Science Seminars

11/17/2016 – Jeff France; CIPS observations of gravity waves and planetary-wave-induced variability in PMCs

Speaker: Jeff France (LASP)
Date: Tuesday, Nov 17, 2020
Time: 4:00 PM
Location: SPSC W120

Seminar Abstract:

For nearly a decade, the Cloud Imaging and Particle Size (CIPS) instrument onboard the NASA Aeronomy of Ice in the Mesosphere (AIM) satellite has observed various properties of polar mesospheric clouds (PMCs). PMCs, which are located near the summer polar mesopause, occur as a result of upwelling and cooling associated with the gravity-wave-driven global residual circulation, and are therefore sensitive to large-scale dynamics that influence the propagation and breaking of gravity waves in the summer mesosphere.
Here, I will discuss two cases in which large-scale variability led to anomalies in the occurrence frequency of PMCs. In August 2014, there was a sharp decline in Northern Hemisphere PMCs. This decline is attributed to interhemispheric coupling (IHC) triggered by planetary wave activity in the Antarctic stratosphere. The results indicate that the IHC in 2014 occurred via a pathway that previous studies have not emphasized. The second case considers the early onset of PMCs in the Northern Hemisphere during 2015. The early onset is attributed to the presence of a large 5-day wave in the PMC region, resulting in sufficiently cold temperatures (150 K) in the trough for PMCs to form. This is the first instance of the 5-day wave directly affecting the timing of PMC onset.
I will also provide a first look at the recently developed CIPS albedo perturbation product, which provides observations of gravity waves near 50 km with horizontal wavelengths between 15 km and 300 km. Examples of waves from various sources are considered and compared to observations from the Atmospheric Infrared Sounder (AIRS).