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95-602: Chibchacum or Chichebachun is the rain and thunder god in the religion of the Muisca who inhabited the Altiplano Cundiboyacense in pre-Columbian times. In myth, when Chibchacum was angry, he sent heavy rains to the flatlands, causing the rivers to flood, destroying the agriculture and the houses ( bohíos ) of the Muisca. When the rains were over and the Sun was shining again, causing Cuchavira to appear,

190-419: A strain gauge is fixed to the collection bucket so that the exact rainfall can be read at any moment. Each time the collector tips, the strain gauge (weight sensor) is re-zeroed to null out any drift. To measure the water equivalent of frozen precipitation, a tipping bucket may be heated to melt any ice and snow that is caught in its funnel. Without a heating mechanism, the funnel often becomes clogged during

285-494: A device to measure the number of chemicals contained in the location's atmosphere. This is extremely helpful for scientists studying the effects of greenhouse gases released into the atmosphere and their effects on the levels of the acid rain . Some Automated Surface Observing System (ASOS) units use an automated weighing gauge called the AWPAG (All Weather Precipitation Accumulation Gauge). The tipping bucket rain gauge consists of

380-529: A field study published in 2021 by researchers at Stockholm University found that they are often transferred from water to air when waves reach land, are a significant source of air pollution , and eventually get into rain. The researchers concluded that pollution may impact large areas. In 2024, a worldwide study of 45,000 groundwater samples found that 31% of samples contained levels of PFAS that were harmful to human health; these samples were taken from areas not near any obvious source of contamination. Rain

475-417: A fraction of that amount has actually fallen. Tipping buckets also tend to underestimate the amount of rainfall, particularly in snowfall and heavy rainfall events. The advantage of the tipping bucket rain gauge is that the character of the rain (light, medium, or heavy) may be easily obtained. Rainfall character is decided by the total amount of rain that has fallen in a set period (usually 1 hour) by counting

570-414: A frozen precipitation event, and thus no precipitation can be measured. Many Automated Surface Observing System (ASOS) units use heated tipping buckets to measure precipitation. This type of gauge has a row of collection funnels. In an enclosed space below each is a laser diode and a photo transistor detector . When enough water is collected to make a single drop, it drops from the bottom, falling into

665-405: A funnel that collects and channels the precipitation into a small seesaw -like container. After a pre-set amount of precipitation falls, the lever tips, dumping the collected water and sending an electrical signal. An old-style recording device may consist of a pen mounted on an arm attached to a geared wheel that moves once with each signal sent from the collector. In this design, as the wheel turns

760-403: A graduated sheet of cardboard, which has the time at the abscissa while the y-axis indicates the height of rainfall in mm of rain . This height is recorded with a pen that moves vertically, driven by a buoy, marking on the paper the rainfall over time. Each cardboard sheet is usually used for one day. As the rain falls, the water collected by the funnel falls into the container and raises

855-578: A hundred years. In 1870 he produced an account of rainfall in the British Isles starting in 1725. Due to the ever-increasing numbers of observers, standardisation of the gauges became necessary. Symons began experimenting with new gauges in his own garden. He tried different models with variations in size, shape, and height. In 1863 he began a collaboration with Michael Foster Ward from Calne , Wiltshire , who undertook more extensive investigations. By including Ward and various others around Britain,

950-483: A long duration. The final droplet size distribution is an exponential distribution . The number of droplets with diameter between d {\displaystyle d} and D + d D {\displaystyle D+dD} per unit volume of space is n ( d ) = n 0 e − d / ⟨ d ⟩ d D {\displaystyle n(d)=n_{0}e^{-d/\langle d\rangle }dD} . This

1045-460: A particular air temperature. How much water vapor a parcel of air can contain before it becomes saturated (100% relative humidity) and forms into a cloud (a group of visible tiny water or ice particles suspended above the Earth's surface) depends on its temperature. Warmer air can contain more water vapor than cooler air before becoming saturated. Therefore, one way to saturate a parcel of air

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1140-602: A period of 15 years from 1677 to 1694, publishing his records in the Philosophical Transactions of the Royal Society . Towneley called for more measurements elsewhere in the country to compare the rainfall in different regions, although only William Derham appears to have taken up Towneley's challenge. They jointly published the rainfall measurements for Towneley Park and Upminster in Essex for

