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Simulating changes of spring Asian-Pacific oscillation and associated atmospheric circulation in the mid-Holocene

Authors

  • Botao Zhou,

    1. National Climate Center, China Meteorological Administration, Beijing 100081, China
    2. Nansen-Zhu International Research Center, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
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  • Ping Zhao

    Corresponding author
    1. National Meteorological Information Center, China Meteorological Administration, Beijing 100081, China
    • National Meteorological Information Center, China Meteorological Administration, Beijing 100081, China.
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Abstract

Changes of the upper-tropospheric temperature teleconnection and the associated atmospheric circulations in spring (Mar-April-May, MAM) during the mid-Holocene are preliminarily examined by using the CCSM3 simulation data archived in the Paleoclimate Modeling Intercomparison Project (PMIP) database. The simulation result shows that in the mid-Holocene the atmospheric circulation over the Asian-North Pacific region showed the variability of the teleconnection pattern resembling the present Asian-Pacific oscillation (APO), which is characterized by a warming (cooling) upper troposphere over Asia corresponding to a cooling (warming) upper troposphere over the North Pacific and indicates a thermal contrast between Asia and the North Pacific. In comparison with the present climate, the mid-Holocene upper-tropospheric temperature in spring was modelled to be lower over Asia and higher over the North Pacific, indicative of a weaker spring APO. Associated with such a condition, both the upper-tropospheric high (low) and the lower-tropospheric low (high) over Asia (central-eastern Pacific) were weakened in the mid-Holocene. Accordingly, anomalous descending (ascending) motion appeared over East Asia (central-eastern Pacific). This circulation background is unfavourable (favourable) for the occurrence of precipitation, and thus the mid-Holocene precipitation decreases (increases) in this region as compared with the present. Hence, the change of the spring thermal contrast between Asia and the North Pacific played a crucial role in the anomalies of the atmospheric circulations and precipitation over the Asian-Pacific region during the mid-Holocene. Copyright © 2012 Royal Meteorological Society

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