MTP's Role In Supporting Ozone Hole Missions
This web page attempts to descibe the several ways in which the Microwave Temperature Profiler, MTP, has supported NASA missions for the study of the "ozone hole" in both the Antarctic and Arctic regions.
The MTP has been included in all NASA-sponsored airborne missions for ozone hole studies, starting with the first one in 1987. I will first list "contributions," then review the missions with brief descriptions of MTP highlights from each mission. It is noteworthy that none of the contributions listed below (except #5 and #6) were anticipated before the mission started; most of them are therefore serendipitous.
List of MTP Contributions
1) Observational evidence that mountain waves extend into the Antarctic stratosphere during the ozone depletion season, providing an additional cooling of several degrees K that creates PSCs at the wave crests, and must therefore enhance the process of dehydration and denitrification, which is a precondition for ozone loss by chemical reactions of chlorine atoms with ozone molecules. 1987
2) Discovered presence of ever-present mesoscale temperature fluctuations, as revealed by the presence of isentrope vertical displacements. MTP has characterized the typical amplitude of these mesoscale fluctuations as a funcrtion of latitude, season, underlying toporaphy and altitude. This information should be useful in refining models of reaction rates that are highly tempearture dependent, and polar stratospheric cloud formation properties. Previously used cooling rates (and heating rates) were vastly underestiamted because the mesoscale effects were neglected in model calculations. The MTP has provided quantitative information from which realistic cooling rates can be chosen for superimposition on synoptic scale cooling rates in model calculations. 1989
3) Observational evidence that aircraft encounters with large particles only are associated with MTP-determined layers 1 or 2 km above the aircraft that are cold enough to condense water vapor and produce PSCs. The large particles apparently fall fast enough to reach the aircraft altitude without evaporating. (Bruce Gandrud made this discovery using MTP data and his MFS instrument data). 1989
4) Measurements of filaments from polar vortex over New Zealand, as well as filaments from the tropics. This helps constrain models for "vortex peeling off" process, and rates of latitude exchange of air in the stratosphere. 1994
5) During DC-8 flights the MTP provided temperature information at altitudes where lidar measurements indicated the presence of clouds; knowing the temperature allowed a distinction to be made between PSC Type I and Type II. 1992
6) For all DC-8 flights the MTP determines the tropopause altitude, which allows in situ sampling data to be assigned properly as belonging to either the troposphere or stratosphere. Improved models have been produced for the dependence of NOx and NOy versus altitude with respect to the tropopause, and versus latitude, based on MTP data (reported by Weinheimer et al, 1994). 1991
7) The vortex edge frequently has an abrupt "change of slope" of the isentropes at the winter polar vortex edge. The isentropes are steeply sloped upward in moving toward the pole, and the intersection of the two slopes marks the vortex edge to within a degree of latitude. 1992
History of MTP Contributions to Ozone Missions
The MTP/ER2 was included in the first NASA-led airborne Antarctic "ozone hole" mission, called AASE (Airborne Antarctic Ozone Experiment), which was based in Punta Arenas, Chile in August and September, 1987. The anticipated role for MTP was to calculate potential vorticity versus latitude in order to determine the latitude of the poalr vortex. This didn't work well because winds had too much mesoscale structure (Hartmann et al, 1989), but it wasn't necessary because the winds usually showed a clear maximum which adequately identified the vortex edge. The MTP's main contribution to AAOE turned out to be a surprise: mountain waves protruded through the tropopause and extended throughout the entire lower stratosphere, increasin gin amplitude with altitude. The altitude excursions were so large at ER-2 altitudes that air parcels underwent several degrees of cooling at the wave crests, which was sufficient to produce polar stratospheric clouds, PSCs. These PSCs play a crucial role in denitrification, which is a precursor for the cehmical destruction of ozone by chlorine atoms, so it is very likely that the mountain waves play an important role in the Antarctic "ozone hole" process. For evidence of this, click on SAGE II and MTP Mountain Waves. Other links that describe MTP mountain wave results are First Mountain Wave Encounter and Observational Results.
The MTP/ER2 was again used on a NASA ER-2 aircraft during the AASE (Airborne Arctic Stratospheric Experiment), based in Stavanger, Norway in January and February,1989.
AASE II, 1991/92
By this mission we had two MTP instruments, the MTP/ER2 again but also a MTP/DC8 mounted in the lower altitude NASA DC-8 aircraft. AASE II was based in Bangor, Maine and Stavanger, Norway. Deployemnts consisted of several deployments during August, 1991 and march, 1992.
ASHOE (Airborne Southern Hemisphere Ozone Experiment) was based at Ames Research Center, CA; Barber's Point, Hawaii and Christchurch, New Zealand. Again, several deployments occurred between March and November, 1994.
STRAT (Stratospheric Tracers of Atmospheric Transport) was based at Ames Research Center, CA and Barber's Point, Hawaii. Several deployemnts were made between May, 1995 and December, 1996. Only the MTP/ER2 participated in this mission.
TOTE/VOTE (Tropical Ozone Transport Experiment, Vortex Ozone Transport Experiment) was based at Ames Research Center, CA; Fairbanks, AK; Barber's Poin, Hawaii and Reykjavik, Iceland. Deployments occurred from December, 1995 to February, 1996. Only the MTP/DC8 participated in theis mission.
POLARIS (Photochemistry of Ozone Loss in the Arctic Region in Summer) was based at Fairbanks, AK and Barber's Point, Hawaii. The MTP/ER2 participated in deployments from April to September, 1997.
SONEX (SASS Ozone and Nitrogen Oxides Experiment) was a DC-8 mission based at Ames Research Cener, CA; Bangor, Maine; Shannon, Ireland and Lajes, Azores. Flights occurred in October and November, 1997.
SOLVE (SAGE III Ozone Loss and validation Experiment) included both
the MTP/DC8 and MTP/ER2. Deployments went from November, 1999 to
March, 2000 for the DC-8 and January to March, 2000 for the ER-2.
Work on this web page is still in progress.
This site opened: September 9, 2000. Last Update: June 22, 2007