Bremen 2000 – scientific programme
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UP: Umweltphysik
UP 16: Poster: Modellierung (Atmosph
äre)
UP 16.4: Poster
Friday, March 24, 2000, 10:45–11:45, Foyer
Calculation of Photolysis Frequencies — •Julian Meyer-Arnek — Inst. f. Umweltphysik, 28334 Bremen
The photolysis frequency J is defined by the integral of the actinic flux multiplied by the absorption coefficient of the considered chemical species and its quantum yield:
| J (z) = | ∫ | F (λ, z) · σ (λ, T(z)) · γ (λ) dλ . (1) |
The actinic flux F(λ, z) is determined by SCIATRAN, the radiative-transfer-model of the University of Bremen.
SCIATRAN uses a pseudo-spherical-approximation to solve the radiative-transfer-equation. The profiles of atmospheric absorber like O2, O3, H2O etc. are included into the model. Moreover it is possible to study the effect of clouds on the actinic flux. Two regimes are offered: The cloud as reflecting layer or as an optical thick medium. The latter is interesting for use within the troposphere where the sun’s radiation is often strongly limited by clouds. SCIATRAN supports full Rayleigh-scattering and Mie-scattering at aerosol-particles.
The aim of my work is to provide an accurate photolysis table to our photochemical model BRAPHO (BRemen’s Atmospheric PHotochemical model), especially for tropospheric reactions. That is why the presentation will focus on the impact of clouds and the tropospheric aerosol concentration on the photolysis frequencies of some exemplarily reactions.