Land‐sea thermal contrast determines the trend of Walker circulation simulated in atmospheric general circulation models

• Published in: Geophysical research letters 2017-06, Vol.44 (11), p.5854-5862
• Main Authors: Yim, Bo Young, Yeh, Sang‐Wook, Song, Hwan‐Jin, Dommenget, Dietmar, Sohn, B. J.
• Format: Article
• Language: English
• Subjects: AMIP climate models; Atmospheric circulation; Atmospheric General Circulation Models; Atmospheric models; Atmospheric precipitations; Atmospheric pressure; Climate; Climate models; Climate variability; Climatology; Computer simulation; General circulation models; Global weather; Heating; Intercomparison; Land surface temperature; land‐sea thermal contrast; Ocean temperature; Ocean-atmosphere interaction; Precipitation; Pressure; Sea level; Sea level pressure; Sea surface; Sea surface temperature; Surface temperature; Temperature; Temperature effects; Trends; Tropical climate; Variability; Walker circulation; Weather
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2017GL073778

Strengthening or weakening of the Walker circulation can highly influence the global weather and climate variability by altering the location and strength of tropical heating. Therefore, there is considerable interest in understanding the mechanisms that lead to the trends in the Walker circulation intensity. Conventional wisdom indicates that a strengthening or weakening of the Walker circulation is primarily controlled by inhomogeneous sea surface temperature (SST) patterns across the tropical Pacific basin. However, we show that Atmospheric Model Intercomparison Project climate model simulations with identical SST forcing have different Walker circulation trends that can be linked to differences in land surface temperatures. More prominently, stronger land‐sea thermal contrast leads to increases in the precipitation in South America as well as the sea level pressure in the eastern tropical Pacific through a local circulation, resulting in a strengthening of the Walker circulation trend. This implies that correctly simulating the land temperature in atmospheric models is crucial to simulating the intensity of the Walker circulation in the present climate as well as its future change. Key Points AMIP climate model simulations with identical SST forcing have very different Walker circulation trends Trends of Walker circulation can be linked to differences in land surface temperatures in two sides in the tropical Pacific Land temperature simulation is crucial to simulating the intensity of the Walker circulation in the present climate and its future change