Fog drip
Encyclopedia
Fog drip is a type of precipitation
that forms when fog
droplets condense on the needles or leaves of trees or other objects, and drips to the ground.
Fog drip may be an important source of precipitation in areas of low rainfall, or in areas that are seasonally dry.
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...
that forms when fog
Fog
Fog is a collection of water droplets or ice crystals suspended in the air at or near the Earth's surface. While fog is a type of stratus cloud, the term "fog" is typically distinguished from the more generic term "cloud" in that fog is low-lying, and the moisture in the fog is often generated...
droplets condense on the needles or leaves of trees or other objects, and drips to the ground.
Fog drip may be an important source of precipitation in areas of low rainfall, or in areas that are seasonally dry.
- On the leeward slopes of MauiMauiThe island of Maui is the second-largest of the Hawaiian Islands at and is the 17th largest island in the United States. Maui is part of the state of Hawaii and is the largest of Maui County's four islands, bigger than Lānai, Kahoolawe, and Molokai. In 2010, Maui had a population of 144,444,...
, the original drylandHawaiian tropical dry forestsThe Hawaiian tropical dry forests are a tropical dry broadleaf forest ecoregion in the Hawaiian Islands. They cover an area of on the leeward side of the main islands and the summits of Niihau and Kahoolawe. These forests are either seasonal or sclerophyllous. Annual rainfall is less than and...
cloud forests were destroyed during the 19th century but historically were inhabited by native HawaiiansNative HawaiiansNative Hawaiians refers to the indigenous Polynesian people of the Hawaiian Islands or their descendants. Native Hawaiians trace their ancestry back to the original Polynesian settlers of Hawaii.According to the U.S...
, so there must have been watersources. Isotopic (Oxygen-18Oxygen-18Oxygen-18 is a natural, stable isotope of oxygen and one of the environmental isotopes.18O is an important precursor for the production of fluorodeoxyglucose used in positron emission tomography...
) analyses of one of the few remaining areas of native forest, at 1220 meters 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. - One of the few areas in the world where people climb to the hilltops to get water in times of drought is the DownsSouth DownsThe South Downs is a range of chalk hills that extends for about across the south-eastern coastal counties of England from the Itchen Valley of Hampshire in the west to Beachy Head, near Eastbourne, East Sussex, in the east. It is bounded on its northern side by a steep escarpment, from whose...
in EnglandEnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, where fog blows in from the English ChannelEnglish ChannelThe English Channel , often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about long and varies in width from at its widest to in the Strait of Dover...
to form what locals call "dew pondDew pondA dew pond is an artificial pond usually sited on the top of a hill, intended for watering livestock. Dew ponds are used in areas where a natural supply of surface water may not be readily available. The name dew pond is first found in the Journal of the Royal Agricultural Society in 1865...
s", although they are in fact formed by fog drip instead of dew. - In the Bull Run RiverBull Run River (Oregon)The Bull Run River is a tributary of the Sandy River in the U.S. state of Oregon. Beginning at the lower end of Bull Run Lake in the Cascade Range, it flows generally west through the Bull Run Watershed Management Unit , a restricted area meant to protect the river and its tributaries from...
, OregonOregonOregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
, fog drip from mature Douglas-fir (Pseudotsuga menziesii) forest adds 35 inches of precipitation per year, a 41% increase over that from rain and snow, and importantly, 1/3 of all precipitation in the dry May to September season. - In California Coast Ranges, a single 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 water coming into a forest over a year". Dawson reported that in a study of northern California redwood forests, 34% of annual hydrologic input was from fog drip. In areas were trees had been cut down, the average annual input from fog was only 17%, proving that the redwoods were required for the fog water input to the ecosystem. In an Occidental, CaliforniaOccidental, CaliforniaOccidental is a census-designated place in Sonoma County, California, United States. The population was 1,115 at the 2010 census, down from 1,272 at the 2000 census.-Geography:Occidental is located at...
study beneath a single 200 foot tall Douglas-fir on a ridge dividing the moister western slope of the California Coast Range from the drier eastern slope annual precipitation was 58 inches versus 27 inches in an adjacent open meadow. Further south, on Cahill Ridge on the San Francisco PeninsulaSan Francisco PeninsulaThe San Francisco Peninsula is a peninsula in the San Francisco Bay Area that separates the San Francisco Bay from the Pacific Ocean. On its northern tip is the City and County of San Francisco. Its southern base is in Santa Clara County, including the cities of Palo Alto, Los Altos, and Mountain...
