Modeling and Analysis of the Lower Stratospheric Radiation Field during SOLVE

 

Principal Investigator:Steven A. Lloyd
Co-Investigator:Donald E. Anderson, Jr., William H. Swartz, and Thomas L. Kusterer
Organization:Atmospheric and Ionospheric Remote Sensing Group
Applied Physics Laboratory (APL)
The Johns Hopkins University
11100 Johns Hopkins Road
Laurel, MD 20723-6099

Measurement Description: The goals of the Johns Hopkins University Applied Physics Laboratory (APL) Theory Team's research effort for SOLVE are to:

  1. calculate a set of photolysis rate coefficients or j–values for photochemical reactions of interest in the lower stratosphere and upper troposphere, calculated along the ER–2 and DC–8 flight tracks for each flight during the SOLVE campaigns;
  2. provide a consistency check based on our theoretical modeling for actinic fluxes (and the j–values derived therefrom) obtained by Environment Canada's Composition and Photodissociative Flux Measurement (CPFM) instrument aboard the ER–2, as well as the National Center for Atmospheric Research's (NCAR) Scanning Actinic Flux Spectroradiometer (SAFS) instrument aboard the DC–8;
  3. provide a consistency check based on our theoretical modeling for j–values calculated from observed species concentrations, specifically for the photolysis of NO2 and ClONO2; and
  4. provide an ozone climatology for the SOLVE campaign, based on a comparison between in situ ozonesonde measurements, Total Ozone Mapping Spectrometer (TOMS) total ozone measurements, other ground–based (Brewer, Dobson) and satellite (SAGE II, POAM III, MSX) ozone observations, and existing high–latitude ozone climatologies.
The most important scientific question that can be directly addressed by our radiation field calculations (and validated by the SOLVE dataset) is the sensitivity of photolytic ozone loss processes to a variety of atmospheric conditions: total ozone, ozone profile, season or solar zenith angle, effective surface albedo, cloud height and atmospheric refraction.

Overview: The primary data product of The APL Theory Team is a set of photolysis rate coefficients or j–values for photochemical reactions of interest in the lower stratosphere and upper troposphere, calculated along the ER–2 and DC–8 flight tracks for each flight during the SOLVE campaign. These calculated j–values can be compared with those obtained with Environment Canada's Composition and Photodissociative Flux Measurement (CPFM) instrument aboard the ER–2, with the National Center for Atmospheric Research's (NCAR) Scanning Actinic Flux Spectroradiometer (SAFS), and with j–values calculated from observed species concentrations. They can also be incorporated into photochemical models used by a variety of instrument groups and other theory groups in their data analysis.

Radiation field calculations are only as good as the inputs to these models. Therefore, a considerable portion of our effort will be spent in acquiring and assessing the quality of the input model atmospheres used, with emphasis placed on an accurate description of the total column ozone and partial column above the aircraft along the flight tracks. We are working cooperatively with other groups to provide additional data products, in particular with NASA Goddard to acquire high resolution (level 2) TOMS total ozone data and to implement an improved high–latitude ozone climatology in calculating the optical depth along the line–of–sight to the Sun. Analysis of ground–based and satellite ozone datasets will allow us to establish the seasonal trend of total ozone during the SOLVE campaign, as well as a composite climatology of pressure, temperature and ozone profiles for each deployment.

While there were significant discrepancies in the j–values produced by our group and those observed by the CPFM instrument and calculated by the JPL theory team during the 1994 ASHOE/MAESA campaign (often 50% differences for j(NO2) and factors of 2–3 for j(O3)), working cooperatively with these groups in the field during the 1997 POLARIS campaign has significantly reduced these differences in the radiation field to the level of the uncertainties in the cross sections/quantum yields (typically within 5% for j(NO2) and better than 25% for j(O3)). This excellent agreement between the CPFM and two independently–calculated radiation field models provides a validation of the CPFM dataset, which holds the advantage of finer spatial resolution than the TOMS satellite data, as well as simultaneity with the in situ trace species observations. We have also calculated j–values for POLARIS which use the CPFM observations of overhead ozone and effective surface albedo as inputs to the radiation field model, which agree well with the calculations of the JPL theory team.

References:

Del Negro, L. A., D. W. Fahey, R. S. Gao, S. G. Donnelly, E. R. Keim, J. A. Neuman, R. C. Cohen, K. K. Perkins, L. C. Koch, R. J. Salawitch, S. A. Lloyd, M. H. Proffitt, J. Margitan, R. M. Stimpfle, G. P. Bonne, P. B. Voss, P. O. Wennberg, C. T. McElroy, W. H. Swartz, T. L. Kusterer, D. E. Anderson, L. R. Lait, and T. P. Bui, Comparison of modeled and observed values of NO2 and JNO2 during the POLARIS mission, J. Geophys. Res., in press, 1999.

Gao, R. S., D. W. Fahey, R. J. Salawitch, S. A. Lloyd, D. E. Anderson, R. DeMajistre, C. T. McElroy, E. L. Woodbridge, R. C. Wamsley, S. G. Donnelly, L. A. Del Negro, M. H. Proffitt, R. M. Stimpfle, D. W. Kohn, S. R. Kawa, L. R. Lait, M. Loewenstein, J. R., Podolske, E. R. Keim, J. E. Dye, J. C. Wilson, and K.R. Chan, Partitioning of the reactive nitrogen reservoir in the lower stratosphere of the southern hemisphere: Observations and modeling, J. Geophys. Res., 102 (D3), 3935–3949, 1997.

Lloyd, S., W. H. Swartz, T. Kusterer, D. Anderson, C. T. McElroy, C. Midwinter, R. Hall, K. Nassim, D. Jaffe, W. Simpson, J. Kelley, D. Griffin, D. Nicks, B. Johnson, R. Evans, D. Quincy, S. Oltmans, P. Newman, R. McPeters, G. Labow, L. Moy, C. Seftor, G. Toon, B. Sen, and J.–F. Blavier, Intercomparison of total ozone observations at Fairbanks, Alaska during POLARIS, J. Geophys. Res., in press, 1999.

Stimpfle, R. M., R. C. Cohen, G. P. Bonne, P. B. Voss, K. K. Perkins, L. C. Koch, J. G. Anderson, R. J. Salawitch, S. A. Lloyd, R. S. Gao, L. A. Del Negro, E. R. Keim, and T. P. Bui, The coupling of ClONO2, ClO and NO2 in the lower stratosphere from in situ observations using the NASA ER–2 aircraft, J. Geophys., in press, 1999.

Swartz, W. A., S. A. Lloyd, T. L. Kusterer, D. E. Anderson, C. T. McElroy, and C. Midwinter, A sensitivity study of photolysis rate coefficients during POLARIS, J. Geophys. Res., in press, 1999.

Wennberg, P. O., R. J. Salawitch, D. J. Donaldson, T. F. Hanisco, E. J. Lanzendorf, K. K. Perkins, S. A. Lloyd, V. Vaida, R. S. Gao, E. J. Hintsa, R. C. Cohen, W. H. Swartz, T. L. Kusterer, and D. E. Anderson, Twilight observations suggest unknown sources of HOx, Geophys. Res. Lett., 26 (10), 1373–1376, 1999.

Zhu, X., J.–H. Yee, S. A. Lloyd, and D. F. Strobel, Numerical modeling of chemical–dynamical coupling in the upper stratosphere and mesosphere, J. Geophys. Res., 104 (D18), 23995–24011, 1999.