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88-547: Lopé National Park has dry weather compared to the rest of Gabon, being located in the rain shadow of the Chaillu Massif. In addition, there is a low band of rainfall along the Ogooué River. As a result, the landscape contains a complex mosaic of dense tropical rainforests and savannas. The boundary (called an ecotone ) between the two habitats has shifted since the last ice age , with the rainforest expanding into

176-499: A channel around 11 micron wavelength and primarily give information about cloud tops. Due to the typical structure of the atmosphere, cloud-top temperatures are approximately inversely related to cloud-top heights, meaning colder clouds almost always occur at higher altitudes. Further, cloud tops with a lot of small-scale variation are likely to be more vigorous than smooth-topped clouds. Various mathematical schemes, or algorithms, use these and other properties to estimate precipitation from

264-705: A dramatic effect on agriculture. All plants need at least some water to survive, therefore rain (being the most effective means of watering) is important to agriculture. While a regular rain pattern is usually vital to healthy plants, too much or too little rainfall can be harmful, even devastating to crops. Drought can kill crops and increase erosion, while overly wet weather can cause harmful fungus growth. Plants need varying amounts of rainfall to survive. For example, certain cacti require small amounts of water, while tropical plants may need up to hundreds of inches of rain per year to survive. In areas with wet and dry seasons, soil nutrients diminish and erosion increases during

352-425: A layer of above-freezing air exists with sub-freezing air both above and below. This causes the partial or complete melting of any snowflakes falling through the warm layer. As they fall back into the sub-freezing layer closer to the surface, they re-freeze into ice pellets. However, if the sub-freezing layer beneath the warm layer is too small, the precipitation will not have time to re-freeze, and freezing rain will be

440-411: A physical barrier such as a mountain ( orographic lift ). Conductive cooling occurs when the air comes into contact with a colder surface, usually by being blown from one surface to another, for example from a liquid water surface to colder land. Radiational cooling occurs due to the emission of infrared radiation , either by the air or by the surface underneath. Evaporative cooling occurs when moisture

528-453: A portion of the atmosphere becomes saturated with water vapor (reaching 100% relative humidity ), so that the water condenses and "precipitates" or falls. Thus, fog and mist are not precipitation; their water vapor does not condense sufficiently to precipitate, so fog and mist do not fall. (Such a non-precipitating combination is a colloid .) Two processes, possibly acting together, can lead to air becoming saturated with water vapor: cooling

616-567: A single year. A significant portion of the annual precipitation in any particular place (no weather station in Africa or South America were considered) falls on only a few days, typically about 50% during the 12 days with the most precipitation. The Köppen classification depends on average monthly values of temperature and precipitation. The most commonly used form of the Köppen classification has five primary types labeled A through E. Specifically,

704-409: A slow-falling drizzle , which has been observed as Rain puddles at its equator and polar regions. Precipitation is a major component of the water cycle , and is responsible for depositing most of the fresh water on the planet. Approximately 505,000 km (121,000 cu mi) of water falls as precipitation each year, 398,000 km (95,000 cu mi) of it over the oceans. Given

792-752: A subject of research. Although the ice is clear, scattering of light by the crystal facets and hollows/imperfections mean that the crystals often appear white in color due to diffuse reflection of the whole spectrum of light by the small ice particles. The shape of the snowflake is determined broadly by the temperature and humidity at which it is formed. Rarely, at a temperature of around −2 °C (28 °F), snowflakes can form in threefold symmetry—triangular snowflakes. The most common snow particles are visibly irregular, although near-perfect snowflakes may be more common in pictures because they are more visually appealing. No two snowflakes are alike, as they grow at different rates and in different patterns depending on

880-407: A variety of datasets possessing different formats, time/space grids, periods of record and regions of coverage, input datasets, and analysis procedures, as well as many different forms of dataset version designators. In many cases, one of the modern multi-satellite data sets is the best choice for general use. The likelihood or probability of an event with a specified intensity and duration is called

968-420: Is IC. Occult deposition occurs when mist or air that is highly saturated with water vapour interacts with the leaves of trees or shrubs it passes over. Stratiform or dynamic precipitation occurs as a consequence of slow ascent of air in synoptic systems (on the order of cm/s), such as over surface cold fronts , and over and ahead of warm fronts . Similar ascent is seen around tropical cyclones outside of

