Sunshine duration

Sunshine duration or sunshine hours is a climatological indicator, measuring duration of sunshine in given period (usually, a day or a year) for a given location on Earth, typically expressed as an averaged value over several years. It is a general indicator of cloudiness of a location, and thus differs from insolation, which measures the total energy delivered by sunlight over a given period.

Sunshine duration is usually expressed in hours per year, or in (average) hours per day. The first measure indicates the general sunniness of a location compared with other places, while the latter allows for comparison of sunshine in various seasons in the same location.[1] Another often-used measure is percentage ratio of recorded bright sunshine duration and daylight duration in the observed period.

An important use of sunshine duration data is to characterize the climate of sites, especially of health resorts. This also takes into account the psychological effect of strong solar light on human well-being. It is often used to promote tourist destinations.[1]

Daytime duration

Refracción
Diagram showing displacement of the Sun's image at sunrise and sunset

If the Sun were to be above the horizon 50% of the time for a standard year consisting of 8,760 hours, apparent maximal daytime duration would be 4,380 hours for any point on Earth. However, there are physical and astronomical effects that change that picture. Namely, atmospheric refraction allows the Sun to be still visible even when it physically sets below the horizon. For that reason, average daytime (disregarding cloud effects) is longest in polar areas, where the apparent Sun spends the most time around the horizon. Places on the Arctic Circle have the longest total annual daytime, 4,647 hours, while the North Pole receives 4,575. Because of elliptic nature of the Earth's orbit, the Southern Hemisphere is not symmetrical: the Antarctic Circle, with 4,530 hours of daylight, receives five days less of sunshine than its antipodes. The Equator has a total daytime of 4,422 hours per year.[2]

Definition and measurement

Campbell-Stokes recorder
Campbell–Stokes recorder measures sunshine

Given the theoretical maximum of daytime duration for a given location, there is also a practical consideration at which point the amount of daylight is sufficient to be treated as a "sunshine hour". "Bright" sunshine hours represent the total hours when the sunlight is stronger than a specified threshold, as opposed to just "visible" hours. "Visible" sunshine, for example, occurs around sunrise and sunset, but is not strong enough to excite the sensor. Measurement is performed by instruments called sunshine recorders. For the specific purpose of sunshine duration recording, Campbell–Stokes recorders are used, which use a spherical glass lens to focus the sun rays on a specially designed tape. When the intensity exceeds a pre-determined threshold, the tape burns. The total length of the burn trace is proportional to the number of bright hours.[3] Another type of recorder is the Jordan sunshine recorder. Newer, electronic recorders have more stable sensitivity than that of the paper tape.

In order to harmonize the data measured worldwide, in 1962 the World Meteorological Organization (WMO) defined a standardized design of the Campbell–Stokes recorder, called an Interim Reference Sunshine Recorder (IRSR).[1] In 2003, the sunshine duration was finally defined as the period during which direct solar irradiance exceeds a threshold value of 120 W/m².[1]

Geographic distribution

Sunshine
Annual sunshine hours map of the world
  < 1200 h
  1200–1600 h
  1600–2000 h
  2000–2400 h
  2400–3000 h
  3000–3600 h
  3600–4000 h
  > 4000 h

Sunshine duration follows a general geographic pattern: subtropical latitudes (about 25° to 40° north/south) have the highest sunshine values, because these are the locations of the eastern sides of the subtropical high pressure systems, associated with the large-scale descent of air from the upper-level tropopause. Many of the world's driest climates are found adjacent to the eastern sides of the subtropical highs, which create stable atmospheric conditions, little convective overturning, and little moisture and cloud cover. Desert regions, with nearly constant high pressure aloft and rare condensation—like North Africa, the Southwestern United States, Western Australia, and the Middle East—are examples of hot, sunny, dry climates where sunshine duration values are very high.

