Sunlight duration or sunlight is a climatological indicator, measuring the duration of sunlight in a given period (usually, a day or a year) for a particular location on Earth, usually expressed as average value over several years. This is a general indicator of the location turbidity, and thus differs from insolation, which measures the total energy delivered by sunlight over a given period.
The duration of sunlight is usually expressed in hours per year, or in (hourly) hours per day. The first size shows the general sunniness of the location compared to other places, while the latter allows for comparison of sunlight in different seasons in the same location. Another frequently used measure is the percentage ratio of bright sunlight duration records and the duration of daylight in the observed period.
An important use of sunlight duration data is to characterize the site's climate, especially from health resorts. It also takes into account the psychological effects of strong sunlight on human well-being. These are often used to promote tourist destinations.
Video Sunshine duration
Day duration
If the Sun is above the horizon 50% of the time for a standard year consisting of 8,760 hours, the maximum clear daylight duration will be 4,380 hours for every point on Earth. However, there are physical and astronomical effects that change the image. That is, atmospheric refraction allows the Sun to remain visible even when it is physically immersed beneath the horizon. Therefore, daytime averages (regardless of cloud effect) are the longest in the polar regions, where the visible Sun spends the most time on the horizon. Places in the Arctic Circle have the longest total day length of day, 4,647 hours, while the North Pole receives 4,575. Due to the elliptical nature of Earth's orbit, the Southern Hemisphere is not symmetrical: The Antarctic Circle, with 4,530 hours of daylight, receives five days less sun than antipodes. The equator has a total daytime of 4,422 hours per year.
Maps Sunshine duration
Definitions and measurements
Given the theoretical maximum of daytime duration for a particular location, there is also a practical consideration in which the point of daytime amount is enough to be treated as "hours of sunlight". The sunlight "Light" represents the total hours when sunlight is stronger than the specified threshold, not just the "visible" clock. The "Visible" sunlight, for example, occurs around sunrise and sunset, but is not strong enough to evoke sensors. Measurements are made by instruments called sun recorders. For the specific purpose of recording the duration of sunlight, Campbell-Stokes recorders are used, which use round glass lenses to focus sunlight on specially designed bands. When the intensity exceeds a predetermined threshold, the tape burns. The total length of the fuel footprint is proportional to the number of light hours. Another type of recorder is the Jordan sun recorder. New, electronic recorders have a more stable sensitivity than paper tape.
To align measured data worldwide, in 1962 the World Meteorological Organization (WMO) defined the standard design of Campbell-Stokes recorders, called the Sunshine Recorder Interim Reference (IRSR). In 2003, the duration of sunlight was finally defined as the period in which the direct solar radiation exceeds the threshold value of 120 W/m².
Geographic distribution
The duration of sunlight follows a general geographical pattern: subtropical latitudes (about 25 ° to 40 ° north/south) have the highest sunlight values, as this is the location of the eastern side of the subtropical high pressure system, due to the large-scale decline of air from the tropopause top level. Many of the world's driest climates are found adjacent to the eastern side of subtropical heights, which create stable, slightly convective, upside-down atmospheric conditions, and little moisture and cloud cover. The desert areas, with almost constant stress and rare condensation - such as North Africa, the Southwest United States, Western Australia and the Middle East - are examples of hot, sunny, dry climates where the value of sunlight duration is very high.
The two main areas with the highest duration of sunlight, measured as the annual mean, are the middle and eastern Sahara Desert - covering vast desert countries, especially as Egypt, Sudan, Libya, Chad and Niger - and the Southwest United States Arizona, California, Nevada). The city that claims the brightest official title in the world is Yuma, Arizona, with over 4,000 hours (about 91% of the day time) of bright sunshine every year, but many climatology books suggest there may be brighter areas in Africa North. In the belt that includes northern Chad and Tibesti Mountains, northern Sudan, southern Libya, and Upper Egypt, the duration of the annual sunshine is estimated to be over 4,000 hours. There is also a smaller area, isolated from maximum sunlight in the heart of the western part of the Sahara Desert around Eglab Massif and Erg Chech, along the border of Algeria, Mauritania, and Mali where the 4,000 hour mark is exceeded, too. Some places in the interior of the Arabian Peninsula receive 3,600-3,800 hours of bright sunshine each year. The largest solar region in the world (more than 3,000 hours of sunshine each year) is North Africa. The brightest month in the world is December in the East Antarctic, with nearly 23 hours of sunny sun every day.
In contrast, higher latitudes (above 50 Â ° north/south) lying in winds of windstorms have more clouds and more unstable weather and rain, and often have the lowest values ​​of sunlight duration each year. The temperate climates of the ocean like in northwestern Europe, Canada's west coast, and New Zealand's South Island are examples of cold, cloudy, wet, humid climate where the value of sunless duration without clouds is very low. Areas with the lowest sunlight duration each year are mostly located in the polar oceans, as well as parts of northern Europe, southern Alaska, northern Russia, and areas near the Okhotsk Sea. The cloudiest place in the United States is Cold Bay, Alaska, with an average of 304 days of overcast weight (covering more than 3/4 sky). In addition to this polar ocean climate, some low-latitude lowlands surrounded by mountains, such as the Sichuan and Taipei Basins, can have sunlight duration as low as 1,000 hours per year, because cold air is consistently submerged to form a mist that the wind can not disappear. TÃÆ'³rshavn in the Faroe Islands is among the world's most cloudiest places with only 840 hours of sunlight.
See also
- List of cities based on the duration of the sun
References
External links
- UNdata portal: World Meteorological Organization Normals Standard: Sunshine
- Map of the Australian sunshine hours
- World map of the sun (June snapshot)
- Sunshine world map (Average yearly)
Source of the article : Wikipedia
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