(LDS5) Comparative studies of the polar MLT from ground and space (Final Report)

Conveners:
Bob Vincent (robert.vincent@adelaide.edu.au),
Susan Avery (susan.avery@colorado.edu),
Scott Palo (scott.palo@colorado.edu)

2004 Wednesday 30 June 0930-1130 AM

Over the past 5 years there has been a significant increase in instrumentation located at polar latitudes with the capability to study the basic structure and evolution of the polar mesosphere and lower-thermosphere. This includes radars, lidars and passive optical instrumentation with the capabilities to monitor the neutral winds, measure gravity wave parameters, provide vertically resolved temperature profiles, probe metallic layers and spatially resolve layered phenomenon. This increased network of regularly operating ground-based instrumentation is currently augmented by measurements from the SABER, GUVI and TIDI instruments on the TIMED spacecraft that provide regular observations of both the Arctic and Antarctic mesosphere, lower-thermosphere and ionosphere. It was the focus of this workshop to discuss open topics in polar mesosphere and lower-thermosphere (MLT) science that can be addressed given the increasing availability of polar observations.

This workshop was divided into the following areas for focused discussion:

  1. Current and future instrumentation
  2. Open scientific questions
  3. Current initiatives relevant to polar MLT science
  4. Future workshops and memorandum of understanding (MOU)

I. Current and future instrumentation

The initial discussion on current and future instrumentation was lead by Bob Vincent (U. Adelaide). Maps of both the Antarctic and Arctic were shown displaying the location of current instrumentation. From the Antarctic data are available from sites at South Pole (US), McMurdo (US), Davis (Australia), Scott Base (New Zealand), Syowa (Japan), Halley (UK), Rothera (UK), Zhong Shan (China). These sites create two longitude chains; one at ~68S (Rothera, Davis, Zhong Shan, and Syowa) and one at ~78S (McMurdo, Scott Base and Halley) in addition to a site at 90S (South Pole). It was noted that there is a large gap in measurements between Adelaide (35S) and the coast of Antarctica (68S) in the southern hemisphere. Discussions about developing a longitude chain near 55S, conjugate to the current northern hemisphere chain, included the possibility of installing future systems in Ushuaia Argentina (55S), South Georgia Island (54.5S) and Macquarie Island (54.3S).

The distribution of sites in the northern hemisphere is more established and comprehensive than that of the southern hemisphere and includes latitude chains around 77N (Svalbard, Resolute Bay, Eureka), 70N (Barrow, Dixon Island, Tromso, Alomar), 65N (Poker Flat, Sondrestrom, Esrange, Yellowknife), 55N (Obninsk, Collm, London, Saskatoon). What was obvious from the map is the lack of measurements from Russia, that comprises most of the landmass in the Arctic. There was some discussion about a possible Russian supported effort to install radar systems at Heiss Island (80N) and near the north pole for the upcoming IPY. It could be possible to operate other portable instrumentation in conjunction with these systems if they are supported.

In addition to the MLT polar sites Bill Bristow (U. Alaska) spoke about the growing network of SuperDARN radar systems distributed throughout the Arctic and Antarctic. Bill discussed the current construction and deployment plans for SuperDARN systems in New Zealand, Tasmania, Zhong Shan, Syowa and the South Pole - thus providing almost full coverage of the southern hemisphere. Of particular interest is the use of SuperDARN radar systems to detect meteors and hence provide additional measurements of the neutral winds. Work is progressing to provide regular MLT wind estimates from the SuperDARN network. Such a data set would complement the current ground-based network of wind measurements and would be of great interest to dynamicists.

Xinzhao Chu (U. Illinois) spoke about the possibility of locating a portable lidar system on the NCAR HIAPER and the ability of such a system to fly from Colorado to the north pole and back without needing to refuel. Such a system would enable future gravity wave and noctulucent cloud studies in collaboration with currently operating ground-based instrumentation.