(between Pilarcitos CreekPilarcitos CreekPilarcitos Creek is a coastal stream in San Mateo County, California, USA, that rises on the western slopes of the Santa Cruz Mountains and descends through Pilarcitos Canyon to discharge into the Pacific Ocean at Pilarcitos Creek Beach, a unit of Half Moon Bay State Beach.-History:The Portolà...
and Crystal Springs ReservoirCrystal Springs ReservoirCrystal Springs Reservoir is a pair of artificial lakes located in the northern Santa Cruz Mountains of San Mateo County, California situated in the rift valley created by the San Andreas Fault just to the west of the cities of San Mateo and Hillsborough, and I-280...
at an altitude of 1,000 feet, Oberlander measured fog drip beneath TanoakTanoakTanoak, formerly known taxonomically as Lithocarpus densiflorus, was recently moved into a new genus, Notholithocarpus, based on multiple lines of evidence....
(Lithocarpus densiflorus), Coast redwood and three Douglas-fir trees, the latter 125 feet tall. He found that the trees most exposed produced the most precipitation and in five weeks of measurement (July 20-August 28, 1951) fog drip below the tanoak produced 59 inches of precipitation, more than the total annual precipitation on nearby grasslandsCalifornia coastal prairieCalifornia coastal prairie, also known as northern coastal grassland, is a grassland plant community of California and Oregon in the Temperate grasslands, savannas, and shrublands Biome...
and chaparralCalifornia montane chaparral and woodlandsThe California montane chaparral and woodlands ecoregion covers , including the mountains of the Transverse, Peninsular, and Santa Lucia Ranges of California. It is part of the Mediterranean forests, woodlands, and scrub biome, with cool, wet winters and hot, dry summers...
. The Douglas-fir produced 7-17 inches of fog drip and appeared to provide unique conditions supporting the orchids Giant helleborineEpipactis giganteaEpipactis gigantea is a species of orchid known by the common names stream orchid and giant helleborine. This wildflower is native to western North America from western Canada to central Mexico...
(Epipactis gigantea) and Phantom orchidCephalanthera austiniaeCephalanthera austiniae is a species of orchid known by the common names phantom orchid and snow orchid because the entire plant is white. Native to the western United States and Canada, it is the only species of genus Cephalanthera found outside of Europe and Asia, and the only one entirely...
(Cephalanthera austiniae), since these plants were found exclusively in these moist ridge tops. - In the Green MountainsGreen MountainsThe Green Mountains are a mountain range in the U.S. state of Vermont. The range extends approximately .-Peaks:The most notable mountains in the range include:*Mount Mansfield, , the highest point in Vermont*Killington Peak, *Mount Ellen,...
of northern VermontVermontVermont is a state in the New England region of the northeastern United States of America. The state ranks 43rd in land area, , and 45th in total area. Its population according to the 2010 census, 630,337, is the second smallest in the country, larger only than Wyoming. It is the only New England...
at elevations above 2,500 ft in the spruce-fir zone on the western slope of Camel's HumpCamel's HumpCamel's Hump is Vermont's third-highest mountain and highest undeveloped peak; moreover, because of its distinctive profile, it is perhaps the state's most recognized mountain. Part of the Green Mountain range, it is one of the oldest mountains on Earth...
, fog drip increased precipitation up to 67% over rainfall. 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. - In PeruPeruPeru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
and northern ChileChileChile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
, in the nearly complete absence of any annual rainfall, fog drip allows a type of forest to grow, called "loma". - In the arid climate of northern KenyaKenyaKenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...
, 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.