High Latitude Dynamical Studies Using Radar and Satellite Observations

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The investigators will observe, model and study the spatial-temporal structure and variability of the semidiurnal tide in the middle atmosphere. The focus will be on the Arctic and Antarctic mesosphere and lower thermosphere horizontal wind and temperature fields. The mesosphere and lower thermosphere, at an altitude between 80 and 120km above the surface of the earth, is a highly dynamic region that couples the lower atmosphere (troposphere/stratosphere) with the upper atmosphere thermosphere/ionosphere). Of particular importance in this region are both the upward propagating thermally forced atmospheric tides and global scale planetary waves. Both of these phenomena transport heat and momentum from the lower atmosphere into the upper atmosphere. Studies in recent years have indicated that the high latitude (Arctic and Antarctic) mesosphere and lower thermosphere possess a rich spectrum of planetary waves that had previously gone undiscovered. These planetary waves can interact with the sun-synchronous migrating semidiurnal tide modifying its spatial and temporal structure while giving rise to the nonmigrating semidiurnal tide. Understanding the structure and variability of the semidiurnal tide is an important step to understanding the global heat and energy balance of the mesosphere and lower thermosphere. The data used for this project will include horizontal wind measurements from a global network of 30 ground-based meteor and medium frequency radars. Additionally, wind and temperature measurements from the NASA TIMED satellite will be combined with the radar data. It is expected, from previous observations, that planetary waves will play a significant role in the variability of the semidiurnal tide. For this reason the structure of the semidiurnal tide and the structure of the planetary waves will be estimated simultaneously. These estimates will be analyzed in conjunction with both linear mechanistic and global circulation models to aid in the interpretation of the observations and increase knowledge about the semidiurnal tide. As part of this effort a web based tool to ingest the radar data from the global network will be employed. Data submitted to the database will be processed and then disseminated via a website, the TIMED database and the CEDAR database. Such a database is required for this and future efforts that propose to make use of the global network of mesosphere and lower-thermosphere radar wind measurements.