1235-410: 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

1330-543: A point are estimated by using the value of reflectivity data at individual grid points. A radar equation is then used, which is Z = A R b , {\displaystyle Z=AR^{b},} where Z represents the radar reflectivity, R represents the rainfall rate, and A and b are constants. Satellite-derived rainfall estimates use passive microwave instruments aboard polar orbiting as well as geostationary weather satellites to indirectly measure rainfall rates. If one wants an accumulated rainfall over

1425-406: A rare rainfall event occurring on average once every 10 years. The rainfall will be greater and the flooding will be worse than the worst storm expected in any single year. A 100-year storm describes an extremely rare rainfall event occurring on average once in a century. The rainfall will be extreme and flooding worse than a 10-year event. The probability of an event in any year is the inverse of

1520-407: A result of this warming, monthly rainfall is about 28% greater between 32 and 64 km (20 and 40 mi) downwind of cities, compared with upwind. Some cities induce a total precipitation increase of 51%. Increasing temperatures tend to increase evaporation which can lead to more precipitation. Precipitation generally increased over land north of 30°N from 1900 through 2005 but has declined over

1615-649: A teardrop. The biggest raindrops on Earth were recorded over Brazil and the Marshall Islands in 2004 — some of them were as large as 10 mm (0.39 in). The large size is explained by condensation on large smoke particles or by collisions between drops in small regions with particularly high content of liquid water. Raindrops associated with melting hail tend to be larger than other raindrops. 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

1710-425: A tendency to break up at larger sizes. Smaller drops are called cloud droplets, and their shape is spherical. As a raindrop increases in size, its shape becomes more oblate, with its largest cross-section facing the oncoming airflow. Large rain drops become increasingly flattened on the bottom, like hamburger buns; very large ones are shaped like parachutes . Contrary to popular belief, their shape does not resemble

1805-470: A time period, one has to add up all the accumulations from each grid box within the images during that time. Rainfall intensity is classified according to the rate of precipitation, which depends on the considered time. The following categories are used to classify rainfall intensity: Terms used for a heavy or violent rain include gully washer, trash-mover and toad-strangler. The intensity can also be expressed by rainfall erosivity R-factor or in terms of

1900-465: A valley to wash away the floodwaters, he knew he had to punish Chibchacum. Bochica cursed Chibchacum by forcing him to carry Mother Earth on his back. To this day the Muisca believe that when there is an earthquake, it is Chibchacum shifting his heavy load. Rain Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity . Rain is a major component of

1995-472: 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 is associated with large storms that

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2090-511: Is a time when air quality improves, freshwater quality improves, and vegetation grows significantly. 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

2185-654: 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 South 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. In 2022, levels of at least four perfluoroalkyl acids (PFAAs) in rain water worldwide greatly exceeded

2280-718: 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. Water vapor normally begins to condense on condensation nuclei such as dust, ice, and salt in order to form clouds. Elevated portions of weather fronts (which are three-dimensional in nature) force broad areas of upward motion within

2375-563: Is also causing changes in the precipitation pattern, including wetter conditions across eastern North America and drier conditions in the tropics. Antarctica is the driest continent. The globally averaged annual precipitation over land is 715 mm (28.1 in), but over the whole Earth, it is much higher at 990 mm (39 in). Climate classification systems such as the Köppen classification system use average annual rainfall to help differentiate between differing climate regimes. Rainfall

2470-842: Is commonly referred to as the Marshall–Palmer law after the researchers who first characterized it. The parameters are somewhat temperature-dependent, and the slope also scales with the rate of rainfall ⟨ d ⟩ − 1 = 41 R − 0.21 {\displaystyle \langle d\rangle ^{-1}=41R^{-0.21}} (d in centimeters and R in millimeters per hour). Deviations can occur for small droplets and during different rainfall conditions. The distribution tends to fit averaged rainfall, while instantaneous size spectra often deviate and have been modeled as gamma distributions . The distribution has an upper limit due to droplet fragmentation. Raindrops impact at their terminal velocity , which

2565-410: Is derived from natural sources such as volcanoes, and wetlands (sulfate-reducing bacteria); and anthropogenic sources such as the combustion of fossil fuels , and mining where H 2 S is present. Nitric acid is produced by natural sources such as lightning, soil bacteria, and natural fires; while also produced anthropogenically by the combustion of fossil fuels and from power plants. In the past 20 years,

