• Introduction
• RegCM2 - Regional Climate Model
• Ozone Profile Tests
• Ozone Profile Reconstruction
• Parameters Values
• Results
• Conclusions
• Acknowledgements
• References
• List of figures

FIGURES

• Figure 1.
• Figure 2.
• Figure 3.
• Figure 4.
• Figure 5.
• Figure 6.
• Figure 7.
• Figure 8.
• Figure 9.
• Figure 10.
• Figure 11.
• Figure 12.
• Figure 13.
• Figure 14.
• Figure 15.
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• Figure 18.
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• Figure 21.
• Figure 22.
• Figure 23.
• Figure 24.
• Figure 25.
• Figure 26.
• Figure 27.
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• Figure 30.
• Figure 31.
• Figure 32.
• Figure 33.
• Figure 34.
• Figure 35.
• Figure 36.
• Figure 37.
• Figure 38.
• Figure 39.
• Figure 40.
• Figure 41.
• Figure 42.
• Figure 43.
• Figure 44.
• Figure 45.
• Figure 46.
• Figure 47.
• Figure 48.
• Figure 49.
• Figure 50.
• Figure 51.
• Figure 52.

Introduction

Regional climate model RegCM2 is used for study of climate change impact on regional scales. The simple ozone profile parameterization based on standard atmosphere composition neglecting the monthly and regional variability is prescribed in standard version of the model. Sensitivity tests for appropriate ozone changes both in troposphere and stratosphere with respect to possible antropogeneous changes are presented resulting in quite significant changes in radiative characteristics of the model. The great effect is usually connected with other parameters and variables of the model with important role of water vapour and cloudness. For the purposes of this study the model top was moved up to 10 hPa and the resolution was increased in stratosphere. For the tests of validity of the model in real climate simulation modification of the model introducing TOMS data is presented. Real TOMS data can be used recovering the ozone profile by means of the analytical curve. Its parameters can be analysed on ozone profiles data and also their climatology, ie. at least their monthly and latitudinal variability is available for real extrapolation. The comparison of such an inclusion of ozone profile into the RegCM2 based on TOMS climatology with the appropriate ozone profile based on day to day and point to point variable real ozone information from TOMS data is presented as well. It can be seen that the effect of the improvement of ozone profile incorporation into the model can be at least in some of model points quite significant mainly for radiative characteristics. Actually, for climate models without the chemistry of ozone we could hardly have proper detailed ozone data for long term simulations, but it should be possible to include into such models better parameterization of both seasonal and at least latitudinal ozone profile variability.

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RegCM2 - Regional Climate Model

The use of regional climate model as a tool for so-called dynamical downscaling became quite popular in 90’. It means to run a limited area model nested in GCM for long-period simulations. There are some advantages of such an access, i.e. finer resolution of results, possibility of more detailed parameterization etc., but it is more demanding on computer resources and computer time. After couple year of experience with the first generation of NCAR RegCM (Regional Climate Model) (Dickinson et al., 1989; Giorgi, 1990) based on NCAR-PSU (National Center for Atmospheric Research – Pennsylvania State University) MM4 compressible hydrostatic grid point model but with modified physics for use in climate studies Giorgi et al. (1993a,b) upgraded the model resulting in the second generation RegCM, hereafter reffered to as RegCM2. The physics of the model moved to MM5 (Grell et al., 1991) and NCAR CCM2, during the last few years some other modifications appeared. Radiation package has been replaced by that of CCM3 (Kiehl et al., 1996), an option concerning parameterization of deep convection has been added, changes in moisture scheme adopted, lake effects included etc. The model has a lot of optional parameters, it is possible to run it with different selections of geometry parameters, domain size and position, gridsize (B type of Arakawa-Lamb classification), projections, orography resolution, number of sigma levels, top of the atmosphere etc. For numerical integration, split-explicit time scheme is used, boundary conditions being interpolated from global data with selected step, but the minimum in our sample data for June 1994 is 6 hours. 13 land-use climatologic categories are involved with seasonal resolution for parameterization of surface processes of land – atmosphere interactions.

For the purposes of this study we run the model with number of levels set on 20, one month experiment takes about 4.5 hours for gridsize of 180 km on the domain of Europe using Sun Ultra 60 workstation with two 360MHz processors. We have run several sensitivity tests on the influence of ozone profile parameterization in the model for June 1994 as well as some real month study for June, March and October 1994.

