1990年代中国东部NCEP再分析高空资料的问题探讨

Potential Uncertainties of Upper Air Data over Eastern China during the 1990s in the NCEP Reanalyses

资料是气候变化研究的基础。关于NCEP再分析资料与其他资料的对比和可靠性评估等问题一直以来都受到广泛关注。重点介绍了最近的相关研究成果,指出相对于中国探空观测资料,NCEP再分析资料中的中国东部对流层温度和位势高度在1992—2000年系统性偏低,即该资料高估了1990年代对流层温度和位势高度的年代际下降程度。与此相联系,NCEP再分析资料中中国东部对流层和地面气候变化出现了不匹配。NCEP正好在1992年改变了观测数据偏差订正表,这可能是造成上述不一致的主要原因。NCEP资料的这一偏差可能影响到对高空气候变化趋势和年代际突变的正确判断,因此使用该资料研究中国东部气候变化时,需特别谨慎。

Data are the basis of research on climate change. The comparison of the NCEP reanalyses with other data and their reliability assessments have long received extensive attention. The present paper reports recent results on the assessment of the NCEP reanalyses. Our analysis shows that the tropospheric temperature and geopotential height over eastern China during the period 1992–2000 were systematically low in the NCEP reanalyses compared to the upper radiosonde observations. This implies that the NCEP reanalyses overestimate the decadal decrease in tropospheric temperature and potential height in the 1990s. Because of the above-mentioned uncertainties in the NCEP reanalyses, the climate changes in the troposphere and at the surface do not match with each other. Further analysis shows that the uncertainties in the NCEP reanalyses are possibly related to an operational change in the bias correction tables since 1992. This potential uncertainties may be unfavorable to identifying the trend and the abrupt change of tropospheric climate. Therefore, cautions are needed in utilizing the upper-tropospheric variables of the NCEP reanalyses.