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1056-410: Is RA, while the coding for rain showers is SHRA. Ice pellets or sleet are a form of precipitation consisting of small, translucent balls of ice. Ice pellets are usually (but not always) smaller than hailstones. They often bounce when they hit the ground, and generally do not freeze into a solid mass unless mixed with freezing rain . The METAR code for ice pellets is PL . Ice pellets form when

1144-482: Is a grassland biome located in semi-arid to semi-humid climate regions of subtropical and tropical latitudes, with rainfall between 750 and 1,270 mm (30 and 50 in) a year. They are widespread on Africa, and are also found in India, the northern parts of South America, Malaysia, and Australia. The humid subtropical climate zone is where winter rainfall (and sometimes snowfall) is associated with large storms that

1232-480: Is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass. It can also form due to the lifting of advection fog during breezy conditions. There are four main mechanisms for cooling the air to its dew point: adiabatic cooling, conductive cooling, radiational cooling , and evaporative cooling. Adiabatic cooling occurs when air rises and expands. The air can rise due to convection , large-scale atmospheric motions, or

1320-449: Is a time when air quality improves, freshwater quality improves, and vegetation grows significantly. Soil nutrients diminish and erosion increases. Animals have adaptation and survival strategies for the wetter regime. The previous dry season leads to food shortages into the wet season, as the crops have yet to mature. Developing countries have noted that their populations show seasonal weight fluctuations due to food shortages seen before

1408-582: Is accompanied by plentiful precipitation year-round. The Mediterranean climate regime resembles the climate of the lands in the Mediterranean Basin, parts of western North America, parts of western and southern Australia, in southwestern South Africa and in parts of central Chile. The climate is characterized by hot, dry summers and cool, wet winters. A steppe is a dry grassland. Subarctic climates are cold with continuous permafrost and little precipitation. Precipitation, especially rain, has

1496-620: Is added to the air through evaporation, which forces the air temperature to cool to its wet-bulb temperature , or until it reaches saturation. The main ways water vapor is added to the air are: wind convergence into areas of upward motion, precipitation or virga falling from above, daytime heating evaporating water from the surface of oceans, water bodies or wet land, transpiration from plants, cool or dry air moving over warmer water, and lifting air over mountains. Coalescence occurs when water droplets fuse to create larger water droplets, or when water droplets freeze onto an ice crystal, which

1584-437: Is associated with their warm front is often extensive, forced by weak upward vertical motion of air over the frontal boundary which condenses as it cools and produces precipitation within an elongated band, which is wide and stratiform , meaning falling out of nimbostratus clouds. When moist air tries to dislodge an arctic air mass, overrunning snow can result within the poleward side of the elongated precipitation band . In

1672-404: Is carried by the prevailing onshore breezes towards the drier and hotter inland areas. When encountering elevated landforms , the moist air is driven upslope towards the peak , where it expands, cools, and its moisture condenses and starts to precipitate . If the landforms are tall and wide enough, most of the humidity will be lost to precipitation over the windward side (also known as

1760-487: Is equally distributed through the year. Some areas with pronounced rainy seasons will see a break in rainfall mid-season when the Intertropical Convergence Zone or monsoon trough move poleward of their location during the middle of the warm season. When the wet season occurs during the warm season, or summer, rain falls mainly during the late afternoon and early evening hours. The wet season

1848-416: Is filled by 2.5 cm (0.98 in) of rain, with overflow flowing into the outer cylinder. Plastic gauges have markings on the inner cylinder down to 1 ⁄ 4  mm (0.0098 in) resolution, while metal gauges require use of a stick designed with the appropriate 1 ⁄ 4  mm (0.0098 in) markings. After the inner cylinder is filled, the amount inside is discarded, then filled with

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1936-401: Is intermittent and often associated with baroclinic boundaries such as cold fronts , squall lines , and warm fronts. Convective precipitation mostly consist of mesoscale convective systems and they produce torrential rainfalls with thunderstorms, wind damages, and other forms of severe weather events. Orographic precipitation occurs on the windward (upwind) side of mountains and is caused by

