ABSTRACT
We have utilized Solar Backscatter Ultraviolet (SBUV) instrument measurements of atmospheric radiance to create a 40-year record of polar mesospheric cloud (PMC) behavior. While this series of measurements is nearing its end, we show in this paper that Ozone Mapping and Profiling Suite (OMPS) Nadir Profiler (NP) instruments can be added to the merged SBUV PMC data record. Regression analysis of this extended record shows smaller trends in PMC ice water content (IWC) since approximately 1998, consistent with previous work. Current trends are significant at the 95% confidence level in the Northern Hemisphere, but not in the Southern Hemisphere. The PMC IWC response to solar activity has decreased in the Northern Hemisphere since 1998, but has apparently increased in the Southern Hemisphere.
ABSTRACT
Water-rich rocket exhaust plumes, in particular those emitted by the National Aeronautics and Space Administration Space Shuttle, have been suggested to make a significant contribution to long-term trends in polar mesospheric cloud (PMC) ice water content. We investigate this claim using the combined Solar Backscatter Ultraviolet (SBUV) PMC data record from eight separate instruments, which includes 60 Shuttle launches during PMC seasons between 1985 and 2011. No statistically significant postlaunch signal in PMC total ice is observed based on superposed epoch analysis of the SBUV record. Only a few launches show individual peaks in total ice anomaly above the seasonal background that exceed an empirical threshold, and the maximum cumulative signature from these infrequent cases is typically less than 5% of the season total in ice mass. Other non-Shuttle launches show circumstantial evidence of possible PMC effects, although supporting evidence for plume transport is not available. We conclude that space traffic effects have been a negligible component of long-term PMC behavior.
