{{short description|Stage of water cycle}} {{Use mdy dates|date=December 2016}} [[File:Dew drops in the fog.jpg|thumb|Drops of water collecting on branches during fog.|300px]] '''Fog drip''' is water dripping to the ground during [[fog]]. It occurs when water droplets from the fog adhere to the needles or leaves of trees or other objects, coalesce into larger drops and then drop to the ground.<ref>{{cite web |title=Fog drip - AMS Glossary |publisher=[[American Meteorological Society]] |url=http://glossary.ametsoc.org/wiki/Fog_drip |access-date=December 15, 2014}}</ref>
Fog drip can be an important source of moisture in areas of low rainfall, or in areas that are seasonally dry.
==Studies in the United States== * On the leeward slopes of [[Maui]], the original [[Hawaiian tropical dry forests|dryland]] cloud forests were destroyed during the 19th century but historically were inhabited by [[native Hawaiians]], so there must have been water sources. Isotopic ([[Oxygen-18]]) analyses of one of the few remaining areas of native forest, at {{convert|4000|ft|m}} elevation in the fog belt, found that fog drip was a major component of stream flow and shallow ground water at higher altitudes in the watershed.<ref>{{cite journal |title=The influence of microclimates and fog on stable isotope signatures used in interpretation of regional hydrology: East Maui, Hawaii |first=Martha A. |last=Scholl |author2=Stephen B. Gingerich |author3=Gordon W. Tribble |journal=Journal of Hydrology |date=July 2002 |volume=264 |pages=170–184 |url=https://water.usgs.gov/nrp/proj.bib/hawaii/mauigwiso_jhydrol.pdf |access-date=October 16, 2010 |issue=1–4 |doi=10.1016/S0022-1694(02)00073-2 |bibcode=2002JHyd..264..170S}}</ref> * On arid [[Santa Cruz Island]], a study of the southernmost [[Bishop pine]] (''Pinus muricata'') forest in [[California]] found that summer cloud shading and fog drip mitigate the effects of summer drought. Even though fog cover in summer only occurs 15% of the day, this minor amount of fog enabled trees and soil microbes to grow at an increased rate. However, winter rainfall was the primary driver of summer tree growth, which is only aided by reduced soil evaporation in summer due to fog drip. Cloud cover and fog drip have enabled this relict pine forest to persist from prehistoric times when the climate was wetter.<ref>{{cite journal |title=Cloud shading and fog drip influence the metabolism of a coastal pine ecosystem |author=Mariah S. Carbone |journal=Global Change Biology |year=2012 |volume=19 |issue= 2 |pages=484–497 |doi=10.1111/gcb.12054|pmid= 23504786 |display-authors=etal|bibcode=2013GCBio..19..484C |s2cid= 16511876 }}</ref> * In the [[Bull Run River (Oregon)|Bull Run River]], [[Oregon]], fog drip from mature [[Douglas fir]] (''Pseudotsuga menziesii'') forest adds {{convert|35|in|mm}} of moisture per year, a 41% increase over that from rain and snow, and importantly, {{frac|1|3}} of all moisture in the dry May to September season.<ref>{{cite journal |title=Fog Drip in the Bull Run Municipal Watershed, Oregon |author=R. Dennis Harr |date=October 1982 |journal=Journal of the American Water Resources Association |doi=10.1111/j.1752-1688.1982.tb00073.x |volume=18 |issue=5 |pages=785–789|bibcode=1982JAWRA..18..785H }}</ref> * In [[California Coast Ranges]], a single [[Sequoia sempervirens|Coast redwood]] (''Sequoia sempervirens'') can "douse the ground beneath it with the equivalent of a drenching rainstorm and the drops off redwoods can provide as much as half the moisture coming into a forest over a year".