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A Moments View of Climatology and Variability of the Asian Summer Monsoon Anticyclone
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  • Gloria L Manney,
  • Zachary D Lawrence,
  • Michelle L Santee,
  • Krzysztof Wargan,
  • Michael J Schwartz
Gloria L Manney
NorthWest Research Associates

Corresponding Author:[email protected]

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Zachary D Lawrence
Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado
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Michelle L Santee
Jet Propulsion Laboratory, California Institute of Technology
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Krzysztof Wargan
Science Systems and Application, Inc / NASA Goddard Space Flight Center
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Michael J Schwartz
Jet Propulsion Laboratory, California Institute of Technology
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A moments/area study of meteorological reanalyses (focusing on MERRA-2, ERA-Interim, and JRA-55) allows a novel investigation of the climatology of and interannual variability and trends in the Asian summer monsoon anticyclone (ASMA). The climatological ASMA is nearly elliptical, with its major axis aligned along its centroid latitude and an aspect ratio of ∼5–8. The ASMA centroid shifts northward with height, northward and westward during development, and in the opposite direction as it weakens. ASMA position and seasonal evolution generally agree among the reanalyses, except that MERRA-2 shows over 40% larger area at 350 K. No evidence of climatological bimodality is seen in the ASMA, consistent with previous studies using modern reanalyses. ASMA moments trends are mostly neither statistically significant nor consistent among reanalyses, but area and duration increase significantly over 1979–2018, and over 1958–2018 in JRA-55; JRA-55 trends are largest for 1979–2018, suggesting that reanalysis trends may have accelerated in recent decades. ASMA centroid latitude is significantly negatively (positively) correlated with subtropical jet core latitude (altitude), and significantly negatively correlated with concurrent ENSO. Other ASMA moments and area are not strongly correlated with concurrent ENSO, but ASMA area is significantly positively correlated with ENSO two months previously. Significant (negative) correlations of ASMA area with QBO are seen only during June at 370, 390, and 410 K. These results provide a unique and comprehensive view of the structure and evolution of the ASMA and introduce new tools that can be used to further explore ASMA characteristics and impacts.