Moisture recycling

{{short description|Contribution to precipitation over some area by water previously precipitated in that area}}

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 ({{mvar|P{{sub|L}}}}) to total precipitation ({{mvar|P}}) is known as the recycling ratio, {{mvar|ρ}}:{{Cite journal|last=Eltahir|first=E.A|title=Precipitation Recycling in the Amazon Basin|url=http://web.mit.edu/people/eltahir/www/Publications_files/1994%20Eltahir%20Bras%20precip%20recy%20Amazon%20basin%20QJRMetSoc.pdf|journal=Massachusetts Institute of Technology, USA}}

$$\backslash rho\; =\; \backslash frac\{P\_L\}\{P\}.$$

The recycling ratio is a diagnostic measure of the potential for interactions between land surface hydrology and regional climate.{{cite journal|last1=Koster|first1=R.|last2=Jouzel|first2=J.|last3=Suozzo|first3=R.|last4=Russell|first4=G.|last5=Broecker|first5=W.|last6=Rind|first6=D.|last7=Eagleson|first7=P.|title=Global sources of local precipitation as determined by the Nasa/Giss GCM|journal=Geophysical Research Letters|date=February 1986|volume=13|issue=2|pages=121–124|doi=10.1029/GL013i002p00121|bibcode=1986GeoRL..13..121K}}{{cite journal|last1=Trenberth|first1=Kevin E.|title=Atmospheric Moisture Recycling: Role of Advection and Local Evaporation|journal=Journal of Climate|date=May 1999|volume=12|issue=5|pages=1368–1381|doi=10.1175/1520-0442(1999)012<1368:amrroa>2.0.co;2|bibcode=1999JCli...12.1368T|s2cid=59584165|doi-access=free}}{{cite journal|last1=Brubaker|first1=Kaye L.|last2=Entekhabi|first2=Dara|last3=Eagleson|first3=P. S.|title=Estimation of Continental Precipitation Recycling|journal=Journal of Climate|date=June 1993|volume=6|issue=6|pages=1077–1089|doi=10.1175/1520-0442(1993)006<1077:eocpr>2.0.co;2|bibcode=1993JCli....6.1077B|doi-access=free}}{{cite journal|last1=van der Ent|first1=Rudi J.|last2=Savenije|first2=Hubert H. G.|last3=Schaefli|first3=Bettina|last4=Steele-Dunne|first4=Susan C.|title=Origin and fate of atmospheric moisture over continents|journal=Water Resources Research|date=1 September 2010|volume=46|issue=9|pages=W09525|doi=10.1029/2010WR009127|language=en|issn=1944-7973|bibcode=2010WRR....46.9525V|url=http://resolver.tudelft.nl/uuid:365bc45f-fb92-41ce-864e-03812be8a440|doi-access=free}} 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%.[http://www.waterandclimate.org/MoistureWeb/Overview_Paper.htm Moisture recycling] {{webarchive |url=https://web.archive.org/web/20060116022258/http://www.waterandclimate.org/MoistureWeb/Overview_Paper.htm |date=January 16, 2006 }}

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 statistically defined area within which evaporation, traveling via moisture recycling, provides precipitation for a specific point.