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University of East Anglia (2006)

The relationship between atmospheric circulation patterns and surface climatic elements in Saudi Arabia

Almazroui, Mansour

Titre : The relationship between atmospheric circulation patterns and surface climatic elements in Saudi Arabia

Auteur : Almazroui, Mansour.

Université de soutenance : University of East Anglia

Grade : Doctor of Philosophy (Ph.D.) : 2006

Résumé
Observed daily temperature and rainfall time series at four locations ; Riyadh, Jeddah, Madinah and Dhahran are considered here. Data from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP-NCAR) Reanalysis (hereafter, NNR) are also used for circulation typing. The statistical homogeneity assessments of all the long-term Saudi temperature records (1958-2003) identified artificial breaks caused by relocation, bad exposure and elevation of the screen from the ground. Adjustments to the infected periods of the temperature time series have been applied using smoothed daily correction factors. The new homogenised and adjusted temperature series are named "Saudi Adjusted Temperature Series" (SATS), and are used throughout this thesis. Trends in climate extremes have been assessed using four long-term daily series of rainfall and SATS. Patterns of warming are identified in the minimum and maximum temperature series as well as the upper and lower tails of each distribution, particularly in the second half of the period (1981-2003). The increased warming rates in this period are associated with more frequent warm extremes and fewer cold ones, particularly at Dhahran and Madinah. The daily large-scale atmospheric circulation in the wet season (October-May) is found to be well represented by 12 weather types derived from NNR mean sea level pressure data. The identification scheme is based on a Principal Component Analysis technique, which provided the main modes of variability over the region. The identified types are consistent with the recognised synoptic situations at the surface. The relationships between the weather types and the local surface climate are examined using local observational data. These indicate that types 5, 10 and 12 are wet and warm, while type 4 is dry and cold. Transitions between different weather types are also examined and discussion provided.

Présentation : EThOS (UK)

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