Many surfaces reflect UV radiation and add to the overall UV levels you experience. With every 1000 m in altitude, UV levels increase by approximately 10 per cent.īe careful not to underestimate the amount of UV radiation passing through clouds. With increasing altitude less atmosphere is available to absorb UV radiation. Closer to the equator the sun's rays have a shorter distance to travel through the atmosphere and therefore less of the harmful UV radiation can be absorbed.
UV levels are higher closer to the equator. Much more UV radiation is absorbed and less reaches the Earth. In contrast, during early morning or late afternoon hours the sun's rays pass at a greater angle through the atmosphere. During these times the sun's rays take the most direct path to earth. UV levels vary mainly with the height of the sun in the sky and in mid-latitudes are highest during the summer months during the 4-hour period around solar noon.
Nir color index of the sun skin#
Recent studies strongly suggest that it may also enhance the development of skin cancers. For a long time it was thought that UVA could not cause any lasting damage. Furthermore, it also contributes to skin ageing and wrinkling. It can penetrate into the deeper layers of the skin and is responsible for the immediate tanning effect. The relatively long-wavelength UVA accounts for approximately 95 per cent of the UV radiation reaching the Earth's surface. Most solar UVB is filtered by the atmosphere. It is responsible for delayed tanning and burning in addition to these short-term effects it enhances skin ageing and significantly promotes the development of skin cancer. Medium-wavelength UVB is very biologically active but cannot penetrate beyond the superficial skin layers. However, it is completely filtered by the atmosphere and does not reach the earth's surface. Short-wavelength UVC is the most damaging type of UV radiation. The UV region covers the wavelength range 100-400 nm and is divided into three bands: However, shorter wavelength UV radiation is less able to penetrate the skin. The shorter the wavelength, the more harmful the UV radiation. They differ in their biological activity and the extent to which they can penetrate the skin. The three types of UV radiation are classified according to their wavelength. Raised awareness and changes in life-style are urgently needed to alter ongoing trends. More outdoor activities and altered sunbathing habits often result in excessive UV exposure.
However, most evidence now suggests that the major cause for the increased cancer rates is altered behaviour rather than ozone depletion. Some people claim that this is due to ozone depletion and enhanced levels of UV. The incidence of different types of skin cancer has been growing dramatically over the past decades.
Nir color index of the sun full#
A full recovery of the ozone level is not expected until 2050. However, the long life span of the chemicals already released will cause ozone depletion problems to persist for many years to come. International agreements, in particular the Montreal Protocol, are gradually succeeding in phasing out the production of ozone-depleting substances.
Ozone depletion is caused by human-made chemicals released into the atmosphere and will continue until the use of chlorine and bromine compounds is drastically reduced. Consequently, the people and the environment are exposed to higher levels of UV radiation, especially UVB. As the ozone layer gets thinner, the protective filter activity of the atmosphere is progressively reduced. Ozone is a particularly effective absorber of UV radiation.