Verlag des Forschungszentrums Jülich
JUEL-3960
After the introduction the physical background entering the simulations is descri-bed. To determine photodissociation coefficients it is not necessary to follow single rays. On the contrary, in this model each 'ray' represents a whole bunch of light covering a large portion of the earth surface area. This model philosophy has some implications for the use of the model.
Next, the algorithms used to solve the differential equations for the flux and to in-tegrate the scattering functions to determine the phase function are described. A detailed description of the frame program and the subroutines follows. The frame program governs the input and output of the model and calls the subprograms. The routine FLUXES actually calculates the photon fluxes and then the routine PHOTO is used to determine either the rate coefficients or the radiometer signals.
In the chapter which follows next the handling of the model is explained. Here, especially the meaning of the different steering parameters and the different possibilities for running the model are described.
Typical results of the simulations for different purposes are shown in chapter "Results". Within this chapter the model's results are compared to measurements and to other more sophisticated models. Additionally, results of diverse specific tests are displayed.
In the last section the model outcome is compared to published spectral radiometer measurements (Herman and Mentall,1982) at 40 km altitude and to actinometer observations of the photolysis frequency of NO2 (Shetter et al., 1992). An especially crucial test for the accuracy of the model is the simulation of filter radiometer signals during ascent and descent while the UV-B edge is moving through the sensitivity range of the device. An example of the simulation of such a measurement (Schiller et al., 1994) is also included.
Röth, Ernst-Peter
Description of the anisotropic radiation transfer model ART to determine Photodissociation coefficients
180 S., 2002
The purpose of the anisotropic radiation transfer model ART is to determine the photodissociation coefficients for the interpretation of measurements of radicals. Likewise, radiometer signals measuring a hemispheric actinic photon flux can be simulated by means of this model. Such radiometer measurements were carried out since 1980 at the Institute for Atmospheric Chemistry of the Research Centre at Jülich, both at ground level and on balloons. By comparison of the simulated upward and downward fluxes to the radiometer signals the model was validated.
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