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	Dynamics of the Mesosphere & Lower Thermosphere

	Dynamics of the Mesosphere & Lower Thermosphere
	Telecommunications, Space & Radio Group
	Department of Electronic & Electrical Engineering
	The University of Bath MLT dynamics group uses ground-based VHF meteor radars to study the dynamics and temperature of the Earth’s mesosphere and lower thermosphere – in particular mean winds, tides and planetary waves

The group members are:

Prof. Nick Mitchell (group leader), Charlie Beldon, Dr. Dora Pancheva, David Sandford & Dr. Peter Younger


Nick	Charlie	Dora	Dave	Pete

Honorary research fellow:

Heinz Muller

Collaborator on the UK meteor radar

People who have recently worked in the group include:

Dr. Helen Middleton

(PhD, 2003)

Dept. Physics, University of Wales, Aberystwyth

Dr. Vikki Howells

(PhD, 2000)

EISCAT group, Rutherford Appleton Laboratory

1. Scientific Background

The Mesosphere and Lower Thermosphere (MLT) region is that part of the Earth’s atmosphere at heights between ~ 50 – 110 km. It includes the mesopause, at heights near 85 km or 100 km, which is the coldest naturally occurring place on Earth. The MLT region is believed to play a key role in the coupling between the lower, middle and upper atmosphere.

The dynamics of the MLT region are dominated by atmospheric waves and tides of large amplitude, mostly originating in the lower atmosphere. As the waves and tides ascend into the rarified MLT region they grow in amplitude and eventually may become unstable - dissipating their energy and momentum rather like ocean waves breaking on a beach. Thermal tides and planetary waves thus combine with gravity waves to provide up to 70% of the MLT region’s energy and momentum budget. This wave driving (forcing) pushes the temperature and planetary-scale circulation of the MLT region into states very different from those predicted by a simple radiative equilibrium model. Physical processes acting in the MLT then filter the field of ascending waves and tides and so control the dynamic coupling of the middle atmosphere to the upper atmosphere.

The Bath Group is involved in studies of the winds, waves and tides of the MLT region in the very different physical regimes encountered at Polar, middle and equatorial latitudes. Our goal is to understand the physical processes that control the waves and tides in the MLT region, and to understand the role these phenomena play in coupling the lower, middle and upper atmosphere.

2. Experimental Work – A Global Array of VHF Meteor Radars

The group carries out active experimental studies of the MLT region. Ground-based VHF meteor radars are used to study the dynamics of the atmosphere in key latitudinal regimes – ranging from the Arctic to the Antarctic. The group’s radars observe the dynamics of the atmosphere at heights of ~ 80-100 km by recording the drifting of meteor trails as they are carried by the flow. Most of the radars are Skiymet systems, equipped with an interferometric array of receiver antennas. This allows determination of meteor heights and so enables investigation of the vertical structure of the atmosphere in the MLT region.

The locations of the radars are given in the figure and table below:

Latitude	Location	Operational Date	Notes
1. Arctic	Esrange, Sweden, 68°N, 21°E	August 1999	PPARC-funded Skiymet
2. Middle latitude	Castle Eaton, UK, 51°N, 2°W	January 1988	PPARC-funded collaboration
3. Equatorial	Ascension Island, 8°S, 14°W	May 2001	PPARC-funded Skiymet
4. Middle latitude	El Leoncito, Argentina, 32ºS, 69ºW	In deployment	PPARC-funded Skiymet
5. Antarctic	Rothera, 68°S, 68°W	February 2005	NERC-funded Skiymet

1. The Arctic Esrange radar (68°N) was deployed in August 1999. Apart from a single break of 12 days, it has produced uninterrupted, continuous data.

2. The middle-latitude UK radar at Castle Eaton (51°N) is a simple system operated in collaboration with H. G. Muller of RMCS Shrivenham. The16-year data set from this radar is one of the longest available.

3. The equatorial Ascension Island radar (8°S) was deployed in 2001. It has produced excellent data coverage since October of that year.

4. The El Leoncito radar (32ºS) is a project in development with J. Scheer of the Instituto de Astronomía y Física del Espacio (IAFE), Argentina.

5. The Antarctic radar is sited at Rothera (68°S). It was installed in February 2005 as part of a joint project with P. J. Espy of the British Antarctic Survey funded by the NERC Antarctic Funding Initiative. Rothera is at a conjugate geographical latitude to Esrange and the radar will be used in collaboration with the Esrange radar to investigate inter-hemispheric differences between the Arctic and Antarctic atmospheres.

3. Images of the Radar Sites

Click on the thumbnails below to view a larger image

Esrange

Images from Esrange, Northern Sweden: Nick next to a receiver antenna, one of the Esrange receiver antennas and the main buildings at Esrange

Castle Eaton, UK

The UK meteor radar at Castle Eaton and our collaborator, Heinz Muller

Ascension Island

Ascension Island, the transmitter antenna, a receiver antenna and preparing for a barbeque

El Leoncito (in preparation)

The CASLEO observatory, proposed site for the meteor radar in Argentina and our collaborator, Juergen Scheer

Rothera

The Antarctic meteor radar and the base at Rothera Point

4. Links to Collaborators and Colleagues

The British Antarctic Survey – collaborators in the Antarctic Skiymet meteor radar project

Genesis Software and Mardoc Inc – who together produce the excellent Skiymet radars used by the group

Instituto de Astronomía y Física del Espacio (The institute of Astronomy and Space Physics, Buenos Aires) – Collaborators in the Argentine meteor radar

The TIMED satellite – NASA’s Thermosphere Ionosphere Mesosphere Energetics & Dynamics satellite

TIMED at CU – a site for Colorado University’s NASA TIMED satellite work, including a data base of ground-based radar data and various models

Esrange – the Swedish Space Corporation’s rocket range and site of the Bath Arctic meteor radar

The Institute for Meteorology at the University of Leipzig in Germany – the home of Christoph Jacobi, a regular collaborator

ISAS – the Institute of Space & Atmospheric Science at Saskatoon in Canada. Home of Alan Manson, a regular collaborator

The Global Scale Wave Model – the NCAR HAO linear model of migrating and non-migrating tides

5. Related Links

The University of Bath

PPARC (the UK’s Particle Physics & Astronomy Research Council that funds our work)

NERC (the UK’s Natural Environment Research Council that funds our work)

Ascension Island – Office of the Administrator (includes a very good virtual tour. The Bath meteor radar is at Donkey Plain)

Ascension Island from space – an extraordinary image

Miscellaneous Ascension Island links

Contact Details

N. J. Mitchell

Department of Electronic & Electrical Engineering

The University of Bath

Bath

BA2 7AY

Tel: 00 44 (0) 1225 386327

Fax: 00 44 (0) 1225 386305

Email: N.J.Mitchell@bath.ac.uk

University of Bath

Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY
Tel: +44 (0) 1225 386327· Fax: +44 (0) 1225 386305
E-mail: N.J.Mitchell@bath.ac.uk

Dynamics of the Mesosphere & Lower Thermosphere

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