2024-759: Is known as the Bergeron process . The fall rate of very small droplets is negligible, hence clouds do not fall out of the sky; precipitation will only occur when these coalesce into larger drops. droplets with different size will have different terminal velocity that cause droplets collision and producing larger droplets, Turbulence will enhance the collision process. As these larger water droplets descend, coalescence continues, so that drops become heavy enough to overcome air resistance and fall as rain. Raindrops have sizes ranging from 5.1 to 20 millimetres (0.20 to 0.79 in) mean diameter, above which they tend to break up. Smaller drops are called cloud droplets, and their shape

2112-607: Is limited to precipitation that crosses over the Continental Divide . While many locations west of the Divide may receive as much as 1,000 millimetres (40 in) of precipitation per year, some places on the eastern side, notably the cities of Denver and Pueblo, Colorado , typically receive only about 12 to 19 inches. Thus, the Continental Divide acts as a barrier for precipitation. This effect applies only to storms traveling west-to-east. When low pressure systems skirt

2200-540: Is made, various networks exist across the United States and elsewhere where rainfall measurements can be submitted through the Internet, such as CoCoRAHS or GLOBE . If a network is not available in the area where one lives, the nearest local weather office will likely be interested in the measurement. A concept used in precipitation measurement is the hydrometeor. Any particulates of liquid or solid water in

2288-532: Is much less forested than its surroundings, making an open landscape that may have been used as a corridor and migration route from the coast to the interior of Africa. The oldest Stone Age tools currently known were discovered at Elarmékora in the central region of the valley, in addition to several other Stone Age archeological sites. In the Neolithic , between 3500 and 2000 years ago, the Bantu people may have used

2376-431: Is possible within a cyclone's comma head and within lake effect precipitation bands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation. On the leeward side of mountains, desert climates can exist due to the dry air caused by compressional heating. Most precipitation occurs within the tropics and is caused by convection . The movement of

2464-519: Is spherical. As a raindrop increases in size, its shape becomes more oblate , with its largest cross-section facing the oncoming airflow. Contrary to the cartoon pictures of raindrops, their shape does not resemble a teardrop. Intensity and duration of rainfall are usually inversely related, i.e., high intensity storms are likely to be of short duration and low intensity storms can have a long duration. Rain drops associated with melting hail tend to be larger than other rain drops. The METAR code for rain

2552-489: Is the temperature to which a parcel of air must be cooled in order to become saturated, and (unless super-saturation occurs) condenses to water. Water vapor normally begins to condense on condensation nuclei such as dust, ice, and salt in order to form clouds. The cloud condensation nuclei concentration will determine the cloud microphysics. An elevated portion of a frontal zone forces broad areas of lift, which form cloud decks such as altostratus or cirrostratus . Stratus

2640-457: Is the time of year, covering one or more months, when most of the average annual rainfall in a region falls. The term green season is also sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the tropics and subtropics. Savanna climates and areas with monsoon regimes have wet summers and dry winters. Tropical rainforests technically do not have dry or wet seasons, since their rainfall

2728-400: Is typically active when freezing rain occurs. A stationary front is often present near the area of freezing rain and serves as the focus for forcing moist air to rise. Provided there is necessary and sufficient atmospheric moisture content, the moisture within the rising air will condense into clouds, namely nimbostratus and cumulonimbus if significant precipitation is involved. Eventually,

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2816-678: The Great Basin and Mojave Deserts . Similarly, in Asia, the Himalaya mountains create an obstacle to monsoons which leads to extremely high precipitation on the southern side and lower precipitation levels on the northern side. Extratropical cyclones can bring cold and dangerous conditions with heavy rain and snow with winds exceeding 119 km/h (74 mph), (sometimes referred to as windstorms in Europe). The band of precipitation that

2904-547: The Rocky Mountains and approach from the south, they can generate high precipitation on the eastern side and little or none on the western slope. Further east: Precipitation In meteorology , precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle , rain , sleet , snow , ice pellets , graupel and hail . Precipitation occurs when

