South Asia and Adjacent Ocean Environments

Shielding from frigid air by theMountainsHimalaya Himalaya MountainsHimalaya Mountains and the Tibetan Plateau causescontinental tropical continental tropical (cT), maritime equatorialmaritime equatorial (mE), and maritime tropicalmaritime tropical (mT) air massesHumidityand Africaand air masses to dominate South and Southeast AsiaTropical Wet-dry (Aw) climatein and around Africain and around Southeast Asia. Monsoonal circulation creates a strong summer precipitation maximum in most of the region, with temperatures commonly peaking immediately before the wet monsoon onset. Much of Arid (B climate) northwest and south-central parts of South AsiaAsia receive a somewhat higher percentage of precipitation in winter than elsewhere in the region. Northern Indian precipitation totals increase from west to east as the northwestward bending of the southwesterly counter-tradesSouthwesterly counter-trades advects Bay of Bengal moisture onshore. Southern Indian precipitation totals decrease from the west coast to the south-central peninsula, because of orographic and rain shadow effects of the Western GhatWestern Ghats Mountains. From north to south, Mesothermal Winter Dry–hot summer (Cwa), Tropical Wet-dry (Aw), Tropical Monsoon (Am), and Tropical Rain Forest (Af) climates dominate South AsiaAsia and adjacent waters. Southeast AsianTemperatureand Indian Ocean Dipole temperature and precipitation patterns resemble those of adjacent South Asian latitudes, but some eastern coastalcoastal areas are partially blocked from summer monsoonal flow. ThePositive phase (Indian Ocean Dipole) Indian Ocean Dipole (IOD) and Madden–Julian Oscillation (MJO) areTrade windsand Indian Ocean Dipole important sources of inter- and intra-annual climate variability.