The response of precipitation minus evapotranspiration to climate warming: why the "wet-get-wetter, dry-get-drier" scaling does not hold over land

Michael Patrick Byrne, Paul A. O'Gorman

Research output: Contribution to journalArticlepeer-review

241 Citations (Scopus)

Abstract

Simulations with climate models show a land–ocean contrast in the response of P − E (precipitation minus evaporation or evapotranspiration) to global warming, with larger changes over ocean than over land. The changes over ocean broadly follow a simple thermodynamic scaling of the atmospheric moisture convergence: the so-called “wet-get-wetter, dry-get-drier” mechanism. Over land, however, the simple scaling fails to give any regions with decreases in P − E, and it overestimates increases in P − E compared to the simulations. Changes in circulation cause deviations from the simple scaling, but they are not sufficient to explain this systematic moist bias. It is shown here that horizontal gradients of changes in temperature and fractional changes in relative humidity, not accounted for in the simple scaling, are important over land and high-latitude oceans. An extended scaling that incorporates these gradients is shown to better capture the response of P − E over land, including a smaller increase in global-mean runoff and several regions with decreases in P − E. In the zonal mean over land, the gradient terms lead to a robust drying tendency at almost all latitudes. This drying tendency is shown to relate, in part, to the polar amplification of warming in the Northern Hemisphere, and to the amplified warming over continental interiors and on the eastern side of midlatitude continents.
Original languageEnglish
Pages (from-to)8078-8091
Number of pages15
JournalJournal of Climate
Volume28
Issue number20
Early online date13 Oct 2015
DOIs
Publication statusPublished - 15 Oct 2015

Keywords

  • Circulation dynamics
  • Atmospheric circulation
  • Hydrologic cycle
  • Atm/Ocean structure/phenomena
  • Precipitation

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