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Ozone Profile Tests

We have made control run with the original ozone profile parameterization geographically independent and with only seasonal value on individual levels. This was used as a basis for further comparisons. We have tried simple modification of ozone profile by 50% reduction in the stratosphere or 200% increase in troposphere with very rough connection to possible antropogeneous changes. Actually, it was not intended to be a serious study of antropogeneous influence but as a real model sensitivity test on reasonable ozone changes influence in the model. Finally, we have used TOMS database for ozone profile reconstruction for the appropriate month of simulation. We restore the ozone profiles for whole domain by means the formula of Lacis and Hansen (1974), both on daily and monthly basis. The first one gives the best possibility (except taking real ozone soundings data into account) for a model validity evaluation by means of nesting in the observations, the latter could be used for improving of the ozone profile parameterization even for some extrapolation with regard to the temporal and geographical variability, as we can have the climatology of the ozone profile parameters.

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Ozone Profile Reconstruction

In some cases, e.g. for radiative transfer procedure in numerical models of the atmosphere, one can need simple method of reconstruction of ozone profile from total ozone value only. The empirical formula of Lacis and Hansen (1974) can be used for such a purpose written in a form

where u(h) represents the integrated amount of ozone from the top of atmosphere, h is the height above mean sea level and A, B, C are the parameters of the profile. The meaning of the parameter A can be found immediately

,

thus A represents total ozone amount in atmospheric column. Differentiating the formula with respect to h yields

,

which means actually well known ozone profile, with unit transformation by Claude et al. (1986)

for partial pressure of ozone, or, for mass mixing ratio

where p₀, T₀ are standard pressure and temperature on sea level height, R, R_N are gas constant of air and universal gas constant, respectively, N Avogadro‘s number and m mass unit. T represents the temperature on the level of h.

Differentiating the formula again with respect to h yields

,

where searching extreme (maximum) of ozone profile

,

thus parameter B represents the height of ozone partial pressure maximum. Differentiating the formula again with respect to h yields

,

where searching for further points of inflections we have

, i.e. .

It means that parameter C is in relation to the depth of the main ozone partial pressure maximum.

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Parameters Values

The method was originally suggested to approximate the average ozone profile with values of the parameters A=400 D.U., B=20000 m, C=5000 m. Even individual integrated ozone profiles seem to be smooth enough for approximation by means of the analytical formula and applied to the database of ozone profiles from WODC for period of 1980-91, it made available a statistical analysis of these parameters with aim to obtain their temporal (seasonal) and geographical variability. Therefore, ozone profiles from selected ozone sounding sites were analyzed. Unfortunately, there were only a few stations covering all the period in the 5^o latitudinal belts, in some of them we have to use even shorter series of ozone sounding or we do not have any sounding available at all. For better estimation of the ozone profile by the formula we used TOMS measurement additionally. Fig. 1 represents the seasonal variability of the parameters for Churchill, Hohenpeissenberg and Payerne, where seasonal and latitudinal dependences are well expressed except the latter for the parameter C that is analyzed with greater error. In Fig. 2 final analysis of the ozone profile parameters is presented for northern hemisphere.

Figure 1. Annual cycle of the ozone profile parameters on individual stations.

Figure 2. Annual cycle of the ozone profile parameters on the northern hemisphere.

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Results

The model sensitivity of the ozone profile changes (see Fig. 3) is not so high in general. Tropospheric increase of ozone results in rather positive effect about 2-4% of solar heating in troposphere and about 2% negative in stratosphere (see Fig. 4, Fig. 5). Stratospheric ozone reduction means strong influence on solar heating in stratosphere (about 25% negative) and up to 5% of positive effect in troposphere (see Fig. 6, Fig. 7). The effect of real ozone profiles or monthly mean profiles (Fig. 8, Fig. 9) is rather little. For June 1994 it can be seen in Fig. 10, Fig. 11 or Fig. 12, Fig. 13, respectively. But, there are some locations on some days where this small direct effects probably due to changes in stability can change cloud formation (see Fig. 14, Fig. 15, Fig. 16, Fig. 17, respectively, for individual experiments), and thus greater impact not only in solar heating but in long wave radiation and other parameters can be seen under these circumstances. The complete series of the first one is presented in Fig. 18, Fig. 19, Fig. 20, Fig. 21 as the differences for individiual experiments against control run, relative differences in Fig. 22, Fig. 23, Fig. 24, Fig. 25, respectively, with a sample of detail in Fig. 26. For comparison with IPCC figures some other heating parameters are presented in terms of monthly means for whole model domain. For all individual June 1994 experiments solar flux absorbed at the surface is displayed in Fig. 27, Fig. 28, Fig. 29 and Fig. 30. Further, for tropospheric and stratospheric sensitivity tests we present long wave cooling of the surface (Fig. 31, Fig. 32, respectively), solar flux absorbed in whole column of the atmosphere (Fig. 33, Fig. 34, respectively), net up flux at the top of the atmosphere (Fig. 35, Fig. 36), cloudness (Fig. 37, Fig. 38) and for surface air temperature all individual experiments, i.e. Fig. 39, Fig. 40, Fig. 41 and Fig. 42, respectively. We have also made some preliminary test of the ozone influence for the months with ozone extremes, we selected episodes from March 1994 as a month with high ozone values and variability (see Fig. 43), October 1994 was chosen as a month of low ozone value (see Fig. 44). We present solar heating and long wave cooling relative biases in Fig. 45 and Fig. 46, respectively, and mean departures of solar flux absorbed at the surface and long wave cooling at the surface in Fig. 47 and Fig. 48 for March 1994. Similarly, Fig. 49, Fig.50, Fig. 51 and Fig. 52 display the same parameters of the model simulation for October 1994.