2660-487: 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

2755-498: Is greater for larger drops due to their larger mass-to-drag ratio. At sea level and without wind, 0.5 mm (0.020 in) drizzle impacts at 2 m/s (6.6 ft/s) or 7.2 km/h (4.5 mph), while large 5 mm (0.20 in) drops impact at around 9 m/s (30 ft/s) or 32 km/h (20 mph). Rain falling on loosely packed material such as newly fallen ash can produce dimples that can be fossilized, called raindrop impressions . The air density dependence of

2850-497: Is measured in units of length per unit time, typically in millimeters per hour, or in countries where imperial units are more common, inches per hour. The "length", or more accurately, "depth" being measured is the depth of rain water that would accumulate on a flat, horizontal and impermeable surface during a given amount of time, typically an hour. One millimeter of rainfall is the equivalent of one liter of water per square meter. The standard way of measuring rainfall or snowfall

2945-408: Is measured using rain gauges . Rainfall amounts can be estimated by weather radar . Air contains water vapor, and the amount of water in a given mass of dry air, known as the mixing ratio , is measured in grams of water per kilogram of dry air (g/kg). The amount of moisture in the air is also commonly reported as relative humidity ; which is the percentage of the total water vapor air can hold at

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3040-420: Is present, precipitation falls from convective clouds (those with strong upward vertical motion) such as cumulonimbus (thunder clouds) which can organize into narrow rainbands . In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation which forces moist air to condense and fall out as rainfall along the sides of mountains. On

3135-424: Is referred to as banded structure. Rainbands in advance of warm occluded fronts and warm fronts are associated with weak upward motion, and tend to be wide and stratiform in nature. Rainbands spawned near and ahead of cold fronts can be squall lines which are able to produce tornadoes . Rainbands associated with cold fronts can be warped by mountain barriers perpendicular to the front's orientation due to

3230-561: Is the expected amount of liquid precipitation accumulated over a specified time period over a specified area. A QPF will be specified when a measurable precipitation type reaching a minimum threshold is forecast for any hour during a QPF valid period. Precipitation forecasts tend to be bound by synoptic hours such as 0000, 0600, 1200 and 1800  GMT . Terrain is considered in QPFs by use of topography or based upon climatological precipitation patterns from observations with fine detail. Starting in

3325-411: Is the presence of a thick layer of air aloft which is above the melting point of water, which melts the frozen precipitation well before it reaches the ground. If there is a shallow near-surface layer that is below freezing, freezing rain (rain which freezes on contact with surfaces in subfreezing environments) will result. Hail becomes an increasingly infrequent occurrence when the freezing level within

3420-440: Is the standard rain gauge, which can be found in 100-mm (4-in) plastic and 200-mm (8-in) metal varieties. The inner cylinder is filled by 25 mm (0.98 in) of rain, with overflow flowing into the outer cylinder. Plastic gauges have markings on the inner cylinder down to 0.25 mm (0.0098 in) resolution, while metal gauges require use of a stick designed with the appropriate 0.25 mm (0.0098 in) markings. After

3515-399: Is to cool it. The dew point is the temperature to which a parcel must be cooled in order to become saturated. 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

3610-589: The Great Basin and Mojave Deserts . The wet, or rainy, season 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

3705-404: The leeward side of mountains, desert climates can exist due to the dry air caused by downslope flow which causes heating and drying of the air mass . The movement of the monsoon trough , or Intertropical Convergence Zone , brings rainy seasons to savannah climes . The urban heat island effect leads to increased rainfall, both in amounts and intensity, downwind of cities. Global warming

3800-409: 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 is intermittent and often associated with baroclinic boundaries such as cold fronts , squall lines , and warm fronts. Orographic precipitation occurs on the windward side of mountains and is caused by

3895-406: The water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water for hydroelectric power plants , crop irrigation , and suitable conditions for many types of ecosystems . The major cause of rain production is moisture moving along three-dimensional zones of temperature and moisture contrasts known as weather fronts . If enough moisture and upward motion

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3990-455: 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 away 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

4085-726: The British Isles. He set up a voluntary network of observers, who collected data which were returned to him for analysis. So successful was he in this endeavour that by 1866 he was able to show results that gave a fair representation of the distribution of rainfall and the number of recorders gradually increased until the last volume of British Rainfall which he lived to edit, for 1899, contained figures from 3,528 stations — 2,894 in England and Wales , 446 in Scotland , and 188 in Ireland . He also collected old rainfall records going back over

