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.

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.

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.