1. CFCs over the North and South Poles(GIF image).
1. CFCs over the North and South Poles(GIF image).
(Or download postscript image - 680K).
This shows the distribution of CFC-12 (CF2Cl2) at a height of about 21 km over the northern and southern hemispheres for dates close to the autumnal equinoxes in both hemispheres. ( The blank areas between 80 deg latitude and the poles in both hemispheres are the regions not seen by CLAES). CFC-12 is one of the primary CFCs used in industry. It is transported into the stratosphere mainly at tropical latitudes then migrates to the polar regions, where it thins out, as the data shows, but it is still present in sufficient quantities to make it a major source of ozone-destructive chlorine at this altitude in the stratosphere. The data also shows roughly equal amounts and distributions of the gas over the Arctic and Antarctic. This reflects the fact that although CFC-12 is produced mainly in the northern hemisphere, it is rapidly spread around the globe by winds and weather in the lower atmosphere, then diffuses vertically upward to the stratosphere more or less uniformly in both hemispheres.
2. Global distribution of CFCs(GIF image).
(Or download postscript image - 498K).
This image is a representation of how CFC-12 in the stratosphere varies with latitude from pole to pole, and displays the mean value around latitude circles as a function of altitude. Data from days on either side of a spacecraft yaw were combined to give a pseudo 80S to 80N coverage.The picture shows very clearly how CFC-12 rises relatively high into the stratosphere near the tropics, then migrates poleward and downward. In both panels there is a steeper downward slope near the spring poles ( north in the upper panel, south in the lower). This is mainly because polar regions are colder in the spring than in the autumn and the colder air descends more steeply. It is particularly noticeable in the lower panel in the spring southern hemisphere, because the Antarctic winter and spring are so much colder than the equivalent seasons in the Arctic. Very similar behavior is seen in other "long-lived" tropospheric source gases such as Methane and Nitrous Oxide.
3. Temperature, clouds and chemicals over Antarctica, Southern Winter,
1992(GIF image).
(Or download postscript image - 993K).
This picture shows the relationship between temperature, Polar Stratospheric Clouds (PSCs), Nitric Acid (HNO3) and Chlorine Nitrate (ClONO2) over the antarctic region on August 17, 1993. It demonstrates some of the critical elements in "conditioning" antarctic air during the polar winter, which set the air up for the appearance of the antarctic ozone hole in the spring. Very cold temperatures are seen over the whole antarctic continent, cold enough to condense PSCs which can be seen as the purple regions in the upper right hand panel. These PSCs form in part by freezing-out nitric acid, a gas which normally builds up in the winter, and which inhibits the destruction of ozone by chlorine. This freezing-out is why we see very low levels of the gas around the pole in the lower left hand panel. Once the PSCs have formed, they liberate active chlorine gas normally bound in an inert state in chlorine nitrate. Chlorine nitrate, which comes mainly from CFCs, also normally builds up in winter, but the process of liberating chlorine destroys the chlorine nitrate, and it too drops to very low levels near the pole as seen in the lower right panel. Evidence that indeed free chlorine has been formed in the process comes from the MLS instrument on UARS which shows the build-up of the gas chlorine monoxide, formed when chlorine reacts with ozone. The result of all of this is that by the beginning of the south pole spring, there is now a lot of free chlorine and very little nitric acid, so that the chlorine can begin to rapidly destroy ozone when the sun reappears, and the antarctic ozone hole forms.
4. Temperature, clouds, and chemicals over the Arctic, Northern Winter,
1993(GIF image).
(Or download postscript image - 1474K).
When we look at the situation in the northern polar region for a similar season, February 22 (1993), we find a quite different picture. There are regions of very cold temperature, but they are much less extensive than in the south and we know from other data that they don't stay cold as long as they do in the south. Where the temperature is cold enough we do see PSCs, but they are far fewer and more localized than in the south. We can also see evidence for freezing-out of the nitric acid, and destruction of chlorine nitrate near the PSC cloud, as we saw in the south, but to a far lesser degree, and in general much higher levels of both gases are seen over the whole North polar region. the result in the north is that there is less production of free chlorine during the winter, and more nitric acid is available to inhibit chemical destruction of ozone in the spring. Therefore, although ozone can be reduced over the north pole in the spring, to date it has been much less severe than in the south. Since we start with just as many CFCs in the north as in the south, as we showed in the first two data images, and CFCs are the main source of chlorine nitrate, it is not a lack of chlorine that inhibits the formation of an arctic ozone hole, but rather the absence to date of sustained and widespread cold temperatures during the arctic winter and early spring.
5. Ozone depletion over Antarctica, Southern Spring, 1992(GIF image).
(Or download postscript image - 355K).