4180-461: The EPA's lifetime drinking water health advisories as well as comparable Danish, Dutch, and European Union safety standards, leading to the conclusion that "the global spread of these four PFAAs in the atmosphere has led to the planetary boundary for chemical pollution being exceeded". It had been thought that PFAAs would eventually end up in the oceans, where they would be diluted over decades, but

4275-404: The Earth's atmosphere which form clouds decks such as altostratus or cirrostratus . Stratus 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. Coalescence occurs when water droplets fuse to create larger water droplets. Air resistance typically causes

4370-678: The Internet, such as CoCoRAHS or GLOBE. If a network is not available in the area where one lives, the nearest local weather or met office will likely be interested in the measurement. One of the main uses of weather radar is to be able to assess the amount of precipitations fallen over large basins for hydrological purposes. For instance, river flood control , sewer management and dam construction are all areas where planners use rainfall accumulation data. Radar-derived rainfall estimates complement surface station data which can be used for calibration. To produce radar accumulations, rain rates over

4465-889: The Northeast and Midwest, which in the past decade, have seen 31 and 16 percent more heavy downpours compared to the 1950s. Rhode Island is the state with the largest increase, 104%. McAllen, Texas is the city with the largest increase, 700%. Heavy downpour in the analysis are the days where total precipitation exceeded the top one percent of all rain and snow days during the years 1950–2014. The most successful attempts at influencing weather involve cloud seeding , which include techniques used to increase winter precipitation over mountains and suppress hail . Rainbands are cloud and precipitation areas which are significantly elongated. Rainbands can be stratiform or convective , and are generated by differences in temperature. When noted on weather radar imagery, this precipitation elongation

4560-405: The atmosphere exceeds 3,400 m (11,000 ft) above ground level. 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

4655-402: The buoy that makes the pen arm rise in the vertical axis, marking the cardboard accordingly. If the rainfall does not vary, the water level in the container remains constant, and while the drum rotates, the pen's mark is more or less a horizontal line, proportional to the amount of water that has fallen. When the pen reaches the top edge of the recording paper, it means that the buoy is "up high in

4750-517: The concentrations of nitric and sulfuric acid has decreased in presence of rainwater, which may be due to the significant increase in ammonium (most likely as ammonia from livestock production), which acts as a buffer in acid rain and raises the pH. 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,

4845-612: The contiguous United States, total annual precipitation increased at an average rate of 6.1 percent since 1900, with the greatest increases within the East North Central climate region (11.6 percent per century) and the South (11.1 percent). Hawaii was the only region to show a decrease (−9.25 percent). Analysis of 65 years of United States of America rainfall records show the lower 48 states have an increase in heavy downpours since 1950. The largest increases are in

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4940-710: The course of the week, the likelihood of rain increases: it peaks by Saturday, after five days of weekday pollution has been built up. In heavily populated areas that are near the coast, such as the United States' Eastern Seaboard , the effect can be dramatic: there is a 22% higher chance of rain on Saturdays than on Mondays. The urban heat island effect warms cities 0.6 to 5.6 °C (33.1 to 42.1 °F) above surrounding suburbs and rural areas. This extra heat leads to greater upward motion, which can induce additional shower and thunderstorm activity. Rainfall rates downwind of cities are increased between 48% and 116%. Partly as

5035-412: The crystal and neighboring water droplets. This process is temperature dependent, as supercooled water droplets only exist in a cloud that is below freezing. In addition, because of the great temperature difference between cloud and ground level, these ice crystals may melt as they fall and become rain. Raindrops have sizes ranging from 0.1 to 9 mm (0.0039 to 0.3543 in) mean diameter but develop

5130-476: The cylinder is 0.5 mm (0.02 in). In areas using Imperial units, each horizontal line represents 0.01 in (0.25 mm) inches. The pluviometer of intensities (or Jardi's pluviometer) is a tool that measures the average intensity of rainfall in a certain interval of time. It was initially designed to record the rainfall regime in Catalonia but eventually spread throughout the world. It employs

5225-559: 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 is amongst the places in the world with the highest levels of rainfall, with 9,500 mm (373 in). Systems known as Kona storms affect the state with heavy rains between October and April. Local climates vary considerably on each island due to their topography, divisible into windward ( Koʻolau ) and leeward ( Kona ) regions based upon location relative to

