Tag: precipitation

Climate Change Signals from North-Eastern India, the Wettest Place on Earth

In a recent study, researchers from IIT Kharagpur have observed a significant change in the rainfall in the northeast in general and specifically at the wettest place on Earth, Cherrapunji-Mawsynram.

The researchers observed rainfall changes in the past century (1901–2019) over the wettest place on the Earth and unveiled the first evidence for the signals of climate change and anthropogenic influence on rainfall changes in the region.

Image: The figure shows the study region and rainfall received at Cherrapunji and Mawsynram in the past 50 years. The spatial change in rainfall shifted the wettest place on the Earth from Cherrapunji to Mawsynram in the early 1980s.

The analysis of 119 years of rainfall data at 17 stations in Northeast India revealed that most of the stations show negative trends in rainfall, the highest in the summer monsoon and the smallest in the winter. A clear shift in the rainfall pattern is observed in the mid-1970s. This abrupt shift in the rainfall can be attributed to the climate shift that occurred in the Pacific Ocean.

The large variability and rapid warming associated with climate change in the equatorial Indian Ocean and associated atmospheric circulation patterns, and the changes in land use/land cover are the main reasons for the inter-annual variability and negative trends in the rainfall in the northeast region, particularly at Cherrapunji and Shillong.

The seasonal rainfall cycles at these locations are also found to be changed one month ahead as compared to that before 1973. The spatial shift in the rainfall from Cherrapunji to Mawsynram in the early 1980s can also be viewed as a part of the above-mentioned temporal change and the westward movement of rainfall there.

The expansion of western subtropical Pacific high is another reason for this rainfall pattern change.

“The analyses uncover signals of regional climate change in India. Since the changes in the rainfall amount would affect drinking water, irrigation, agriculture, energy production and the economy of our country, this study cautions us about the impact of imminent climate change in our country,” says researcher Dr. J Kuttippurath, Assistant Professor, Centre for Oceans, Rivers, Atmosphere and Land Sciences (CORAL). 
Northeast India houses about 64% forest, 30% under the Brahmaputra valley and the rest has steep slopes, hills and mountains. The region has the highest vegetation cover in India and is one of the 18 biodiversity hotspots of the world; indicating the importance of the region in terms of its greenery and climate change sensitivity. Agriculture and allied activities form the backbone of the economy in the region, where more than 60% of the crop area is under rain-fed agriculture.
“The northeast region is well known as the wettest region of the world because it receives nearly 2000 mm of rainfall annually, which is about three times higher than the mean annual rainfall of India. Furthermore, the population of this region mainly depends on agriculture and horticulture, which is fed by the seasonal rainfall and therefore, any change in the rainfall would alter the economy and affect the well-being of the society,” remarked Prof. Madan Kumar Jha, Professor, Dept. of Agricultural and Food Engineering.
Citation J Kuttippurath et al 2021 Environ. Res. Lett. 16 024018, Journal: Environmental Research Letters [Impact Factor: 6.09], DOI: https://doi.org/10.1088/1748-9326/abcf78

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About IIT Kharagpur: Indian Institute of Technology Kharagpur is a higher educational institute known globally for its graduate output and affordable technology innovations. Set up in 1951 in a detention camp as an Institute of National Importance, the Institute is ranked among the top five in India and has been awarded Institute of Eminence by the Govt. of India in 2019. The key areas of research of IIT Kharagpur are Affordable Healthcare Technologies, Advanced Manufacturing, Advanced Transportation, Precision Agriculture and Food Technology, Cyberphysical Systems, Ecology & Environment, Mining, Water Resources and Architecture. The Institute is engaged in several international and national mission projects and ranks significantly in research output including 50-100 IPR filed annually and about 2000 research publications in top journals and conferences. At present, the Institute has about 750 full-time equivalent faculty members, more than 14000 students and over 70000 Alumni. For more information visit: www.iitkgp.ac.in

Study Reveals Southward Shift of Precipitation Extremes over South Asia

Has your monsoon experience across India changed over the years?

The reason could be blamed on shifts in the spatio-temporal pattern of monsoon. In a recent study published in Scientific Reports by Nature Publishing Group, IIT Kharagpur researchers reveal that the pattern of monsoon and daily extreme rainfall is changing in India with more extremes expected over southern India and Himalayan foothills. They further predicted a continued southward shift of precipitation extremes over South Asia. 

The researchers have studied data of Indian Summer Monsoon precipitation for close to five decades, 1971 – 2017 (base period: 1930-1970). The data shows more increase in the magnitude of extreme precipitation over South India  (~18.5 mm/day for the worst climate change scenario) compared to Northern and Central India (~2.7 mm/day). 

“Our analysis of precipitation from the Coordinated Regional Downscaling Experiment, indicates a southward shift of precipitation extremes over South Asia. For instance, the Arabian Sea, South India, Myanmar, Thailand, and Malaysia are expected to have the maximum increase to about 18.5 mm per day for an RCP8.5 scenario in mean extreme precipitation,” said lead researcher Prof. Rajib Maity from the Dept. of Civil Engineering. 

Refer to the journal paper: Suman, M., Maity, R. Southward shift of precipitation extremes over south Asia: Evidences from CORDEX data. Sci Rep 10, 6452 (2020). https://doi.org/10.1038/s41598-020-63571-x

PhD student Mayank Suman, co-author added, “We based our predictions on average precipitation for the days with more than 99th percentile of daily precipitation. Our study showed a contrasting feature for North and Central India, and Tibetan Plateau with relatively less increase, to only about 2.7 mm per day for RCP8.5 scenario.”

Talking about the possible reason behind such a significant phenomenon, Prof. Maity remarked on the intensification of large-scale circulation phenomena over the tropical Indian Ocean (known as Indian Ocean Dipole) which could be leading to the contrasting trends across large regions in India. As a result of this intensification the Indian monsoon is expected to be enhanced across the country. The prediction is based on the analysis of air temperature at 850 mb and precipitable water for RCP4.5 and RCP8.5.

“Our convergence analysis along with the moisture flux show a change in the direction of the South-West Monsoon winds blowing towards the east over the Indian Ocean. This directional change will intensify the already observed precipitation contrast in future between South and North India, and cause more extreme precipitation events in countries like Myanmar, Thailand, Malaysia, etc.” remarked Prof. Maity

What could be the socio-economic impact of such change, particularly in the context of India? 

Prof. Virendra Tewari, Director, IIT Kharagpur, who has extensively worked with both industrial and rural sectors opined on getting ready for the monsoonal shifts based on predicted timelines and precipitation volume.

“South Asia, as we know, despite advances in irrigation systems, is highly dependent on the monsoons. Results of this study will be useful to the designers of water infrastructure and agricultural communities, especially in the southern parts of India and Himalayan foothills, to prompt a possible change in design criteria and agricultural practices including cropping pattern,” he said. 

Media Coverage:

Hindustan Times Financial Express Danik Jagran
Deccan Herald Outlook Navbharat Times
Yahoo News Asian Age Deccan Chronicle
Nature India The Weather Channel

Project information: Prof. Rajib Maity, Dept. of Civil Engineering,rajib@civil.iitkgp.ac.in; 

Institute Information: Prof. B N Singh, registrar@hijli.iitkgp.ac.in;

Media Outreach: Shreyoshi Ghosh, shreyoshi@adm.iitkgp.ac.in; 

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