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Double‐ITCZ as an Emergent Constraint for Future Precipitation Over Mediterranean Climate Regions in the North Hemisphere
Author(s) -
Dong Lu,
Leung L. Ruby,
Lu Jian,
Song Fengfei
Publication year - 2021
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 - 10.1029/2020gl091569
Subject(s) - intertropical convergence zone , climatology , precipitation , mediterranean climate , environmental science , atmospheric circulation , climate model , convergence zone , climate change , northern hemisphere , atmospheric sciences , geology , geography , oceanography , meteorology , archaeology
The semiarid Mediterranean climate regions feature wet winter and dry summer, distinct from most other regions on Earth. In response to warming, climate models project increased precipitation in US Southwest (USSW) and decreased in Mediterranean basin (MED) during winter, but with marked uncertainty. Using a multimodel ensemble, we found that models with excessive double Intertropical Convergence Zone (ITCZ) biases tend to exaggerate the precipitation increase over USSW and understate the precipitation decrease over MED in the future. These relationships are attributed to the atmospheric circulation changes driven by the increased tropical rainfall and the weaker slowdown of the Atlantic Meridional Overturning Circulation under warming, respectively. Constraining the present‐day double‐ITCZ with observations, the projected wetting over USSW is reduced to no change and the drying over MED is intensified by 32%. A relative reduction in future precipitation has profound societal and economic implications for these regions already under severe water stress.