The two major areas with the highest sunshine duration, measured as annual average, are the central and the eastern Sahara Desert—covering vast, mainly desert countries such as Egypt, Sudan, Libya, Chad, and Niger—and the Southwestern United States (Arizona, California, Nevada).[4] The city claiming the official title of the sunniest in the world is Yuma, Arizona, with over 4,000 hours (about 91% of daylight time) of bright sunshine annually,[4][5] but many climatological books suggest there may be sunnier areas in North Africa. In the belt encompassing northern Chad and the Tibesti Mountains, northern Sudan, southern Libya, and Upper Egypt, annual sunshine duration is estimated at over 4,000 hours. There is also a smaller, isolated area of sunshine maximum in the heart of the western section of the Sahara Desert around the Eglab Massif and the Erg Chech, along the borders of Algeria, Mauritania, and Mali where the 4,000-hour mark is exceeded, too.[6] Some places in the interior of the Arabian Peninsula receive 3,600–3,800 hours of bright sunshine annually. The largest sun-baked region in the world (over 3,000 hours of yearly sunshine) is North Africa. The sunniest month in the world is December in Eastern Antarctica, with almost 23 hours of bright sun daily.[7]

Conversely, higher latitudes (above 50° north/south) lying in stormy westerlies have much cloudier and more unstable and rainy weather, and often have the lowest values of sunshine duration annually. Temperate oceanic climates like those in northwestern Europe, the western coast of Canada, and areas of New Zealand's South Island are examples of cool, cloudy, wet, humid climates where cloudless sunshine duration values are very low. The areas with the lowest sunshine duration annually lie mostly over the polar oceans, as well as parts of northern Europe, southern Alaska, northern Russia, and areas near the Sea of Okhotsk. The cloudiest place in the United States is Cold Bay, Alaska, with an average of 304 days of heavy overcast (covering over 3/4 of the sky).[8] In addition to these polar oceanic climates, certain low-latitude basins enclosed by mountains, like the Sichuan and Taipei Basins, can have sunshine duration as low as 1,000 hours per year, as cool air consistently sinks to form fogs that winds cannot dissipate.[9] Tórshavn in the Faroe Islands is among the cloudiest places in the world with yearly only 840 sunshine hours.

See also

References

  1. ^ a b c d "8. Measurement of Sunshine Duration", Guide to Meteorological Instruments and Methods of Observation (PDF), WMO, 2008, archived from the original (PDF) on 2013-02-03
  2. ^ Gerhard Holtkamp, The Sunniest and Darkest Places on Earth, Scilogs, archived from the original on 2009-10-27
  3. ^ Definitions for other daily elements, Australian Bureau of Meteorology
  4. ^ a b Sunniest places in the world, Current Results.com
  5. ^ Ranking of cities based on % annual possible sunshine, NOAA, 2004
  6. ^ Godard, Alain; Tabeaud, Martine (2009), Les climats: Mécanismes, variabilité et répartition (in French), Armand Colin, ISBN 9782200246044
  7. ^ Antarctic climatic data, archived from the original on 2008-05-07
  8. ^ Cloudiest places in the United States, Current Results.com
  9. ^ Domrös, Manfred; Peng, Gongbing, The Climate of China, pp. 75–78, ISBN 9783540187684

External links

Altar, Sonora

Altar (O'odham: Wawuk) is small city and municipal seat of Altar Municipality in the Mexican state of Sonora. It is located in the northwest region of the state at 30°42′49″N 111°50′07″W.

The town of Altar is situated on the important Mexicali to Hermosillo Highway (Federal Highway 2). Most of the roads leading into the desert are not paved.

Automated Meteorological Data Acquisition System

AMeDAS (Automated Meteorological Data Acquisition System), commonly known in Japanese as "アメダス" (amedasu), is a high-resolution surface observation network developed by the Japan Meteorological Agency (JMA) used for gathering regional weather data and verifying forecast performance. The system began operating on 1 November 1974, and currently comprises 1,300 stations throughout Japan (of which over 1,100 are unmanned), with an average separation of 17 km (11 mi).