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Figure 3. Ozone profiles used in experiments. Values in g/kg against pressure levels in hPa, empty circles for control profile, full circles for tropospheric increase by 200%, empty squares represent stratospheric reduction by 50% and full squares mean ozone profile based on TOMS data for 15^o E, 50^o N.

Figure 4. Solar heating rate difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 sensitivity run with 200% increase of ozone in troposphere against the control run (deg s^-1).

Figure 5. Solar heating rate relative difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 sensitivity run with 200% increase of ozone in troposphere against the control run (%).

Figure 6. Solar heating rate difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 sensitivity run with 50% decrease of ozone in stratosphere against the control run (deg s^-1).

Figure 7. Solar heating rate relative difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 sensitivity run with 50% decrease of ozone in stratosphere against the control run (%).

Figure 8. Ozone mass mixing ratio relative difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (%).

Figure 9. Ozone mass mixing ratio relative difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 run with ozone profile reconstruction based on TOMS monthly mean of total ozone data against the control run (%).

Figure 10. Solar heating rate difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (deg s^-1).

Figure 11. Solar heating rate relative difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (%).

Figure 12. Solar heating rate difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 run with ozone profile reconstruction based on TOMS monthly mean of total ozone data against the control run (deg s^-1).

Figure 13. Solar heating rate relative difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 run with ozone profile reconstruction based on TOMS monthly mean of total ozone data against the control run (%).

Figure 14. Cloud fractional cover difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 sensitivity run with 200% increase of ozone in troposphere against the control run.

Figure 15. Cloud fractional cover difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 sensitivity run with 50% decrease of ozone in stratosphere against the control run.

Figure 16. Cloud fractional cover difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run.

Figure 17. Cloud fractional cover difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 run with ozone profile reconstruction based on TOMS monthly mean of total ozone data against the control run.

Figure 18. Long wave cooling rate difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 sensitivity run with 200% increase of ozone in troposphere against the control run (deg s^-1).

Figure 19. Long wave cooling rate difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 sensitivity run with 50% decrease of ozone in stratosphere against the control run (deg s^-1).

Figure 20. Long wave cooling rate difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (deg s^-1).

Figure 21. Long wave cooling rate difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 run with ozone profile reconstruction based on TOMS monthly mean of total ozone data against the control run (deg s^-1).

Figure 22. Long wave cooling rate relative difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 sensitivity run with 200% increase of ozone in troposphere against the control run (%).

Figure 23. Long wave cooling rate relative difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 sensitivity run with 50% decrease of ozone in stratosphere against the control run (%).

Figure 24. Long wave cooling rate relative difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (%).

Figure 25. Long wave cooling rate relative difference in the middle of model domain (for 15^o E, 50^o N) in June 1994 run with ozone profile reconstruction based on TOMS monthly mean of total ozone data against the control run (%).

Figure 26. Detail of the greater negative impact of ozone profile based on monthly mean TOMS data on longwave heating rate. Relative difference (%) against control experiment, for 15^o E, 50^o N.

Figure 27. Surface absorbed solar flux difference in June 1994 sensitivity run with 200% increase of ozone in troposphere against the control run (Wm²).

Figure 28. Surface absorbed solar flux difference in June 1994 sensitivity run with 50% decrease of ozone in stratosphere against the control run (Wm²).

Figure 29. Surface absorbed solar flux difference in June 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (Wm²).

Figure 30. Surface absorbed solar flux difference in June 1994 run with ozone profile reconstruction based on TOMS monthly mean of total ozone data against the control run (Wm²).

Figure 31. Long wave cooling flux of the surface in June 1994 sensitivity run with 200% increase of ozone in troposphere against the control run (Wm²).

Figure 32. Long wave cooling flux of the surface in June 1994 sensitivity run with 50% decrease of ozone in stratosphere against the control run (Wm²).

Figure 33. Solar flux absorbed in whole column of the atmosphere in June 1994 sensitivity run with 200% increase of ozone in troposphere against the control run (Wm²).

Figure 34. Solar flux absorbed in whole column of the atmosphere in June 1994 sensitivity run with 50% decrease of ozone in stratosphere against the control run (Wm²).

