Dec. 2, 1999
"This is an extremely low measurement of ozone for the Northern Hemisphere," said Dr. Richard McPeters, Principal Investigator for Earth Probe TOMS. The measurement showed 165 Dobson Units (DU) over the North Sea between Scotland and Norway.
The previous low value of 167 DU was observed in the same region on Oct. 30, 1985. The lowest values of ozone in the Northern Hemisphere are typically seen in the late fall period. However, these low northern values rarely drop below 180 DU.
"A combination of stratospheric and tropospheric weather systems can occasionally create these extreme low ozone events," said Dr. Paul A. Newman of the NASA Goddard Space Flight Center in Greenbelt, Md. "We understand that dynamics can cause these low ozone events, but we're unsure why this event set a new record low value."
Scientists and others have a keen interest in polar ozone depletion. While this particular record low value results from a convergence of weather systems, severe depletions of ozone can result from chemical processes. The Antarctic ozone hole is an example of a large ozone loss caused by chemistry. Chemically caused Arctic ozone losses have also been observed, particularly in the Northern Hemisphere springs of 1996 and 1997.
This winter, NASA in collaboration with the European Commission, is staging the largest polar ozone campaign yet. The SAGE III Ozone Loss and Validation Experiment (SOLVE) is being conducted jointly with the European Commission sponsored Third European Stratospheric Experiment on Ozone (THESEO 2000). These collaborative campaigns will examine the processes that control polar and mid-latitude ozone levels at mid to high latitudes over the course of the Arctic winter. NASA Goddard has provided theoretical contributions, a high altitude light detection and ranging system for measuring ozone and temperature, and the operational support for some of the heavy lift balloons. Goddard scientists and instruments are integral parts of the SOLVE campaign being conducted this winter.
TOMS ozone data and pictures are available on the Internet-
More information (including a list of participating institutions) about the U.S. SOLVE and European THESEO components.
TOMS-EP and airborne field programs are key parts of a global environmental effort of NASA's Earth Science enterprise, a long-term research program designed to study Earth's land, oceans, atmosphere, ice and life as a total integrated system. Goddard developed and manages the operation of the TOMS-EP for NASA's Office of Earth Science, Washington, D.C
The TOMS instrument measures the total number of ozone molecules between the Earth's surface and space. The measurements units are Dobson units. Dobson units are convenient thickness measurements. The total ozone value represents the physical thickness of the ozone layer if all of those overhead ozone molecules could be brought down to the Earth's surface. The global average ozone layer thickness is 300 Dobson units, which equals three millimeters or 1/8th of an inch, and while not uniform, averages the thickness of two stacked pennies.
NASA Headquarters, Washington, DC
Ames Research Center, Moffett Field, CA
Nov. 18, 1999
This collaborative campaign will measure ozone and other atmospheric gases using satellites, airplanes, heavy-lift and small balloons, and ground-based instruments. From November 1999 through March 2000, researchers will examine the processes that control ozone amounts during the Arctic winter at mid to high latitudes.
"The combined campaign will provide an immense new body of information about the Arctic stratosphere," said program scientist Dr. Michael Kurylo, NASA Headquarters, Washington, DC. "Our understanding of the Earth's ozone will be greatly enhanced by this research."
The Earth's ozone layer protects life below from the harmful ultraviolet radiation coming from the Sun. This radiation can damage DNA molecules, thereby leading to the formation of skin cancers. Very low levels of ozone were observed over the Arctic in several winters during the 1990s, raising concerns that an Arctic ozone hole might be forming. Recent modeling work has suggested that greenhouse gas warming might lead to larger-than-expected Arctic ozone losses in the future and also may delay the expected recovery of the ozone layer globally.
For the first time, measurements of stratospheric composition over the Arctic will be made using a large suite of instruments aboard several European aircraft, as well as on NASA's DC-8 and ER-2, based at NASA's Dryden Flight Research Center, Edwards, CA. Balloons, carrying payloads ranging from several pounds to several thousand pounds and ground-based instruments will also take atmospheric readings.
"Handling all the hardware and coordinating the personnel, aircraft, balloons, and ground observations involved in the campaign is an immense challenge," said project manager Michael Craig of NASA's Ames Research Center, Moffett Field, CA. More than 350 scientists, technicians and support workers are involved in the experiment.
More than 15 years ago, scientists detected an "Ozone Hole" over the South Pole that has reappeared each year during the Southern Hemisphere winter and spring. Researchers from around the world recognized more than a decade ago that the ozone depletion is caused primarily by man-made chlorine and bromine compounds. The chlorine compounds have been produced for use as refrigerants, aerosol sprays, solvents and foam blowing agents, while bromine-containing halons have been used in fire extinguishing. Man-made production of chlorofluorocarbons ceased in 1996 in developed countries under the terms of the Montreal Protocol and its Amendments.
