Tag: Geophysics

Devastating Aftermath of Cyclones

Isotope studies by IIT Kharagpur and Academia Sinica, Taiwan scientists shed light on how the cyclones sustain their energy.

Cyclones are increasingly becoming perilous to the coastal populations of the subcontinent. Climate change due to global warming, projects that the frequency of category 4 and 5 storms (60 to >70 m/s sustained wind speed) will be doubled by the end of the 21st century. However, the question remains: why some cyclones are devastating while others are not? What controls the intensity of cyclonic winds and rains? Cyclones are gigantic vortex, 500-700 km in diameter and 20 km in height, which form when sea surface temperature is higher than normal. They get their energy from evaporation of the underlying seawaters, forming spirally rotating rain bands around the centre called eye where the winds are strongest. The latent heat released during conversion of vapor to rain acts as fuel and the raining vortex moves on.  However, one critical question has been bothering scientists: what is the exact mechanism and the source that supply moisture to the cyclone? Is it evaporation alone from the sea beneath, or the pre-existing atmospheric vapors?

The scientists from IIT Kharagpur and Institute of Earth Sciences, Academia Sinica, Taiwan have found the exact mechanism and the source that supply moisture to the cyclones. The research analyses the devastating aftermath of cyclones in respect to Cycle Sitrang which made its landfall on Bangladesh on 25 October 2022 . The study indicates that the cyclone movement through the atmosphere continuously scavenges the existing vapour over the vortex cross-section much like a moving suction pump and provide the first experimental evidence of a theoretical model.

Prof. Anindyo Sarkar
Dept. of Geology & Geophysics
IIT Kharagpur

“West Pacific Ocean waters are the warmest in the world, producing nearly 30% cyclones of the world that routinely devastate Taiwan, China and Japan. There cannot be any better place to study the internal mechanism of these cyclones. In Chinese the cyclones are called ‘Typhoons’ (daaihfùng) meaning “great wind”. We have studied four such typhoons, named Nepartak, Meranti, Malakas and Megi of category 4/5, which devastated Taiwan in the year 2016. Billions of dollars of properties and lives were damaged in the due course which formed basis of this study. Our study indicates that the cyclone movement through the atmosphere continuously scavenges the existing vapour over the vortex cross-section much like a moving suction pump and provide the first experimental evidence of a theoretical model suggested by Russian atmospheric scientists,” said Sarkar” said Prof. Anindya Sarkar, Department of Geology & Geophysics and co-author of the research paper that has just been published in prestigious, ‘Journal of Geophysical Research Atmospheres of American Geophysical Union.’

Prof. Mao-Chang Liang
Academia Sinica
Taipei, Taiwan

“Flying experimental airplanes through the typhoons have been attempted but is pretty dangerous. To circumvent this, we placed a mass spectrometer on top of a tall building to continuously measure the isotopes of oxygen and hydrogen in the vapor as these typhoons approached Taiwan. This technique provided us real-time variation inside typhoons every ten minutes as it was raining and vapour compositions changed. Since both cyclone frequency and intensities are increasing due to on-going climate change, this observation will be very important while studying the tropical cyclones that recurrently hit both India and Taiwan/Japan region. It also opened up avenues for future collaboration between the two countries,” stated Prof. Mao-Chang Liang of Academia Sinica and the collaborator of the study.

Sourendra Bhattacharya,
Former Visiting Professor
IIT Kharagpur

Sourendra Bhattacharya, a former visiting Professor at IIT Kharagpur and the lead author of the paper cited,”Cyclones are extremely dynamic systems and rainfall as high as ~150 mm per hour is very common. As the cyclone moves, shedding of this enormous amount of rain causes a progressive reduction in the ratio of the isotopes of oxygen and hydrogen in the leftover vapor mass. We tracked this magnitude of reduction, calculated and modelled to see how much rains were scavenged by these moving cyclones.”

