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Solar Insolation

What is Solar Insolation?

The sun is the sole source of energy for the earth's atmosphere which has to travel 93 million miles through space before reaching Earth as solar energy or incident radiation through a process known as insolation. This insolation is measured in a unit called 'Langley'

Rate of Insolation on Earth: The Earth's surface is insolated at a rate of 1.94 calories per square cm each minute. The amount of solar radiation falling on the Earth's surface in a single day is estimated to be sufficient to supply the world's home and industrial energy needs for the next 100 years if captured efficiently.

What are the factors that affect the variation in temperature?

The angle of the Sun's rays, the length of the day, and the quantity of insolation per unit area on the Earth's surface all have an effect on the amount of insolation per unit area. This results in variation in temperature on the earth's surface, for example, the temperature near the equator can have an average of 35°C whereas the places closer to poles have average temperatures of about -55°C.

The following table summarises the factors that contribute to temperature differences in a particular location.

Altitude and Elevation: A location's temperature is strongly influenced by its altitude or elevation since the temperature lowers by 6.5°C every kilometre. This is why, despite its tropical surroundings, Mount Kilimanjaro - a dormant volcano in Tanzania is perpetually coated with ice.

Latitude: Latitudinal position also affects the temperature difference. Normally, the temperature drops as one travels from the equator to the pole. Temperatures are quite cold in high latitude areas, whereas they are quite hot in low latitude locations.

Continentality: Continentality is a climate state in which heating a location requires less energy and water bodies have little or no effect on temperature. This indicates that the further you are from an ocean or other significant body of water, the larger the seasonal temperature variation. Temperature changes are also impacted by the land and water surface characteristics. The land is more rapidly heated and cooled than a body of water.

A location's temperature is affected by its distance from the sea. Coastal regions enjoy the sea breezes during the day and the land winds at night, as a result, the temperatures in coastal areas are moderate. By contrast, areas in the interior that are not near the water have a severe environment.

Wind System: The prevailing winds and local winds have an effect on the temperature because cold winds drop the temperature while hot breezes raise it. In France, for example, the mistral wind brings temperatures below freezing, whereas the Chinook wind in the United States brings temperatures up, melting ice.

Ocean Currents: The ocean current has an effect on temperature. The warmer stream boosts the ambient temperature, whereas the cold stream reduces it.

Texture and Colour of Land: The colour, vegetation, soil, land usage, and snow cover of the ground surface all affect the temperature of an area. The desert's sandy surface absorbs the majority of solar energy, while snow with a high albedo reflects the majority. It is hotter in open areas than it is in jungles.

Slope: Temperatures are greater on sun-facing slopes; for example, mountains aligned east-west, such as the Alps, have a higher temperature on the'sunny slope' facing south. Mountain ranges such as the Himalayas deflect cold winds, minimising temperature reductions.

Angle of Sun's Rays: At different latitudes, the angle formed by the earth's axis with the plane of its orbit around the sun has a bigger effect on the amount of insolation received. This is determined by a site's latitude. As latitude increases, the angle they form with the earth's surface narrows, resulting in slanting sun beams. Slant rays have less area coverage than vertical rays. As more space is covered, the energy is distributed more equally, resulting in a drop in the net energy obtained per unit area.

Additionally, slant rays must penetrate deeper into the atmosphere, leading to increased absorption, scattering, and diffusion. Throughout the year, insolation is greatest towards the equator and diminishes toward the poles. At the equator, insolation varies the least throughout the year.

What is Temperature Anamoly?

A temperature anomaly or thermal anomaly is the difference between the mean temperature of a site and the mean temperature of its associated latitude. It denotes an exception to the norm.

The Northern Hemisphere exhibits the greatest number of anomalies, whereas the Southern Hemisphere exhibits the fewest. When the temperature at a site is lower than the expected temperature for the latitude, the anomaly is said to be negative. When the temperature at a site exceeds the expected temperature for the latitude, the anomaly is positive.

The anomalies are negative over the continents from around 40° latitude to the poles and positive near the equator for the entire year. Positive anomalies on the ocean surface are found north of 40 degrees latitude while negative anomalies are found south of the equator.


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