Moisture recycling

In hydrology, moisture recycling or precipitation recycling refer to the process by which a portion of the precipitated water that evapotranspired from a given area contributes to the precipitation over the same area. Moisture recycling is thus a component of the hydrologic cycle. The ratio of the locally derived precipitation ($P_{L}$) to total precipitation ($P$) is known as the recycling ratio, $\rho$: $\rho = P_{L}/P$.

The recycling ratio is a diagnostic measure of the potential for interactions between land surface hydrology and regional climate.^[1] Land use changes, such as deforestation or agricultural intensification, have the potential to change the amount of precipitation that falls in a region. The recycling ratio for the entire world is one, and for a single point is zero. Estimates for the recycling ratio for the Amazon basin range from 24% to 56%, and for the Mississippi basin from 21% to 24%.^[2]

The concept of moisture recycling has been integrated into the concept of the precipitationshed. A precipitationshed is the upwind ocean and land surface that contributes evaporation to a given, downwind location's precipitation. In much the same way that a watershed is defined by a topographically explicit area that provides surface runoff, the precipitationshed is a probabilistically defined area within which evaporation, traveling via moisture recycling, provides precipitation for a specific point.

The American Institute of Biological Sciences published a paper in support of this concept in 2009.^[3]

See also

• Water cycle
• Precipitationshed

References

1. Archived March 11, 2007 at the Wayback Machine
2. Archived January 16, 2006 at the Wayback Machine
3. http://lomaprieta.sierraclub.org/forest_protection/FeatureArticles/HowForestsAttractRain.pdf