This data shows the distribution of ozone at 21 km over the antarctic region on September 17, early spring in the southern hemisphere. A region of low ozone is seen encompassing the whole continent, and more or less covering the same area where we saw cold temperatures, PSCs and low levels of nitric acid and chlorine nitrate in August in the earlier data images. This is the beginning of the antarctic ozone hole as seen by CLAES at 21 km. Total column destruction of ozone typically becomes most severe by mid October. Because of the alternating viewing to the antarctic and southern hemispheres, September 17 is the last time CLAES can look at the south pole again until November 1, by which time the hole has dissipated).
6. Aerosol dispersal(GIF image).
(Or download postscript image - 622K).
The decay and dispersal of the Mt. Pinatubo stratospheric aerosol veil measured by the CLAES instrument on the Upper Atmosphere Research Satellite. In the first half of the dataset very high optical depths associated with volcanic aerosol are confined to +/-20 degrees latitude with seasonal dispersal into the winter hemisphere. Also shown are high optical depths in the Antarctic winter when polar stratospheric clouds (PSC's) appear inside the Antarctic polar vortex, and the clean southern vortex air in November of 1991 and 1992 after the PSC's have gone. [see paper by Mergenthaler et al., Geophys. Res. Lett, 22, 3497-3500, 12/15/95, entitled, "CLAES observations of Mt. Pinatubo stratospheric aerosol".]
7. Stratospheric Clouds during the Antarctic Winter(GIF image).
(Or download postscript image - 1622K).
A multi-level view of polar stratospheric clouds for selected days during the Antarctic winter of 1992 as observed by CLAES on UARS. Thermal emission is measured on the Earth's limb and mathematically inverted to retrieve the absorption coefficient values shown here. CLAES acquired data through the polar night to achieve a unique look at the mid and late season 3-D distribution PSC's. Temperature contours at 187 and 193K from the UKMO are overlayed to show the correspondence with areas near the ice and NAT frost points.
8. Temperature in the Southern Hemisphere(GIF image).
(Or download postscript image - 1272K).
Polar orthographic projections of 24 hours of temperature data at 21 km as measured by CLAES in the Antarctic stratosphere for individual days between January 1992 and January 1993. These days emphasize the southern winter vortex region and the decreased temperature therein. [Similar to figures and discussion in "Observations of Lower-Stratospheric ClONO2, HNO3, and Aerosol by the UARS CLAES Experiment between January 1992 and April 1993", by Roche et al., J. Atmos. Sci., 51, 2877-2902, Oct. 15, 1994.]
9. Temperature in the Northern Hemisphere(GIF image).
(Or download postscript image - 2400K).
Polar orthographic projections of 24 hours of temperature data at 21 km as measured by CLAES in the Arctic stratosphere for individual days between July 1992 and May 1993. These days emphasize the northern winter vortex region and the decreased temperature therein. [Similar to figures and discussion in "Observations of Lower-Stratospheric ClONO2, HNO3, and Aerosol by the UARS CLAES Experiment between January 1992 and April 1993", by Roche et al., J. Atmos. Sci., 51, 2877-2902, Oct. 15, 1994.]
10. Ozone in the Southern Hemisphere(GIF image).
(Or download postscript image - 1469K).
Polar orthographic projections of 24 hours of ozone data at 21 km as measured by CLAES in the Antarctic stratosphere for individual days between January 1992 and January 1993. These days emphasize the southern winter vortex region and the ozone hole therein.
11. Ozone in the Northern Hemisphere(GIF image).
(Or download postscript image - 2562K).
Polar orthographic projections of 24 hours of ozone data at 21 km as measured by CLAES in the Arctic stratosphere for individual days between July 1992 and May 1993. These days emphasize the northern vortex region and the ozone depletion therein.
12. Chlorine Nitrate in the Southern Hemisphere(GIF image).
(Or download postscript image - 1350K).
Polar orthographic projections of 24 hours of ClONO2 data at 21 km as measured by CLAES in the Antarctic stratosphere for individual days between January 1992 and January 1993. These days emphasize the southern winter vortex region and the band or collar of increased ClONO2 around it. [Similar to figures and discussion in "Observations of Lower-Stratospheric ClONO2, HNO3, and Aerosol by the UARS CLAES Experiment between January 1992 and April 1993", by Roche et al., J. Atmos. Sci., 51, 2877-2902, Oct. 15, 1994.]
13. Chlorine Nitrate in the Northern Hemisphere(GIF image).
(Or download postscript image - 2381K).
Polar orthographic projections of 24 hours of ClONO2 data at 21 km as measured by CLAES in the Arctic stratosphere for individual days between July 1992 and May 1993. These days emphasize the northern winter vortex region and the band or collar of increased ClONO2 around it. [Similar to figures and discussion in "Observations of Lower-Stratospheric ClONO2, HNO3, and Aerosol by the UARS CLAES Experiment between January 1992 and April 1993", by Roche et al., J. Atmos. Sci., 51, 2877-2902, Oct. 15, 1994.]
