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Evaluating the Contribution of Land‐Atmosphere Coupling to Heat Extremes in CMIP5 Models
Author(s) -
Ukkola A. M.,
Pitman A. J.,
Donat M. G.,
De Kauwe M. G.,
Angélil O.
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl079102
Subject(s) - atmosphere (unit) , coupled model intercomparison project , environmental science , climate extremes , dryness , climate model , climatology , atmospheric sciences , coupling (piping) , climate change , meteorology , precipitation , geology , geography , materials science , oceanography , metallurgy , medicine , surgery
Land‐atmosphere coupling can amplify heat extremes under declining soil moisture. Here we evaluate this coupling in 25 Coupled Model Intercomparison Project Phase 5 models using flux tower observations over Europe and North America. We compared heat extremes (2.5% of the hottest days of the year) and the evaporative fraction (EF; a measure of land surface dryness) on the day the heat extremes occurred. We found a negative relationship between the magnitude of heat extremes and EF in both models and observations in transitional regions, with the hottest temperatures occurring during the driest days, with a similar but less certain relationship in dry regions. Surprisingly, many models also showed an amplification of heat extremes by low EF in wet regions, a finding not supported by observations. Many models may therefore overamplify heat extremes over wet regions by overestimating the strength of land‐atmosphere coupling, with consequences for future projections of heat extremes.