Super Cloudy Stratosphere Foretells Biggest Ozone Hole Ever
- Accept the Challenge
- About NRL
- Doing Business
- Public Affairs & Media
- Public Affairs Office
- News Releases
- 2015 News Releases
- 2014 News Releases
- 2013 News Releases
- 2012 News Releases
- 2011 News Releases
- 2010 News Releases
- 2009 News Releases
- 2008 News Releases
- 2007 News Releases
- 2006 News Releases
- 2005 News Releases
- 2004 News Releases
- 2003 News Releases
- 2002 News Releases
- 2001 News Releases
- 2000 News Releases
- 1999 News Releases
- 1998 News Releases
- 1997 News Releases
- 1996 News Releases
- NRL Videos
- Email Updates
- Social Media
- NRL Events
- Popular Images
- Public Notices
- Field Sites
- Visitor Info
- Contact NRL
Scientists at the Naval Research Laboratory (NRL) report that measurements from their space-based Polar Ozone and Aerosol Measurement instrument, (POAM III) indicate that polar stratospheric clouds (PSCs) over Antarctica this winter were unusually extensive compared to earlier years. The researchers believe that this increase in the extent of PSCs over the winter season set the stage for the near record size (in terms of area coverage) of the Antarctic ozone hole this year reported by NASA and NOAA. POAM scientists will present a mission overview and results from the 1998 Antarctic ozone hole at the Fall 1998 American Geophysical Union meeting in San Francisco, California, in December.
PSCs form in the cold wintertime polar stratosphere, high above the region in which more familiar tropospheric clouds form. They are known to be a crucial ingredient in the large chemical destruction of ozone which occurs in the Antarctic ozone hole. These clouds typically begin to form over Antarctica in the southern hemisphere late fall, and are observed until the end of winter. In 1998 POAM III observed its first PSC on May 22.
The POAM III measurements indicate that the extent of stratospheric cloudiness was remarkable in 1998, say the scientists. POAM's orbit takes it over Antarctica 14 times each day, and from August 5 through September 6, every POAM III measurement indicated a PSC. This is by far the longest continuous stretch of 100% cloudiness ever observed by the POAM instruments. During this period, the latitude of the POAM measurements varied from 72°S on August 5 to 83°S on September 6. Since this latitude range spans a large part of the Antarctic continent, it could be inferred from these observations that, during this entire period, the stratosphere over Antarctica was essentially covered by PSCs. These very thin clouds are not readily visible from the ground.
The POAM III measurements also
show a pronounced decrease in stratospheric water vapor coincident
with the development of the PSCs. This decrease in water vapor
is presumably the result of the drying out (or dehydration) of
the lower polar stratosphere by the settling out of ice
particles in PSCs. This phenomenon is thought to be important in the formation of the Antarctic ozone hole.
The unusually large extent of
PSCs this year observed by POAM III is consistent with the recent
report by NOAA that temperatures at 20 km over Antarctica this
winter were among the lowest observed in the past twenty years.
Lower temperatures should lead to more PSCs. The increased extent
of PSCs has, in turn, presumably led to the record size of the
ozone hole reported by both NASA and NOAA from their Total Ozone
Mapping Spectrometer (TOMS) and Solar Back Scattered Ultraviolet
Instrument (SBUV) measurements. Also, consistent with NOAA
ozone measurements obtained at the South Pole, the POAM III ozone profile observations show ozone near the South Pole decreasing at a very rapid rate during September (especially the latter half of the month). The rate of ozone destruction at 20 km (about 65,000 feet) is similar to that observed in 1996, but larger than that observed in 1994 and 1995.
Supported by the Office of Naval Research and the DoD Space Test Program, POAM III is currently the only operational satellite instrument providing continuous coverage of the vertical distribution of ozone with good resolution (1 km), and of PSCs in the polar stratosphere. As such, it complements the measurements of the total ozone column abundance obtained by the NASA/NOAA TOMS and SBUV instruments.
POAM III was launched on March 20,1998, and has been operational since late April. It is a follow-on to the highly successful POAM II experiment, which provided unique, simultaneous data on ozone depletion and PSCs from October 1993 through November 1996. POAM III measurements will provide valuable information on the way the earth's ozone layer is responding to the expected decrease in abundances of chlorine in the atmosphere, as a result of restrictions in CFC emissions mandated in the international Montreal Protocol, and to possible global temperature changes.
About the U.S. Naval Research Laboratory
The U.S. Naval Research Laboratory is the Navy's full-spectrum corporate laboratory, conducting a broadly based multidisciplinary program of scientific research and advanced technological development. The Laboratory, with a total complement of approximately 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 90 years and continues to meet the complex technological challenges of today's world. For more information, visit the NRL homepage or join the conversation on Twitter, Facebook, and YouTube.
Comment policy: We hope to receive submissions from all viewpoints, but we ask that all participants agree to the Department of Defense Social Media User Agreement. All comments are reviewed before being posted.