Radiation, solar, altitude

Blumthaler M, Ambach W, Elhnger R (1997) Increase in solar U V radiation with altitude. J Photochem Photobiol B 39 130-134... 

An average variation of incident solar radiation for cloudy and cloudless sit uations as a function of solar altitude angle is given in Table 8-5. 

Calculate the heat-generation rate resulting from solar-radiation absorption in a lake with an extinction coefficient of 0.328 m and a solar altitude of 90° on a clear day. Perform the calculation for a depth of 1 ft [0.3048 m]. 

Calculate the absorption rate for solar radiation on bright fine sand for a solar altitude angle of 50° and a turbidity factor of 3.5. 

Part of the solar radiation entering the earth s atmosphere is scattered and absorbed by air and water vapor molecules, dust particles, and water droplets in the clouds, and thus the solar radiation incident on earth s surface is less than tlie solar couslanl. The extent of the attenuation of solar radiation depends on the length of the path of the rays through the atmosphere as well as the composition of the atmosphere (the cloud.s, dust, humidity, and smog) along the path. Most ultraviolet radiation is absorbed by the ozone in the upper atmosphere. At a solar altitude of 41.8°, the total energy of direct solar radiation incident at sea level on a clear day consists of about 3 percent ultraviolet, 38 percent visible, and 59 percent infrared radiation. 

M. Blumthaler, W. Ambach, R. Ellinger (1997). Increase in solar UV radiation with altitude. J. Photochem. Photobiol. B Biol., 39,130-134. 

Spectral radiation intensity ofgiobai radiation depending on solar altitude [87]... 

Not all this shortwave solar radiation reaches Earth s surface, however some is absorbed by the atmosphere and clouds, and some is reflected from the atmosphere and clouds back into space. When skies are clear, approximately 80-85% of the solar radiation reaches Earth s sruface when skies are cloudy, approximately 50% reaches Earth s surface. Earth s surface itself has an albedo that averages approximately 0.35. The amount of solar radiation received per unit of surface area also varies with the sine of the solar altitude (the angle between the sun and the horizon). Total shortwave solar radiation arriving on Earth s surface ranges from zero at night, to hundreds of watts per square meter when the solar altitude is moderate, to over a kilowatt per square meter under clear conditions when the sun is directly overhead. 

Most ozone is formed near the equator, where solar radiation is greatest, and transported toward the poles by normal circulation patterns in the stratosphere. Consequendy, the concentration is minimum at the equator and maximum for most of the year at the north pole and about 60°S latitude. The equihbrium ozone concentration also varies with altitude the maximum occurs at about 25 km at the equator and 15—20 km at or near the poles. It also varies seasonally, daily, as well as interaimuaHy. Absorption of solar radiation (200—300 nm) by ozone and heat Hberated in ozone formation and destmction together create a warm layer in the upper atmosphere at 40—50 km, which helps to maintain thermal equihbrium on earth. 

The density of the atmosphere varies greatly from place to place, as does its composition and temperature. The average composition of dry air (air from which water vapor has been removed) is shown in Table 4.4. One reason for the nonuniformity of air is the effect of solar radiation, which causes different chemical reactions at different altitudes. The density of air also varies with altitude. For example, the air outside an airplane cruising at 10 km is only 25% as dense as air at sea level. 

Fig. 17-1 The global climate system, (a) Energy fluxes, including incoming solar radiation, reflected radiation, emitted longwave radiation (from an effective altitude of ca. 6 km), and atmospheric and oceanic heat flux toward the polar regions, (b) The atmospheric circulation corresponding to part (a). Refer back to Fig. 7-4 and associated text for a discussion of the general circulation.

The kinetics of the various reactions have been explored in detail using large-volume chambers that can be used to simulate reactions in the troposphere. They have frequently used hydroxyl radicals formed by photolysis of methyl (or ethyl) nitrite, with the addition of NO to inhibit photolysis of NO2. This would result in the formation of 0( P) atoms, and subsequent reaction with Oj would produce ozone, and hence NO3 radicals from NOj. Nitrate radicals are produced by the thermal decomposition of NjOj, and in experiments with O3, a scavenger for hydroxyl radicals is added. Details of the different experimental procedures for the measurement of absolute and relative rates have been summarized, and attention drawn to the often considerable spread of values for experiments carried out at room temperature (-298 K) (Atkinson 1986). It should be emphasized that in the real troposphere, both the rates—and possibly the products—of transformation will be determined by seasonal differences both in temperature and the intensity of solar radiation. These are determined both by latitude and altitude. 

We receive radiation from outer space as cosmic rays, solar radiation, and upper-atmosphere radiation. The higher the altitude at which you live, the greater will he your exposure to cosmic radiation from space. Since nuclear radiation accumulates in our bodies... 

Airplane travel can increase our exposure to cosmic and solar radiation that is normally blocked by the atmosphere. Radiation intensity is greater across the poles and at higher altitudes, thus individual exposure varies depending on the route of travel. Storms on the sun can produce solar flares that can release larger amounts of radiation than normal. For the occasional traveler this radiation exposure is well below recommended limits established by regulatory authorities. However, frequent... 

In the mesosphere, from 50 to 85 km, the temperature again falls with altitude and vertical mixing within the region occurs. This temperature trend is due to the decrease in the CL concentration with altitude. At about 85 km the temperature starts to rise again because of increased absorption of solar radiation of wavelengths < 200 nm by 02 and N2 as well as by atomic species. This region is known as the thermosphere. 

FIGURE 3.13 Approximate regions of maximum light absorption of solar radiation in the atmosphere by various atomic and molecular species as a function of altitude and wavelength with the sun overhead (from Friedman, 1960). 

The thermosphere is the thin outer layer of our atmosphere extending from the mesopause near 80 km. altitude out to the exosphere, some several thousand kin. altitude, where the mean free path is sufficiently long to allow escape of atomic hydrogen and helium and atmospheric capture of coronal gas constituents. In the lower thermosphere, heated by solar ultraviolet and x-radiation, the temperature increases rapidly with altitude, with temperatures above 400 km. varying between about 700° and 2100°K., depending on solar activity. 

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