Typhoon Nepartak (left) and Megi (right) those devastated Taiwan in 2016 just like cyclone Amphan that struck Indian east coast in 2020 caused death, misery and destruction.

The mass spectrometer (right) that continuously measured isotopes on the top of Academia Sinica building (left) as the typhoons passed over.

Details of the paper: Vapor isotope probing of typhoons invading the Taiwan region in 2016 by S.K. Bhattacharya, Anindya Sarkar, Mao-Chang Liang. Journal of Geophysical Research Atmospheres, American Geophysical Union.

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022JD036578

Media Coverage :

The Print Career 360 Bizzbuzz

Contact Person: Prof. Prof. Anindyo Sarkar, Department of Geology & Geophysics, IIT Kharagpur
Email: anindya@gg.iitkgp.ac.in

Edited By : Poulami Mondal, Digital & Creative Media Executive (Creative Writer)
Email: poulami.mondal@iitkgp.ac.in, media@iitkgp.ac.in, Ph. No.: +91-3222-282007

Follow us: Facebook – IIT Kharagpur; Twitter – @IITKgp;  Instagram – @iit.kgp; LinkedIn – Indian Institute of Technology
For news visit: https://kgpchronicle.iitkgp.ac.in/ 

IIT Kharagpur Professor Abhijit Mukherjee has been inducted as a Fellow of the Geological Society of America

“Proud moment for IIT Kharagpur, Prof Abhijit Mukherjee, Associate Professor of the Department of Geology & Geophysics and School of Environmental Science and Engineering, has been inducted as a Fellow of the Geological Society of America (GSA) in the year 2021. I must mention that Prof Mukherjee is the first Indian who has got elected to the Fellowship of the prestigious GSA”, said Prof. Virendra Kumar Tewari, the Director of Indian Institute of Technology Kharagpur. “On behalf of the entire institute, I heartily congratulate Prof Mukherjee on his well-deserved achievements. Best wishes to bring more and more laurels for him and his profession. I look forward to many such recognitions and achievements from our faculty.”

Hydrogeoscience expert Prof Abhijit Mukherjee has directed a recent research work which was intended on groundwater insights. Prof Mukherjee has been awarded the prestigious Shanti Swarup Bhatnagar Prize for Science and Technology in the field of Earth Atmosphere Ocean and Planetary Sciences. Also he has been inducted as the Fellow of the Royal Society of Chemistry, UK. He has been selected by the Department of Science and Technology as one of the top fifty Indian scientists below fifty years age. In fact, he has been conferred the National Geoscience Award by the President of India. His book “Global Groundwater: Source, Scarcity, Sustainability, Security and Solutions” has been published by Elsevier.

Prof Mukherjee said, “I am humbled and honored to have been elected as a Fellow to the Geological Society of America (GSA). GSA, estd. in 1888, is regarded as one of the oldest, largest and most prestigious International geoscience societies across the world. I further feel honored to be one of the first person from any Indian institute to be elected for this prestigious Fellowship. GSA has defined Fellowship as an honor that is bestowed on the best of our profession. GSA members are elected to Fellowship in recognition of a sustained record of distinguished contributions to geosciences (www. geosociety.org). So, being recognized by my peers, internationally, is certainly a dream coming true.”

Before joining IIT Kharagpur as an Assistant Professor, he served as the Physical Hydrogeologist at Albert Geological Survey in Canada. Prior to that, he completed postdoctoral work at the University of Texas at Austin, USA. Early to it he served as the Research Assistant in Geology at University of Kentucky, USA and Instructor and Teaching Assistant in Geology at University of Kentucky in USA.

He earned his Master of Science (M. Sc) and Bachelor of Science (B. Sc) in Geology from University of Calcutta. Also, he pursued Master of Science (M.S) from University of Kentucky, USA. He then achieved the prestigious degree of Doctor of Philosophy from University of Kentucky, USA.

