Skip to main content

INDIAN OCEAN WARMING CAUSE FOR MONSOON WEAKNESS

Rapid warming of the Indian Ocean in the past century has led to a significant decrease in summer monsoon rainfall over the central-east and northern regions of India, a new study led by an Indian scientist said today. An international team of researchers led by Dr Roxy Mathew Koll, from the Indian Institute of Tropical Meteorology (IITM), Pune, found that the summer monsoon rainfall during 1901-2012 showed a weakening trend over parts of South Asia. The reduction in rainfall was significant over the central-east and northern regions of India, along the Ganges-Brahmaputra basins and the Himalayan foothills. In the study published today in the journal Nature Communications, the researchers reported that the reduction in summer rainfall over central-east India during the past century is about 10 to 20 per cent. "The Gangetic plains of India are the most heavily populated, and where agriculture is still largely rain-fed. Hence a significant reduction in rainfall over this region can be detrimental to the socio-economic livelihood in this region," Koll told PTI. The researchers used climate model experiments to demonstrate that the reduction in rainfall is linked to the rapid warming of the Indian Ocean, especially its western part, during the past century. The Indian Ocean warming, along with a relatively subdued warming of the Indian subcontinent, has played a key role in weakening the land-sea thermal contrast, a major driver of the South Asian monsoon, researchers said. Under the global warming scenario, the monsoon drivers are supposed to get stronger, which should result in increased rainfall. One of the major monsoon drivers is the land-sea temperature difference in summer, which drives the monsoon circulation towards the subcontinent. Previous studies suggested that the land in the northern hemisphere is warming much faster than the oceans, which implies that the monsoon driver should be getting stronger. Also, the rising ocean surface temperatures entail increased moisture availability in the atmosphere due to increase in evaporation and moisture holding capacity of air. Increased land-sea temperature contrast and moisture availability hence, should increase the monsoon rainfall. However, that is not the case for the South Asian monsoon, the study found.
The researchers said that contrary to what earlier studies have found, the land-sea thermal contrast over the South Asian domain has in fact reduced in the past decades. This reduction in land-sea temperature is primarily contributed by a strong warming in the Indian Ocean. The surface warming in the Indian Ocean, especially that in the western regions, have reached values of up to 1.2 degrees Celsius during the past century, much larger than the warming trends in the other tropical oceans. Apart from the ocean warming, a part of the decrease in land-sea temperature difference is also due to suppressed warming over the Indian land mass, possibly due to increased aerosols or reasons which are still uncertain, researchers said. The warming Indian Ocean also plays a role in weakening the monsoon circulation. Increased warming in the ocean enhances the large-scale upward motion of warm moist air over the equatorial ocean. This enhanced upward motion over the ocean is compensated by subsidence of dry air over the subcontinent, inhibiting convection and rainfall over the Indian landmass. "This means that a warming Indian Ocean has resulted in enhanced rain over the ocean but at the cost of rainfall over land, thereby drying the Indian subcontinent," Koll said. The study noted that climate models suggest that Indian Ocean will continue to warm under increasing greenhouse gases. It remains to be seen whether this will weaken the monsoon further. The researchers at IITM are working to address questions such as these. "We have developed an Earth System Model at IITM, which will be the first climate model from South Asia contributing a set of climate simulations for the next Intergovernmental Panel on Climate Change (IPCC) Assessment Reports," Koll said. "Development of this model is carried out with a focus on the Indian monsoon, and future climate projections for the monsoon region may be available in two to three years," he added. The study was part of an Indo-French collaboration under the National Monsoon Mission setup by India's Ministry of Earth Sciences. Koll conducted the research in collaboration with other IITM scientists Ritika Kapoor, Ashok Karumuri and B N Goswami. The research team also included Raghu Murtugudde at the Earth System Science Interdisciplinary Center (ESSIC) at the University of Maryland, College Park, US, and French scientist Pascal Terry at Sorbonne University.

Comments

Popular posts from this blog

JIO TARIFF CICK FOR TELECOM STOCKS

Telecom stocks today surged up to 8 per cent after the recent increase in Reliance Jio tariffs, which is largely seen as positive for the sector. Shares of Bharti Airtel jumped 4.99 per cent to close at Rs 497.50 on BSE. Bharti Airtel was the biggest gainer among the 30-share index components. The scrip of Idea Cellular soared 7.74 per cent to end at Rs 98.15 and Reliance Communications zoomed 7.60 per cent to Rs 17.70. Reliance Jio made its service dearer by about 15 per cent for its popular 84-day plan at Rs 459 from October 19, under which subscribers get 1GB 4G data at high speed per day. The company restructured its various schemes by reducing their validity period. The recent increase in Reliance Jio tariffs will increase its average revenue per user by up to 20 per cent and is a positive for the telecom sector, which is seeing a rapid consolidation, says a Philip Capital report. Established telecom sector players have seen huge reduction in their margins. Idea Cellular and Reli…

INVESTORS RICHER BY Rs. 25 LAKH CRORES IN SAMVAT 2073

Stock markets ended on a flat note on Wednesday, just below their record highs, but finished Samvat 2073 with robust gains of over 16 per cent. Equities added over Rs 25 lakh crore to investors' wealth this Samvat year. The benchmark Sensex has gained 4642.84 points, or 16.61 per cent, in the Hindu Samvat year 2073, while the broader NSE Nifty surged 1572.85 points, or 18.20 per cent during this period.
Small loss in last session
In the last session of the Samvat 2073 on Wednesday, the 50-share Nifty fell by 23.60 points or 0.23 per cent to close at 10,210.85 after moving between 10,175.75 and 10,236.45. The Sensex resumed lower at 32,518.56 and fell further to a low of 32,462.85 before ending at 32,584.35, down 24.81 points or 0.08 per cent. Investors adopted a cautious approach ahead of the long Diwali weekend, while a weak rupee too affected sentiment, brokers said.
- Axis Bank emerged as the worst performer among Sensex components, tumbling 9.52 per cent following a spike in ba…

BIRLAS ENTER TOP LEAGUE WITH $50 BILLION M CAP

The Aditya Birla group has entered the top valuation league with a market cap of over USD 50 billion post listing of financial services arm Aditya Birla Capital (ABCL), but Tatas remain on top with over USD 132 billion.
The combined market valuation of the Kumar Mangalam Birla-led listed companies stood at Rs 3,42,354.87 crore (USD 53.5 billion) at the end of Friday's trade.
Among various listed companies of the group, UltraTech Cement's valuation stood at Rs 1,10,097.70 crore at the end of Friday's trade while that of Grasim Industries was Rs 76,881.73 crore.
The newly-listed Aditya Birla Capital's market capitalisation was over Rs 55,000 crore, Hindalco (Rs 54,607.09 crore), Idea Cellular (Rs 32,064.91 crore), Aditya Birla Fashion and Retail (Rs 13,155.73 crore) and Aditya Birla Money (Rs 547.71 crore).
Among Indian conglomerates, the Tata group remains on the top in terms of total valuation of listed firms with about Rs 8,46,567 crore (USD 132.5 billion).
There are 29 pu…