Solar cycle effects in mesospheric ice clouds (Invited)

Details Solar cycle effects in mesospheric ice clouds (Invited) Solar cycle effects in mesospheric ice clouds (Invited)

Dec 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsa44a..04l&link_type=abstract

American Geophysical Union, Fall Meeting 2009, abstract #SA44A-04

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[0340] Atmospheric Composition And Structure / Middle Atmosphere: Composition And Chemistry

Scientific paper

Ground based observations of mesospheric ice layers known as noctilucent clouds (NLC) are now available since 12 years. This allows to study solar cycle effects on NLC parameters such as altitudes, brightness, and occurrence rates. We present observations from our lidar stations in Kuehlungsborn (54°N) and ALOMAR (69°N). Different from general expectations the mean layer characteristics at ALOMAR do not show a persistent anti-correlation with solar cycle. Although a nice anti-correlation of Ly-alpha and occurrence rates is detected in the first half of the solar cycle, occurrence rates decreased with decreasing solar activity thereafter. Interestingly, in summer 2009 record high NLC parameters were detected as expected in solar minimum conditions. The morphology of NLC suggests that other processes except solar radiation may affect NLC. We present recent results from GCM modeling of ice clouds which suggests that the stratosphere can significantly affect mesospheric clouds. We present LIMA results regarding NLC sensitivity on temperatures, water vapor, and Ly-alpha radiation. NLC heights show little variation with background parameters whereas brightness and occurrence rates show large variations. None of the background parameters can be ignored regarding its influence on ice layers. At ALOMAR NLC altitudes do not change with solar cycle. Since these altitudes are highly correlated with temperatures at NLC heights this imposes a severe constraint on solar cycle modulation of temperatures. We will compare our NLC measurements with predictions of solar cycle modulations of temperatures and water vapor, and present first results from LIMA on solar cycle effects on NLC. We will also compare our measurements with other model results and with with long term observations of ice clouds from satellites.

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