Intercomparison of the Summertime Subtropical High
from the ERA-40 and NCEP/NCAR Reanalysis over
East Eurasia and the western North Pacific |
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Authors: | ZHAO Tianbao and FU Congbin |
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Institution: | Global Change System for Analysis, Research and Training, Regional Center for Temperate East Asia,
Key Laboratory of Regional Climate-Environment Research for the Temperate East Asia,
Institute of Atmospheric Physics, Chinese Aca;Global Change System for Analysis, Research and Training, Regional Center for Temperate East Asia,
Key Laboratory of Regional Climate-Environment Research for the Temperate East Asia,
Institute of Atmospheric Physics, Chinese Aca |
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Abstract: | An intercomparison of summertime (JJA) subtropical geopotential heights from the ERA-40 and NCEP/NCAR
reanalysis is specifically conducted over East Eurasia and the western North Pacific. The NCEP/NCAR is obviously
lower than the ERA-40 in the mid-to-lower troposphere in most regions of East Eurasia before the mid-1970s, but
becomes higher than the ERA-40 after the mid-1970s and thus demonstrates stronger increased trends during the
period of 1958--2001. Both reanalyses are lower than the observations in most regions of China. The NCEP/NCAR
especially shows tremendously systematic lower values before the mid-1960s and displays abrupt changes before
the 1970s. Several indices of the western North Pacific subtropical high (WNPSH), calculated from both reanalyzed
summer geopotential heights, also reveal that the variation trend of the NCEP/NCAR is stronger than that of the
ERA-40 in the mid-to-lower troposphere from 1958 to 2001. Through singular value decomposition (SVD) analysis,
the summer geopotential heights at 500 hPa from the ERA-40 are better than the NCEP/NCAR counterparts at
interacting with the precipitation over the East Asian monsoon region. The results indicate that the NCEP/NCAR
in the mid-and-lower troposphere may overestimate interdecadal changes and should be used cautiously to study
the relationship between the WNPSH and precipitation ove ther East Asia Monsoon region before the mid-1970s. |
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Keywords: | summertime subtropical high reanalysis comparison and analysis |
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