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King Abdulaziz University (2017)

NORTHERN ARABIAN PENINSULA SAND STORM ACTIVITIES DURING THE WET SEASON

Alobaidi, Meshari Jumaa

Titre : NORTHERN ARABIAN PENINSULA SAND STORM ACTIVITIES DURING THE WET SEASON

العواصف الترابية في شمال الجزيرة العربية خلال موسم الأمطار

Auteur : Alobaidi, Meshari Jumaa

Université de soutenance : King Abdulaziz University

Grade : Doctorate Thesis 1438 AH 2017 AD

Résumé
A dust storm climatic regionalization of the Arabian Peninsula (AP) that aims to categorize the region into several cohesive sub-regions is conducted. This approach was carried out by grouping together similar wet season climatological features of dust storm activity (DSA). A common period of 30 years (1983 – 2013) for 38 meteorological weather stations across the AP was utilized. The mathematical, statistical and subjective methods that are employed in the process of regionalization resulted in dividing the region into three sub-regions. Each of the sub-regions north, northwestern and central, northeast and south, west and coastal shows distinct features of its own. Subsequently, the temporal trend of the representative station (key station) for each sub-region is examined. It is found that only the northeastern part of the region has a significant positive trend over the last 30 years. However, this positive increase in DSA is not associated with an increase in wind speed. Subsequently, the influence of mid latitude circulation on the wet season (October – May) Dust Storm Activity (DSA) over the northern Arabian Peninsula for the period 1983-2013 is examined using observational and reanalysis gridded datasets. Dusty and clear days composites of the 200 hPa geopotential height anomalies reveals a pattern in the upper levels which is strongly correlated with mid latitude circumglobal wave train (CGT) and exists three days prior to the outbreak of dust storms. The regional surface conditions (such as mean sea level pressure, low level temperature and winds etc.) that favors the DSA over the northern Arabian Peninsula display significant correlations with the CGT. A time lagged analysis reveals that the eastward propagating CGT influences the surface pressure over the norther Arabian Peninsula and adjacent areas. The upper level low pressure anomaly center associated with the regional DSA is significantly correlated with the surface low over the northern Arabian Peninsula three days prior to the occurrence of dust storm event, whereas the maximum correlation occurs during the dust storm day. The DSA over the northern Arabian Peninsula is found to be more (less) frequent during the positive (negative) phase of the North Atlantic Oscillation (NAO). This is because of the enhanced (reduced) surface winds (precipitation) activity over the Arabian Peninsula during NAO that leads to further reductions in surface soil moisture content and hence favors the DSA over this region. Furthermore, the DSA over northern Arabian Peninsula is also associated with El Niño–Southern Oscillation. The frequency of DSA is higher during the cold phase of the El Niño–Southern Oscillation (La Niña) than the warm phase (El Niño). This thesis assists future research in exploring the relationship between large-scale forcing and the AP sub-regional DSA. As well, this could enhance regional DSA forecast and future projections.

Présentation

Page publiée le 23 janvier 2019