<p>Summer Shamal, a strong low-level northwesterly wind in the Middle Eastern region, is the major trigger for dust storm activity with a broad impact on regional transport and human safety. Due to the scarcity of high-frequency data, near-ground turbulent mixing analyses under Shamal are still rare. The current study investigates the near-surface turbulence characteristics of the atmospheric boundary layer (ABL) in the coastal region of Qatar under summer Shamal conditions (26.08 N, 51.36 E). The results show that, in the absence of monsoon, Shamal prevents the development of summer sea breezes in the Persian Gulf. Compared to non-Shamal days (NSD), Shamal days (SD) are characterized by higher sensible heat flux magnitude and turbulent kinetic energy (TKE) with lower humidity, especially around noon time. Turbulence stability analysis indicates the probability of different dust activities during summer SD and NSD. Wind velocity spectra are investigated to evaluate the TKE dissipation rate. A Weibull distribution is observed for PDFs of TKE dissipation rate under SD for both stable and unstable conditions.</p>

Shamal wind, a strong northwesterly wind in the Persian Gulf (and the larger Middle East region), has a broad effect on the health, transportation, and safety of the regional environment (Membery, 1983;Yu et al., 2016). For instance, Shamal is known to be the major trigger for dust storm activities across the Arabian Peninsula (Middleton, 1986). Severe dust storms triggered by Shamal cause considerable environmental concerns in >10 countries in the Middle East (Hamidi et al., 2014), which seem to be intensifying due to global warming and excessive drought in the region (Namdari et al., 2018). Shamal wind also plays an important role in the propagation and transportation of atmospheric pollutants in the region, like ozone and discharged plume related to the oil industry (Smoydzin et al., 2012;Yu et al., 2016). Further, Shamal wind velocity creates a high wind load (up to 30 m/s at 300 m above the ground) that can become a threat to tall building stability (Irvin, 2009). It is important to emphasize that Shamal is not an event limited only to the Persian Gulf, but also the Gulf of Oman, the North Arabian Sea, and even as far as the west coast of India (Al Senafi & Anis, 2015;Glejin et al., 2013).

<p>The atmospheric stability condition in the coastal region of Qatar are analyzed using the measurements conducted on the shoreline (26.08N, 51.36E). The micrometeorological data are collected, from August 2015 to September 2016, using sonic anemometers (20 Hz) at three heights and a weather station on the top of a 9 m tower. Two different atmospheric daily stability patterns, ‘orderly’ and ‘disheveled’, are identified based on the wind conditions. A day is classified as ‘orderly’ if the amount of wind from the sea lasts less than 10% of the day. Otherwise, a day with an onshore wind of more than 10% is considered ‘disheveled’. The orderly stability pattern shows a daily descending and ascending trend during the sunrise and sunset periods, respectively, while the disheveled days follow a random pattern with no clear order. The probability distribution of the stability parameter shows a narrower distribution for the ‘orderly’ days, containing fewer unstable periods than the ‘disheveled’ days. The chaotic trend during disheveled days could be caused by the inhomogeneity of the roughness between the land and the sea (1000 times). The integral length scales are further investigated to clarify the influence of the local thermally forced flow to the disheveled patterns.</p>