<ref>{{cite news |title=Clues To Redwoods' Mighty Growth Emerge in Fog |author=Carol Kaesuk Yoon |newspaper=New York Times |date=November 24, 1998 |url=https://www.nytimes.com/1998/11/24/science/clues-to-redwoods-mighty-growth-emerge-in-fog.html?ref=carol_kaesuk_yoon |access-date=October 16, 2010}}</ref> Dawson reported that in a study of [[Northern California coastal forests|northern California redwood forests]], 34% of annual hydrologic input was from fog drip. In areas where trees had been cut down, the average annual input from fog was only 17%, proving that the redwoods were required for the fog moisture input to the ecosystem.<ref>{{cite journal |title=Fog in the California redwood forest: ecosystem inputs and use by plants |author=T. E. Dawson |journal=Oecologia |date=September 1998 |doi=10.1007/s004420050683 |pmid=28307672 |volume=117 |issue=4 |pages=476–485|bibcode=1998Oecol.117..476D |s2cid=26820268 }}</ref> In an [[Occidental, California]] study beneath a single {{convert|200|ft|m|adj=mid|-tall}} Douglas fir on a ridge dividing the moister western slope of the California Coast Range from the drier eastern slope, moisture collected under the tree averaged {{convert|58|in|mm}} versus {{convert|27|in|mm}} in an adjacent open meadow.<ref>{{cite web |title=Capturing the Clouds: Fog Drip & Cisterns |author=Robert W. Kourik |year=1995 |url=http://www.robertkourik.com/media/fog-drip-research.pdf |access-date=October 16, 2010}}</ref> On Inverness Ridge in [[Point Reyes National Seashore]] fog drip from Douglas firs in summer may add {{convert|20|in|mm}} to the otherwise {{convert|40|in|mm}} of annual average rainfall.<ref>{{cite magazine |title=In the Fog Drip at Point Reyes |magazine= Bay Nature |author=Jules Evens |date=August 12, 2012 |url=http://baynature.org/articles/in-the-fog-drip-at-point-reyes/ |access-date=April 8, 2013}}</ref> Further south, on Cahill Ridge on the [[San Francisco Peninsula]] (between [[Pilarcitos Creek]] and [[Crystal Springs Reservoir]]) at an altitude of {{convert|1000|ft|m}}, Oberlander measured fog drip beneath [[Tanoak]] (''Lithocarpus densiflorus''), Coast redwood and three Douglas fir trees, the latter {{convert|125|ft|m}} tall. He found that the trees most exposed produced the most moisture and in five weeks of measurement (July 20–August 28, 1951) fog drip below the tanoak produced {{convert|59|in|mm}} of moisture, more than the total annual precipitation on nearby [[California coastal prairie|grasslands]] and [[California montane chaparral and woodlands|chaparral]]. The Douglas fir produced {{convert|7|-|17|in|mm}} of fog drip and appeared to provide unique conditions supporting the orchids [[Epipactis gigantea|Giant helleborine]] (''Epipactis gigantea'') and [[Cephalanthera austiniae|Phantom orchid]] (''Cephalanthera austiniae''), since these plants were found exclusively in these moist ridge tops.<ref>{{cite journal |title=Summer Fog Precipitation on the San Francisco Peninsula |author=G. T. Oberlander |journal=Ecology |date=October 1956 |jstor=1933081 |volume=37 |issue=4 |pages=851–852 |doi=10.2307/1933081 |bibcode=1956Ecol...37..851O }}</ref> * In the [[Green Mountains]] of northern [[Vermont]] at elevations above {{convert|2500|ft|m}} in the spruce–fir zone on the western slope of [[Camel's Hump]], fog drip increased the total moisture available up to 67% over rainfall alone. The authors concluded that the needlelike leaves and twiggy character of the conifers in the spruce–fir zone serve as effective mechanical collectors of the wind-driven cloud droplets.<ref>{{cite journal |title=Precipitation from Fog Moisture in the Green Mountains of Vermont |journal=Ecology |date=November 1968 |pages=1205–1207 |jstor=1934518 |author1=H. W. Vogelmann |author2=Thomas Siccama |author3=Dwight Leedy |author4=Dwight C. Ovitt |volume=49 |issue=6 |doi=10.2307/1934518 |bibcode=1968Ecol...49.1205V }}</ref>