2992-459: The electromagnetic spectrum that theory and practice show are related to the occurrence and intensity of precipitation. The sensors are almost exclusively passive, recording what they see, similar to a camera, in contrast to active sensors ( radar , lidar ) that send out a signal and detect its impact on the area being observed. Satellite sensors now in practical use for precipitation fall into two categories. Thermal infrared (IR) sensors record

3080-446: The eyewall , and in comma-head precipitation patterns around mid-latitude cyclones . A wide variety of weather can be found along an occluded front, with thunderstorms possible, but usually their passage is associated with a drying of the air mass. Occluded fronts usually form around mature low-pressure areas. Precipitation may occur on celestial bodies other than Earth. When it gets cold, Mars has precipitation that most likely takes

3168-443: The leopard , protecting healthy populations of its prey species including the red river hog , African forest buffalo , and cane rat . Other mammal species found in the part include the endangered giant pangolin and tree pangolin , often sharing nests with Microchiroptera bat species. Lopé National Park and its surroundings contain evidence of almost continual human occupation over the last 400,000 years. The Ogooué River Valley

3256-468: The monsoon trough , or Intertropical Convergence Zone , brings rainy seasons to savannah regions. Precipitation is a major component of the water cycle , and is responsible for depositing fresh water on the planet. Approximately 505,000 cubic kilometres (121,000 cu mi) of water falls as precipitation each year: 398,000 cubic kilometres (95,000 cu mi) over oceans and 107,000 cubic kilometres (26,000 cu mi) over land. Given

3344-451: The rainward side) before ever making it past the top. As the air descends the leeward side of the landforms, it is compressed and heated, producing foehn winds that absorb moisture downslope and cast a broad "shadow" of dry climate region behind the mountain crests . This climate typically takes the form of shrub–steppe , xeric shrublands or even deserts . The condition exists because warm moist air rises by orographic lifting to

3432-425: The return period or frequency. The intensity of a storm can be predicted for any return period and storm duration, from charts based on historical data for the location. The term 1 in 10 year storm describes a rainfall event which is rare and is only likely to occur once every 10 years, so it has a 10 percent likelihood any given year. The rainfall will be greater and the flooding will be worse than

3520-700: The trade winds is the zone between about 30° N and 30° S, blowing predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere . The westerlies are the prevailing winds in the middle latitudes between 30 and 60 degrees latitude , blowing predominantly from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere. Some of

3608-832: The Cordillera, in the direct lee of specific mountain ranges. This includes much of the Basin and Range Province in the United States and Mexico . The Pacific Coast Ranges create rain shadows near the West Coast: Most rain shadows in the western United States are due to the Sierra Nevada mountains in California and Cascade Mountains , mostly in Oregon and Washington . The Colorado Front Range

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3696-738: The Earth's surface area, that means the globally averaged annual precipitation is 990 millimetres (39 in), but over land it is only 715 millimetres (28.1 in). Climate classification systems such as the Köppen climate classification system use average annual rainfall to help differentiate between differing climate regimes. Global warming is already causing changes to weather, increasing precipitation in some geographies, and reducing it in others, resulting in additional extreme weather . Precipitation may occur on other celestial bodies. Saturn's largest satellite , Titan , hosts methane precipitation as

3784-610: The Earth's surface area, that means the globally averaged annual precipitation is 990 millimetres (39 in). Mechanisms of producing precipitation include convective, stratiform , and orographic rainfall. Convective processes involve strong vertical motions that can cause the overturning of the atmosphere in that location within an hour and cause heavy precipitation, while stratiform processes involve weaker upward motions and less intense precipitation. Precipitation can be divided into three categories, based on whether it falls as liquid water, liquid water that freezes on contact with

3872-535: The IR data. The second category of sensor channels is in the microwave part of the electromagnetic spectrum. The frequencies in use range from about 10 gigahertz to a few hundred GHz. Channels up to about 37 GHz primarily provide information on the liquid hydrometeors (rain and drizzle) in the lower parts of clouds, with larger amounts of liquid emitting higher amounts of microwave radiant energy . Channels above 37 GHz display emission signals, but are dominated by