5320-428: The equipment survives) due to wind extremes. Also, rain gauges only indicate rainfall in a localized area. For virtually any gauge, drops will stick to the sides or funnel of the collecting device, such that amounts are very slightly underestimated, and those of .01 inches or .25 mm may be recorded as a " trace ". Another problem encountered is when the temperature is close to or below freezing. Rain may fall on

5415-511: The formation of a low-level barrier jet . Bands of thunderstorms can form with sea breeze and land breeze boundaries if enough moisture is present. If sea breeze rainbands become active enough just ahead of a cold front, they can mask the location of the cold front itself. Once a cyclone occludes an occluded front (a trough of warm air aloft) will be caused by strong southerly winds on its eastern periphery rotating aloft around its northeast, and ultimately northwestern, periphery (also termed

5510-482: The front is unstable enough for convection. Banding within the comma head precipitation pattern of an extratropical cyclone can yield significant amounts of rain. Behind extratropical cyclones during fall and winter, rainbands can form downwind of relative warm bodies of water such as the Great Lakes . Downwind of islands, bands of showers and thunderstorms can develop due to low-level wind convergence downwind of

5605-401: The funnel and ice or snow may collect in the gauge, blocking subsequent rain. To alleviate this, a gauge may be equipped with an automatic electric heater to keep its moisture-collecting surfaces and sensor slightly above freezing. Rain gauges should be placed in an open area where there are no buildings, trees, or other obstacles to block the rain. This is also to prevent the water collected on

5700-400: The ground. This is termed virga and is more often seen in hot and dry climates. Stratiform (a broad shield of precipitation with a relatively similar intensity) and dynamic precipitation (convective precipitation which is showery in nature with large changes in intensity over short distances) occur as a consequence of slow ascent of air in synoptic systems (on the order of cm/s), such as in

5795-464: The height of the water in the small graduated cylinder is measured, and the excess overflow in the large container is carefully poured into another graduated cylinder and measured to give the total rainfall. A cone meter is sometimes used to prevent leakage that can result in alteration of the data. In locations using the metric system, the cylinder is usually marked in mm and will measure up to 250 mm (9.8 in) of rainfall. Each horizontal line on

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5890-552: 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 desert-like climate just downwind across western Argentina. The Sierra Nevada range creates the same effect in North America forming

5985-438: The inner cylinder is filled, the amount inside it is discarded, then filled with 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. Other types of gauges include the popular wedge gauge (the cheapest rain gauge and most fragile), the tipping bucket rain gauge, and the weighing rain gauge. For those looking to measure rainfall

6080-523: The investigations continued until 1890. The experiments were remarkable for their planning, execution, and drawing of conclusions. The results of these experiments led to the progressive adoption of the well-known standard gauge, still used by the UK Meteorological Office today, namely, one made of "... copper, with a five-inch funnel having its brass rim one foot above the ground ..." Most modern rain gauges generally measure

6175-422: The island edges. Offshore California , this has been noted in the wake of cold fronts. Rainbands within tropical cyclones are curved in orientation. Tropical cyclone rainbands contain showers and thunderstorms that, together with the eyewall and the eye, constitute a hurricane or tropical storm . The extent of rainbands around a tropical cyclone can help determine the cyclone's intensity. The phrase acid rain

6270-416: The laser beam path. The sensor is set at right angles to the laser so that enough light is scattered to be detected as a sudden flash of lights. The flashes from these photodetectors are then read and transmitted or recorded. Different type of optical range gauges have been used throughout the decades. The technology has also improved. Acoustic disdrometers , also referred to as hydrophones, are able to sense

6365-427: The maximum raindrop diameter together with fossil raindrop imprints has been used to constrain the density of the air 2.7 billion years ago. The sound of raindrops hitting water is caused by bubbles of air oscillating underwater . The METAR code for rain is RA, while the coding for rain showers is SHRA. In certain conditions, precipitation may fall from a cloud but then evaporate or sublime before reaching

6460-717: The mid to late 1990s, QPFs were used within hydrologic forecast models to simulate impact to rivers throughout the United States. Rain gauge The first known rainfall records were kept by the Ancient Greeks , at around 500 BCE. People living in India began to record rainfall in 400 BCE The readings were correlated against expected growth. In the Arthashastra , used for example in Magadha , precise standards were set as to grain production. Each state storehouse

