Prof Subimal Ghosh, Professor at the Department of Civil Engineering, Indian Institute of Technology Bombay (IIT Bombay), has been awarded the Shanti Swarup Bhatnagar Prize 2019 by the Council of Scientific and Industrial Research (CSIR). This award recognises his significant contributions to our understanding of how land surface processes influence the Indian monsoon, as well as for improving regional monsoon simulations and predictions.
The Shanti Swarup Bhatnagar Prize, named after the founder Director of CSIR, is a prestigious award in Science and Technology in the country. As a recipient of this award in the Earth, Atmosphere, Ocean and Planetary Science category, Dr Ghosh will receive ₹5,00,000 as prize money, a citation and a plaque and a fellowship of ₹15,000 per month until the age of 65.
"I am taking the award on behalf of my students; it is all their good work. In fact, I learn from my students every day," says an ecstatic Prof. Ghosh. "I would like to acknowledge my PhD advisor, Prof Pradeep Mujumdar from the Indian Institute of Science, Bengaluru. I am very grateful because he taught me everything I know about research and to never compromise on quality," he adds.
Prof. Ghosh's work focuses on the areas of hydro-climatology and hydrology. Hydro-climatology is the study of how climate influences the water cycle and hydrology is the study of water on and beneath the surface of the Earth. It also includes studying the different forms of water in the water cycle, like water vapour, moisture and oceans, their movement and their chemical and physical properties.
The water cycle has multiple components and processes—atmospheric processes, land processes and oceanic processes. Perturbations in any of these affects the entire cycle. For example, the leaves of plants return water vapour to the atmosphere through a process called transpiration, which is essential for the proper functioning of the water cycle. Due to deforestation, there is a significant decrease in this process, which affects rainfall over that region.
Prof. Ghosh and his group are using theoretical and experimental knowledge of climate studies to solve today's climate crises of floods and heatwaves. He led a major project to design the first-ever 'expert system' to forecast floods after the 2015 Chennai floods. This system was developed in a record time of one and a half years, and it can be adapted to other cities like Mumbai and Kolkata.
Prof. Ghosh and his team have also looked at the link between monsoon and deforestation. Monsoon is a product of large-scale circulation mostly from the moisture coming from the ocean. The effect of land had been neglected in monsoon science. Therefore, Prof. Ghosh and his student Dr. Amey Pathak, in collaboration with Dr Praveen Kumar from the University of Illinois at Urbana–Champaign, developed a Lagrangian approach to track the moisture's source. A Lagrangian approach is a fluid dynamics technique by which individual water particles are marked, and their positions and velocities are described as a function of time, thus allowing their precise source to be located. The study found that during the last two months of the monsoon, 20% of the rainfall was due to land evaporation, not just evaporation from the ocean. By coupling the community land usage pattern to their weather research and forecasting models, the researchers could quantify the decrease in rainfall due to deforestation.
Scientists use General Circulation Models or GCMs for many simulation-based climate studies. National level rainfall models are unable to capture regional-scale weather phenomena. Instead, these models are useful in predicting average rainfall over the whole country. For example, in 2019, the national-level rainfall was above average. However, the rains over Odisha and West Bengal were deficient, resulting in drought. Prof Ghosh and his team have developed statistical downscaling algorithms for capturing regional-level climate change information from GCM simulations. They have used regional hydro-meteorological projections over India at river basin scale.
With a broader crisis of climate change looming, every attempt to understand the underlying dynamics help us be prepared to face the consequences. As India depends on the monsoon for most of its water needs, more studies on understanding climate interactions are necessary.
"Interdisciplinary research is needed to understand the complete water cycle," says Prof. Ghosh. "We need to develop techniques to predict better and analyse India's rainfall. To achieve this, we have to work together," he concludes.