All Climate Events
Webinar: Neutral Temperatures in the Upper Atmosphere
Wednesday, 28 November 2018, 4:00
Wednesday, November 28, 2018. 4:00PM Eastern. Webinar: Neutral Temperatures in the Upper Atmosphere. Alan Burns, HAO. Sponsored by NCAR | UCAR. More information here.
The Global-scale Observations of the Limb and Disk (GOLD) mission was launched on a communications satellite in January 2018. It is now in geostationary orbit and is measuring high quality Far UltraViolet (FUV) data. These airglow originate from an altitude of about 150 km. This region is one of transition. Composition is changing rapidly with altitude and, of relevance to this presentation, the temperatures are transitioning from the region where they are high (commonly up to 1400 K) and isothermal with altitude in the upper thermosphere, down to the coldest region in the atmosphere, the mesopause, where temperatures are typically 200 K. In order to understand the morphology of the temperatures that GOLD is observing, we need to understand the processes at work in this region and how they vary in a three-dimensional sense.
Temperatures in the thermosphere undergo huge morphological and temporal changes. In the upper thermosphere, normal quiet time temperatures are dominated by diurnal, seasonal and solar cycle changes. The solar cycle variation can be as large as 600 K. Seasonal and diurnal variations can be as large as 350 K, even at solar minimum, with the hottest temperatures in the daytime summer and the coldest temperatures in the nighttime winter. This is in contrast with the mesopause, where summer temperatures of are typically 50-70 K colder than winter temperatures, and the semidiurnal tides dominate the dynamical changes in temperatures. This raises the question of what temperature structures do we expect to see in the transition region and what creates this temperature structure? This presentation uses a general circulation model to determine the temperature structure in the region where GOLD makes its measurements and applies post-processors to determine why the observed temperature structure occurs.