対流圏界面の決め方(NCEP/NCAR Reanalysis データの場合)
モデルのσ面の気温から推定。
450hPaより上層の気圧面において、鉛直方向の気温減率が0.2K/100mを下回る最も
下の高度を対流圏界面とする
(対流圏界面は85hPaより上層にはならないとする)。
対流圏界面における気圧・気温はlog-p での線形内挿より計算。
以下に原文を掲載
The model level analyses are used to calculate tropopause data.
(A post processor is used). The procedure at NCEP looks for the
lowest level above 450 mb where the lapse rate is under 0.2K per km.
A more exact location for the tropopause between two model levels is
determined, and the pressure and temperature are calculated for that
spot in the vertical. The trop is not allowed to be above 85 mb.
In spite of changing observations, the analyses should be quite stable
over time. Therefore the derived tropopause data should be stable
over time. [From Masao Kanamitsu, NCEP. NCEP has a listing of
the program used.]
以上の情報は NCEP/NCAR Reanalysis の FAQ.html と random_notes を参照した。