14. Chlorine Nitrate at 46.4 mbar(GIF image).
(Or download postscript image - 532K).
Measurement of ClONO2 at 46.4 mbar over length of CLAES observing period.
15. Aerosol at 46.4 mbar(GIF image).
(Or download postscript image - 558K).
CLAES aerosol extinction coefficient measurement at 46.4 mbar over length of CLAES observing period.
16. Nitric Acid in the Southern Hemisphere(GIF image).
(Or download postscript image - 1518K).
Polar orthographic projections of 24 hours of HNO3 data at 21 km as measured by CLAES in the Antarctic stratosphere for individual days between January 1992 and January 1993. These days emphasize the southern winter vortex region and the band or collar of increased HNO3 around it. [Similar to figures and discussion in "Observations of Lower-Stratospheric ClONO2, HNO3, and Aerosol by the UARS CLAES Experiment between January 1992 and April 1993", by Roche et al., J. Atmos. Sci., 51, 2877-2902, Oct. 15, 1994.]
17. Nitric Acid in the Northern Hemisphere(GIF image).
(Or download postscript image - 2558K).
Polar orthographic projections of 24 hours of HNO3 data at 21 km as measured by CLAES in the Arctic stratosphere for individual days between July 1992 and May 1993. These days emphasize the northern winter vortex region and the depletion of HNO3 therein. [Similar to figures and discussion in "Observations of Lower-Stratospheric ClONO2, HNO3, and Aerosol by the UARS CLAES Experiment between January 1992 and April 1993", by Roche et al., J. Atmos. Sci., 51, 2877-2902, Oct. 15, 1994.]
18. Nitric Acid at 46.4 mbar(GIF image).
(Or download postscript image - 585K).
CLAES HNO3 measurement at 46.4 mbar over length of CLAES observing period.
19. Nitric Acid Zonal Means(GIF image).
(Or download postscript image - 333K).
The CLAES HNO3 zonal-mean maps for March 1992 and March 1993 show a distinct downward trend from year to year at tropical and southern mid latitudes and a smaller trend at northern mid latitudes. This trend is assumed to be due to the decreasing importance of the heterogeneous hydrolysis of N2O5 on the sulfate aerosol as the Mt. Pinatubo aerosol loading drops off.
20. Nitric Acid Zonal Mean Differences(GIF image).
(Or download postscript image - 255K).
The percent change in CLAES zonal-mean HNO3 for March 1992 and March 1993 is presented and shows a distinct downward trend from year to year at tropical and southern mid latitudes and a smaller trend at northern mid latitudes. This trend is assumed to be due to the decreasing importance of the heterogeneous hydrolysis of N2O5 on the sulfate aerosol as the Mt. Pinatubo aerosol loading drops off.
21. F-12 and Nitrous Oxide Correlation(GIF image).
(Or download postscript image - 1690K).
Correlation scatter diagrams of CLAES CF2Cl2 and N2O zonal-mean mixing ratios over the altitude range of 19-48 km for the indicated a) latitude bins by symbol and altitude bins by color for the southern-spring yaw period of March 23 through April 23, 1993, b) latitude bins by symbol and color for the same yaw period as in a), and c) latitude bins by symbol and color for the year earlier southern-spring yaw period of March 27 through April 28, 1992. The lines are linear fits for N2O > 100 ppbv to all of the data (solid black line), to the extratropical data (long-short dashed pink line), and to the data (dashed blue line) used in the M & M Model corrected to 1993 in panel b and to 1992 in panel c. The fit parameters are slope (S), intercept (I), correlation coefficient (R), and standard deviation (SD) the scatter of N points perpendicular to the fit line. More discussion on this figure can be found in section 3.3.2 of the paper, "Global CF2Cl2 measurements by UARS cryogenic limb array etalon spectrometer: Validation by correlative data and a model," by R. W. Nightingale et al., J. Geophys. Res., 101, 9711-9736, April 30, 1996.
22. Chlorine Nitrate at 465 K(GIF image).
(Or download postscript image - 1979K).
CLAES ClONO2 at 465 K on Oct. 25, 1992, Dec. 3, 1992, Feb. 22, 1993, and Mar. 14, 1993 in the Northern Hemisphere and on Apr. 28, 1993, Jun. 12, 1993, Aug. 17, 1993, and Sep. 17, 1993 in the Southern Hemisphere.
23. Nitric Acid at 465 K(GIF image).
(Or download postscript image - 2002K).
CLAES HNO3 at 465 K on Oct. 25, 1992, Dec. 3, 1992, Feb. 22, 1993, and Mar. 14, 1993 in the Northern Hemisphere and on Apr. 28, 1993, Jun. 12, 1993, Aug. 17, 1993, and Sep. 17, 1993 in the Southern Hemisphere.
You may also view zonal mean data at CLAES Zonal Mean Maps .