This part of the workshop concluded with a presentation from Scott Palo (U. Colorado) about space based observations of the polar MLT region. This included a discussion on the current availability of TIMED observations and the measurements expected from the near future Aeronomy of Ice in the Mesosphere (AIM) mission. Both the TIMED and AIM missions provide measurements of the polar MLT from space that have not previously been available.

II. Open scientific questions

The second section of the workshop focused on current scientific questions relevant to the polar MLT. This discussion was lead by Susan Avery (U. Colorado) and she began with a report from two previous MLT polar science workshops that were held in Australia (Feb '02, Sep '03). These workshops were largely focused on dynamics. The conclusions from these workshops were:
  1. The basic state (thermal and dynamical) of the Arctic and Antarctic MLT on a seasonal basis must be determined. This should include a characterization of the zonal average state and any significant, persistent perturbations such as tides, planetary waves and gravity waves or phenomena such as polar summer mesospheric echoes or noctilucent clouds.
  2. The basic state of the Arctic and Antarctic MLT must be compared to determine if significant asymmetries exists. If such asymmetries exist then an effort to understand their sources should be pursued.
  3. A specific effort should be focused on analyzing and interpreting southern hemisphere observations from 2002 when a dramatic sudden stratospheric warming occurred.
  4. Polar MLT observations should not be analyzed in a vacuum. Auroral and upward propagating inputs to the system must be considered.

Other speakers in this session included Jeff Thayer (SRI) who discussed the use of incoherent scatter radar (ISR) to probe the MLT and proposed coordinated investigations on:

  1. Electrodynamic coupling in the polar MLT
  2. Onset and evolution of thin ion layers and sporadic sodium layers
  3. Effects of polar cap absorption events
  4. Structure and evolution of meteor head echoes
Jeff also spoke about the possibilities for new ISR related MLT science that will be enabled through AMISR.

Irfan Azeem (Embry Riddle) followed with a discussion of the longterm (10 year) Michelson interferometeor OH measurements that have been made at the South Pole. He spoke about trying to lead a collaboration to investigate long-term changes observed in the Antarctic MLT. If you are interested in such a collaboration you should contact Irfan (azeem71d@erau.edu).

Kim Cierpik (Ph.D. student, U. Colorado) spoke about her work trying to utilize satellite data in the Antarctic region to extract nonmigrating tidal signatures. Kim is currently using data from the Kyushu GCM as a proxy to prove her method is viable and will then begin working with satellite observations.

The last speaker during this part of the workshop was Mike Taylor (Utah State) who provided input on small-scale wave in Antarctic. Mike proposed three areas for investigation with respect to small-scale waves. These were:

  1. characterization of wave events
  2. identification of wave sources
  3. vertical propagation of gravity waves and their influence on the mesosphere, lower-thermosphere and ionosphere

III. Current initiatives relevant to polar MLT science

In the next session of the workshop Scott Palo lead a short discussion on current initiatives that are of interest to the polar MLT community. These included the recent ICESTAR proposal to the Scientific Commission on Antarctic Research (SCAR), the SCOSTEP CAWSES program, DASI an initiative for distributed instrumentation and the international polar year 2007-2008 (IPY). Maura Hagan (NCAR) also mentioned the international heliophysical year (IHY). Details about the SCOSTEP CAWSES program, DASI and IHY were also discussed during the plenary session of the CEDAR meeting. There was some discussion about IPY and the fact that it appears that the middle and upper atmosphere has been largely neglected. However the Russian group lead by Yuri Portnyagin is using IPY as a mechanism to secure funding to operate a radar at Heiss Island and the north pole. The ICESTAR program, currently a proposal to SCAR, is requesting support for 5 years to study interhemispheric conjugacy effects in the polar regions from the mesosphere through the magnetosphere.

IV. Future workshops and memorandum of understanding (MOU)

The final section of the workshop included discussion about possible future workshops and the development of a memorandum of understanding. There was broad consensus that future workshops focusing on polar science are warranted and should be planned. The idea behind the memorandum of understanding is to formalize the desire to collaborate and share data products. This is particularly important for polar MLT science that requires considerable international collaboration. Susan Avery is current in charge of drafting and distributing the memorandum of understanding.