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Document Type |
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Thesis |
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Document Title |
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The Impact of Interannual and Intraseasonal Tropical Oscillations on the Climate Variability over Arabian Peninsula تأثير التذبذبات المدارية البين - سنوية والبين - فصلية على تقلب المناخ على شبه الجزيرة العربية |
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Subject |
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Faculty of Meteorology, Environment and Arid Land Agriculture |
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Document Language |
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Arabic |
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Abstract |
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The interannual and intraseasonal precipitation variability over Arabian Peninsula (AP) has a significant impact on the regional water resources and agriculture sectors. The predictability of seasonal to subseasonal rainfall anomaly distributions and extreme rainfall events is a big challenge in the region. Mediterranean storms play the role of an atmospheric bridge between large scale atmospheric circulation patterns and the AP wet season (November to April) precipitation anomaly distributions. This thesis investigated the interannual and intraseasonal impact of El Niño Southern Oscillation (ENSO) and Madden-Julian Oscillation (MJO) on AP wet season precipitation. The Melbourne University objective cyclone tracking scheme was used to track the individual Mediterranean storms by using 500-hPa reanalysis geopotential height data. The Sea Surface Temperatures (COBE-SST) dataset was used for the purpose of correlation and regression analysis between the ENSO variability and AP precipitation. From the composite analysis, it was found that the frequency and intensity of East Mediterranean rainfall increase during ENSO warm phases. During El Niño events the subtropical jet shifts relatively southward from its climatological position, increasing both rainfall frequency and intensity over the East Mediterranean. This leads to low-level convergence and upper air divergence, and consequently to increased anomalous rainfall in the region. The reverse happens for La Niña events. During El Niño events, the vertically integrated moisture convergence and horizontal moisture transport from the Arabian Sea and the Red Sea both increase, which favours wetter conditions. Conversely, drier conditions are linked with the La Niña events. For intraseasonal climate variability, it was observed that MJO influences the daily rainfall variability of the Kingdom of Saudi Arabia (KSA) at periods between 40 and 75 days. The chance occurrence of extreme rainfall events in KSA during the wet season is larger during the deep tropical convection linked with MJO phases 1 and 8 (wet), and smaller during MJO phases 4 and 5 (dry). The wet and dry MJO phases are defined concerning wet and dry conditions in KSA. The analyses were further validated by constructing composites of daily precipitation rate anomalies during all MJO phases during the period of study. The atmospheric cyclonic circulation anomalies during the wet MJO phases favour more moisture convergence and moisture transport from the Arabian and Red Seas, which in turn leads to more extreme rainfall events. During the dry MJO phases, the atmospheric anticyclonic circulation anomalies provide unfavourable conditions for extreme rainfall events.
These findings help to explain the impact of ENSO and MJO on the rainfall variability of the Arabian Peninsula. The results can be used to improve deterministic forecasts on sub-seasonal to seasonal timescales over the Arabian Peninsula, which is important for risk management of climate hazards, and for the socio-economic, water and agricultural sectors. |
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Supervisor |
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Dr. Mansour Al Mazrouei |
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Thesis Type |
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Doctorate Thesis |
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Publishing Year |
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1440 AH
2019 AD |
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Added Date |
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Tuesday, January 22, 2019 |
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Researchers
| كامل شهزاد | Shahzad, Kamel | Researcher | Doctorate | |
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