Trends in Seventeen Years of TIMED/SABER OH Measurements
Abstract
The TIMED/SABER mission data comprise what is by far the most comprehensive geographical and temporal compendium of long term information on the nature of the OH Meinel-emission layer and thus may provide information on the possible long term changes near the mesopause. Any identifiable changes in the characteristics of the Meinel emission provide quantitative markers of how the mesosphere and lower thermosphere (MLT) may be affected by climate change, or by quasi-periodic large-scale influences like solar activity or ENSO. Here we present a 1 7 -year record (2002-2018) of the mean OH layer height and brightness, using the retrieved volume emission rate (VER) in the 2.0 μ m OH channel. The layer height is the altitude of the VER maximum, and the zenith radiance is our measure of the brightness. We considered the entire database of nighttime events (solar zenith angle greater than 105 º ) in the latitude range 52°N-52°S, where observations are possible year-round. We eliminated events (~25%) lacking a single clearly-defined peak, and took suitable annual and yaw-cycle averages over discrete latitude ranges, eliminating systematic shorter-term variability so as to highlight the trends. The results (from over 150,000 profiles per year) show that the layer altitude trend is -140 ± 30 m/decade, comparable to estimates of middle-atmospheric shrinkage under global climate change. The brightness, on the other hand, shows an unmistakable signature of the solar cycle presumably due to solar-cycle modulation of MLT atomic oxygen densities.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSA21B3091W
- Keywords:
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- 0340 Middle atmosphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0355 Thermosphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3369 Thermospheric dynamics;
- ATMOSPHERIC PROCESSES;
- 2447 Modeling and forecasting;
- IONOSPHERE