Some Closing Remarks

With the improved modeling of the troposphere-stratosphere system, model results are showing increasing consistency with the observational analyses of Labitzke, van Loon, Chanin, and others. The relatively recent work of Lesley Gray and her colleagues suggests that solar UV influences on the lower stratosphere are most sensitive to alterations in atmospheric structure in the tropical upper stratosphere, and Matthes et al. (2004) find that proper inclusion of this does indeed improve their general circulation model results. Another interesting line of research is the recent work originally due to Murry Salby that suggests a solar effect on the quasi-biennial oscillation in the stratospheric mean zonal wind in the tropics. If this is a mechanism by which solar activity affects the lower stratosphere and troposphere, there are several implications. One is that to treat this mechanism properly, one must use an atmospheric model that extends through the stratosphere and goes sufficiently high for the stratosphere to be well modeled. To account for the indirect effect of solar ultraviolet heating of the stratosphere, the ozone variations that result from the solar UV variations should also be in the model. Another point relates to comments made in the Kodera (2006) and Schmidt and Brasseur (2006) papers. This is that the solar UV ^ stratosphere ^ lower atmosphere effect on climate mainly influences regional climate whereas variations in the solar constant affect globally averaged temperatures and other climate parameters.

Finally, there is the interesting suggestion in Kodera (2006) of a completely new mechanism by which solar-induced effects in the stratosphere can affect the troposphere, and that is the effect of modulations in the Brewer-Dobson circulation on tropical convection, and its possible subsequent possible effect on the global circulation. In this regard, it should be noted that Collimore et al. (2003) have found evidence of a QBO effect on tropical convection, and they conclude that this is most likely related to QBO modulations in tropical tropopause heights.

This summary paper has discussed several of the papers that follow in this book, but it is certainly not a comprehensive presentation of all mechanisms for solar influences on climate. One such mechanism is discussed elsewhere in this volume, and that is the mechanism that involves cosmic rays on cloud amounts. The Curtius (2006) and Arnold (2006) papers address this issue.

Other topics relating to mechanisms for solar influences on the climate are also not covered here. One is the suggestion of Meehl et al. (2003) that variations in total solar insolation lead to more evaporation in the cloud-free subtropics, which in turn affects moisture transports and latent heat release. To treat the solar UV/QBO/planetary wave mechanism properly in a climate model, the model (i) should extend at least into the mesosphere; (ii) include solar modulation of ozone, (iii) ideally should account for the QBO; and (iv) include good resolution of the solar variations in the UV portion of the solar spectrum. The Meehl et al. (2003) mechanism does not require all these things. It also is not yet being researched as intensively as the solar UV/planetary waves mechanism.

It is clear that the study of solar influences on climate is now in a new phase where quantitative treatments of mechanisms are being studied. Furthermore, in the case of solar UV effects on climate, these studies contribute to the more general study of stratospheric influences on climate, where the stratospheric changes may occur from natural or anthropogenic influences. The introduction started with a rather pessimistic quote from Pittock (1978). Five years later, Pittock (1983) said the following:

"Advances have been made in the modeling of variable ultraviolet influences on middle stratosphere temperatures and ozone content, and of the modulation of reflection and absorption of tropospheric planetary wave energy by solar-induced variations in stratospheric winds and temperature profiles."

He went on to say that this solar UV/planetary wave mechanism was

"... a complex phenomenon which as yet has only been modeled in a very simplified manner."

How right he was, and how far we have come.

References

Andrews, D. G., Holton, J. R., and Leovy, C. B.: 1987, Middle Atmosphere Dynamics, Academic Press, San Diego, 489 pp.

Arnold, F.: 2006, 'Atmospheric aerosol and cloud condensation nuclei formation: A possible influence of cosmic rays', Space Sci. Rev., this volume, doi: 10.1007/s11214-006-9055-4.

Bates, J. R.: 1981, 'A dynamical mechanism through which variations in solar ultra violet radiation can affect tropospheric climate', J. Geophys. Res. 104, 27,321-27,339.

Calisesi, Y., and Matthes, K.: 2006, 'The middle atmospheric ozone response to the 11-year solar cycle', Space Sci. Rev., this volume, doi: 10.1007/s11214-006-9063-4.

Callis, L. B., Alpert, J. C., and Geller, M. A.: 1985, 'An assessment of thermal, wind, and planetary wave changes in the middle and lower atmosphere due to 11-year UV flux variations', J. Geophys. Res. 90, 2273-2282.

Chanin, M.-L.: 2006, 'Signature of the 11-year cycle in the upper atmosphere', Space Sci. Rev., this volume, doi: 10.1007/s11214-006-9062-5.

Collimore, C. C., Martin, D. W., Hitchman, M. H., Huesmann, A., and Waliser, D. E.: 2003, 'On the relationship between the QBO and tropical deep convection', J. Clim. 16, 2552-2568.

Cordero, E. C., and Nathan, T. R.: 2005, 'A new pathway for communicating the 11-year solar cycle signal to the QBO', J. Geophys. Res. 32, doi:10.1029/2005GL023696.

Crucifix, M.: 2006, 'The climate response to the astronomical forcing', Space Sci. Rev., this volume, doi: 10.1007/s11214-006-9058-1.

Curtius, J.: 2006, 'Atmospheric ion-induced aerosol nucleation', Space Sci. Rev., this volume, doi: 10.1007/s11214-006-9054-5.

Friis-Christensen, E., and Lassen, K.: 1991, 'Length of the solar cycle: An indicator of solar activity closely associated with climate', Science 254, 698-700.

