Solar energy flux

Direct photochemical reactions in the stratosphere induced by far ultraviolet solar light are well known to be important for the chemistry of the atmosphere. However, only a small fraction of the solar energy flux is in this spectral region. 

STEP International program to study solar energy fluxes in land ecosystems. 

Table 1 - Solar energy flux averaged over the Earth during T-Tauri phase (Values in parentheses correspond to today).

To place future energy needs in proper perspective, let us look at the natural energy flux on the earth. The sun provides 8.38 Joules/cm /min at earth s distanee. The earth intercepts a circular area of 4.068 X 10 cm . There are 525,600 minutes per year. Thus, solar energy flux on earth is 1.792 x lO ... 

We assume a C4 species of grass will be produced. An average solar energy flux of 20MJ/m will... 

FIGURE 7 Terrestrial radiation energy balance. Overall solar energy flux is340 W/m. [From Manahan, S. E. (1984). Environmental Chemistry, 4th ed., Willard Grant Press, Boston. Reproduced by permission.]... 

The sun s energy at the earth s surface varies continuously in time and space. The solar constant derived from ground-based measurements has varied from 1323 to 1428 W m (1). Outside the atmosphere (air mass = 0) the sun s energy is more predictable (American Society for Testing and Materials [ASTM, E490]). At the annual mean solar distance from the sun, we define a solar constant of radiation for the earth. This is the measured amount of solar energy flux incident normally on a unit area in a unit of time (1.373 0.008 x 10 erg/sec cm ). Typical atmospheric absorbers (water, ozone, CO2, dust, and industrial pollutants) scatter and absorb... 

The sun radiates approximately as a blackbody, with an effective temperature of about 6000 K. The total solar flux is 3.9 x 10 W. Using Wien s law, it has been found that the frequency of maximum solar radiation intensity is 6.3 x 10 s (X = 0.48 /rm), which is in the visible part of the spectrum 99% of solar radiation occurs between the frequencies of 7.5 X 10 s (X = 4/um) and 2 x 10 s (X = 0.15/um) and about 50% in the visible region between 4.3 x 10 s (X = 0.7 /rm) and 7.5 X 10 s (X = 0.4 /Ltm). The intensity of this energy flux at the distance of the earth is about 1400 W m on an area normal to a beam of solar radiation. This value is called the solar constant. Due to the eccentricity of the earth s orbit as it revolves around the sun once a year, the earth is closer to the sun in January (perihelion) than in July (aphelion). This results in about a 7% difference in radiant flux at the outer limits of the atmosphere between these two times. 

Fig. 7-7 (a) Average annual precipitation (P) and evaporation (E) per unit area versus latitude. Arrows represent the sense of the required water vapor flux in the atmosphere, (b) Incoming solar energy (top of atmosphere and surface) and outgoing terrestrial energy versus latitude. 

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.

At later times, solar heat fluxes and convective heat transfer from the atmosphere become important. For a spill onto an insulated dike floor these fluxes may be the only energy contributions. This approach seems to work adequately for liquefied natural gas (LNG) and perhaps for ethane and ethylene. The higher hydrocarbons (C3 and above) require a more detailed heat transfer mechanism. This model also neglects possible water freezing effects in the ground, which can significantly alter the heat transfer behavior. More details on boiling pools is provided elsewhere.19... 

The important uses of lithium fluoride are as flux in glasses, vitreous enamels and glazes in soldering and welding aluminum and its prisms in infrared spectrophotometers. The compound also is used for storing solar energy. 

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