Preprints
https://doi.org/10.5194/hess-2022-154
https://doi.org/10.5194/hess-2022-154
 
02 May 2022
02 May 2022
Status: this preprint is currently under review for the journal HESS.

Break in precipitation – temperature scaling over India predominantly explained by cloud-driven cooling

Sarosh Alam Ghausi1,2, Subimal Ghosh3,4, and Axel Kleidon1 Sarosh Alam Ghausi et al.
  • 1Biospheric Theory and Modelling Group, Max Planck Institute for Biogeochemistry, Jena 07745, Germany
  • 2International Max Planck Research School for Global Biogeochemical Cycles (IMPRS – gBGC), Jena 07745, Germany
  • 3Department of Civil Engineering, Indian Institute of Technology Bombay 400076, India
  • 4Interdisciplinary Programme in Climate Studies, Indian Institute of Technology Bombay 400076, India

Abstract. Climate models predict an intensification of precipitation extremes as a result of a warmer and moister atmosphere at the rate of 7 %/K. However, observations in tropical regions show contrastingly negative precipitation-temperature scaling at temperatures above 23°–25 °C. We use observations from India and show that this negative scaling can be explained by the radiative effects of clouds on surface temperatures. Cloud radiative cooling during precipitation events make observed temperatures co-vary with precipitation, with wetter periods and heavier precipitation having a stronger cooling effect. We remove this confounding effect of clouds from temperatures using a surface energy balance approach constrained by thermodynamics. We then find a diametric change in precipitation scaling with rates becoming positive and coming closer to the Clausius – Clapeyron scaling rate (7 %/K). Our findings imply that the intensification of precipitation extremes with warmer temperatures expected with global warming is consistent with observations from tropical regions when the radiative effect of clouds on surface temperatures and the resulting covariation with precipitation is accounted for.

Sarosh Alam Ghausi et al.

Status: open (until 27 Jun 2022)

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Sarosh Alam Ghausi et al.

Sarosh Alam Ghausi et al.

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Short summary
The observed response of extreme precipitation to global warming remains unclear with significant regional variations. We show that a large part of this uncertainty can be removed when the imprint of clouds in surface temperatures is being removed. We used a thermodynamic systems approach to remove the radiative effect of clouds from temperatures. We then found precipitation extremes to intensify with global warming at positive rates consistent with physical arguments and model simulations.