Abstract
For atmospheric photochemistry, clouds can significantly affect actinic flux distributions. In this paper, we examine the effects of convective clouds on the three-dimensional distribution of the spectral actinic flux and on photolysis frequencies for various chemical species. Three-dimensional solutions of the UV-VIS radiative transfer equation are produced using the Spherical Harmonic Discrete Ordinary Method solution technique. This solver uses as input the 3-D cloud characteristics simulated by a dynamical cloud model. The ultraviolet and visible spectra are divided into 5 intervals in order to explore the wavelength dependency of the cloud effect on the actinic flux. Results show that the distribution of the actinic flux over the cloud domain is far from homogeneous and depends primarily on the cloud extinction associated with the hydrometeors. Maximum actinic flux is found at the top edge of the cloud and is related to scattering by ice crystals. The actinic flux is enhanced by a factor of 2 to 5, compared to clear air values, above, at the top edge, and around the cloud. The 3-D actinic flux is used to calculate the photolysis rates for some chemical species (e.g. NO2, O3, and HCHO). Forcomputing photolysis rates, a discretized spectral representation of the absorption wavelengths is used in the model. The calculated photolysis rates are distributed inhomogeneously throughout the cloud, and maxima are found in regions where the actinic flux is enhancement is large. Temperature effects on absorption are found in the photolysis frequencies of some species. Finally, the potential importance of this photolysis enhancement on photochemistry is studied using box model simulations. Results show that enhanced OH concentrations are found in the upper troposphere (120–200%) overthe clouds and changes in ozone production rates (+15%) are obtained in quasi-steady state conditions.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Atkinson, R., Baulch, D. L., Cox, R. A., Hampson, R. F., Kerr, J. A., and Troe, J., 1992: Kinetic and photochemical data for atmospheric chemistry, J. Phys. Chem. Ref. Data 21(6), 1148–1315.
Chandrasekhar, S., 1960: Radiative Transfer, Dover, New York, pp. 1–4.
Claveau, J. and Ramaroson, R., 1996: First simulation of the transport and the chemical transformation of chemical species with a mesoscale-regional model: MEDIUM, in International Colloquium on Effects of Aircraft upon the Atmosphere, Paris, France.
Crawford, J., Davis, D., Chen, G., Shetter, R., Müller, M., Barrick, J., and Olson, J., 1999: An assessment of cloud effects on photolysis rate coefficients: Comparison of experimental and theoretical values, J. Geophys. Res. 104, 5725–5734.
Crutzen, P., 1973: A discussion of the chemistry of some minor constituents in the stratosphere and troposphere, Pure Appl. Geophys. 106, 1385.
DeMore, W. B., Sander, S. P., Golden, D. M., Hampson, R. F., Kurylo, M. J., Howard, C. J., Ravishankara, A. R., Kolb, C. E., and Molina, M. J., 1997: Chemical kinetics and photochemical data for use in stratospheric modeling, JPL publication 97-4, Evaluation nr. 12.
Derwent, R. G., Jenkin, M. E., Saunders, S. M., and Pilling, M. J., 1998: Photochemical ozone creation potentials for organic compounds in northwest Europe calculated with a master chemical mechanism (MCM), Atmos. Environ. 32, 2429.
Evans, K. F., 1998: The spherical harmonics discrete ordinate method for three-dimensional atmospheric radiative transfer, J. Atmos. Sci. 55, 429–446.
Finlayson-Pitts, B. J. and Pitts J. N., 1986: Atmospheric Chemistry: Fundamentals and Experimental Techniques, Chap. 3, Wiley-Interscience, New York, pp. 93–206.
Josefsson, W. and Landelius, T., 2000: Effect of clouds on UV irradiance: As estimated from cloud amount, cloud type, precipitation, global radiation and sunshine duration, J. Geophys. Res. 105, 4927–4935.
Isaksen, I. S. A., Midtbo, K. H., Sunde, J., and Crutzen, P. J., 1977: A simplified method to include molecular scattering and reflection in calculations of photon fluxes and photodissociation rates, Geophys. Norv. 31, 11–26.
Kelley, P., Dickerson, R. R., Luke, W. T., and Kok, G. L., 1995: Rate of NO2 photolysis from the surface to 7.6 km altitude in clear-sky and clouds, Geophys. Res. Lett. 22(19), 2621–2624.
Liou, K. N., 1980: An Introduction to Atmospheric Radiation, Academic Press, San Diego, U.S.A.
