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HOME > Stratosphere Home > Winter Bulletins > Northern Hemisphere Winter 1995-1996 Summary
Northern Hemisphere Winter Summary


National Oceanic and Atmospheric Administration

April 1998

National Weather Service

National Centers for Environmental Prediction



  • Angell, J.K. ERL/Air Resources Laboratory
  • Gelman, M.E. NWS/Climate Prediction Center
  • Hofmann, D. ERL/Climate Monitoring and Diagnostic Lab.
  • Long, C.S. NWS/Climate Prediction Center
  • Miller, A.J. NWS/Climate Prediction Center
  • Nagatani, R.M. NWS/Climate Prediction Center
  • Oltmans, S. ERL/Climate Monitoring and Diagnostic Lab.
  • Planet, W.G. NESDIS/Satellite Research Laboratory
  • Solomon, S. ERL/Aeronomy Laboratory

Concerns of possible global ozone depletion (e.g., WMO/UNEP, 1994) have led to major international programs to monitor and explain the observed ozone variations in the stratosphere. In response to these, and other long-term climate concerns, NOAA has established routine monitoring programs using both ground-based and satellite measurement techniques (OFCM, 1988).

Selected indicators of stratospheric climate are presented in each Summary from information contributed by NOAA personnel. A Summary for the Northern Hemisphere is issued each April, and, for the Southern Hemisphere, each December. These Summaries are available on the World-Wide-Web at the site:
with location: products/stratosphere/winter_bulletins

Further information may be obtained from Alvin J. Miller
NOAA, Climate Prediction Center
5200 Auth Road
Camp Springs, MD 20746-4304
Telephone: (301) 763-8000 ext.7552
Fax: (301) 763-8125

ABSTRACT Ozone measurements during the winter of 1995-1996 indicate that total column ozone values were substantially lower than values observed during these months in 1979 and the early 1980's. Over the north polar regions, the Barents Sea, Greenland, northern Europe and northern Siberia, total ozone for March 1996 was lower by 20 to 25 percent than during the earlier period. Total ozone has decreased since 1979 over the Northern Hemisphere mid-latitudes at the rate of about -4 percent per decade. Little or no significant long-term trend is observed for the equatorial region. Lower stratosphere winter temperatures over the north polar region reached record low values. Temperatures observed were sufficiently low within the polar vortex for chemical destruction of ozone on polar stratospheric clouds .


The data available and appropriate references are listed below. This combination of complementary data, from different platforms and sensors, provides a strong capability to monitor global ozone and temperature.

Parameter Method Reference
Total Ozone Dobson Komhyr et al., 1986
CMDL, 1990
Ozone Profiles Balloons Komhyr et al., 1989
CMDL, 1990
Parameter Method Reference
Total Ozone NOAA/SBUV/2 Planet et al., 1994
Nimbus-7 SBUV Mateer et al., 1971
Ozone Profiles Miller, 1989
Planet et al., 1994
Mateer et al., 1971
Temperature Profiles NOAA/TOVS Gelman et al., 1986

We have used the total column ozone data from the NASA Nimbus -7 SBUV instrument from 1979 through 1988, the NOAA-11 SBUV/2 from January 1989 to August 1994, and the NOAA-9 SBUV/2 instrument beginning September 1994. Solar Backscatter Ultra-Violet instruments can only produce data for daylight-viewing conditions, so no SBUV/2 data are available at polar latitudes during winter darkness conditions. In addition, increasing data loss of NOAA-11 data, at sub-Arctic latitudes, was caused by satellite precession over several years and resulting changes of SBUV/2 viewing to later times of the day.


Anomalies of zonal mean total column ozone are shown in Figure 1, as a function of latitude and time, from January 1979 to March 1996. The monthly mean anomalies (percent difference) are derived relative to each month's long-term, 1979-1996, average. For the winter of 1995-96, negative total ozone anomalies of greater than 10 percent are seen for the Northern Hemisphere Arctic latitudes. Thus in recent years, zonal mean total ozone at high-latitudes, was substantially lower, by up to 25 percent, than in the earlier years. At mid-latitudes, the anomaly was slightly positive during 1995-96, in contrast to the widespread negative anomalies in 1992-93 and 1994-95. Large negative anomalies in the Northern Hemisphere extra-tropics during 1992-1993 (Gleason et al., 1993) could be related to the Mt. Pinatubo eruption in mid-1991. Stolarski et al. (1992), Hollandsworth et al. (1994) and Miller et al. (1994) have indicated that middle latitude Northern Hemisphere total ozone trends of about -2 to -4 % per decade are statistically significant, and that little or no significant trend exists over the equatorial region. For the region 30N-50N (the basic latitude range of the coterminous United States), the trend, based on the SBUV - SBUV/2 data sets, and updated from 1979 through March 1996 is about -4 percent per decade, with a 95 percent confidence estimate of about 2 percent. In the tropical region, a weak low anomaly is seen in 1995-96, as part of the quasi-biennial oscillation of total ozone.