Observations at manned stations cover weather, wind direction and speed, types and amounts of precipitation, types and base heights of clouds, visibility, air temperature, humidity, sunshine duration, and atmospheric pressure. All of these (except weather, visibility and cloud-related meteorological elements) are observed automatically.

At unmanned stations, observations are performed every 10 minutes. About 700 of the unmanned stations observe precipitation, air temperature, wind direction and speed, and sunshine duration, while the other stations observe only precipitation.

For about 280 stations (manned or unmanned) located in areas of heavy snowfall, snow depth is also observed.

All the observational data is transmitted to the AMeDAS Center at JMA Headquarters in Tokyo on a real time basis via dedicated telephone lines. The data is then delivered to the whole country after a quality check.

As well as weather conditions, AMeDAS is also used in the observation of natural disasters. Temporary observation points are set up in areas where there are signs of volcanic eruptions or earthquakes.

Climate of Africa

Owing to Africa's position across equatorial and subtropical latitudes in both the northern and southern hemisphere, several different climate types can be found within it. The continent mainly lies within the intertropical zone between the Tropic of Cancer and the Tropic of Capricorn, hence its interesting density of humidity. Precipitation intensity is always high, and it is a hot continent. Warm and hot climates prevail all over Africa, but the northern part is that most marked by aridity and high temperatures. Only the northernmost and the southernmost fringes of the continent have a Mediterranean climate.The equator runs through the middle of Africa, as do the Tropic of Cancer and the Tropic of Capricorn, making Africa the most tropical continent.

The climate of Africa is a range of climates such as the equatorial climate, the tropical wet and dry climate, the tropical monsoon climate, the semi-desert climate (semi-arid), the desert climate (hyper-arid and arid), the subtropical highland climate etc. Temperate climates are rare across the continent except at very high elevations and along the fringes. In fact, the climate of Africa is more variable by rainfall amount than by temperatures, which are consistently high. African deserts are the sunniest and the driest parts of the continent, owing to the prevailing presence of the subtropical ridge with subsiding, hot, dry air masses. Africa holds many heat-related records: the continent has the hottest extended region year-round, the areas with the hottest summer climate, the highest sunshine duration etc.

Climate of Gibraltar

The climate of Gibraltar is Mediterranean/Subtropical with mild winters and warm summers. Gibraltar has two main prevailing winds, an easterly one known as the Levante coming from the Sahara in Africa which brings humid weather and warmer sea currents and the other as Poniente which is westerly and brings fresher air and colder sea. Its terrain consists of the 430-metre (1,411 ft) high Rock of Gibraltar and the narrow coastal lowland surrounding it. Rain occurs mainly in winter; the summers are generally dry.

Average morning relative humidity: 82%, evening relative humidity: 64%. Sunshine hours are up to 2,778 per year, from 150 in November (~5 hours of sunshine per day) to 341 in July (~11 hours of sunshine per day).

Climate of Lisbon

Lisbon and its metropolitan area has a Subtropical-Mediterranean climate (Köppen climate classification: Csa), with short and very mild winters and warm summers. According to Troll-Paffen climate classification, Lisbon has a warm-temperate subtropical climate (Warmgemäßigt-subtropisches Zonenklima). According to Siegmund/Frankenberg climate classification, Lisbon has a subtropical climate.

Cloud cover

Cloud cover (also known as cloudiness, cloudage, or cloud amount) refers to the fraction of the sky obscured by clouds when observed from a particular location. Okta is the usual unit of measurement of the cloud cover. The cloud cover is correlated to the sunshine duration as the least cloudy locales are the sunniest ones while the cloudiest areas are the least sunny places.

The global cloud cover averages around 0.68 when analyzing clouds with optical depth larger than 0.1. This value is lower (0.56) when considering clouds with an optical depth larger than 2, and higher when counting subvisible cirrus clouds.

