Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsa33b..08m&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #SA33B-08
Physics
[0340] Atmospheric Composition And Structure / Middle Atmosphere: Composition And Chemistry, [0341] Atmospheric Composition And Structure / Middle Atmosphere: Constituent Transport And Chemistry, [3305] Atmospheric Processes / Climate Change And Variability
Scientific paper
It is clear from observational record that polar mesospheric clouds (PMCs) exhibit long-term variability, and it is reasonable to assume that this variability is the result of changes in the background mesopause environment. Factors responsible for these changes include variations in solar irradiance over the 11-year sunspot cycle and trends in mesopause composition and temperature caused by increasing anthropogenic emissions in the troposphere. In this study we use the Whole Atmosphere Community Climate Model (WACCM), modified to include parameterized PMCs, to investigate this long-term variability. WACCM is driven with observed changes in the surface composition and solar spectral irradiance. Using multiple-linear regression analysis of WACCM PMC albedos, we calculate that in the northern hemisphere there was an increase of between 19% and 39% over the last 30 years, and that albedos can be reduced by up to 55% during solar maximum relative to solar minimum. Both responses increase with increasing latitude. In the southern hemisphere the solar response is similar to that in the northern hemisphere, but we find no long-term trend. Good agreement is found between WACCM and observations made by the Solar Backscattered Ultraviolet instrument when PMC detection thresholds are accounted for. Finally, we examine the relative importance of composition versus temperature changes using a series of sensitivity experiments.
Marsh Daniel R.
Merkel Aimee W.
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