本文分析氣候研究上最常用的四種氣象再分析資料產品，包括 NCEP-R2、CFSR、ERA-40 以及ERA-interim 資料，在熱帶地區氣柱水汽量的時空分佈特徵，並與 SSM/I 衛星反演氣柱水汽量進行統計比對。分析結果顯示， ERA-40 的垂直積分氣柱水汽量，無論在空間分佈和時間變化趨勢上，都與 SSM/I觀測值最為吻合。此結果似乎顛覆了傳統上我們對氣象再分析資料的認知，亦即第三代氣象再分析資料表現不一定優於上一代，值得氣候變遷研究者注意。本研究純屬不同再分析資料氣注水汽量比較，資料間存在差異原因並不在本文討論範圍內。

In this study, the vertically-integrated total column water vapor (TCWV) generated from four popular meteorological reanalysis data, including NCEP-R2, CFSR, ERA-40 and ERA-interim, were compared against the SSM/I TCWV, with a focus on spatial distribution and temporal variation patterns. The analyses showed that the TCWV from ERA-40 bears strong resemblance to that from SSM/I in both spatial distribution and temporal variation patterns. This result seems to be in contradiction to what we have anticipated, i.e., the third generation reanalysis products are not necessarily superior to the previous ones, which is a noteworthy caveat for the climate research community. This study simply compares the differences among various reanalysis data; while the underlying causes responsible for such differences are not discussed as those are beyond the scope of this study.