Long-Term Ground-Based Measurements of Aerosol Optical Depth over Kuwait City

Abstract

We analyze ten years (2008–2017) of ground-based observations of the Aerosol Optical Depth (AOD) in the atmosphere of Kuwait City, in Middle East. The measurements were conducted with a CIMEL sun-sky photometer, at various wavelengths. The daily average AOD at 500 nm (AOD500) is 0.45, while the mean Ångström coefficient (AE), calculated from the pair of wavelengths 440 and 870 nm, is 0.61. The observed high AOD500 values (0.75–2.91), are due to regional sand and dust storm events, which are affecting Kuwait with a mean annual frequency of almost 20 days/year. The long-term record analysis of AOD500 and AE, shows a downward and upward tendency respectively, something which could be attributed to the continuous expansion and industrialization of the main city of Kuwait, in combination with the simultaneous increase of soil moisture over the area. By utilizing back trajectories of air masses for up to 4 days, we assessed the influence of various regions to the aerosol load over Kuwait. The high aerosol loads during spring, are attributed to the dominance of coarse particles from Saudi Arabia (AOD500 0.56–0.74), a source area that contributes the 56% to the mean annual AOD500. Other dust sources affecting significantly Kuwait originated from the regions of Iraq and Iran with contribution of 21%.

The influence of simulated surface dust lofting and atmospheric loading on radiative forcing

“…The downward shortwave profile shows reductions from 200 to 800 W m −2 , which scales with the trend in average dust amounts. The shortwave reductions by dust of ∼ 200-250 W m −2 for the Ginoux and Walker simulations are similar to those shown by Slingo et al (2006) and Kosmopoulos et al (2017) for corresponding dust AOD in the range of 1.5-2.5. These reductions by themselves would tend to induce a cooling ef-fect near the ground during the daytime by limiting the landsurface heating.…”

“…They are known to strongly influence the radiation budget due to their significant scattering and absorption properties (Carlson and Benjamin, 1980;Kinne et al, 2003;Sokolik and Toon, 1996;Dubovik et al, 2006). Dust aerosol layers can contribute to low-level atmospheric cooling due to the attenuation of shortwave radiation (solar dimming) through both scattering and absorption at solar wavelengths (Carlson and Caverly, 1977;Tegen and Lacis, 1996;Slingo et al, 2006;Lau and Kim, 2007;Kosmopoulos et al, 2017). Solar dimming can also lead to reduced surface heating and thus reduced latent and sensible heat fluxes (Wang et al, 2004;Prakash et al, 2015).…”

Forward Simulation of Multi-Frequency Microwave Brightness Temperature over Desert Soils in Kuwait and Comparison with Satellite Observations

“…Summer is from May until August. During June and July, north-westerly winds may develop, generating extensive dust storms [25]. Autumn starts from the month of September and is characterized by winds switching from the southeast to the northwest.…”

Climatology of Iraqi dust events during 1980–2015

“…The results revealed that the elevated values of AOD from 0.75 to 2.91 are because of dust episodes, which are affecting Kuwait with an annual average frequency of about 20 days per year. The backward trajectories of air masses showed the elevated main source areas of dust affecting Kuwait significantly originated from Saudi Arabia with the contribution of the 56% and other source areas from Iraq and Iran that the contribution of 21% to the mean annual AOD [43]. Pi et al [27] indicated considerable spatial variability of dust storm frequencies in the Xinjiang Province in northwest China, where the annual mean number of dusty days was 111.3 in the south and 10.9 in the north.…”