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Precipitable water is the depth of water in a column of the atmosphere, if all the water in that column were precipitated as rain. As a depth, the precipitable water is measured in millimeters or inches. Often abbreviated as "TPW" = total precipitable water. == Measurement == There are different measurement techniques: *One type of measurement is based on the measurement of the solar irradiance on two wavelengths, one in a water absorption band, and the other not. The precipitable water column is determined using the irradiances in these bands and the Beer-Lambert law. *The precipitable water can also be calculated by integration of radiosonde data (relative humidity, pressure and temperature) over the whole atmosphere. *Data can be viewed on a Lifted-K index. The numbers represent inches of water as mentioned above for a geographical location. *Recently, methods using the Global Positioning System have been developed. *Some work has been performed to create empirical relationships between surface specific humidity and precipitable water based on localized measurements (generally a 2nd to 5th order polynomial). However, this method has not received widespread use in part because humidity is a local measurement and precipitable water is a total column measurement. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「precipitable water」の詳細全文を読む スポンサード リンク
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