Figure 35. Net up flux at the top of the atmosphere in June 1994 sensitivity run with 200% increase of ozone in troposphere against the control run (Wm²).

Figure 36. Net up flux at the top of the atmosphere in June 1994 sensitivity run with 50% decrease of ozone in stratosphere against the control run (Wm²).

Figure 37. Total cloud fractional cover in June 1994 sensitivity run with 200% increase of ozone in troposphere against the control run.

Figure 38. Total cloud fractional cover in June 1994 sensitivity run with 50% decrease of ozone in stratosphere against the control run.

Figure 39. Surface air temperature difference in June 1994 sensitivity run with 200% increase of ozone in troposphere against the control run.

Figure 40. Surface air temperature difference in June 1994 sensitivity run with 50% decrease of ozone in stratosphere against the control run.

Figure 41. Surface air temperature difference in June 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run.

Figure 42. Surface air temperature difference in June 1994 run with ozone profile reconstruction based on TOMS monthly mean of total ozone data against the control run.

Figure 43. Ozone mass mixing ratio relative difference in the middle of model domain (for 15^o E, 50^o N) in March 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (%).

Figure 44. Ozone mass mixing ratio relative difference in the middle of model domain (for 15^o E, 50^o N) in October 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (%).

Figure 45. Solar heating rate relative difference in the middle of model domain (for 15^o E, 50^o N) in March 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (%).

Figure 46. Long wave cooling rate relative difference in the middle of model domain (for 15^o E, 50^o N) in March 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (%).

Figure 47. Surface absorbed solar flux difference in March 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (Wm²).

Figure 48. Long wave cooling flux difference at the surface in March 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (Wm²).

Figure 49. Solar heating rate relative difference in the middle of model domain (for 15^o E, 50^o N) in October 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (%).

Figure 50. Long wave cooling rate relative difference in the middle of model domain (for 15^o E, 50^o N) in October 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (%).

Figure 51. Surface absorbed solar flux difference in October 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (Wm²).

Figure 52. Long wave cooling flux difference at the surface in October 1994 run with ozone profile reconstruction based on TOMS daily total ozone data against the control run (Wm²).

Conclusions

The method of ozone profile restoring from total ozone values (TOMS, surface measurement) provides good tool for the improvement of ozone inclusion into the models, e.g. ozone radiative impact parameterization in numerical models of the atmosphere. Actually, such a representation of the profile will not match the real ozone profile structure with a lot of disturbances or laminae, but using the proper "climatology" of the parameters more realistic estimate of ozone amount in the model layers is available comparing to constant or more simplyfied ozone profile. Actually, the effect of real ozone profiles or monthly mean profiles seems to be rather little, although sometimes in some locations probably due to changes in stability and thus changes in cloud formation it can produce quite great impact not only in solar heating but in long wave radiation and other parameters as well.

Acknowledgments

The RegCM2 was kindly provided by ICTP. Thanks go to F. Giorgi for advices concerning the model utilization and NASA for TOMS data. The work was partly supported in framework of research project CEZ: J13/98:113200004.

References

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Giorgi, F., 1990: Simulation of regional climate using a limited area model nested in a general circulation model. J. Clim., 3, 941-963.

Giorgi, F., M.R. Marinucci, and G.T. Bates, 1993a: Development of a second generation regional climate model (RegCM2) I: Boundary layer and radiative transfer processes. Mon. Wea. Rev., 121, 2794-2813.

Giorgi, F., M.R. Marinucci, G.T. Bates, and G. DeCanio, 1993b: Development of a second generation regional climate model (RegCM2) II: Convective processes and assimilation of lateral boundary conditions. Mon. Wea. Rev., 121, 2814-2832.

Grell, G., Y.-H. Kuo, and R.J. Pasch, 1991: Semi-prognostic tests of cumulus parameterization schemes in the middle latitudes..Mon. Wea. Rev., 119, 5-31.

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Halenka, T., 2000: On the parameters of the ozone profile structure, In: Proceedings of 2000 International Quadrennial Ozone Symposium, Sapporo, Japan, 3-8 July 2000, 417-418.

Kiehl, J.T., J.J. Hack, G.B. Bonan, B.A. Boville, B.P. Breigleb, D.L. Williamson, and P.J. Rasch, 1996: Description of the NCAR Community Climate Model (CCM3), NCAR Tech. Note, NCAR/TN-420+STR, 152pp., Natl. Cent. for Atmos. Res., Boulder, Colo.

Lacis, A.A., and J.E. Hansen (1974): A parameterization for the absorption of solar radiation in the Earth’s Atmosphere. Journal of the Atmospheric Sciences, 31, 118-133.

Mazurek, J. (1997): Changes of ozone vertical profile as a consequence of huge volcanic eruptions and their influence on climate. Diploma thesis, Charles University, Prague, 90 pages.

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