June 18, 2012 ( a commentary on 2012 Monsoon progress over India) by Madhav Khandekar ((retd scientist Environment Canada & IPCC Reviewer 2007)
Indian Monsoon 2012: After a delayed start and playing “hide & seek”, monsoon rains seem poised to soak Peninsular India (18 June 2012)
The South-West (SW) Monsoon arrived at the southern tip of India (in the State of Kerala) on June 5th against the normal date of June 1st. The “arrival criteria” used by the India Meteorological Department (IMD) is based on reported rains ( of amount 2.5mm or more) at 60% of selected locations in Kerala State for two consecutive days. Following the declaration of Monsoon arrival by the IMD, further progress of the rains into the interior of the Peninsula stalled once again ( as it did in June 2009) and this has caused anxiety among many agriculturists and policymakers who monitor the progress of the SW monsoon for socio-economic planning. The SW Monsoon rains are the most important rains for India’s agricultural sector, which accounts for 15 to 20% of India’s economy today and employs up to 50% or more people in rural areas plus many more elsewhere (possibly up to 500 Million people). The SW Monsoon is also the most important climate event on an annual basis for the entire Indian subcontinent and its seven Nations (India, Bangladesh, Bhutan, Myanmar/Burma, Nepal, Pakistan & Sri Lanka) with a total population of about 1.75 billion people!
What caused the stalling of monsoon progress after June 5th? A lack of general convective activity in the Bay of Bengal which is now identified as the key area for providing well distributed rains during June, the first month of the SW monsoon season. The lack of convective activity was probably due to the evolving El Nino phase in the equatorial Pacific plus possibly an unfavorable phase of IOD (Indian Ocean Dipole), which together with the ENSO Phase modulate the convective activity in the Bay of Bengal. In 2009 a significant lack of such convective activity led to a deficit of 54% in June rainfall which could NOT be overcome during the rest of that season (June-September 2009) and this made the 2009 monsoon a major drought year. The latest satellite map (June 18 2012) from the Indian satellite INSAT shows developing convective activity over the Bay and also in the Arabian Sea in the west ‘bringing in’ moisture to many west coast locations like Mumbai, Goa, Mangalore & Cochin. Per latest communiqué from the IMD, ‘A low pressure area may develop over the northwest Bay of Bengal leading to increase in rainfall activity over Andhra Pradesh ( on the east coast) and adjoining central India and east Uttar Pradesh’. The satellite map does show signs of a developing low pressure which may bring in much-needed rains over most of the Peninsular India and also in the north, especially in the Gangetic Plains & in the Himalayan foothills, which is the agricultural heartland of India with a regional population of over 200 Million. The map at the top of the post shows the latest position of the ‘Monsoon progress” over the Indian subcontinent.
In the last three days, Mumbai (India’s largest city, population ~27 Million) received over 15 cm of rains, Goa over 25 cm, Mangalore and Cochin at about 12cm. Also interior cities like Bangalore (7 Million) and Hyderabad (8 Million) have been getting sporadic rains and bringing down maximum temperatures (by 3C to 5C ) as the low to mid-level cloud cover increases with monsoonal flow. Hyderabad recorded max temp of over 40C for several days during latter half of May and also in early June, while Bangalore recorded max temp of about 30-31C for a few days in May and June so far. ( Bangalore being at an elevation of over 1000 m has in general a moderate summertime climate). Northwest India is still sweltering in hot and humid conditions with max temp at 40C and above in New Delhi and vicinity.
Most climate models from UK and US have projected a below normal (possibly ‘significantly’ below normal) monsoon for 2012. Among the large-scale factors that adversely impact Indian Monsoon are: El Nino, heavier Eurasian snow cover in the previous winter, easterly phase of the QBO ( Quasi-Biennial Oscillation of the equatorial stratosphere) and unfavorable (west-to-east) phase of the IOD. With a developing El Nino, an easterly QBO Phase and higher than normal Eurasian snow cover the prospect of “above normal” monsoon this year seems rather small at this time. However, a possible favorable IOD phase later may help enhance convective activity in the Bay of Bengal which may help bring this year’s monsoon close to normal. The IMD has projected this year’s monsoon rains to be about 97% of the long-term normal (~90 cm for the country as a whole). How the monsoon evolves over next several weeks remains unclear at this time.
From a socio-economic perspective of many south Asian countries, timely arrival and evolution of the Indian Monsoon is very critical. Many aspects of this complex climate event are not fully understood so far. There is an urgent need for a significantly improved understanding and simulation of Indian Monsoon, the most important regional climate event for south Asia.
Acknowledgements: I am grateful to Roger Pielke sr for encouraging me to prepare this commentary. Thanks are also due to my wife Shalan for helping me extract the Figure from the IMD website.