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Interannual Variability of Regional Hadley Circulation Intensity Over Western Pacific During Boreal Winter and Its Climatic Impact Over Asia‐Australia Region
Author(s) -
Huang Ruping,
Chen Shangfeng,
Chen Wen,
Hu Peng
Publication year - 2018
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2017jd027919
Subject(s) - climatology , troposphere , advection , hadley cell , precipitation , zonal and meridional , boreal , environmental science , atmospheric circulation , atmospheric sciences , sea surface temperature , subsidence , walker circulation , geology , climate change , structural basin , geography , oceanography , general circulation model , paleontology , physics , meteorology , thermodynamics
This study investigates interannual variability of boreal winter regional Hadley circulation over western Pacific (WPHC) and its climatic impacts. A WPHC intensity index (WPHCI) is defined as the vertical shear of the divergent meridional winds. It shows that WPHCI correlates well with the El Niño–Southern Oscillation (ENSO). To investigate roles of the ENSO‐unrelated part of WPHCI (WPHCI res ), variables that are linearly related to the Niño‐3 index have been removed. It reveals that meridional sea surface temperature gradient over the western Pacific plays an essential role in modulating the WPHCI res . The climatic impacts of WPHCI res are further investigated. Below‐normal (above‐normal) precipitation appears over south China (North Australia) when WPHCI res is stronger. This is due to the marked convergence (divergence) anomalies at the upper troposphere, divergence (convergence) at the lower troposphere, and the accompanied downward (upward) motion over south China (North Australia), which suppresses (enhances) precipitation there. In addition, a pronounced increase in surface air temperature (SAT) appears over south and central China when WPHCI res is stronger. A temperature diagnostic analysis suggests that the increase in SAT tendency over central China is primarily due to the warm zonal temperature advection and subsidence‐induced adiabatic heating. In addition, the increase in SAT tendency over south China is primarily contributed by the warm meridional temperature advection. Further analysis shows that the correlation of WPHCI res with the East Asian winter monsoon (EAWM) is weak. Thus, this study may provide additional sources besides EAWM and ENSO to improve understanding of the Asia‐Australia climate variability.