Different influences of various El Niño types on low-level atmospheric circulation over the subtropical western North Pacific
发布日期: 2019/04/01

报告人:Wei Tan, Lecturer, Shandong University of Science and Technology

时间:9:30-10:30 04/04 2019, Thursday

地点:IOO Meeting Room, Xuhui Campus

摘要:

This study focuses on different evolutions of the low-level atmospheric circulations between eastern Pacific (EP) El Niño and central Pacific-II (CP-II) El Niño. There are three anomalous anticyclonic centers over the subtropical Indo-Pacific region during both EP El Niño and CP-II El Niño. The western two centers anchor over the Arabian Sea and Bay of Bengal, showing no zonal shift. While the easternmost center originates from the South China Sea, and moves to the western North Pacific afterwards, thus is called western North Pacific anomalous anticyclone (WNPAC). Compared with EP El Niño, the eastward displacement of the WNPAC is weaker in CP-II El Niño. Such inconsistencies are attributed to different evolutions of the cyclonic response, which can suppress the convection in the western flank. The eastward retreat of the anomalous cyclone is significant in EP El Niño, but less evident in CP-II El Niño. These discrepancies are further related to zonal evolutions of the increased precipitation over the equatorial Pacific. Following the southward migration of the intertropical convergence zone (ITCZ), the deep-convection region extends eastward along the equator, reinforcing the atmospheric response to the eastern Pacific warming in EP El Niño. While for CP-II El Niño, the atmospheric response is insignificant over the eastern Pacific without warming. Moreover, the meridional migration of the ITCZ can modulate the zonal variations of the specific humidity and easterly trade wind as well, finally bring about different shifts of the precipitation center through the wind-induced and specific humidity-induced moist enthalpy advection.

 

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