The NOAA Climate Monitoring and Diagnostics Laboratory operates a 16-station global Dobson spectrophotometer network for total ozone trend studies. Recently, the data have been reanalyzed, and ozone trends re-calculated for the period 1979 through 1995. Figure 2 shows the corrected total ozone data for four central U.S. stations. The large annual variation is a result of ozone transport processes which cause a winter-spring maximum and a summer-fall minimum at northern midlatitudes. Monthly means for the period 1979-1995 have been subtracted from each individual monthly mean, and are shown in Figure 3 as a four-station average percent deviation. The resulting trends, for the 1979-1995 period for seven northern hemisphere stations, are given in Table 1.

Table 1. Ozone Trends for the Period 1979-1995

Station Latitude Trend 95%
(percent/decade) confidence
Caribou, ME 46.9°N -4.00 1.42
Bismarck, ND 46.8°N -3.30 1.26
Boulder, CO 40.0°N -3.85 1.22
Wallops Island. VA 37.9°N -3.67 1.36
Fresno, CA 36.8°N -3.81 2.74
Nashville, TN 36.3°N -3.09 1.40
Mauna Loa, HI 19.5°N -0.53 1.54

Northern hemisphere distributions of ozone and ozone changes are illustrated in the next two figures. Monthly mean total ozone amounts for March 1996 are shown in Figure 4. Lowest values are shown over the north polar region (green, less than 300 DU), extending from Greenland, to northern Europe and northern Siberia. Total ozone values of less than 250 DU are typical for tropical values, but are unusual for the polar region. Indeed, at the beginning of March 1996, extremely low values of total ozone (near 200 DU) were observed over northern Europe. The March 1996 monthly mean map also shows a region of high ozone (yellow and red colors), typical for this region and season, located over middle to high northern latitudes. Figure 5 shows the percent difference in monthly mean total ozone, between the distribution during March 1996 and the mean for eight March monthly means, 1979-1986. The 1979 to 1986 base period is chosen because these values are indicative of the early data record. Decreases of 20 to 25 percent (blue) cover a very large area over the Arctic, from Greenland, over the Baltic Sea, to northern Europe and northern Siberia. Over western United States, March 1996 values were lower than those for March 1979-1986 by 2 to 4 percent. Small percent increases are shown over some local areas of the tropics and mid-latitudes, but these increases are short-term, regional effects, and are not representative of general, long-term trends of ozone.

Temperatures in the lower stratosphere are closely coupled to ozone through dynamics and photochemistry. Extremely low temperatures (lower than -78 C) over the Arctic region in the lower stratosphere are believed to lead to depletion of ozone. Low temperatures contribute to the presence of polar stratospheric clouds (PSCs). PSCs enhance the production and lifetime of reactive chlorine, leading to ozone depletion (WMO/UNEP, 1994).

Daily minimum temperatures over the polar region, 65N to 90N at 50 mb (approximately 19 km) are shown in Figure 6. We see that for much of the winter of 1995-96, the daily minimum temperatures were near record low values, and were sufficiently low (lower than -78 C) for polar stratospheric clouds to form and allow enhanced ozone depletion. Indeed, during the entire 1995-96 winter, minimum 50 mb temperatures were below the long-term average minimum temperatures

Temperature anomalies for the 100-50 mb layer derived from radiosonde data (updated from Angell, 1988) are shown in Figure 7. The winter of 1995-96 had the lowest temperatures ever for the Northern Hemisphere as a whole and for the north polar region. Figure 8 at 50 mb for three latitude regions, 65N-90N, 25N-65N, and 25N-25S (updated from Gelman et al., 1986) shows that temperature anomalies for 1995-96 were near record low values for polar and equatorial latitudes. However for recent months, near average temperatures prevailed over middle latitudes.

Aerosol concentration is another important component of stratospheric variation, and a possible source of ozone depletion (e.g. Hofmann et al., 1992). Aerosol optical thickness from the NOAA/AVHRR instrument (Long and Stowe, 1993) showed that stratospheric aerosol concentrations continued to diminish from the maximum values observed a few weeks after the eruption of Mount Pinatubo in June 1991. Stratospheric aerosols were at such low levels in 1994, that it was difficult to discern stratospheric aerosols from variations in tropospheric values. The NOAA 11 AVHRR instrument failed in September 1994.

Recent studies have demonstrated the importance of heterogeneous chemistry, not only in Antarctica, but also at mid-latitudes. Chlorine-catalyzed ozone loss processes are enhanced following major volcanic eruptions which inject sulfur into the stratosphere, and greatly increase the surface area of stratospheric aerosols. Several eruptions have strongly influenced the stratospheric aerosol and ozone contents of past decades. Solomon et al. (1996a) showed that for an atmosphere with pre- anthropogenic (natural) levels of chlorine, slight ozone increases are expected for mid-latitudes following volcanic eruptions. Current understanding suggests that the increasing levels of chlorine caused by human activities interact with volcanic aerosols, and lead to decreases of stratospheric ozone.