3960-665: The Northern Hemisphere, poleward is towards the North Pole, or north. Within the Southern Hemisphere, poleward is towards the South Pole, or south. Southwest of extratropical cyclones, curved cyclonic flow bringing cold air across the relatively warm water bodies can lead to narrow lake-effect snow bands. Those bands bring strong localized snowfall which can be understood as follows: Large water bodies such as lakes efficiently store heat that results in significant temperature differences (larger than 13 °C or 23 °F) between

4048-1000: The action of solid hydrometeors (snow, graupel, etc.) to scatter microwave radiant energy. Satellites such as the Tropical Rainfall Measuring Mission (TRMM) and the Global Precipitation Measurement (GPM) mission employ microwave sensors to form precipitation estimates. Additional sensor channels and products have been demonstrated to provide additional useful information including visible channels, additional IR channels, water vapor channels and atmospheric sounding retrievals. However, most precipitation data sets in current use do not employ these data sources. The IR estimates have rather low skill at short time and space scales, but are available very frequently (15 minutes or more often) from satellites in geosynchronous Earth orbit. IR works best in cases of deep, vigorous convection—such as

4136-414: The air or adding water vapor to the air. Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called showers . Moisture that is lifted or otherwise forced to rise over a layer of sub-freezing air at the surface may be condensed by the low temperature into clouds and rain. This process

4224-497: The atmosphere are known as hydrometeors. Formations due to condensation, such as clouds, haze , fog, and mist, are composed of hydrometeors. All precipitation types are made up of hydrometeors by definition, including virga , which is precipitation which evaporates before reaching the ground. Particles blown from the Earth's surface by wind, such as blowing snow and blowing sea spray, are also hydrometeors , as are hail and snow . Although surface precipitation gauges are considered

4312-413: The atmosphere due to their mass, and may collide and stick together in clusters, or aggregates. These aggregates are snowflakes, and are usually the type of ice particle that falls to the ground. Guinness World Records list the world's largest snowflakes as those of January 1887 at Fort Keogh , Montana; allegedly one measured 38 cm (15 in) wide. The exact details of the sticking mechanism remain

4400-484: The average time between observations exceeds three hours. This several-hour interval is insufficient to adequately document precipitation because of the transient nature of most precipitation systems as well as the inability of a single satellite to appropriately capture the typical daily cycle of precipitation at a given location. Since the late 1990s, several algorithms have been developed to combine precipitation data from multiple satellites' sensors, seeking to emphasize

4488-413: The base, including several chalets and a large open air dining room, from which the rainforest is a mere five meters away. The park also hosts CEDAMM Training Centre, a Wildlife Conservation Society -run international conservation education center. Because of global climate change , the dense forest ecosystem is expanding into the savanna ecosystem in the north, leading to the loss of habitat diversity in

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4576-531: The best analyses of gauge data take two months or more after the observation time to undergo the necessary transmission, assembly, processing and quality control. Thus, precipitation estimates that include gauge data tend to be produced further after the observation time than the no-gauge estimates. As a result, while estimates that include gauge data may provide a more accurate depiction of the "true" precipitation, they are generally not suited for real- or near-real-time applications. The work described has resulted in

4664-420: The best instantaneous satellite estimate. In either case, the less-emphasized goal is also considered desirable. One key aspect of multi-satellite studies is the ability to include even a small amount of surface gauge data, which can be very useful for controlling the biases that are endemic to satellite estimates. The difficulties in using gauge data are that 1) their availability is limited, as noted above, and 2)

4752-532: The changing temperature and humidity within the atmosphere through which they fall on their way to the ground. The METAR code for snow is SN, while snow showers are coded SHSN. Diamond dust, also known as ice needles or ice crystals, forms at temperatures approaching −40 °C (−40 °F) due to air with slightly higher moisture from aloft mixing with colder, surface-based air. They are made of simple ice crystals, hexagonal in shape. The METAR identifier for diamond dust within international hourly weather reports

4840-447: The cloud droplets will grow large enough to form raindrops and descend toward the Earth where they will freeze on contact with exposed objects. Where relatively warm water bodies are present, for example due to water evaporation from lakes, lake-effect snowfall becomes a concern downwind of the warm lakes within the cold cyclonic flow around the backside of extratropical cyclones . Lake-effect snowfall can be locally heavy. Thundersnow