Scientists also will take measurements that will be useful in validating data from an instrument called SAGE III aboard the Russian Meteor-3 satellite. Once the spacecraft is launched, SAGE III will measure the vertical structure of aerosols, ozone, water vapor and other trace gases in the Arctic upper troposphere and stratosphere. NASA's Langley Research Center, Hampton, VA, manages the SAGE III project.
Project scientists will be based above the Arctic Circle at the airport in Kiruna, Sweden. "Arena Arctica," a large hangar especially built for research, will house the aircraft and many of the scientific instruments. Balloons will be launched from Esrange, a balloon and rocket launch facility near Kiruna. Wintertime conditions can be very severe, with temperatures falling below 50 degrees below zero Fahrenheit.
The NASA-sponsored SAGE III Ozone Loss and Validation Experiment (SOLVE) is being conducted jointly with the European Commission-sponsored Third European Stratospheric Experiment on Ozone (THESEO 2000).
More information (including a list of participating institutions) can be found at:
SOLVE
and and
THESEO 2000
NASA Space Science News for October 6, 1999
New Antarctic Ozone Data -- A NASA satellite has shown that the area of ozone depletion over the Antarctic is still large, but a bit less in 1999 than it was last year.
NASA Headquarters, Washington, DC
Goddard Space Flight Center, Greenbelt, MD
Oct. 6, 1999
"This Antarctic year's ozone depletion area, or ozone 'hole,' is very large, but slightly smaller than that of 1998," said Dr. Richard McPeters, principal investigator for the instrument that made the measurements.
This year's study found that an ozone "low" had formed between New Zealand and Antarctica on Sept. 17. This sort of ozone low, commonly referred to as a "mini-hole," is a result of the redistribution of ozone by a large weather system. The "mini- hole" moved eastward along the rim of the Antarctic "ozone hole" for a number of days after Sept. 17.
Preliminary data from the satellite show that this year's Antarctic ozone depletion covered 9.8 million square miles on Sept. 15. The record area of Antarctic ozone depletion of 10.5 million square miles was set on Sept. 19, 1998.
The ozone levels are expected to decrease over the next two weeks. The lowest amount of total-column ozone recorded to date this year was 92 Dobson Units on Oct. 1. In contrast, ozone levels of 90 Dobson Units were observed at one point last year. Dobson units measure how thick the ozone layer would be if all the overhead ozone molecules in a column of atmosphere could be brought down to the Earth's surface.
Globally, the ozone layer averages approximately 300 Dobson Units, which would correspond to a layer about 1/8th of an inch (3 millimeters) thick at the Earth's surface, about the thickness of two stacked pennies. In contrast, during the annual Antarctic ozone "hole," the amount of ozone in the ozone "hole" is about 100 Dobson Units, about 1/25th of an inch, or approximately the thickness of a single dime.
The slightly decreased size of the ozone "hole" from last year is not an indication of the recovery of Antarctic ozone levels. The current year-to-year variations of size and depth of the ozone "hole" depend primarily on the variations in meteorological conditions.
The Antarctic ozone losses are caused by chlorine and bromine compounds released by chlorofluorocarbons (CFCs) and halons. Due to international treaties regulating the production of these gases, the amount of chlorine in the stratosphere is close to maximum value and, in some regions, is beginning to decline. In the next century, chlorine-induced ozone losses will be reduced as chlorine amounts throughout the stratosphere decline, and ozone levels will begin to recover. The actual rate of recovery will likely be affected by the increasing abundance of greenhouse gases in the atmosphere. Detecting the recovery of the ozone hole will require a number of years of measurements.
Ozone molecules, made up of three atoms of oxygen, comprise a thin layer of the atmosphere that absorbs harmful ultraviolet radiation from the Sun. Most atmospheric ozone is found between 6 and 18 miles above the Earth's surface.
Ozone shields life on Earth from the harmful effects of the Sun's ultraviolet radiation. Scientists and others have a keen interest in ozone depletion. Increased amounts of ultraviolet radiation that reach the Earth's surface due to ozone loss might increase the incidence of skin cancer and cataracts in humans, depress the human immune system, harm some crops and interfere with marine life.
These measurements were obtained between mid-August and early October using the Total Ozone Mapping Spectrometer (TOMS) instrument aboard NASA's Earth Probe (TOMS-EP) satellite. NASA instruments have been measuring Antarctic ozone levels since the early 1970s. Since the discovery of the ozone "hole" in 1985, TOMS has been a key instrument for monitoring ozone levels over the Earth.
