Atmospheric Turbulent Characteristics Under Summer Shamal in Coastal Qatar

Summer Shamal, a strong low-level northwesterly wind in the Middle Eastern, is the major trigger for dust storm activity with a broad impact on regional transport and human safety. However, near-ground turbulent mixing analysis under Shamal is still rare due to the lack of available high frequency data. The present study explores the near-surface turbulence characteristics under summer Shamal, compared with those of non-Shamal, in the coastal region of Qatar (26.08 degrees N, 51.36 degrees E). The results show that Shamal prevents the development of summer sea breezes in the Persian Gulf. A "Shamal day" (SD) is commonly defined as a day with a strong, continuous, north-northwesterly wind. Compared to non-Shamal days (NSD), SDs are characterized by higher surface sensible heat flux and turbulent kinetic energy (TKE) with lower humidity, especially around noon time. At night, the wind turbulence energy is contained in smaller eddies for SD due to the more stable atmospheric conditions. The streamwise velocity spectra analysis displays a power-law trend with a coefficient of -1.53 as compared to the traditional Kolmogorov -1.67 (-5/3) power law, indicating a higher TKE dissipation rate for SD. The smaller scatter of the normalized TKE dissipation rate observed for SD is related to lower streamwise turbulence intensity. A Weibull distribution is observed for probability distribution of TKE dissipation rate under SD in log scale for both stable and unstable conditions. This distribution for TKE dissipation rate is different than the results from other field measurements due to Shamal. Plain Language Summary Summer Shamal, a strong northwesterly wind in the Middle East region, is the major trigger for dust and pollution dispersion that has a broad impact on regional transport and human safety. A Shamal day (SD) is commonly defined as a day with a strong, continuous, north-northwesterly wind. Because of the higher wind speed of Shamal, the atmospheric mixing near ground is different with the lower speed wind. Atmospheric mixing is of vital importance for the understanding of climate, the dispersion of pollutants, and the exchange of heat, and water vapor with the earth surface. The present study explores the near-surface atmospheric mixing behavior of Shamal obtained from wind data collected in the coastal region of Qatar (26.08N, 51.36E) during summer 2016. This study highlights the difference between the atmospheric wind characteristics of SD and non-Shamal days. Specifically, the mechanism of atmospheric turbulence energy decay is different between Shamal and non-Shamal conditions. Finally, it is observed that Shamal wind suppresses sea breeze in the coastal region.