6555-428: 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 is made, various networks exist across the United States and elsewhere where rainfall measurements can be submitted through

6650-462: The number of heavy precipitation events over many areas during the past century, as well as an increase since the 1970s in the prevalence of droughts—especially in the tropics and subtropics. Changes in precipitation and evaporation over the oceans are suggested by the decreased salinity of mid- and high-latitude waters (implying more precipitation), along with increased salinity in lower latitudes (implying less precipitation and/or more evaporation). Over

6745-445: The number of pulses during that period. Algorithms may be applied to the data as a method of correcting the data for high-intensity rainfall. Modern tipping rain gauges consist of a plastic collector balanced over a pivot. When it tips, it actuates a switch (such as a reed switch ) which is then electronically recorded or transmitted to a remote collection station. Tipping gauges can also incorporate elements of weighing gauges whereby

6840-445: The paid weather observer with a network of volunteers to obtain precipitation data (and other types of weather) for sparsely populated areas. In most cases the precipitation is not retained, but some stations do submit rainfall and snowfall for testing, which is done to obtain levels of pollutants. Rain gauges have their limitations. Attempting to collect rain data in a tropical cyclone can be nearly impossible and unreliable (even if

6935-410: The pen arm moves either up or down leaving a trace on the graph and at the same time making a loud "click". The tipping bucket rain gauge is not as accurate as the standard rain gauge, because the rainfall may stop before the lever has tipped. When the next period of rain begins it may take no more than one or two drops to tip the lever. This would then indicate that a pre-set amount has fallen when only

7030-433: The people offered low-grade gold or gold - copper alloys ( tumbaga ), marine snails and small emeralds to thank him. One tale tells how the Muisca venerated a rock and worshipped Bochica . Chibchacum was very angry and rebelled against Bochica. He went down to Earth and noticed a woman , Chié coming to get some water. Chibchacum wooed her into joining his rebellion, promising that Chié would be his queen once Bochica

7125-435: The precipitation in millimetres in height collected during a certain period, equivalent to litres per square metre. Previously rain was recorded as inches or points, where one point is equal to 0.254 mm or 0.01 of an inch. Rain gauge amounts are read either manually or by automatic weather station (AWS). The frequency of readings will depend on the requirements of the collection agency. Some countries will supplement

7220-478: 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. The fine particulate matter produced by car exhaust and other human sources of pollution forms cloud condensation nuclei leads to the production of clouds and increases the likelihood of rain. As commuters and commercial traffic cause pollution to build up over

7315-579: 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

7410-415: The principle of feedback  ... the incoming water pushes the buoy upwards, making the lower "adjusting conic needle" to let pass the same amount of water that enters into the container, this way ... the needle records on the drum the amount of water flowing through it at every moment—in mm of rainfall per square meter. It consists of a rotating drum that rotates at constant speed , this drum drags

7505-399: The rainfall time-structure n-index . The average time between occurrences of an event with a specified intensity and duration is called the return period . The intensity of a storm can be predicted for any return period and storm duration, from charts based on historic data for the location. The return period is often expressed as an n -year event. For instance, a 10-year storm describes

7600-572: The reign of Sejong the Great of the Joseon Dynasty of Korea as the first standardized rain gauge. In 1662, Christopher Wren created the first tipping-bucket rain gauge in Britain in collaboration with Robert Hooke . Hooke also designed a manual gauge with a funnel that made measurements throughout 1695. Richard Towneley was the first to make systematic rainfall measurements over

7695-428: The return period (assuming the probability remains the same for each year). For instance, a 10-year storm has a probability of occurring of 10 percent in any given year, and a 100-year storm occurs with a 1 percent probability in a year. As with all probability events, it is possible, though improbable, to have multiple 100-year storms in a single year. The Quantitative Precipitation Forecast (abbreviated QPF)

7790-442: 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

7885-411: The roofs of buildings or the leaves of trees from dripping into the rain gauge after a rain, resulting in inaccurate readings. Types of rain gauges include graduated cylinders , weighing gauges, tipping bucket gauges, and simply buried pit collectors. Each type has its advantages and disadvantages while collecting rain data. The standard United States National Weather Service rain gauge, developed at

7980-408: The start of the 20th century, consists of an 8 in (200 mm) funnel emptying into a graduated cylinder, 2.525 in (64.1 mm) in diameter, which fits inside a larger container that is 8 in (200 mm) in diameter and 20 in (510 mm) tall. If the rainwater overflows the graduated inner cylinder, then the larger outer container will catch it. When measurements are taken, then