Liou, K. N. and Rao, N., 1996: Radiative transfer in cirrus clouds. Part IV: On cloud geometry, inhomogeneity, and absorption, J. Atmos. Sci. 53, 3046–3065.
Logan, J. A., Prather, M. J., Wofsy, S. C., and McElroy, M. B., 1981: Tropospheric chemistry: A global perspective, J. Geophys. Res. 86, 7210.
Los, A., vanWeele, M., and Duynkerke, P.G., 1997: Actinic fluxes in broken cloud fields, J. Geophys. Res. 102, 4257–4266.
Madronich, S., 1987: Photodissociation in the atmosphere 1-Actinic Flux and the effects of ground reflections and clouds, J. Geophys. Res. 92, 9270–9752.
Madronich, S. and Weller, G., 1990: Numerical integration errors in calculated tropospheric photodissociation rate coefficients, J. Atmos. Chem, 10, 289–300.
Matthijsen, J., Slaper, H., and Reinen, H. A. M., 2000: Reduction of solar UV by clouds: A comparison between satellite-derived cloud effects and ground-based radiation measurements, J. Geophys. Res. 105, 5069–5080.
Platt, C. M., 1997: A parameterization of the visible extinction coefficient of ice clouds in terms of ice/water content, J. Atmos. Sci. 54, 2083–2097.
Raïsänen, P., 1999: Effect of vertical resolution on cloud-sky radiation calculations: Tests with two schemes, J. Geophys. Res. 104, 27407–27419.
Ramaroson, R., 1989: Local, one and three dimensional modeling of photochemical processes in the middle atmosphere, PhD thesis, Paris VI University, France.
Ramaroson, R., Pirre, M., and Cariolle, D., 1992: A box model for on-line computations of diurnal variations in multidimensional models: Application to the one-dimensional case, Ann. Geophys. 10, 416–428.
Shetter, R. E. and Müller, M., 1999: Photolysis frequency measurements using actinic flux spectroradiometry during the PEM-Tropics mission: Instrumentation description and some results, J. Geophys. Res. 104, 5647–5661.
Skamarock, W. C., Powers, J. G., Barth, M., Dye, J. E., Matejka, T., Bartels, D., Baumann, K., Stith, J., Parrish, D. D., and Hubler, G., 2000: Numerical simulations of the 10 July stratospherictropospheric experiment: Radiation, aerosols, and ozone/deep convection experiment convective system: Kinematics and transport, J. Geophys. Res. 105, 19,973–19,990.
Takano, Y. and Liou, K. N., 1989: Solar radiative transfer in cirrus clouds. Part I: Single-scatteringand optical properties of hexagonal ice crystals, J. Atmos. Sci. 46, 3–19.
Tao, W-K. and Simpson, J., 1993: Goddard cumulus ensemble model. Part 1: Model description, Terr. Atmos. Oceanic Sci. 4, 35–72.
Thompson, A. M. and Stewart, R. W., 1991: Effect of chemical kinetics uncertainties on calculated constituents in a tropospheric photochemical model, J. Geophys. Res. 96, 13089–13108.
Trautmann, T., Podgorny, I., Landgraf, J., and Crutzen, P. J., 1999: Actinic fluxes and photodissociation coefficients in cloud fields embedded in realistic atmospheres, J. Geophys. Res. 104, 30173–30192.
Turco, R. P., 1975: Photodissociation rates in the atmosphere below 1000 km, Geophys. Surv. 2, 153–192.
Valero, F. P. J. and Bush, B. C., 1999: Measured and calculated clear-sky solar radiative fluxes during the subsonic Aircraft Contrail and Cloud Effects Special Study (SUCCESS), J. Geophys. Res. 104, 27387–27398.
Van Weele, M., Vilà-Guerau de Arellamo, J., and Kuik, F., 1995: Combined measurements of UV-A actinic flux, UV-A irradiance and global radiation in relation to photodissociation rates, Tellus, serie B, 47, 353–364.
Wicker, L. J. and Wilhelmson. R. B., 1995: Simulation and analysis of tornado development and decay within a three-dimensional supercell thunderstorm, J. Atmos. Sci. 52, 2675–2703.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Brasseur, AL., Ramaroson, R., Delannoy, A. et al. Three-Dimensional Calculation of Photolysis Frequencies in the Presence of Clouds and Impact on Photochemistry. Journal of Atmospheric Chemistry 41, 211–237 (2002). https://doi.org/10.1023/A:1014952630482
Issue Date:
DOI: https://doi.org/10.1023/A:1014952630482