期刊
JOURNAL OF CLIMATE
卷 31, 期 8, 页码 3327-3348出版社
AMER METEOROLOGICAL SOC
DOI: 10.1175/JCLI-D-17-0118.1
关键词
Intertropical convergence zone; Dynamics; Hadley circulation; Monsoons; Climate classification; regimes
资金
- UK-China Research and Innovation Partnership Fund, through the Met Office Climate Science for Service Partnership (CSSP) China, as part of the Newton Fund
- Royal Society (Wolfson Foundation)
- Leverhulme Trust
- NERC [NE/M006123/1]
- Natural Environment Research Council [NE/M006123/1] Funding Source: researchfish
- NERC [NE/M006123/1] Funding Source: UKRI
As the ITCZ moves off the equator on an aquaplanet, the Hadley circulation transitions from an equinoctial regime with two near-symmetric, significantly eddy-driven cells to a monsoon-like regime with a strong, thermally direct cross-equatorial cell, intense low-latitude precipitation, and a weak summer hemisphere cell. Dynamical feedbacks appear to accelerate the transition. This study investigates the relevance of this behavior to monsoon onset by using primitive equation model simulations ranging from aquaplanets to more realistic configurations with Earth's continents and topography. A change in the relationship between ITCZ latitude and overturning strength is identified once the ITCZ moves poleward of approximately 7 degrees. Monsoon onset is associated with off-equatorial ascent in regions of nonnegligible planetary vorticity, and this is found to generate a vortex stretching tendency that reduces upper-level absolute vorticity. In an aquaplanet, this causes a transition to the cross-equatorial, thermally direct regime, intensifying the overturning circulation. Analysis of the zonal momentum budget suggests that a stationary wave, driven by topography and land-sea contrast, can trigger a similar transition in the more realistic model configuration, with the wave extending the ascent region of the Southern Hemisphere Hadley cell northward, and enhanced overturning then developing to the south. These two elements of the circulation resemble the East and South Asian monsoons.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据