Potential flaws of interdecadal changes over eastern China around the early 1990s in the National Centers for Environmental Prediction-National Center for Atmospheric Research reanalyses

摘要

This study compares interdecadal changes in tropospheric temperature and geopotential height over eastern China in four reanalyses and upper air radiosonde (UAR) observations. It is found that the tropospheric temperature and geopotential height over eastern China during the period 1992-2000 were systematically lower in the National Centers for Environmental Prediction (NCEP)-National Center for Atmospheric Research (NCAR) reanalysis-1 and the NCEP-Department of Energy reanalysis-2 compared to the UAR observations. Accordingly, the tropospheric temperature and geopotential height over eastern China in the NCEP reanalyses showed a pronounced interdecadal decrease around 1992, while this decrease was not significant in the UAR observations, the 40 year European Centre for Medium-Range Weather Forecasts (ERA-40) reanalysis, and the 25 year Japanese Meteorological Agency (JRA-25) reanalysis. The overestimated interdecadal change in the NCEP reanalyses may lead to an inconsistent variation between tropospheric and surface climates. When summer surface air temperature increases (decreases) over southern China, summer tropospheric temperature over eastern China generally increases (decreases) in the ERA-40, JRA-25, and UAR data sets, which is physically supported by the NCAR Community Climate System Model version 3. However, this link between the troposphere and surface is not observed in the two NCEP reanalyses. The interdecadal bias in tropospheric temperature after 1992 in the NCEP reanalyses is possibly related to an operational change in the bias correction tables since 1992.