[AAS04-P07] Cloud properties over Arid and Semi-arid regions and their seasonal and diurnal variability from Meteosat satellites
Keywords:Clouds, Meteosat, Arid and semi-arid regions
The seasonal cycle of cloud amount over the UAE and adjoining regions are subjugated by two distinctly different meteorological regimes in winter and summer by the extra-tropical and tropical forcings, respectively. This is clearly reflected in the cloud occurrence where the percentage of high- and mid-level clouds is relatively high during winter than summer due to a strong influence of extra-tropical circulations in the upper troposphere, while the low-level cloud amount is relatively high during the summer. However, the occurrence frequency of clouds is high along the Al Hajr Mountains located in the eastern part of the UAE and the Oman region irrespective of season indicating orography-generated clouds. We also discussed the diurnal variation of the clouds with respect to the liquid water path. The diurnal cycle shows two peaks: one in the morning and other in the late afternoon and post-sunset periods. This indicates a bimodal distribution of occurrence of clouds. Further, the bimodal distribution is independent of the season, implying a strong influence of local factors (sea breeze, winds, topography, solar radiation etc.) for the existence of the bimodality. Finally, we also discuss the microphysical properties of precipitating and non-precipitating clouds over these arid and semi-arid regions.