TOMS ozone data and pictures are available on the Internet:
TOMS-EP and other ozone-measurement programs are important parts of a global environmental effort of NASA's Earth Science enterprise, a long-term research program designed to study Earth's land, oceans, atmosphere, ice and life as a total integrated system.
NASA Headquarters, Washington, DC
Goddard Space Flight Center, Greenbelt, MD
NOAA/NCEP, Silver Spring, MD
October 6, 1998
"This is the largest Antarctic ozone hole we've ever observed, and it's nearly the deepest," said Dr. Richard McPeters, Principal Investigator for Earth Probe TOMS.
Preliminary data from the satellites show that this year's ozone depletion reached a record size of 10.5 million square miles (27.3 million square kilometers) on Sept. 19, 1998. The previous record of 10.0 million square miles was set on Sept. 7, 1996.
The ozone level fell to 90 Dobson units on Sept. 30, 1998. This nearly equals the lowest value ever recorded of 88 Dobson Units seen on Sept. 28, 1994, over Antarctica.
Scientists are not concerned that the hole might be growing because they know it is a direct result of unusually cold stratospheric temperatures, though they do not know why it is colder this year. The decrease in ozone, however, could result in more acute solar or ultraviolet radiation exposure in southern Chile and Argentina if the ozone hole were to pass over that region. One of the primary concerns with an ozone hole of this size is that as the hole "breaks up," the ozone-depleted air will diffuse and reduce the overall ozone levels in the mid-latitudes of the southern hemisphere.
These ozone losses are caused by chlorine and bromine compounds released by chlorofluorocarbons (CFCs) and halons. Year-to-year variations of size and depth of the ozone hole depend on the variations in meteorological conditions. Scientists believe that the decrease in Antarctic ozone is attributed to unusually cold (by 5-9 degrees Fahrenheit) temperatures in the southern middle and polar latitudes. "This year was colder than normal and therefore enables greater activation of reactive chlorine that ultimately causes more ozone loss and lower ozone levels," said Dr. Alvin J. Miller of the National Centers for Environmental Prediction (NCEP).
This decrease in ozone was observed earlier than usual with the hole opening in mid-August about two weeks before a typical year. This is consistent with expectations, since chlorine levels have slightly increased since the early 1990s.
As a result of international agreements known as the Montreal Protocol on ozone-depleting substances (and its amendments), chlorine levels from CFCs already have peaked in the lower atmosphere and should peak in the Antarctic stratosphere within a few years. As we move into the next century, chlorine-catalyzed ozone losses resulting from CFCs and other chlorine-containing species will be reduced.
"An ozone hole of substantial depth and size is likely to continue to form for the next few years or until the stratospheric chlorine amount drops to its pre-ozone hole values," said Dr. Paul Newman at NASA's Goddard Space Flight Center (GSFC), Greenbelt, MD. "The decrease in chlorine in our atmosphere is analogous to using a small air cleaner to recycle all of the air in a large indoor sports stadium -- it will take a very, very long time."
Scientists and others have a keen interest in ozone depletion, given that the increased amounts of ultraviolet radiation that reach the Earth's surface because of ozone loss have the potential to increase the incidence of skin cancer and cataracts in humans, harm some crops, and interfere with marine life.
NASA and NOAA instruments have been measuring Antarctic ozone levels since the early 1970s. Since the discovery of the ozone hole in 1985, TOMS and SBUV have been key instruments for monitoring ozone levels over the Earth.
Analysis of TOMS and SBUV data have traced in detail the annual development of the Antarctic "ozone hole," a large area of intense ozone depletion that occurs between late August and early October. Analysis of the historical data indicated that the hole has existed since at least 1979.
A Dobson unit measures the physical thickness of the ozone layer at the pressure of the Earth's surface. The global average ozone layer thickness is 300 Dobson units, which equals three millimeters or 1/8th of an inch, and while not uniform, averages the thickness of two stacked pennies. In contrast during these annual occurrences, the ozone layer thickness in the ozone hole is about 100 Dobson units (1/25th of an inch or 1 millimeter thick), approximately the thickness of a single dime.
Ozone shields life on Earth from the harmful effects of the Sun's ultraviolet radiation. The ozone molecule is made up of three atoms of oxygen; ozone comprises a thin layer of the atmosphere which absorbs harmful ultraviolet radiation from the Sun. Most atmospheric ozone is found in a thin layer between 6-18 miles up.
TOMS ozone data and pictures are available on the Internet at the following URL:
or through links at URL:
http://pao.gsfc.nasa.gov/ TOMS-EP and other ozone-measurement programs are key parts of a global environmental effort of NASA's Earth Science enterprise, a long-term research program designed to study Earth's land, oceans, atmosphere, ice and life as a total integrated system. Goddard developed and manages the operation of the TOMS-EP for NASA's Office of Earth Science, Washington, DC.
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