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Responses of the MID-Latitude and Tropical Atmospheric Circulation to Climate Change and Connection to the Hydrological Cycle

Author(s): Jian Ma

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Abstract: responses of the atmospheric circulation and their impacts on the hydrological cycle. This review develops a conceptual framework which describes the underlying physical mechanisms for observational and model-projected changes, and places into perspective ongoing research to analyze and constrain uncertainties in climate projections. We first depict large-scale responses of the tropical circulation, and then make the link to regional climate change, showing connections between sea surface temperatures (SSTs), water vapor, winds, clouds, precipitation, and energy transport. The tropical circulation slows down under warming, driven by moisture and stratification changes. This links to a poleward expansion of the Hadley cells and a shift of the intertropical convergence zone (ITCZ), which is related to the mid-latitude synoptic eddies. Meanwhile, redistributions of regional precipitation consist of thermodynamic and dynamical components, including a strong offset between moisture increase and circulation weakening throughout the tropics. This allows other dynamical processes to dominate local circulation changes, such as the SST pattern effect over the ocean and a variety of mechanisms over land. Attempts have emerged to reduce the inter-model diversity in regional circulation change, but they are still at an early stage. Circulation change brings significant uncertainties to climate projections, not only in precipitation but also for water vapor and cloud feedbacks. Future research directions are suggested to improve reliability in global and regional projections, including a more fundamental understanding of SST pattern formation and its effects on ITCZ change, land rainfall, tropical cyclones, cloud radiative feedback, and climate sensitivity.

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Year: 2016

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