Climatology of summer Shamal wind in the Middle East

Abstract

The Middle Eastern Shamal is a strong north‐northwesterly wind, capable of lifting dust from the Tigris‐Euphrates basin and transporting it to the Persian Gulf and Arabian Peninsula. The present study explores the poorly understood spatial and temporal variability of summer Shamal on the diurnal, seasonal, and interannual time scales, along with its influence on dust storm activity and sensitivity to global patterns of sea surface temperature using a comprehensive set of observational data. Statistics of the summer Shamal season are quantified for the first time, including its onset, termination, duration, and the occurrence of distinct break periods. Based on a multistation criteria, the mean onset and termination of the Shamal season occur on 30 May ± 16 days (1 standard deviation) and 16 August ± 22 days, respectively. Anomalously early (late) onset and termination of the Shamal season are typically associated with La Niña (El Niño) conditions, which favor (inhibit) the development of the Iranian heat low in spring and inhibit (favor) its persistence into late summer. Dust source regions in the Tigris‐Euphrates basin and Kuwait, as well as southeastward dust transport during the summer Shamal, which cannot be detected by satellite aerosol products alone, are identified, for the first time, from the Multiangle Imaging Spectroradiometer plume motion vector products and confirmed by surface observations and lidar data. A close interrelationship has been revealed among summertime dust activity across the eastern Arabian Peninsula, frequency of Shamal days, and duration of the Shamal season on the interannual time scales.

Migration of Barchan Dunes in Qatar–Controls of the Shamal, Teleconnections, Sea-Level Changes and Human Impact

“…Records integrating larger parts of the Gulf area, however, even show a very moderate increase of summer Shamal activity after the late 1990s [35,36], instead of a quasi-continuous trend inferred from wind intensity at Doha. Thus, even though NAO and ISM show good correlation with summer Shamal intensity in those years strongly deviating from the average (e.g., 1980/1981, 1983, 1993, 2000, 2013), their indices alone, of course, cannot explain this regional wind phenomenon entirely.…”

“…In combination with an established heat low over Iran, these conditions initiates short-term, multiple-day Shamal activity over Qatar [32] with surface wind speeds of up to 13 m/s [33]. Stronger and longer-duration Shamals during June and July are controlled by a steep gradient between the Mediterranean high-pressure cell, and the regional depression over Iran and adjacent areas resulting from extreme heating of surface air masses [32,34,35]. The winter Shamal (November to March) may even reach wind speeds of 15-20 m/s over the Arabian Gulf [35,36], and is usually associated with a surface low-pressure area over Syria migrating eastward towards Iran and pushing a cold front south and west.…”

“…Stronger and longer-duration Shamals during June and July are controlled by a steep gradient between the Mediterranean high-pressure cell, and the regional depression over Iran and adjacent areas resulting from extreme heating of surface air masses [32,34,35]. The winter Shamal (November to March) may even reach wind speeds of 15-20 m/s over the Arabian Gulf [35,36], and is usually associated with a surface low-pressure area over Syria migrating eastward towards Iran and pushing a cold front south and west. A low-pressure center along this southward moving front in the northern Arabian Gulf and a surface high-pressure cell over the northern Arabian Peninsula finally induce the winter Shamal, which is not as consistent as its summer counterpart [31].…”

“…From the 1970s until the late 1990s, the summer Shamal constantly declined (Figure 8b,c), while afterwards the local average wind speed in June-July fluctuates around a value of 15 km/h [12] and the regional record even shows a moderate increase in the number of Shamal days [35]. If considering the time windows of the multitemporal satellite image analysis of barchan dune migration, the duration of Shamal conditions has initially dropped significantly from 21.5% to 15.2% (1995-2006), followed by a very similar value (14.8%) from 2006 to 2015 (Figure 8e).…”

“…In terms of further mechanisms controlling barchan migration in the longer term, a significant correlation between regional (number of summer Shamal days over the Gulf region, Figure 8b) [35] and local (average wind speed June-July at Doha International Airport, Figure 8c) [12] summer Shamal activity can be observed. From the 1970s until the late 1990s, the summer Shamal constantly declined (Figure 8b,c), while afterwards the local average wind speed in June-July fluctuates around a value of 15 km/h [12] and the regional record even shows a moderate increase in the number of Shamal days [35].…”