Dynamical Analysis of Global Polar Mesospheric Cloud Measurements from the SNOE Spacecraft
Aimee W. Merkel
National Center for Atmospheric Research
The Student Nitric Oxide Explorer (SNOE) has been observing polar mesospheric clouds (PMCs) since 1998 and has successfully measured seven PMC seasons. SNOE is a spinning satellite in a sun-synchronous near-polar orbit at 10:30 am/pm local time. In the summer seasons, the Ultraviolet Spectrometer (UVS) limb measurements include detections of PMCs between 80-88 km. SNOE observations of PMCs have a significant advantage over other PMC measurements in that it is able to observe them globally each day. Because SNOE orbits the earth 15 times a day, daily global images of PMC brightness may be produced. The daily images, shown in a movie format, reveal the day-to-day variability in latitude and longitude of the PMC occurrences. Case studies of 5-day periods show a westward movement of PMC formation with the suggestion of a 5-day Rossby wave. Further analysis shows that in fact, PMCs are modulated by a dominant 5-day wave, which is present in all measured north and south seasons. This is the first direct wave analysis performed on PMC measurements on a global scale and gives a strong indication of the dynamical effects on PMC formation.