Concepción, Paraguay

Concepción (Spanish pronunciation: [konsepˈsjon]) is a city & district in northern Paraguay and capital of the Concepción Department. It lies next to the Paraguay River.

Founded by a Spanish Governor, named Agustín Fernado de Pinedo, the town prospered in the early years of the 20th century, as a centre for the north of the country, exploiting the new wealth of the Gran Chaco, and a river port. The town was also a centre for the Paraguayan Civil War of 1947. The city is the seat of the Roman Catholic Diocese of Concepción en Paraguay.

Fada N'gourma

Fada N'gourma, also written Fada-Ngourma, or Noungu is a city and an important market town in eastern Burkina Faso, lying 219 kilometres (136 mi) east of Ouagadougou, in the Gourmantché area. It is the capital of the East region and of Gourma province. It is known for its blanket and carpet manufacturing as well as its honey.

Faya-Largeau

Faya-Largeau (also known as Faya, Arabic: فايا لارجو‎ or فايا) is the largest city in northern Chad and was the capital of the region of Bourkou-Ennedi-Tibesti. It is now in the Borkou Region, which was formed in 2008 from the Borkou Department of the former Bourkou-Ennedi-Tibesti region.

Felipe Carrillo Puerto, Quintana Roo

Felipe Carrillo Puerto is the municipal seat and largest city in Felipe Carrillo Puerto Municipality in the Mexican state of Quintana Roo. According to the 2010 census, the city's population was 25,744 persons, mostly of Maya descent.The city of Felipe Carrillo Puerto was founded in 1850 by independent Maya people during the Caste War of Yucatán under the name Chan Santa Cruz. After it was conquered by Mexican troops in 1901, it was renamed "Santa Cruz del Bravo" before acquiring its present name. The Sian Ka'an Biosphere Reserve lies just east of the city.

Gerecse Mountains

Gerecse is a mountain range in north-western Hungary, in the Central Transdanubian region, between the ranges Vértes and Pilis and part of the Komárom-Esztergom County. A low limestone mountain situated between the town of Tatabánya and the Danube River. The Gerecse Mountains are part of the Transdanubian Mountains. Gerecse occupies an area of 850 km2 (20,300 ha). The highest point is Nagy-Gerecse at 634 m. The main rock is chalk and limestone.

Deciduous oak Quercus forests cover the lower slopes, with submontane forests of Quercus, Carpinus, Fagus, and karst scrub at higher altitudes. The area is 70% forest, 5% scrubland, 10% grassland, and 15% artificial landscapes. Yearly sunshine duration is around 1,980 hours. The average annual temperature above the height of 350 meters is 9.5 C (in January -2,8 C). The average annual precipitation is 640 millimeters.

List of cities by sunshine duration

The following is a list of cities by sunshine duration. Sunshine duration is a climatological indicator, measuring duration of sunshine in given period (usually, a day or a year) for a given location on Earth, typically expressed as an averaged value over several years. It is a general indicator of cloudiness of a location, and thus differs from insolation, which measures the total energy delivered by sunlight over a given period.

Sunshine duration is usually expressed in hours per year, or in (average) hours per day. The first measure indicates the general sunniness of a location compared with other places, while the latter allows for comparison of sunshine in various seasons in the same location. Another often-used measure is percentage ratio of recorded bright sunshine duration and daylight duration in the observed period.

An important use of sunshine duration data is to characterize the climate of sites, especially of health resorts. This also takes into account the psychological effect of strong solar light on human well-being. It is often used to promote tourist destinations.

Madang

Madang (old German name: Friedrich-Wilhelmshafen) is the capital of Madang Province and is a town with a population of 27,420 (in 2005) on the north coast of Papua New Guinea. It was first settled by the Germans in the 19th century.

Matlapa

Matlapa is a town and municipality in San Luis Potosí in central Mexico.

