Last update in August, 2016. Service since 2002.


年: 月: 日: 時: (現地時間)

タイムゾーン(UTCとの差): (時間)

緯度: (度) 経度: (度)

地面から高度: (メートル)

トラジェクトリー長さ: (日)

モデル: 三次元法 等温位法
モード: Backward フォワード

出力: テキスト 球面図 平面図


平面図x-軸: から まて 目盛:
平面図y-軸: から まて 目盛:


Dataset source: NCEP Climate Forecast System. This serice uses the data with time resolution of 3 hours and spatial resolution of 0.5x0.5 degree on pressure levels of 1000 ,975 ,950 ,925 ,900 ,875 ,850 ,825 ,800 ,775 ,750 ,700 ,650 ,600 ,550 ,500 ,450 ,400 ,350 ,300 ,250 ,225 ,200 ,175 ,150 ,125 ,100 ,70 ,50 ,30 ,20 ,10 ,7 ,5 ,3 ,2, and 1 hPa.

METEXを使用し計算結果を公表される場合、或いはMETEXに関連した報告をされるにはzeng @ 宛に連絡をお願いいたします。

Notes on Trajectory Calculation

METEX uses the method of Petterssen (1954, Weather Analysis and Forecasting. McGraw-Hill Book Company, New York. p221-223) to calculate a parcel's move from position L(t) to L(t+Δt) by first estimating

L'(t+Δt) = L(t) + Γ(L,t)*Δt

where Γ(L,t) is the velocity vector; and then by

L(t+Δt) = L(t) + 0.5*Δt*(Γ(L,t)+Γ(L',t+Δt))

To achieve both good accuracy and fast computing, METEX adopted FLEXTRA's method of using flexible time steps in integration. The time step is determined according to the horizontal wind velocity by

Δt = ΔD/(CFL*sqrt(u*u + v*v))

where ΔD is the distance between two adjacent lateral grids and CFL stands for the Courant-Friedrichs-Lewy criterion.

Discrete meteorological data are interpolated in space and time for the calculation. The spatial interpolation depends on model assumptions.

Kinematic Model

The kinematic model assumes that an air parcel's trajectory is dominated by u- and v-wind and the vertical pressure velocity.

In spatial interpolation, a variable is first interpolated along the vertical grids to the specified vertical position, which may be represented by geopotential height, pressure, or any hybrid coordinate; and then interpolated laterally to a specified latitude and longitude. The assumption for vertical interpolation is that variables vary linearly with height; and the assumption for laterally interpolation is that variables vary linearly with latitude and longitude.

Isentropic Model

The isentropic model assumes that the vertical motion of an air parcel is confined on the isentropic surface of uniform potential temperature.

First of all, the initial altitude of an air parcel is converted to the potential temperature at its position by interpolation and by iteratively re-evaluating the potential temperature until the altitude estimated by interpolation on the isentropic surface equals the initial altitude within a given accuracy. After the initial potential temperature is determined, the isentropic surface is treated as a flat plane in lateral interpolations for u- and v-wind. The flat-plane assumption is valid because the distance between vertical grids are generally much smaller than that between lateral grids.

Interpolation of variable.


Contact: zeng @ nies . go . jp
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