15 June, 2003 Rothera
During the 2002/2003 summer season a new atmospheric research laboratory was installed at Rothera. This facility houses a single piece of equipment, the Iron Boltzmann Temperature Lidar.
Lidar is an acronym for ‘light detection and ranging’ and is basically the same as a radar except that instead of using radio waves, lasers are used to ‘fire’ a pulse of light into the sky and this light is reflected off molecules and atoms in the atmosphere. The following is a summary of how our lidar works;
The system at Rothera has an added complication in that we use two lasers. These are very precisely tuned to two different wavelengths which are resonant with two transitions in atomic iron. Using this system we have the ability to measure the temperature of a thin iron-rich layer that is only a couple of kilometres thick at approximately 90km high.
I’m but one person in a team of researchers at BAS and the University of Illinois working on measuring the temperature and dynamics of the middle atmosphere above Rothera with the lidar (as well as other atmospheric instruments that BAS operates here). The temperature structure of the northern hemisphere middle atmosphere at mid and high latitudes has been studied for a long time. However, due to the inaccessibility of Antarctica until recent times the equivalent southern hemisphere atmosphere is less well understood. The current lidar was operated at the South Pole for 2 years and data from this site and other lidars around the perimeter of Antarctica indicate that there are important differences between the northern and southern hemisphere middle atmospheres. By running this lidar system at Rothera we will be able to build on the body of knowledge that exists and so more fully understand the dynamics of the southern hemisphere atmosphere. Another aspect of the project is to study high altitude ice clouds called polar mesospheric clouds (PMC). Also called noctilucent clouds, these have been observed and studied in the high latitude northern hemisphere and present thinking indicates that these clouds could be an important pointer to global atmospheric changes such as the ‘greenhouse effect’.
My principle job is to run the system, collect the data and make sure that the data being collected actually makes sense. It is often exciting but often very frustrating as well. Exciting; as I get to see what is happening high in the atmosphere in near real-time, especially activity in the iron layer that can vary on a scale of minutes. Frustrating; because two things are required to get quality data, a well performing system and clear skies. UV light is heavily absorbed by water vapour and even clouds that are invisible to the eye can affect the data. So whenever the sky is clear, day or night, I walk up the hill from the base to the laboratory to run the system. I don’t have the worst job on base (Eric is uncontested for that title!) but it does mean that whenever the weather’s good I’ve got to work. Still, as you can see from Fig 3, there’s worse places to be….
Lidar Research Engineer