Precipitable water

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", for 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.^[1]
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).^[2]^[3] ^[4] However, this method has not received widespread use in part because humidity is a local measurement and precipitable water is a total column measurement.

References

^ Bevis, M.; et al. (1992). "GPS Meteorology: Remote Sensing of Atmospheric Water Vapor Using the Global Positioning System". Journal of Geophysical Research. 97 (D14): 15787–15801. Bibcode:1992JGR....9715787B. doi:10.1029/92JD01517.
^ Liu, Timothy (27 February 1986). "Statistical Relation between Mean Precipitable Water and Surface-Level Humidity over Global Oceans". Monthly Weather Review. 114 (8): 1591–1602. Bibcode:1986MWRv..114.1591L. doi:10.1175/1520-0493(1986)114<1591:srbmmp>2.0.co;2.
^ Hsu, S.A.; Blanchard, B.W. (15 October 1989). "The Relationship Between Total Precipitable Water and Surface-Level Humidity Over the Sea Surface: A Further Evaluation". Journal of Geophysical Research. 94 (C10): 14539–14545. Bibcode:1989JGR....9414539H. doi:10.1029/JC094iC10p14539.
^ Guangxiong, Peng; Jing, Li; Yunhao, Chen; Norizan, Abdul; Tay, Liphong (17 July 2006). "High-resolution Surface Relative Humidity Computation Using MODIS Image in Peninsular Malaysia" (PDF). Chinese Geographical Science. 16 (3): 260–264. doi:10.1007/s11769-006-0260-6. S2CID 73558154. Archived from the original (PDF) on 4 March 2016. Retrieved 22 January 2014.

External links

Current global map of precipitable water
Maurellis, A. N.; Lang, R.; van der Zande, W. J.; Aben, I.; Ubachs, W. (2000). "Precipitable water column retrieval from GOME data" (PDF). Geophys. Res. Lett. 27 (6): 903–906. Bibcode:2000GeoRL..27..903M. doi:10.1029/1999GL010897. hdl:1871/23072. S2CID 55326173.
Remote Sensing of Water Vapor From GPS Receivers

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[1] Bevis, M.; et al. (1992). "GPS Meteorology: Remote Sensing of Atmospheric Water Vapor Using the Global Positioning System". Journal of Geophysical Research. 97 (D14): 15787–15801. Bibcode:1992JGR....9715787B. doi:10.1029/92JD01517.

[2] Liu, Timothy (27 February 1986). "Statistical Relation between Mean Precipitable Water and Surface-Level Humidity over Global Oceans". Monthly Weather Review. 114 (8): 1591–1602. Bibcode:1986MWRv..114.1591L. doi:10.1175/1520-0493(1986)114<1591:srbmmp>2.0.co;2.

[3] Hsu, S.A.; Blanchard, B.W. (15 October 1989). "The Relationship Between Total Precipitable Water and Surface-Level Humidity Over the Sea Surface: A Further Evaluation". Journal of Geophysical Research. 94 (C10): 14539–14545. Bibcode:1989JGR....9414539H. doi:10.1029/JC094iC10p14539.

[4] Guangxiong, Peng; Jing, Li; Yunhao, Chen; Norizan, Abdul; Tay, Liphong (17 July 2006). "High-resolution Surface Relative Humidity Computation Using MODIS Image in Peninsular Malaysia" (PDF). Chinese Geographical Science. 16 (3): 260–264. doi:10.1007/s11769-006-0260-6. S2CID 73558154. Archived from the original (PDF) on 4 March 2016. Retrieved 22 January 2014.

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