Summertime secondary convection and interaction with sea‐breeze circulations

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AbstractSummertime convection in the arid United Arab Emirates (UAE) is mostly confined to the eastern and northeastern sides of the country, known as primary convection. Convection can also occur in the drier central and western parts of the country; this is called secondary convection. However, the mechanisms behind the latter are still not fully understood, even though it represents a crucial water source in the hotter months. To this end, a series of real‐case and semi‐idealized numerical simulations are performed to explore the role of sea breezes emanating from the nearby water bodies in triggering convection. We found the primary convection is mostly driven by convergence of the sea breezes from the Sea of Oman and Arabian Gulf with the topography‐driven circulations at the Al Hajar mountains. When the Arabian Gulf sea breeze is removed, which is achieved by replacing the water body with flat desert land, the convection is weaker. Secondary convection is triggered by the convergence of the sea breeze from the Arabian Gulf with the circulation associated with the Arabian heat low (AHL). In the absence of the Arabian Gulf sea breeze, it develops in response to low‐level convergence within the southerly monsoon flow reinforced by the AHL's circulation. It is fed by moisture from the Arabian Sea advected by the southerly flow into the UAE enhanced by surface evaporation. The sea breeze from the Sea of Oman plays a minor role in the secondary convection. Sensitivity experiments confirmed these findings. The results presented here stress that any variation in the characteristics of the sea breezes, such as through changes in surface properties (e.g., land‐use land cover), will impact the nature and intensity of the primary and secondary convection in the UAE. However, summertime convection will continue to occur, owing to favourable dynamic and thermodynamic conditions at regional scale.