Characterization of the atmospheric circulation near the Empty Quarter Desert during major weather events

Abstract

In this study, we characterize the meteorological conditions and planetary boundary layer dynamics in western United Arab Emirates based on 2012–2020 in-situ measurements. This multi-year analysis is then complemented by an intensive field-campaign in winter 2021 from which we address the main patterns of the atmospheric circulation and the boundary layer structure during typical weather events identified in the long-term analysis. We found that, 10-m and 60-m wind speeds are generally below 5 m s−1 and 8 m s−1, respectively, blowing predominantly from a northerly direction. They peak in intensity at around 12–18 Local Time (LT) and 02–09 LT in association with the sea-breeze and the downward mixing of momentum from the nighttime low-level jet, respectively. The wind is stronger in the cold season, varying mostly in response to mid-latitude baroclinic systems, while the proximity of the site to the core of the Arabian Heat Low leads to more quiescent conditions in the summer. Radiation fog is a regular occurrence mostly from December to February owing to the colder nights and weaker wind speeds, with a peak fog occurrence around local sunrise. Sea fog, which develops when the hotter desert air is transported over the cooler Arabian Gulf waters, is advected to the site in the summer. Deep and very deep convective clouds are more common in March-April in association with organized convective systems, with generally reduced cloud cover from May to October. The region of interest exhibits a monthly-mean aerosol optical depth ranging from ∼0.3 in December-January to ∼1.2 in July due to its increased exposure to dust storms in the summer season. Dust activity is also found to peak during winter and spring associated with the intrusion of cold fronts from mid-latitudes.

Recent and projected changes in climate patterns in the Middle East and North Africa (MENA) region

“…In both North Africa and the Arabian Peninsula, the dust emission is reduced in the colder months (Fig. 2 d), but it does occur, mostly in association with mid-latitude weather systems 122 , 125 , 126 .…”

“…5 a) with poorer scores in the summer season and magnitudes in the range 10–15 K for the maximum and minimum temperatures. The day-to-day variability of air temperature in the region in winter months is largely controlled by the passage of mid-latitude weather systems 122 , the timing of which will not be fully captured by the CMIP6 MMEM, and hence the lower correlations of ~ 0.2 (Fig. 5 b).…”

“…5 b). In the summer, mesoscale circulations such as the land-sea breeze play an important role in the day-to-day temperature fluctuations 122 , which are better captured by the CMIP6 MMEM, yielding higher ρ scores of 0.4–0.6 (Fig. 5 b).…”

The Wind‐Blown Sand Experiment in the Empty Quarter Desert: Roughness Length and Saltation Characteristics

“…This observation is expected, as the SHAMS location is further inland compared to other coastal locations, such as Barakah and Abu Dhabi. Previous studies conducted at Barakah reported the persistent occurrence of strong northwesterly winds for several days when the location is under the influence of favorable synoptic conditions (Abida et al, 2022;Nelli et al, 2022;Weston et al, 2022).…”

“…IRBT is a widely recognized metric utilized to infer convection on regional and global scales (e.g., Machado et al, 1998;Nelli et al, 2022;Rao et al, 2013;Reddy & Rao, 2018). In order to discern cloud types at the WISE-UAE site, we adopted the IRBT thresholds specified by Rao et al (2013) and Reddy and Rao (2018).…”