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University of Belgrade (2014)

Analysis of the cumulonimbus clouds characteristics and the efficiency of the precipitation enhancement over the eastern area of the UAE

Al Mandoos, Abdulla A. Y.

Titre : Analysis of the cumulonimbus clouds characteristics and the efficiency of the precipitation enhancement over the eastern area of the UAE

Auteur : Al Mandoos, Abdulla A. Y.

Université de soutenance : University of Belgrade

Grade : Doctor of Philosophy (PhD) 2014

Résumé
The water resource community in the United Arab Emirates (UAE) has had a growing concern about the sustainability of its fresh groundwater resources over longer than the last two decades. In order to enhance precipitation the concept of cloud-seeding is to seed with appropriate cloud condensation nuclei (CCN) or ice nuclei (IN) to either make precipitation develop or more efficiently. A major effort during realization of this research was the development of an infrastructure : a networks of radars and automatic weather stations, an instrumented aircraft with trace gas, aerosol and cloud microphysical instrumentation to determine the background aerosol characteristics of the region and their influence on cloud and precipitation processes. A significant part was intensive collection of observational data including aircraft, radar, surface measurements and satellite.
Measurements of CCN showed that background levels were enhanced due to local pollution sources in the region, which resulted in higher cloud droplet concentrations in clouds, making them more continental in nature. The polluted background particles generally work to suppress precipitation development. When desert dust exists in conjunction with sulfates, the dust particles become coated with sulfate, making them more active as cloud condensation nuclei. When the general weather conditions where not favorable for development of strong convection the convective clouds are developed, mainly inland, along the coast line and some on the western slopes of Oman mountain. The most favorable local conditions for cloud development occur on the sunlight side of Oman mountain. Cb clouds also develop on the front side of the sea-breeze circulation. The sea-breeze circulation was the trigger mechanism for many Cb clouds.
The accumulated precipitation of convective clouds are obtained by using two methods of measurements, with rain gauges and by radars. The high discrepancies in the precipitation amount are found because the precipitation data taken from rain gauge network is poorly depicted due to the limited resolution and that the radar measurements highly overestimate the rain gauge data due to evaporation of precipitation from the level of radar measurement to the ground. The results of analysis of precipitation from two methodology of measurement give sufficient confidence to conclude that both, rain gauge and radar data are needed for better reproduction of the areal accumulated convective precipitation over a small area during convective precipitation events

Mots clés : Storms ; Cloud condensation nuclei ; Accumulated convective precipitation ; Microphysical instrumentation ; Radar measurement ; Cloud lifetime, Cloud displacement

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Page publiée le 6 mars 2015, mise à jour le 3 août 2017