Fabry-Perot Interferometer at Boulder, Colorado

On March 16, 2012, a Fabry-Perot Interferometer (FPI) was installed at the NCAR Marshall field site, just to the south-east of Boulder, to observe thermospheric and mesospheric winds. The FPI measures the Doppler shift in the OH 892 nm, O 557.7 nm, and 630 nm nightglow emissions, from which neutral winds at heights of 87 km, 97 km and 250 km are derived. While HAO operates FPIs from Resolute Bay, Canada (75N), Antarctica Palmer station (64S), and a high-altitude balloon platform, this is the first such dedicated year-round mid-latitude instrument from NCAR. Thermospheric wind controls the ionosphere by pushing the ions upward or downward along the geomagnetic field lines and is a key ingredient for understanding the ionosphere.

Image of FPI, Boulder
FPI at the NCAR Marshall field site

The Boulder FPI greatly enhances thermospheric wind coverage by allowing us to track changes originated in high latitudes (such as traveling atmospheric disturbances) to mid latitudes. It also allows investigation of longitudinal variations in the thermosphere based on joint observations with Millstone Hill FPI near Boston, which is at a similar latitude. Longitudinal variations associated with non-migrating tides are of great current interest, since these signify vertical coupling between the stratosphere and thermosphere. The FPI data are also a valuable source for validating NCAR’s Whole-Atmosphere Climate Circulation Model (WACCM) and its upper-atmosphere global circulation models, TIME-GCM and TIE-GCM.

The new FPI data will be submitted to the community CEDAR Archival Madrigal Database for public use.