(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.
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.
- 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.