==Outside the United States== * One of the few areas in the world where people climb to the hilltops to get water in times of drought is the [[South Downs|Downs]] in [[England]], where fog blows in from the [[English Channel]] to form what locals call "[[dew pond]]s", although they are formed by fog drip instead of dew.<ref name=Frazer>{{cite journal |title=Fog Drip May Hold Key to Drought Relief |author=Calvin Frazer |journal=Popular Mechanics and Inventions |date=June 1931 |url=http://blog.modernmechanix.com/2010/01/25/fog-drip-may-hold-key-to-drought-relief/?Qwd=./ModernMechanix/6-1931/fog_drip&Qif=fog_drip_0.jpg&Qiv=thumbs&Qis=XL#qdig |access-date=October 16, 2010 }}{{Dead link|date=December 2025 |bot=InternetArchiveBot }}</ref> * Near the Pacific coast of [[Peru]] and northern [[Chile]], in the nearly complete absence of any annual rainfall, fog drip allows vegetation, including trees, to grow in small areas called "[[Lomas]]," which contrast with the surrounding areas of barren desert.<ref>{{cite journal |title=Monitoring fog-vegetation communities at a fog site in Alto Patache, South of Iquique, Northern Chile, during 'El NiZo' and 'La NiZa' events (1997–2000) |year=2001 |journal=In Second International Conference on Fog and Fog Collection |editor=Schemenauer R.S. |editor2=Puxbaum H. |pages=293–296 |url=http://www.uc.cl/geografia/cda/pdf/est_patache/id_cda_23.pdf |access-date=October 17, 2010 |author1=Pinto R. |author2=Larrain H. |author3=Cereceda P. |author4=Lazaro P. |author5=Osses P. |author6=Schemenauer R.S. |archive-date=September 27, 2011 |archive-url=https://web.archive.org/web/20110927160612/http://www.uc.cl/geografia/cda/pdf/est_patache/id_cda_23.pdf |url-status=dead }}</ref> * In the arid climate of northern [[Kenya]], fog drip may be an important source of infiltration and [[groundwater recharge]], where isotopic analysis found the latter to be a mixture of rainwater and fog drip.<ref>{{cite journal |title=Fog Drip as a Source of Groundwater Recharge in Northern Kenya |journal=Water Resources Research |pages=1406–1410 |date=August 1988 |url=http://www.agu.org/journals/wr/v024/i008/WR024i008p01406/WR024i008p01406.pdf |access-date=October 16, 2010 |author1=Neil L. Ingraham |author2=Robert A. Matthews |doi=10.1029/wr024i008p01406 |bibcode=1988WRR....24.1406I |volume=24|issue=8 }}</ref> * In the Pacific Ocean off Mexico, [[Cedros Island|Cedros]] and [[Guadalupe Island]]s support [[Monterey pine]] forests. Very sparse rainfall augmented by fog drip permits the existence of the forests.<ref>Oberbauer, Thomas A. (2013), "Floristic Analysis of Vegetation Communities on Isla de Cedros, Baja California, Mexico," https://www.academia.edu/1109025/Floristic_analysis_of_vegetation_communities_on_Isla_de_Cedros_Baja_California_Mexico, accessed 20 Jun 2018</ref>
==See also== *[[Fog desert]] *[[Cloud forest]] *[[Dew]]
==References== {{reflist|30em}}
==External links== * [https://web.archive.org/web/20130317093716/http://www.fogquest.org/index.php/home/ FogQuest is a non-profit Canadian charity dedicated to helping developing countries harvest atmospheric water ] * [https://gallery.usgs.gov/videos/594#.UIgbPWf_LnV Video: "Fog and Wind" - Cloud Forests of Santa Rosa Island, USGS Western Ecology Research Center ] {{Webarchive|url=https://web.archive.org/web/20160304043621/http://gallery.usgs.gov/videos/594#.UIgbPWf_LnV |date=March 4, 2016 }}
[[Category:Fog|drip]]