Frohlich, C.: 2006, 'Solar irradiance variability since 1978', Space Sci. Rev., this volume, doi: 10.1007/s11214-006-9046-5.

Geller, M. A.: 1988, 'Solar cycles and the atmosphere', Nature 332, 584-585.

Geller, M. A., and Alpert, J. V.: 1980, 'Planetary wave coupling between the troposphere and middle atmosphere as a possible sun-weather mechanism', J. Atmos. Sci. 37, 1197-1215.

Giorgetta, M. A., Manzini, E., and Roeckner, E.: 2002, 'Forcing of the quasi-biennial oscillation from a broad spectrum of atmospheric waves', Geophys. Res. Lett. 29, doi:10.1029/2002GL014756.

Goosse, H.: 2006, 'Regional response of the climate system to solar forcing: The role of the ocean', Space Sci. Rev., this volume, doi: 10.1007/s11214-006-9059-0.

Gray, L. J., 2003: The influence of the equatorial upper stratosphere on stratospheric sudden warmings', Geophys. Res. Lett., 30, doi:10.1029/2002GL016430.

Gray, L., Crooks, S., Palmer, M., Pascoe, C., and Sparrow, S.: 2006, 'A possible transfer mechanism for the 11-year solar cycle to the lower stratosphere', Space Sci. Rev., this volume, doi: 10.1007/s11214-006-9069-y.

Haigh, J. D.: 1994, 'The role of stratospheric ozone in modulating the solar radiative forcing of climate', Nature 370, 544-546.

Haigh, J. D.: 1996, 'The impact of solar variability on climate', Science 272, 981-984.

Haigh, J. D.: 1999, 'A GCM study of climate change in response to the 11-year solar cycle', Quart. J. Roy. Meteorol. Soc. 125, 871-892.

Haigh, J. D., and Blackburn, M.: 2006, 'Solar influences on dynamical coupling between the stratosphere and troposphere', Space Sci. Rev., this volume, doi: 10.1007/s11214-006-9067-0.

Hines, C. O.: 1974, 'A possible mechanism for the production of sun-weather correlations', J. Atmos. Sci. 31, 589-591.

IPCC (Intergovernmental Panel on Climate Change): 2001, Climate Change 2001: The Scientific Basis: Contribution of Working Group I to the Third Assessment Report of the Intergovernmental

Panel on Climate Change, 2001, J. T., Houghton, Y., Ding, D. J., Griggs, M., Noguer, van der P. J., Linden, Dai, X., et al. (Eds.), Cambridge University Press, Cambridge, U.K., 881 pp.

Kodera, K.: 2006, 'The role of dynamics in solar forcing', Space Sci. Rev., this volume, doi: 10.1007/s11214-006-9066-1.

Labitzke, K.: 1987, 'Sunspots, the QBO, and the stratospheric temperature in the north polar region', Geophys. Res. Lett. 14, 535-537.

Labitzke, K.: 2006, 'Solar variation and stratospheric response', Space Sci. Rev., this volume, doi: 10.1007/s11214-006-9061-6.

Laut, P.: 2003, 'Solar activity and terrestrial climate: An analysis of some purported correlations', J. Atmos. Solar-Terr. Phys. 65, 801-812.

Matthes, K., Langematz, U., Gray, L. J., Kodera, K., and Labitzke, K.: 2004, 'Improved 11-year solar signal in the Frei Universitat Berlin Climate middle Atmosphere Model (FUB-CHAM)', J. Geophys. Res. 109, doi:10.1029./2003JD004012.

Mayr, H. G., Mengel, J. G., Wolff, C. L., Porter, H. S.: 2006, 'QBO as potential amplifier of solar cycle influence', Geophys. Res. Lett. 33, doi:10.1029/2005GL025650.

Meehl, G. A., Washington, W. M., Wigley, T. M. L., Arblaster, J. M., and Dai, A.: 2003, 'Solar and greenhouse gas forcing and climate response in the twentieth century', J. Clim. 16, 426-444.

Pittock, A. B.: 1978, 'A critical look at long-term Sun-weather relationships', Rev. Geophys. Sp. Phys. 16, 400-420.

Pittock, A. B.: 1983, 'Solar variability, weather, and climate: An update', Q. J. Roy. Met. Soc. 109, 23-55.

Plumb, A.: 1985, 'On the three-dimensional propagation of stationary waves', J. Atmos. Sci. 42, 217-229.

Rottman, G.: 2006, 'Measurement of total and spectral solar irradiance', Space Sci. Rev., this volume, doi: 10.1007/s11214-006-9045-6.

Salby, M., and Callaghan, P. F.: 2006, 'Influence of the solar cycle on the general circulation of the stratosphere and upper troposphere', Space Sci. Rev., this volume, doi: 10.1007/s11214-006-9064-3.

Schmidt, H., and Brasseur, G. P.: 2006, 'The response of the middle atmosphere to solar cycle forcing in the Hamburg Model of the Neutral and Ionized Atmosphere', Space Sci. Rev., this volume, doi: 10.1007/s11214-006-9068-z.

Shindell, D., Rind, D., Balachandran, N., Lean, J., and Lonergan, P.: 1999, 'Solar cycle variability, ozone, and climate', Science 284, 305-308.

Svensmark, H., and Friis-Christensen, E.: 1997, 'Variation of cosmic ray flux and global cloud coverage - a missing link in solar-climate relationships', J. Atmos. Solar-Terr. Phys. 59, 1225-1232.

Was this article helpful?

0 0

Post a comment