Actinic flux spherically integrated

The light available to a molecule in air for absorption and photodissociation includes both direct and scattered and reflected radiation coming from all directions as described earlier and depicted in Fig. 3.16. The term actinic flux or spherically integrated actinic flux, denoted by F( A), is used to describe the total intensity of this light and is the quantity of interest in calculating kp. 

Demerjian, K. L K. L. Schere, and J. T. Peterson, Theoretical Estimates of Actinic (Spherically Integrated) Flux and Photolytic Rate Constants of Atmospheric Species in the Lower Troposphere, Adv. Environ. Sci. Technol., 10, 369-459 (1980). 

Figure 12.8. Normalized monthly regional wet-deposition flux of sulfate for the northeastern United States, 1976-1979, and normalized spherically integrated solar irradi-ance. The figure demonstrates that the wet deposition of sulfate on a regional scale (the northeastern United States) is correlated with solar actinic flux, which initiates the formation of all photooxidants that are responsible for the conversion of SO2 to sulfate. The lifetime of SO2 in the troposphere is on the order of several days. (Adapted from Faust, 1994.)...

Demerjian, K. L., Schere, K. L., and Peterson, J. T., Theoretical estimates of actinic (spherically integrated) flux and photolytic rate constants of atmospheric species in the lower troposphere. Adu. Environ. Sci. Technol. 10, 369 (1980). 

In the calculation for atmospheric photodissociation reactions, how to calculate the effective solar intensity is a major issue, because not only direct irradiation from the sun, but light from all directions reflected and scattered by the ground surface, clouds, atmospheric molecules, and aerosols can contribute to photolysis. Furthermore, in the troposphere for example, only solar radiation that has not been absorbed by atmospheric molecules in the higher atmosphere, the stratosphere and above, can cause photolytic reactions. The spherically integrated solar intensity after considering those many atmospheric processes is called the actinic flux F (X) (photons cm s ), which means solar irradiation valid for photochemical effect. In atmospheric chemistry, jp is often used instead of kp for representing photolysis rate constant. Photodissociation rate constant in the atmosphere can be expressed using these parameters as... 

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