Saikat Sengupta

Title : Understanding daily/monthly scale variation in hydro-meteorological processes during Indian Summer Monsoon through observed and model water isotope data

Abstract:

Stable isotopic ratio (²H/¹H and ¹⁸O/¹⁶O) of atmospheric vapour and rain change during various hydro-meteorological processes viz, evaporation, advection, condensation, moisture recycling, etc. The relationships between isotope ratio and various local meteorological parameters have long been used for climate reconstruction on different time scales. Several recent studies have further documented that the regional-scale atmospheric circulation primarily controls water isotope variability. Therefore, efforts have been made to simulate water isotope ratios constraining atmospheric circulation in various general circulation models (GCM). The historical simulations of these models are often compared with the isotope ratios of various natural archives to reconstruct past atmospheric circulation. These isotope-enabled GCMs depend on the parameterization of the processes mentioned earlier, which are often formulated with several simplifications. These simplifications may incorporate considerable biases and errors. Indian summer monsoon (ISM) is a prototype of complex monsoon dynamics involving considerable heterogeneity in moisture sources and rainout mechanisms. The talk will cover how this heterogeneity is reflected in observed and model water isotope values of ISM on a daily/monthly scale. The talk will further elucidate how quantitatively one can assess the role of various processes in region-specific water isotope biases. Hence, both users and modelers will be benefitted from the talk. While the users will get a scope to evaluate the models for ISM critically, the modelers may get a guideline on how to improve their models by incorporating the complexities of monsoon dynamics.    

Biography:

Dr. Saikat Sengupta is currently a senior scientist at the Centre for Climate Change Research at the Indian Institute of Tropical Meteorology (IITM). An expert in isotope geochemistry and hydrogeology, he is currently working on the application of stable isotopes in modern and past hydrology. Dr. Sengupta actively participated in setting up the Laser isotope laboratory at IITM and the stable isotope laboratory at IIT Kharagpur, the first national stable isotope facility for Geosciences research in India. He graduated from Presidency College, Kolkata, in Geology and did his masters (M.Sc and M.Tech) from IIT Bombay. After Ph.D. from IIT Kharagpur, he received various prestigious post-doctoral fellowships (Golda Meir, Brain Korea, etc) and continued his post-doctoral work at Hebrew University Jerusalem, Israel, and NCKU, Taiwan. He has participated in various geological and dendroclimatological fieldworks and published papers in several reputed international and national journals, including Earth and Planetary Science Letters, Environmental Science and Technology, JGR-Oceans, Quaternary Science Reviews, Journal of Hazardous Materials, Water Research, etc. He is currently guiding several master's and Ph.D. students.