Seasonal climate summary southern hemisphere (spring 2002): the El Niño reaches maturity and dry conditions dominate Australia

Atmospheric and oceanic conditions in the southern hemisphere are reviewed for the 2002 austral spring season. Particular emphasis is given to the Australian and Pacific regions. The El Niño event that emerged in the equatorial Pacific Ocean during autumn and winter reached its peak late in the spring of 2002. Ocean surface and sub surface temperatures in the tropical Pacific remained well above normal throughout the period, driving changes in the overlying Walker circulation and hence modifying many atmospheric parameters, including cloudiness, winds and surface pressures. Teleconnections ensured that such changes induced remote impacts throughout the southern hemisphere. The El Niño event, its growth earlier in the year, the start of its decay late in spring as well as its broadscale modification of the southern hemisphere atmosphere, was highly consistent with theoretically expected behaviour. For Australia, widespread dry conditions dominated the country, with low cloud amounts and a southwards shift in the westerlies; both consistent with the impacts of an El Niño in the Pacific. The generally low rainfall during spring was further exacerbated by very high maximum temperatures and hence greatly increased evaporation, consolidating the event as one of the worst Australian droughts in recorded history. Over the Antarctic, the springtime ozone hole expanded to its smallest size since 1988, reaching only 19 million square kilometres before splitting into two regions.