 K day−1 between 3 and 5 km, dropped to 1.5 K day−1 at 6 km and diminished at 8 km. Longwave radiation initially heated the lower atmosphere by a maximum value of 0.2 K day−1 at surface level, declined sharply at increasing altitude and diminished at 4 km. Above 4 km longwave radiation started to cool the atmosphere slightly reaching a maximum rate of −0.1 K day−1 at 6 km.
Highlights
On Wednesday 26 March 2003, amidst the military Operation Iraqi Freedom, Kuwait and the surrounding northeastern region of the Arabian Peninsula was exposed to a dust storm
The direct radiative forcing (DRF) of the atmosphere, DRFatm, which is the difference between DRFTOA and DRFsurf is stated
In this case study we examine the optical, physical and radiative properties of an extreme case of instantaneous loading of the lower troposphere by dust aerosols caused by a shamal dust storm
Summary
On Wednesday 26 March 2003, amidst the military Operation Iraqi Freedom, Kuwait and the surrounding northeastern region of the Arabian Peninsula was exposed to a dust storm. This dust storm that had already passed through Baghdad a day earlier (25 March) caused a slowdown in the advancement of US Army and hampered all military operations for the following 24 h (Atkinson, 2004). Dust and dust storms interfere with human life and function in various ways They are known to cause health problems, especially to the respiratory system, leading to various forms of allergies (Wilson and Spengler, 1996; Griffin and Kellogg, 2004; Griffin, 2007; Achudume and Oladipo, 2009; Leski et al, 2011).
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