Precipitable water

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Precipitable water (measured in millimeters or inches) is the amount of water in a column of the atmosphere. The precipitable water value is the depth that would be achieved if all the water in that column were precipitated as rain.

[edit] Measurement

There are different 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.

[edit] External links

• Microtops II An instrument to measure precipitable water from ground level.

• GRL Proposal of a method to measure precipitable water measurement by satellite, published in Geophysical Research Letters.