Opposite phase changes of precipitation annual cycle over land and ocean under global warming

Wednesday, December 11, 2019 - 13:40
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The annual cycle of precipitation is a fundamental aspect of the water cycle with global ramification. Climate warming induces a robust phase in the zonal-mean tropical precipitation concomitant with an amplitude enhancement. Here, we find a robust land-ocean contrast in the phase response of precipitation annual cycle, with a delay over land and an advance over ocean as climate warms. As two-thirds of Earth’s surface are occupied by ocean, it is intriguing that land, rather than ocean, dominates the zonal-mean phase delay. The phase delay over land is mainly attributed to the increase in the effective atmospheric heat capacity, while the phase advance over ocean is associated with a shift in the land-ocean precipitation contrast towards ocean during the peak rainy season. Under the energetic constraint, this shift is closely related to the opposite amplitude changes of surface temperature annual cycle between land and ocean. The summer-winter asymmetrical wind changes enhance the temperature annual cycle over ocean, while the increase of atmospheric effective heat capacity and surface feedback possibly reduces the annual cycle over land. Revealing the opposite land-ocean precipitation phase changes is a major step towards understanding regional precipitation changes that have myriad implications for ecosystems and societies.

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