4928-462: The coding of GS, which is short for the French word grésil. Stones just larger than golf ball-sized are one of the most frequently reported hail sizes. Hailstones can grow to 15 centimetres (6 in) and weigh more than 500 grams (1 lb). In large hailstones, latent heat released by further freezing may melt the outer shell of the hailstone. The hailstone then may undergo 'wet growth', where

5016-424: The deeper the clouds get, and the greater the precipitation rate becomes. In mountainous areas, heavy snowfall accumulates when air is forced to ascend the mountains and squeeze out precipitation along their windward slopes, which in cold conditions, falls in the form of snow. Because of the ruggedness of terrain, forecasting the location of heavy snowfall remains a significant challenge. The wet, or rainy, season

5104-531: The descending and generally warming, leeward side where a rain shadow is observed. In Hawaii , Mount Waiʻaleʻale , on the island of Kauai, is notable for its extreme rainfall, as it has the second-highest average annual rainfall on Earth, with 12,000 millimetres (460 in). Storm systems affect the state with heavy rains between October and March. Local climates vary considerably on each island due to their topography, divisible into windward ( Koʻolau ) and leeward ( Kona ) regions based upon location relative to

5192-548: The equator in Colombia are amongst the wettest places on Earth. North and south of this are regions of descending air that form subtropical ridges where precipitation is low; the land surface underneath these ridges is usually arid, and these regions make up most of the Earth's deserts. An exception to this rule is in Hawaii, where upslope flow due to the trade winds lead to one of the wettest locations on Earth. Otherwise,

5280-458: The first harvest, which occurs late in the wet season. Tropical cyclones, a source of very heavy rainfall, consist of large air masses several hundred miles across with low pressure at the centre and with winds blowing inward towards the centre in either a clockwise direction (southern hemisphere) or counterclockwise (northern hemisphere). Although cyclones can take an enormous toll in lives and personal property, they may be important factors in

5368-737: The flow of the Westerlies into the Rocky Mountains lead to the wettest, and at elevation snowiest, locations within North America. In Asia during the wet season, the flow of moist air into the Himalayas leads to some of the greatest rainfall amounts measured on Earth in northeast India. The standard way of measuring rainfall or snowfall is the standard rain gauge, which can be found in 10 cm (3.9 in) plastic and 20 cm (7.9 in) metal varieties. The inner cylinder

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5456-579: The form of ice needles, rather than rain or snow. Convective rain , or showery precipitation, occurs from convective clouds, e.g. cumulonimbus or cumulus congestus . It falls as showers with rapidly changing intensity. Convective precipitation falls over a certain area for a relatively short time, as convective clouds have limited horizontal extent. Most precipitation in the tropics appears to be convective; however, it has been suggested that stratiform precipitation also occurs. Graupel and hail indicate convection. In mid-latitudes, convective precipitation

5544-400: The funnel needs to be removed before the event begins. For those looking to measure rainfall the most inexpensively, a can that is cylindrical with straight sides will act as a rain gauge if left out in the open, but its accuracy will depend on what ruler is used to measure the rain with. Any of the above rain gauges can be made at home, with enough know-how . When a precipitation measurement

5632-425: The gauge. Once the snowfall/ice is finished accumulating, or as 30 cm (12 in) is approached, one can either bring it inside to melt, or use lukewarm water to fill the inner cylinder with in order to melt the frozen precipitation in the outer cylinder, keeping track of the warm fluid added, which is subsequently subtracted from the overall total once all the ice/snow is melted. Other types of gauges include

5720-463: The hailstones to the upper part of the cloud. The updraft dissipates and the hailstones fall down, back into the updraft, and are lifted again. Hail has a diameter of 5 millimetres (0.20 in) or more. Within METAR code, GR is used to indicate larger hail, of a diameter of at least 6.4 millimetres (0.25 in). GR is derived from the French word grêle. Smaller-sized hail, as well as snow pellets, use

