Skip to main content
U.S. flag

An official website of the United States government

Seasonally dependent responses of tropical rainfall and subtropical highs to global warming

Presentation Date
Thursday, December 13, 2018 at 11:35am
Location
Walter E Washington Convention Center 144A-C
Authors

Author

Abstract

The subtropical highs are semi-permanent atmospheric features that strengthen during April-September and exert large influences on regional precipitation. Previous studies of their future changes mainly focused on their peak season (June-August). Here we find a robust seasonally-dependent response of the subtropical highs to warming in a suite of multi-model simulations. Both the North Pacific and North Atlantic subtropical highs strengthen more in April-June than July-September, with opposite changes in the Southern Hemispheric counterpart. These seasonally dependent responses of North Pacific and North Atlantic subtropical highs are mainly contributed by their zonal-mean component. Meanwhile, these responses are closely related to a southward shift of tropical precipitation in April-June relative to July-September, manifesting in a seasonal delay of tropical precipitation and monsoon rainfall onset in the Northern Hemisphere. From theory and analysis of atmospheric energetics, it is found that in a warmer world, the Northern Hemisphere needs more latent energy to warm up during April-June as constrained by the Clausius-Clapeyron relation, and the opposite occurs in the Southern Hemisphere. The interhemispheric energy contrast drives a southward shift of tropical precipitation that strengthens the Hadley cell and the subtropical highs in the Northern Hemisphere in April-June. These changes scale linearly with warming, so they have increasing implications for projecting regional climate changes in the tropics and subtropics as the warming continues.

      Category
      Atmospheric Sciences
      Funding Program Area(s)