8075-585: The tank" leaving the tip of the conical needle in a way that uncovers the regulating hole, i.e. , the maximum flow that the apparatus is able to record. If the rain suddenly decreases, making the container (as it empties) quickly lower the buoy, that movement corresponds to a steep slope line that can reach the bottom of the recorded cardboard if it stops raining. The rain gauge of intensities allowed precipitation to be recorded over many years, particularly in Barcelona (95 years), apart from many other places around

8170-492: The tropics since the 1970s. Globally there has been no statistically significant overall trend in precipitation over the past century, although trends have varied widely by region and over time. Eastern portions of North and South America, northern Europe, and northern and central Asia have become wetter. The Sahel, the Mediterranean, southern Africa and parts of southern Asia have become drier. There has been an increase in

8265-543: The vicinity of cold fronts and near and poleward of surface warm fronts . Similar ascent is seen around tropical cyclones outside 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. What separates rainfall from other precipitation types, such as ice pellets and snow,

8360-408: The warm conveyor belt), forcing a surface trough to continue into the cold sector on a similar curve to the occluded front. The front creates the portion of an occluded cyclone known as its comma head , due to the comma -like shape of the mid-tropospheric cloudiness that accompanies the feature. It can also be the focus of locally heavy precipitation, with thunderstorms possible if the atmosphere along

8455-555: The water droplets in a cloud to remain stationary. When air turbulence occurs, water droplets collide, producing larger droplets. As these larger water droplets descend, coalescence continues, so that drops become heavy enough to overcome air resistance and fall as rain. Coalescence generally happens most often in clouds above freezing (in their top) and is also known as the warm rain process. In clouds below freezing, when ice crystals gain enough mass they begin to fall. This generally requires more mass than coalescence when occurring between

8550-599: The world, such as Hong Kong. A weighing-type precipitation gauge consists of a storage bin, which is weighed to record the mass. Certain models measure the mass using a pen on a rotating drum, or by using a vibrating wire attached to a data logger . The advantages of this type of gauge over tipping buckets are that it does not underestimate intense rain, and it can measure other forms of precipitation, including rain, hail, and snow. These gauges are, however, more expensive and require more maintenance than tipping bucket gauges. The weighing-type recording gauge may also contain

8645-415: The years 1697 to 1704. The naturalist Gilbert White took measurements to determine the mean rainfall from 1779 to 1786, although it was his brother-in-law, Thomas Barker , who made regular and meticulous measurements for 59 years, recording temperature, wind, barometric pressure , rainfall and clouds. His meteorological records are a valuable resource for knowledge of the 18th-century British climate. He

8740-592: Was able to demonstrate that the average rainfall varied greatly from year to year with little discernible pattern. The meteorologist George James Symons published the first annual volume of British Rainfall in 1860. This pioneering work contained rainfall records from 168 land stations in England and Wales. He was elected to the council of the British Meteorological Society in 1863 and made it his life's work to investigate rainfall within

8835-683: Was equipped with a rain gauge to classify land for taxation purposes. Rainfall measurement was also mentioned in the Jewish text in Palestine. In 1247, the Song Chinese mathematician and inventor Qin Jiushao invented Tianchi basin rain and snow gauges to reference rain, and snowfall measurements, as well as other forms of meteorological data. In 1441, the Cheugugi was invented during

8930-450: Was finished. Chié joined, and soon everybody was fighting, believing that they were better than others and lying. This caused a civil war. Chié was cursed by Bochica and was turned into a barn owl . His plan foiled, Chibchacum plotted his revenge. He had his revenge by speaking an evil incantation causing a huge flood. The people screamed to Bochica telling them to let them live and in return they would worship Bochica. So, once Bochica created

9025-558: Was first used by Scottish chemist Robert Augus Smith in 1852. The pH of rain varies, especially due to its origin. On America's East Coast, rain that is derived from the Atlantic Ocean typically has a pH of 5.0–5.6; rain that comes across the continental from the west has a pH of 3.8–4.8; and local thunderstorms can have a pH as low as 2.0. Rain becomes acidic primarily due to the presence of two strong acids, sulfuric acid (H 2 SO 4 ) and nitric acid (HNO 3 ). Sulfuric acid

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