5808-487: The higher mountains. Windward sides face the east to northeast trade winds and receive much more rainfall; leeward sides are drier and sunnier, with less rain and less cloud cover. In South America, the Andes mountain range blocks Pacific moisture that arrives in that continent, resulting in a desertlike climate just downwind across western Argentina. The Sierra Nevada range creates the same effect in North America forming

5896-479: The ice crystals the crystals are able to grow to hundreds of micrometers in size at the expense of the water droplets. This process is known as the Wegener–Bergeron–Findeisen process . The corresponding depletion of water vapor causes the droplets to evaporate, meaning that the ice crystals grow at the droplets' expense. These large crystals are an efficient source of precipitation, since they fall through

5984-454: The liquid outer shell collects other smaller hailstones. The hailstone gains an ice layer and grows increasingly larger with each ascent. Once a hailstone becomes too heavy to be supported by the storm's updraft, it falls from the cloud. Snow crystals form when tiny supercooled cloud droplets (about 10 μm in diameter) freeze. Once a droplet has frozen, it grows in the supersaturated environment. Because water droplets are more numerous than

6072-463: The mountain. The air descends on the leeward side, but due to the precipitation it has lost much of its moisture. Typically, descending air also gets warmer because of adiabatic compression (as with foehn winds) down the leeward side of the mountain, which increases the amount of moisture that it can absorb and creates an arid region. There are regular patterns of prevailing winds found in bands round Earth's equatorial region. The zone designated

6160-501: The park. As a result, annual controlled burns of the savanna have been conducted in the park to reduce the encroachment of the forest vegetation and to provide the required vegetation for the diet of the forest buffalo. Rain shadow A rain shadow is an area of significantly reduced rainfall behind a mountainous region, on the side facing away from prevailing winds , known as its leeward side. Evaporated moisture from water bodies (such as oceans and large lakes )

6248-424: The popular wedge gauge (the cheapest rain gauge and most fragile), the tipping bucket rain gauge , and the weighing rain gauge . The wedge and tipping bucket gauges have problems with snow. Attempts to compensate for snow/ice by warming the tipping bucket meet with limited success, since snow may sublimate if the gauge is kept much above freezing. Weighing gauges with antifreeze should do fine with snow, but again,

6336-490: The precipitation regimes of places they impact, as they may bring much-needed precipitation to otherwise dry regions. Areas in their path can receive a year's worth of rainfall from a tropical cyclone passage. On the large scale, the highest precipitation amounts outside topography fall in the tropics, closely tied to the Intertropical Convergence Zone , itself the ascending branch of the Hadley cell . Mountainous locales near

6424-581: The primary types are A, tropical; B, dry; C, mild mid-latitude; D, cold mid-latitude; and E, polar. The five primary classifications can be further divided into secondary classifications such as rain forest , monsoon , tropical savanna , humid subtropical , humid continental , oceanic climate , Mediterranean climate , steppe , subarctic climate , tundra , polar ice cap , and desert . Rain forests are characterized by high rainfall, with definitions setting minimum normal annual rainfall between 1,750 and 2,000 mm (69 and 79 in). A tropical savanna

6512-406: The remaining rainfall in the outer cylinder until all the fluid in the outer cylinder is gone, adding to the overall total until the outer cylinder is empty. These gauges are used in the winter by removing the funnel and inner cylinder and allowing snow and freezing rain to collect inside the outer cylinder. Some add anti-freeze to their gauge so they do not have to melt the snow or ice that falls into

6600-413: The result at the surface. A temperature profile showing a warm layer above the ground is most likely to be found in advance of a warm front during the cold season, but can occasionally be found behind a passing cold front . Like other precipitation, hail forms in storm clouds when supercooled water droplets freeze on contact with condensation nuclei , such as dust or dirt. The storm's updraft blows

6688-438: The rising air motion of a large-scale flow of moist air across the mountain ridge, resulting in adiabatic cooling and condensation. In mountainous parts of the world subjected to relatively consistent winds (for example, the trade winds ), a more moist climate usually prevails on the windward side of a mountain than on the leeward or downwind side. Moisture is removed by orographic lift, leaving drier air (see katabatic wind ) on

