STATE OF THE CLIMATE IN 2009

drew in the 3rd pentad of October. The intensityindex of the SCSM was -0.35, near normal. Fromthe 6th pentad of May to the 2nd pentad of August,the SCSM was stronger than normal, while aftermid-August it became weaker than normal (Fig.7.42). At the end of September, the warm and wetair swiftly retreated south of 25ºN, and hence by thethird pentad of October the summer monsoon hadwithdrawn from the SCS.3) South Asia—M.Rajeevan, A. K.Srivastava, and J.RevadekarCountries considered in this section include:Bangladesh, India, Pakistan, and Sri Lanka.(i) TemperaturesDuring 2009, South Asia experienced notablywarmer-than-normal conditions. January and Februarywere characterized by unusually high temperatures.Prolonged breaks during the summer monsoonseason also resulted in above-average temperatures,with many stations reporting their highest temperatureson record. Similarly, during the winter season,many parts of India and Pakistan experienced meantemperatures 3°C–5°C above their 1961–90 normal.The annual mean temperature for India was+0.91°C above average, making 2009 the warmest yearsince nationwide records commenced in 1901 (Fig7.43). This superceded the previous five warmest yearson record, notably 2002 (+0.71°C), 2006 (+0.60°C),2003 (+0.56°C), 2007 (+0.55°C), and 2004 (+0.51°C).January (+1.43°C) and August (+1.00°C) mean monthlyanomalies were also the highest since 1901, while theanomalies for February, September, and Decemberwere all second highest since records began. The recentdecade (2001–09) was the warmest decade on recordover India with decadal mean temperature of 0.59°C.Fig 7.42. Variation of pentad zonal wind index over the monitoringregion (10°N–20ºN, 110°E–120ºE). Red open bars areclimatology (Unit: m s –1 ) (Source: China Meteorological Administration.)S176 | juNE 2010Fig 7.43. Annual mean temperature anomalies (withrespect to 1961–90 normal) averaged over India for theperiod 1901–2009. The smoothed time series (9-pointbinomial filter) is shown as a continuous line.(ii) PrecipitationThe summer monsoon season (June–September)contributes 60%–90% of the annual rainfall overmajor portions of South Asia. In 2009, South Asiaexperienced one of its worst droughts since recordsbegan in 1875.For India, the long-term average (LTA) value ofthe summer monsoon rainfall, calculated usingall data from 1941 to 1990, is 890 mm. For 2009,the summer monsoon seasonal rainfall over Indiawas only 78% of its LTA value, marking 2009 asthe driest monsoon season since 1972 (76% ofLTA). During the season, most parts of the countryexperienced large rainfall deficiencies (Fig. 7.44). Theonset phase of monsoon 2009 was characterized by anearly onset (23 May) over the southern parts of India.However, the formation and northward movementof tropical cyclone Aila over the Bay of Bengal andthe persistent intrusion of dry air into theSouth Asian region due to eastward movingmid-latitude troughs disrupted the northwardprogress of the monsoon. The slow progressof the monsoon resulted in a record rainfalldeficiency (47% below normal) for June overthe country. Rainfall activity during July wasnear normal with monthly rainfall of 96% ofthe LTA. However, rainfall activity was againsuppressed both in August (73% of LTA) andSeptember (80% of LTA), making the 2009summer monsoon season the second mostdeficient season since records began in 1875.During the season, of the 36 meteorologicalsubdivisions, only three received