期刊
JOURNAL OF CLIMATE
卷 34, 期 15, 页码 6335-6353出版社
AMER METEOROLOGICAL SOC
DOI: 10.1175/JCLI-D-20-0493.1
关键词
Energy transport; Hadley circulation; Teleconnections
资金
- National Research Foundation of Korea (NRF) - Korea government (MSIT) [2020R1A2C2006860]
- NOAA's Climate Program Office's Modeling, Analysis, Predictions, and Projections (MAPP) program [NA20OAR4310445]
- Ministry of Science and Technology of Taiwan [MOST 106-2923-M-002-007-MY2, 110-2628-M-002-002-]
- National Research Foundation of Korea [2020R1A2C2006860] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
The study found that high-frequency extratropical forcing does not affect tropical precipitation, while low-frequency extratropical forcing allows atmospheric transient eddies to diffuse moist static energy to perturb midlatitude sea surface temperatures, ultimately achieving further equatorward advection through the Hadley circulation.
This study examines the temporal evolution of the extratropically forced tropical response in an idealized aquaplanet model under equinox condition. We apply a surface thermal forcing in the northern extratropics that oscillates periodically in time. It is shown that tropical precipitation is unaltered by sufficiently high-frequency extratropical forcing. This sensitivity to the extratropical forcing periodicity arises from the critical time required for sea surface temperature (SST) adjustment. Low-frequency extratropical forcing grants sufficient time for atmospheric transient eddies to diffuse moist static energy to perturb the midlatitude SSTs outside the forcing region, as demonstrated by a one-dimensional energy balance model with a fixed diffusivity. As the transient eddies weaken in the subtropics, a further equatorward advection is accomplished by the Hadley circulation. The essential role of Hadley cell advection in connecting the subtropical signal to the equatorial region is supported by an idealized thermodynamical-advective model. Associated with the SST changes in the tropics is a meridional shift of the intertropical convergence zone. Since the time needed for SST adjustment increases with increasing mixed layer depth, the critical forcing period at which the extratropical forcing can affect the tropics scales linearly with the mixed layer depth. Our results highlight the important role of decadal-and-longer extratropical climate variability in shaping the tropical climate system. We also raise the possibility that the transient behavior of a tropical response forced by extratropical variability may be strongly dependent on cloud radiative effects.
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