Air–sea interactions and dynamical processes associated with the midsummer drought

摘要: Summer precipitation over most of the tropical Americas exhibits maxima in June and September, a relative minimum July. The summer northeastern (NE) Pacific is known as midsummer drought (MSD). Several theories have been put forward to explain origin MSD, but them fail at addressing simultaneously various elements that characterize it. temporal evolution NE warm pool Intra-Americas Seas (IAS) related, not result same process. Over pool, convective activity closely related sea surface temperature (SST) variations, whereas IAS, Caribbean low-level jet (CLLJ) with maximum intensity July appears be key factor. CLLJ produces ‘gap flow’ Central America reaches stronger easterly winds. This flow leads decrease SSTs westward shift moisture convergence combined subsidence MSD. At exit region, intense convection enhances during reducing chances large-scale circulations, such North Atlantic Subtropical High (NASH) inhibit entire Americas. strong ascending motion off coast Nicaragua Costa Rica contributes enhanced surrounding regions As western weaken August increases once more second completes two peaks distribution precipitation. Therefore, fluctuations appear dynamical element