title: Drying of Indian subcontinent by rapid Indian Ocean warming and a weakening land-sea thermal gradient.
abstract: There are large uncertainties looming over the status and fate of the South Asian summer monsoon, with several studies debating whether the monsoon is weakening or strengthening in a changing climate. Our analysis using multiple observed datasets demonstrates a significant weakening trend in summer rainfall during 1901-2012 over the central-east and northern regions of India, along the Ganges-Brahmaputra-Meghna basins and the Himalayan foothills, where agriculture is still largely rain-fed. Earlier studies have suggested an increase in moisture availability and land-sea thermal gradient in the tropics due to anthropogenic warming, favouring an increase in tropical rainfall. Here we show that the land-sea thermal gradient over South Asia has been decreasing, due to rapid warming in the Indian Ocean and a relatively subdued warming over the subcontinent. Using long-term observations and coupled model experiments, we provide compelling evidence that the enhanced Indian Ocean warming potentially weakens the land-sea thermal contrast, dampens the summer monsoon Hadley circulation, and thereby reduces the rainfall over parts of South Asia.
authors.affiliation: Centre for Climate Change Research, Indian Institute of Tropical Meteorology, Pashan, Pune 411008, India.
authors.forename: Mathew Koll
authors.initials: MK
authors.lastname: Roxy
authors.affiliation: Centre for Climate Change Research, Indian Institute of Tropical Meteorology, Pashan, Pune 411008, India.|Department of Environmental Sciences, Fergusson College, University of Pune, Pune 411004, India.
authors.forename: Kapoor
authors.initials: K
authors.lastname: Ritika
authors.affiliation: Sorbonne Universites (UPMC, Univ Paris 06)-CNRS-IRD-MNHN, LOCEAN Laboratory, 4 place Jussieu, F-75005 Paris, France.|Indo-French Cell for Water Sciences, IISc-IITM-NIO-IRD Joint International Laboratory, IITM, Pune 411008, India.
authors.forename: Pascal
authors.initials: P
authors.lastname: Terray
authors.affiliation: ESSIC, University of Maryland, College Park, Maryland 20740, USA.
authors.forename: Raghu
authors.initials: R
authors.lastname: Murtugudde
authors.affiliation: Centre for Climate Change Research, Indian Institute of Tropical Meteorology, Pashan, Pune 411008, India.|Centre for Earth and Space Sciences, University of Hyderabad, Hyderabad 500046, India.
authors.forename: Karumuri
authors.initials: K
authors.lastname: Ashok
authors.affiliation: Centre for Climate Change Research, Indian Institute of Tropical Meteorology, Pashan, Pune 411008, India.|Earth and Climate Science Department, Indian Institute of Science Education and Research, Pune 411008, India.
authors.forename: B N
authors.initials: BN
authors.lastname: Goswami