Evaluation of ERA-40, NCEP-1, and NCEP-2 reanalysis air temperatures with ground-based measurements in China

Authors

  • Lijuan Ma,

    1. Institute of Climate and Environment, Chinese Academy of Meteorological Sciences, Beijing, China
    2. College of Earth Science, Graduate University of Chinese Academy of Sciences, Beijing, China
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  • Tingjun Zhang,

    1. Institute of Climate and Environment, Chinese Academy of Meteorological Sciences, Beijing, China
    2. Cooperative Institute for Research in Environmental Sciences/National Snow and Ice Data Center, University of Colorado at Boulder, Boulder, Colorado, USA
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  • Qingxiang Li,

    1. National Meteorological Information Center, China Meteorological Administration, Beijing, China
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  • Oliver W. Frauenfeld,

    1. Cooperative Institute for Research in Environmental Sciences/National Snow and Ice Data Center, University of Colorado at Boulder, Boulder, Colorado, USA
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  • Dahe Qin

    1. State Key Laboratory of Cryospheric Science, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, China
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Abstract

[1] We assess the correspondence of reanalysis air temperatures from ERA-40, NCEP-1, and NCEP-2 with homogenized observational data from China for 1958–2001 and 1979–2001. Results indicate that climatologies for annual ERA-40, NCEP-1, and NCEP-2 air temperatures are lower than observations by −0.93°C, −2.78°C, and −2.27°C, respectively. Large negative differences for most of western China primarily contribute to this cool bias. Error analysis indicates that the internal coherence of ERA-40 data is better than NCEP-1 or NCEP-2. Although NCEP-2 air temperatures represent an improvement over NCEP-1, biases of NCEP-1 and NCEP-2 data relative to observations are still much larger than for ERA-40. Areas with positive/negative air temperature differences (dT) between reanalysis and observational data correspond to negative/positive elevation differences (dH). The high correlation coefficients of −0.94, −0.88, and −0.85 between dT and dH for ERA-40, NCEP-1, NCEP-2, and observations, respectively, illustrate that the air temperature differences between reanalysis data and observations are primarily related to elevation differences. Furthermore, a spatial and temporal comparison of trends also indicates that ERA-40 temperature changes correspond most closely to observed trends in China. In general, our comprehensive analysis of the three global reanalysis products indicates that, both on a seasonal and annual basis, ERA-40 temperatures correspond most closely to observations, and biases are due mainly to the elevation differences.

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