Among these, Pedgley's ( 1974) survey of weather and climate over the Red Sea found that along the coasts, “daytime sea breezes and night-time land breezes occur almost daily year round with some evidence that the leading edges of both sea and land breezes form meso-scale fronts separating the diurnal circulations from the broad-scale flow.” Pedgley further assessed that the sea breeze around the Red Sea reaches far inland, to distances ranging from 50 to 100 km. Yet, beyond remote sensing studies, sparse information has been advanced in the characterization of the diurnal cycle above the Red Sea and its regional LSBC in particular. In particular, it has been seen that regions with large amplitude diurnal cycles are principally concentrated in the Tropics (Gille et al., 2005), with the Red Sea having one of the largest diurnal oscillations in the Northern Hemisphere. Advances in satellite wind measurements have enabled the evaluation of LSBC amplitudes globally (Gille et al., 2003 Gille et al., 2005).
#LAND BREEZE FULL#
A full description of the elements comprising the LSBC, as well as a thorough review of previous studies on the subject is presented by Miller et al. In general terms, LSBCs occur in response to the differential heating between land and ocean surfaces which results in the development of mesoscale (2–2,000 km) horizontal pressure gradients driving cross-shore flow (e.g., Miller et al., 2003 Stull, 1988). Here, we focus on new observations in the Red Sea, a region where one of the strongest LSBCs in the world is found. LSBCs and their impacts are most prominent in tropical latitudes where they manifest year-round. It further influences the coastal ocean via effects on coastal upwelling and mixing which are essential to biological productivity (Clancy et al., 1979 Woodson et al., 2007). Through its modification of the atmospheric boundary layer, it plays a central role in regional climates via surface air quality (Arya, 1999, Miller et al., 2003, Simpson, 1994, Stull, 1988), chemical and dust transport (Kitada, 1987 Miller et al., 2003, Dacre et al., 2007), as well as mesoscale convective activity (Hill et al., 2010 Pielke, 1974). The land-sea breeze cycle (LSBC) is an integral part in the atmospheric and ocean dynamics of coastal regions worldwide. Convergence in the lateral moisture flux resulting from this air mass ascending the coastal topography (sea-breeze phase) as well as colliding with air masses from the opposing coastline (land-breeze phase) further resulted in cumulous cloud formation and precipitation. Specifically, the advance and retreat of marine air mass was directly tied to the development of internal boundary layers onshore and offshore throughout the period of study. Observed and simulated conditions also reflected distinct gravity-current characteristics of the intrinsic moist marine air mass during both phases of the LSBC. In the model, the amplitude of the LSBC is significantly larger in the vicinity of the steeper terrain elements encircling the basin, suggesting an enhancement by the associated slope winds. Weather Research and Forecasting climate downscaling simulations and satellite measurements are used to extend the analysis. Observed onshore and offshore features of both the land- and sea-breeze phases of the cycle are presented, and their seasonal modulation is considered. During a 26-month data record spanning 2008–2011, observed LSBC events occurred year-round, frequently exhibiting cross-shore wind velocities in excess of 8 m/s. Unique in situ observations of atmospheric conditions over the Red Sea and the coastal Arabian Peninsula are examined to study the dynamics and regional impacts of the local land-sea breeze cycle (LSBC).
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