Snow Optics and Photochemistry

As a part of an NSF-funded research project, we have investigated photochemistry in snow and developed models for photochemical rate coefficient calculations as a function of depth in the snowpack. We have found excellent agreement between the simple delta-Eddington model used in our previous publications (Simpson et al, 2002) and the DISORT model used by Lee-Taylor and Madronich (2002). We also find that both of these models give excellent agreement with observations of photochemistry in synthetic snowpack (Phillips and Simpson, 2005).

Figure 1: Comparision of radiation-transfer modeled photolysis rate coefficients to experimentally measured photolysis rate coefficients. The arrow on the vertical axis represents the photolysis rate coefficient if there were no snow, thus it is clear that snow amplifies photolysis rates near its surface. The TUV and delta-Eddington model results are essentially identical.

The delta-Eddington model computer code used in this study is available upon request. Please send email to William Simpson, ffwrs@uaf.edu requesting this code. The TUV code can be found at the TUV website.

References

Simpson, W. R., M. D. King, H. J. Beine, R. E. Honrath, and M. C. Peterson (2002), Atmospheric photolysis rates during the Polar Sunrise Experiment ALERT2000 Field Campaign, Atmos. Env., 36, 2471-2480. and minor correction: Simpson, W. R., M. D. King, H. J. Beine, R. E. Honrath, and M. C. Peterson (2002), Corrigendum to "Atmospheric photolysis rates during the Polar Sunrise Experiment ALERT2000" [Atmospheric Environment 36 (15-16) 2471-2480 (2002)], Atmos. Env., 36, 5749.

Lee-Taylor, J., and S. Madronich (2002), Application of TUV Tropospheric Radiative Transfer Model to Snowpack Photochemistry, J. Geophys. Res., 107(D24), 4796, doi:10.1029/2002JD002084

Phillips, G. J., and W. R. Simpson (2005), Verification of snowpack radiation transfer models using actinometry, J. Geophys. Res., 110., D08306, doi: 10.1029/2004JD005552

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created by Bill Simpson (ffwrs@uaf.edu)