Abstract
The spatial pattern of precipitation responses to CO2 concentration increases significantly influences global weather and climate variability by altering the location of tropical heating in a warmer climate. In this study, we analyze the Coupled Model Intercomparison Project Phase 5 (CMIP5) climate model projections of tropical Pacific rainfall response to quadrupled increase of CO2. We found that the precipitation changes to the CO2 concentration increase cannot be interpreted by a weakening or strengthening of large-scale east–west coupling across the tropical Pacific basin, i.e., Walker circulation. By calculating the water vapor transport, we suggest instead that different responses of the Walker and Hadley circulations to the increasing CO2 concentration shape the details of the spatial pattern of precipitation in the tropical Pacific. Therefore, more regionally perturbed circulations over the tropical Pacific, which is influenced by the mean state change in the tropical Pacific and the enhanced precipitation outside the tropical Pacific, lead to greater increases in precipitation in the western equatorial Pacific as compared to the eastern tropical Pacific in a warmer climate.
Highlights
The spatial pattern of precipitation responses to CO2 concentration increases significantly influences global weather and climate variability by altering the location of tropical heating in a warmer climate
In order to understand the precipitation change over the tropics in a warmer climate, we focus on the mass overturning circulation
We conclude that the details of precipitation changes in response to QCO2 are not directly linked by large-scale east–west-coupling across the tropical Pacific basin
Summary
The spatial pattern of precipitation responses to CO2 concentration increases significantly influences global weather and climate variability by altering the location of tropical heating in a warmer climate. The warmer-get-wetter mechanism indicates that the precipitation changes in the tropics are positively correlated with the spatial deviations of SST warming relative to the tropical mean SST, because the moist instability is determined by the relative SST changes These two mechanisms reasonably well explain precipitation changes in a warmer climate, future projection of rainfall patterns is still a challenging issue[27,28]. Recent studies are paying more attention to the respective roles of Walker and Hadley circulation, determining the structure of divergence/convergence driving the pattern of precipitation changes over the tropical Pacific in a warmer climate[29,30,31,32,33]. In this study, we mainly provide results from a quadrupling of CO2 concentration (hereafter referred to as QCO2)
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