The Geological Society of America (GSA) is a global professional society with a membership of more than 20,000 individuals in more than 100 countries. GSA provides access to elements that are essential to the professional growth of earth scientists at all levels of expertise and from all sectors: academic, government, business, and industry. The Society unites thousands of earth scientists from every corner of the globe in a common purpose to study the mysteries of our planet (and beyond) and share scientific findings.

(Inputs from Rituparna Chakraborty, Branding Executive)

Contact: Paramita Dey, Junior Assistant

Email: media@iitkgp.ac.in, Ph. No.: +91-3222-282004

In the quest for the hidden past

Hindustan Times          Economic Times         India Today       The Hindu BusinessLine           Republic       Swarajya       The Sentinel Assam      The Week        Dainik Jagran             UNI          Yahoo News           Outlook                India TV              Times of India          Millennium Post

Indian researchers have for the first time connected the decline of Harappan city Dholavira to the disappearance of a Himalayan snow-fed river which once flowed in the Rann of Kutch. They have connected the dots between the growth and decline of the Dholavira, the most spectacular and largest excavated Harappan city in India located in the Rann with this river which resembles the mythical Himalayan River Saraswati. The study has just been published online in prestigious Wiley Journal of Quaternary Science.

Studies so far made were indirect attempts to find out the river courses, its connection to climate and civilization in areas far away from these ancient cities. But this research team from IIT Kharagpur, Archaeological Survey of India, Deccan College PGRI Pune, Physical research laboratory, and Department of Culture, Gujarat, dated archaeological remains from all the stages and also inferred climate shifts through time which led to the rise and fall of the Harappan city.

“Our data suggest that prolific mangroves grew around the Rann and distributaries of Indus or other palaeochannels dumped water in the Rann near southern margin of Thar Desert. This is the first direct evidence of glacial fed rivers quite like the supposedly mythological Saraswati, in the vicinity of Rann” said IIT Kharagpur’s Prof. Anindya Sarkar who led the research.

Dr. Ravi Bhushan and Navin Juyal from PRL, Ahmedabad dated the carbonates from human bangles, fish otolith and molluscan shells by accelerator mass spectrometer and found that the site was occupied from ~5500 years back i.e. Pre-Harappan period to ~3800 years before present i.e. Late Harappan period. The Dholavirans were probably the original inhabitants in the region, had a fairly advanced level of culture even at its earliest stage. They built spectacular city and survived for nearly 1700 years by adopting water conservation suggested the researchers. The study indicates that the city expanded till 4400 years followed by an abrupt decline nearly ~4000 years back, onset of the newly proposed Meghalayan geological stage.

Researchers Dr. R.S. Bisht and Y.S. Rawat from the Archaeological Survey of India who originally excavated the site concluded this based on degeneration of architecture, craftsmanship, and material culture.

Dr. Arati Deshpande Mukherjee of Deccan College pointed out at the climate evidence coming from high resolution oxygen isotopes in snail shells Terebralia palustris which typically grow in mangroves and was a source of food for the Dholavirans.

The lead author of the paper and a PhD student at IIT Kharagpur Torsa Sengupta said, “the early to Mature Harappan snail isotopes suggested that the mangrove was fed by Glacier River debouching in the Rann of Kutch. However, during late Harappan period the meltwater contribution and seasonality reduced coinciding with the fall of Dholavira.”

“Though the Dholavirans adopted excellent water conservation strategy by building dams, reservoirs and pipelines, but were pushed to the limit by a catastrophic Meghalayan mega-drought collapsing the city. Indeed Dholavira presents a classic case for understanding how climate change can increase future drought risk as predicted by the IPCC working group” added Prof. Anindya Sarkar.

The research indicates that the collapse of Harappan Dholavira was near-synchronous to the decline at all the Harappan sites in India as well as societal collapse of Mesopotamia, Greece, China and the Old Kingdom of Egypt.