Sabha, Libya

Sabha, or Sebha (Arabic: سبها‎ Sabhā), is an oasis city in southwestern Libya, approximately 640 kilometres (400 mi) south of Tripoli. It was historically the capital of the Fezzan region and the Military Territory of Fezzan-Ghadames and is now capital of the Sabha District. Sabha Air Base, south of the city, is a Libyan Air Force installation that is home to multiple MiG-25 aircraft.Sabha was where the erstwhile ruler of Libya, Muammar Gaddafi, grew up and received secondary education and where he also later became involved in political activism. After the Libyan Civil War and the resultant instability in the country, Sabha has grown in importance as a slave auctioning town.

Sunlight

Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is filtered through Earth's atmosphere, and is obvious as daylight when the Sun is above the horizon. When the direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. When it is blocked by clouds or reflects off other objects, it is experienced as diffused light. The World Meteorological Organization uses the term "sunshine duration" to mean the cumulative time during which an area receives direct irradiance from the Sun of at least 120 watts per square meter. Other sources indicate an "Average over the entire earth" of "164 Watts per square meter over a 24 hour day".The ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a requisite for vitamin D3 synthesis and a mutagen.

Sunlight takes about 8.3 minutes to reach Earth from the surface of the Sun. A photon starting at the center of the Sun and changing direction every time it encounters a charged particle would take between 10,000 and 170,000 years to get to the surface.Sunlight is a key factor in photosynthesis, the process used by plants and other autotrophic organisms to convert light energy, normally from the Sun, into chemical energy that can be used to synthesize carbohydrates and to fuel the organisms' activities.

Tuxpan

Tuxpan (or Túxpam, fully Túxpam de Rodríguez Cano) is both a municipality and city located in the Mexican state of Veracruz. The population of the city was 78,523 and of the municipality was 134,394 inhabitants, according to the INEGI census of 2005, residing in a total area of 1,051.89 km² (406.14 sq mi). The municipality includes many smaller outlying communities, the largest of which are Alto Lucero and Santiago de la Peña. A local beachside community is also nearby.

Villahermosa

Villahermosa (Spanish pronunciation: [ˌbiʝa.eɾˈmosa], Beautiful Village) is the capital and largest city of the Mexican state of Tabasco, and the municipal seat of the Centro municipality. Villahermosa reported a population of 658,524 in the 2005 census, whereas its Centro municipality had 558,524 inhabitants. The municipality covers an area of 1,612 km2 (622.4 sq mi). The city is 863 kilometres (536 mi) from Mexico City.

Vértes Hills

Vértes is a mountain range in north-western Hungary, in the Central Transdanubian region, between the ranges Bakony and Gerecse. The Vértes Mountains are part of the Transdanubian Mountains. Area of the Vértes occupies 314 km2. It is about 30 km long and 11c12 km wide. The average altitude is above sea level is 350 meters, in highest points are 487 m (Nagy-Csákány), 480 m (Körtvélyes) and 479 m (Csóka-hegy). Geologically the Vértes constitute a fairlyuniform structure. On the surface of the eptire mountain there are no older rocks than those of the mid-Triassic. The main rock is dolomite—CaMg(CO3)2—from the upper Triassic. All the layers are ancient marine deposits.

The Vértes possesses a well-developed valley network (1260 km), but in spite of this spring and rivers are very rare in the mountain. Yearly sunshine duration is around 1950–2000 hours. The average annual temperature above the height of 350 meters is 8.5 C (in January −3 C). The average annual precipitation is between 600 and 700 millimeters. In winter the land is usually snow-covered.

According to a legend documented in mediaeval Hungarian chronicles, the Vértes mountains were named after a historical incident: during the unsuccessful campaign of 1051–1052, the withdrawing German troops of Henry III, emperor of the Holy Roman Empire, scattered their armours to ease their escape through the mountains; hence the name Vértes (cf. vért, Hungarian for armour).

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