6776-462: The savanna, although the dry climate has allowed the savanna ecosystem to persist in the north of the park. Because of the complex environment, the national park contains unusually high biodiversity across many taxa. Over 1,550 plant species have been recorded to date, with many regions of the park yet to be explored fully. In a survey of land snails in the park, 74 species were found from 12 different families. The park also provides critical habitat for

6864-455: The standard for measuring precipitation, there are many areas in which their use is not feasible. This includes the vast expanses of ocean and remote land areas. In other cases, social, technical or administrative issues prevent the dissemination of gauge observations. As a result, the modern global record of precipitation largely depends on satellite observations. Satellite sensors work by remotely sensing precipitation—recording various parts of

6952-565: The strengths and minimize the weaknesses of the individual input data sets. The goal is to provide "best" estimates of precipitation on a uniform time/space grid, usually for as much of the globe as possible. In some cases the long-term homogeneity of the dataset is emphasized, which is the Climate Data Record standard. Alternatively, the High Resolution Precipitation Product aims to produce

7040-697: The strongest westerly winds in the middle latitudes can come in the Roaring Forties of the Southern Hemisphere, between 30 and 50 degrees latitude. Examples of notable rain shadowing include: On the largest scale, the entirety of the North American Interior Plains are shielded from the prevailing Westerlies carrying moist Pacific weather by the North American Cordillera . More pronounced effects are observed, however, in particular valley regions within

7128-424: The surface, or ice. Mixtures of different types of precipitation, including types in different categories, can fall simultaneously. Liquid forms of precipitation include rain and drizzle. Rain or drizzle that freezes on contact within a subfreezing air mass is called "freezing rain" or "freezing drizzle". Frozen forms of precipitation include snow, ice needles , ice pellets , hail , and graupel . The dew point

7216-512: The time of the beginning of iron-working, it appears that the valley was abandoned sometime between 600 and 1200 AD, before being repopulated by the present-day Okanda people in the 14th and 15th centuries. The park contains a small research station, named as Mikongo and run by the Zoological Society London, based in the village known as Mikongo, from which it gets its name. There exists infrastructure to cater for tourists at

7304-419: The top of a mountain range. As atmospheric pressure decreases with increasing altitude, the air has expanded and adiabatically cooled to the point that the air reaches its adiabatic dew point (which is not the same as its constant pressure dew point commonly reported in weather forecasts). At the adiabatic dew point, moisture condenses onto the mountain and it precipitates on the top and windward sides of

7392-437: The tropics—and becomes progressively less useful in areas where stratiform (layered) precipitation dominates, especially in mid- and high-latitude regions. The more-direct physical connection between hydrometeors and microwave channels gives the microwave estimates greater skill on short time and space scales than is true for IR. However, microwave sensors fly only on low Earth orbit satellites, and there are few enough of them that

7480-432: The valley during the Bantu expansion , leaving behind remains of polished stone axes and pottery. During that time, small villages were constructed on the hilltops with large rubbish pits. Later, when iron-working appeared in the valley around 2000 years ago, the hilltop villages became larger, with nearby iron furnaces, and agriculture began to flourish. Although over 1600 petroglyphs have been discovered dating from around

7568-405: The water surface and the air above. Because of this temperature difference, warmth and moisture are transported upward, condensing into vertically oriented clouds (see satellite picture) which produce snow showers. The temperature decrease with height and cloud depth are directly affected by both the water temperature and the large-scale environment. The stronger the temperature decrease with height,

7656-447: The westerlies steer from west to east. Most summer rainfall occurs during thunderstorms and from occasional tropical cyclones. Humid subtropical climates lie on the east side continents, roughly between latitudes 20° and 40° degrees from the equator. An oceanic (or maritime) climate is typically found along the west coasts at the middle latitudes of all the world's continents, bordering cool oceans, as well as southeastern Australia, and

7744-438: The worst storm expected in any single year. The term 1 in 100 year storm describes a rainfall event which is extremely rare and which will occur with a likelihood of only once in a century, so has a 1 percent likelihood in any given year. The rainfall will be extreme and flooding to be worse than a 1 in 10 year event. As with all probability events, it is possible though unlikely to have two "1 in 100 Year Storms" in

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