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Moist heat stress extremes in India enhanced by irrigation


Intensive irrigation in India has been demonstrated to decrease surface temperature, but the influence of irrigation on humidity and extreme moist heat stress is not well understood. Here we analysed a combination of in situ and satellite-based datasets and conducted meteorological model simulations to show that irrigation modulates extreme moist heat. We found that intensive irrigation in the region cools the land surface by 1 °C and the air by 0.5 °C. However, the decreased sensible heat flux due to irrigation reduces the planetary boundary layer height, which increases low-level moist enthalpy. Thus, irrigation increases the specific and relative humidity, which raises the moist heat stress metrics. Intense irrigation over the region results in increased moist heat stress in India, Pakistan, and parts of Afghanistan—affecting about 37–46 million people in South Asia—despite a cooler land surface. We suggest that heat stress projections in India and other regions dominated by semi-arid and monsoon climates that do not include the role of irrigation overestimate the benefits of irrigation on dry heat stress and underestimate the risks.

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Fig. 1: Irrigation driven cooling in the Indo-Gangetic Plain.
Fig. 2: Changes in three-day maximum heat indicators in India during the summer (April–May) for the 1979–2018 period.
Fig. 3: The role of irrigation on summer heat fluxes, temperature, humidity, SLP and PBL height.
Fig. 4: Influence of irrigation on dry and moist heat stress in India.

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Data availability

All datasets are available in the manuscript or the Supplementary Information, and on the Zenodo database Temperature observations from the India Meteorological Department are available from The ERA5 reanalysis dataset is available from Source data are provided with this paper.

Code availability

All the codes used in this study will be provided by the corresponding author upon reasonable request.


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We acknowledge the data availability from the IMD ERA5, and MERRA reanalysis. The work was funded by the National Water Mission, Ministry of Environment, Forest, and Climate Change (MoEFCC) and the Ministry of Earth Sciences.

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Authors and Affiliations



V.M. conceived and designed the study and discussed it with M.H. A.K.A. conducted the WRF simulations. V.M., A.K.A., A.A., R.K. and S.A. performed the analysis. V.M. wrote the first draft and all the authors contributed to the discussion.

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Correspondence to Vimal Mishra.

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Peer review information Primary handling editor: Tamara Goldin.

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Supplementary information

Supplementary Information

Supplementary Tables 1–6 and Figs. 1–16.

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Mishra, V., Ambika, A.K., Asoka, A. et al. Moist heat stress extremes in India enhanced by irrigation. Nat. Geosci. 13, 722–728 (2020).

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