Gravity Wave Activity over Antarctica:Implications for Ozone Chemistry and Transport These GW variance measurements are obtained from UARS MLS ascending orbits for the month of August in 1992-1994. The salient feature over the Drake Passage region appears to be consistent and repeatable from year to year. The 1992 and 1994 variances are higher at ~28km than one in 1993 but the differences are less prominent at 43km altitude. The peak variance over the Drake Passage region is associated more closely to the tip of the South America at ~28km. At the higher altitude, the center shifts slightly towards the Antarctic Peninsula and spreads over to a larger area. The contrast between the feature over Drake Passage and the surrounding activities also reduces at the higher altitude. The variances from the descending orbits (not shown) exhibit similar patterns but the amplitudes are smaller, as expected for westward propagating waves in the eastward background winds. Elsewhere, the GW activity follows the Antarctic coastline quite well, especially at the lowest altitude, with enhanced regions at longitudes between 90-220 degrees. Unlike the feature over the Drake Passage region, the location of these GW activities varies from year to year but is correlated between low and high altitudes within the same year. In 1992 and 1993 the GW activity at 90-220 degree longitudes appears higher than other coastal regions at 43km. In 1994 the coastal patterns at 43km reveal enhanced activities over a larger area between 45 and 270 degrees in longitude. As found in early MLS variance observations [Wu and Waters, 1996], the enhanced coastal variances reside mostly around the vortex-edge in the stratosphere and correlate well with the stratospheric jetstream. However, the variation of the stratospheric jetstream around the vortex edge is not large enough to explain the modulation of the GW variances, and one must consider the wave source distribution related to topography.

map plot of gravity wave variaces from 1992-1994 at 43km and 28km

 PSC

CLAES 780cm-1 extinction provides PSC measurements in August 1992. The center of high PSC occurrence leans toward the Drake Passage region where MLS GW variances are high.

map of CLAES PSC measurement

O3

MLS ozone measurements are mapped for the same periods according to ascending (left) and descending (right) orbits. All the color scales are in ppmv. Morphologies of the ascending and descending averages differ slightly but they both show an anomaly near the Drake passage region, particularly at 100 and 68hPa.

ascending maps of O3 from 46hPa to 100hPa from 1992-1994 descending maps of O3 from 46hPa to 100hPa from 1992-1994

HNO3

The Drake Passage anomaly is also evident in MLS HNO3 measurements when mapped for the same periods. The maps are separated according to ascending (left) and descending (right) orbits. All the color scales are in ppbv.

ascending maps of HNO3 from 46hPa to 100hPa from 1992-1994 descending maps of HNO3 from 46hPa to 100hPa from 1992-1994

N2O

The N2O data are only available for 1992 from UARS CLAES, which can be used as a tracer of transport at 100-22hPa. The maps are separated according to ascending (left) and descending (right) orbits. The Drake Passage anomaly is evident more strongly in the descending averages at 100-46hPa. All the color scales are in ppbv.

ascending maps of N2O from 46hPa to 100hPa from 1992-1994 descending maps of N2O from 46hPa to 100hPa from 1992-1994

H2O

MLS H2O data come from the v490 retrieval [Pumphery, 1999] but are only available before April 1993. The 100 hPa map is basically the climatology since it is not retrieved. The maps are separated according to ascending (left) and descending (right) orbits. There is little modulation over Drake Passage but overall the dry region inside the vortex seems always toward the Drake Passage side. All the color scales are in ppmv.

ascending maps of H2O from 46hPa to 100hPa from 1992-1994 descending maps of H2O from 46hPa to 100hPa from 1992-1994