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The Sun's rays are attenuated as they pass through the atmosphere, leaving maximum normal surface irradiance at approximately 1000 W/m 2 at sea level on a clear day. When 1361 W/m 2 is arriving above the atmosphere (when the Sun is at the zenith in a cloudless sky), direct sun is about 1050 W/m 2 , and global radiation on a horizontal surface ...
If the extraterrestrial solar radiation is 1,367 watts per square meter (the value when the Earth–Sun distance is 1 astronomical unit), then the direct sunlight at Earth's surface when the Sun is at the zenith is about 1,050 W/m 2, but the total amount (direct and indirect from the atmosphere) hitting the ground is around 1,120 W/m 2. [6]
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.
Brightest sunlight: 111,000 lux: Bright sunlight 109,880 lux: AM 1.5 global solar spectrum sunlight (= 1,000.4 W/m 2) [3] [circular reference] 20,000 lux: Shade illuminated by entire clear blue sky, midday 1,000–2,000 lux: Typical overcast day, midday 400 lux: Sunrise or sunset on a clear day (ambient illumination) <200 lux: Extreme of ...
Most people in the world depend on the sun to get vitamin D, [31] and elderly populations in low UVB countries experience higher rates of cancer. [32] There are not many foods that naturally have vitamin D. [33] Examples are cod liver oil and oily fish. If people cannot get sunlight, then they will need 1,000 IU of vitamin D per day to stay ...
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 ...
Most of the world's population live in areas with insolation levels of 150–300 watts/m 2, or 3.5–7.0 kWh/m 2 per day. [8] Solar radiation is absorbed by the Earth's land surface, oceans – which cover about 71% of the globe – and atmosphere. Warm air containing evaporated water from the oceans rises, causing atmospheric circulation or ...
For an area that receives around four to six hours of sunlight per day, choose full-sun plants like colorful, hardy miniature bushes or ornamental kale. For shadier areas, choose trailing ivy ...