Effect of Height above Earths Surface on F A

The calculated actinic flux typically increases significantly in the first few kilometers. This is partly due to scattering of light by particulate matter and to light absorption by tropospheric 03 close to the surface. The effect of 03 can be seen by comparing the total fluxes at 332.5 nm (Fig. 3.24a), where 03 absorbs, to those at 575 nm (Fig. 3.24b), where it does not. 

These predictions have been borne out experimentally in studies in which the rate of photolysis of N02 was measured from the surface to 7.6-km altitude and found to increase with height by more than 50% (Kelley et al., 1995 Volz-Thomas et al., 1996). 

As discussed earlier, the net actinic flux incident on a volume of air is sensitive to a number of parameters, 

TABLE 3.9 Tabulation of Solar Zenith Angles (deg) as a Function of True Solar Time and Month 

FIGURE 3.22 Effect of latitude on solar zenith angle. On the scale of true solar time, also called apparent solar time and apparent local solar time, the sun crosses the meridian at noon. The latitudes and seasons represented are as follows I, 20°N latitude, summer solstice II, 35°N latitude, summer solstice III, 50°N latitude, summer solstice IV, 20°N latitude, winter solstice V, 35°N latitude, winter solstice VI, 50°N latitude, winter solstice (from Leighton, 1961). 

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