Using a state-of-the-art two-dimensional dynamical-chemical model of the middle atmosphere, with aerosol variability prescribed from SAGE I, SAGE II and SAM observations of extinction, Solomon et al. (1996a) showed that it is highly likely that much of the variability of the northern hemisphere mid-latitude ozone observed from 1979 through 1994 was induced by the modulation of chlorine- catalyzed ozone loss by volcanic aerosols. Updating those findings through the winter of 1995-1996, Solomon et al. (1996b) examined the recovery of the ozone depletion from the eruption of Mt. Pinatubo. Figure 9 shows the calculated and observed ozone column changes for 45 N. Both the model and the observations represent 25-month running means, in order to remove the effects of the quasi-biennial oscillation. The smoothed time series as shown extends to the end of 1994, but reflects observations through the end of 1995.

The abrupt onset of the ozone loss in the model, in the early 1980's, is caused by the effect of the 1982 El Chichon aerosols in the model. During the period from 1985 to that just before Pinatubo in 1991, aerosols decreased, while total chlorine increased due to human activities, causing a flattening of the ozone trend. Following Pinatubo, a much larger ozone loss was shown from observational data and model calculations. The recent moderate recovery of northern hemisphere mid-latitude total ozone, as shown by SBUV and SBUV/2 observations, is also remarkably well-simulated. In contrast to the period after El Chichon, the absence of a continuing large trend in stratospheric total chlorine after Pinatubo (because of control measures) implies that such a recovery is expected. This work strongly suggests that aerosols have controlled much of the observed variability in ozone trends since 1979. Similarly, it is to be expected that the recovery of stratospheric ozone in the next several decades will not be monotonic, but will show fluctuations that follow major volcanic eruptions. We note that Solomon et al. (1996a) also discussed the need to consider temperature fluctuations together with volcanic aerosol content when considering ozone losses at higher latitudes.


Observed total ozone values continued to be very low over high latitude regions of the Northern Hemisphere during the winter of 1995-96. Lower stratosphere temperatures over the north polar region also reached record low values. A full explanation of ozone and temperature anomalies must include all aspects of ozone photochemistry and meteorological dynamics.


Angell, J. K., 1988: Variations and trends in tropospheric and stratospheric global temperatures. J. Climate, 12, 1296-1313.

Climate Monitoring and Diagnostic Laboratory (CMDL), 1990: Summary Report 1989. 141pp. Available from National Technical Information Service, 5285 Port Royal Rd., Springfield, Va. 22161.

Gelman, M.E., A.J. Miller, K.W. Johnson and R.M. Nagatani, 1986: Detection of long-term trends in global stratospheric temperature from NMC analyses derived from NOAA satellite data. Adv. Space Res., 6, 17-26.

Gleason, J., P.K. Bhartia, J.R. Herman, R. McPeters, P. Newman, R.S Stolarski, L. Flynn, G. Labow, D. Larko, C. Seftor, C. Wellemeyer, W.D. Komhyr, A. J. Miller, and W. Planet, 1993: Record low global ozone in 1992. Science, 260, 523-526.

Hofmann, D.J., S.J. Oltmans, J.M. Harris, S. Solomon, T. Deshler, and B.J. Johnson, 1992: Observation and possible causes of new ozone depletion in Antarctica in 1991. Nature, 359, 283.

Hollandsworth S.M., R.D. McPeters, L. Flynn, W.G. Planet, A.J. Miller, and S. Chandra, 1994: Ozone trends deduced from combined Nimbus 7 SBUV and NOAA-11 SBUV/2 data. Geophys. Res. Lett., 22, 905-908.

Komhyr, W.D., R.D. Gross and R.K. Leonard, 1986: Total ozone decrease at South Pole, Antarctica, 1964-1985. Geophys. Res. Lett., 13, 1248-1251.

Komyhr, W.D., R.D. Grass, P.J. Reitelbach, S.E. Kuester, P.R. Franchois and M.L. Fanning, 1989: Total ozone, vertical distributions, and stratospheric temperatures at South Pole, Antarctica, in 1986 and 1987. J. Geophys. Res., 94, 11429-11436.

Long, C.S. and L.L. Stowe, 1993: Using the NOAA/AVHRR to study stratospheric aerosol optical thickness following the Mt. Pinatubo eruption. Geophys. Res. Lett., 21, 2215-2218.

Mateer, C.Y., D. F. Heath and A. J. Krueger, 1971: Estimation of total ozone from satellite measurements of backscatter ultraviolet earth radiance. J. Atmos. Sci., 28, 1307-1311.

Miller, A. J., 1989: A review of satellite observations of atmospheric ozone. Planet. Space Science, 37,1539-1554.

Miller, A.J., G.C. Tiao, G.C. Reinsel, D. Wuebbles, L.Bishop, J. Kerr, R.M. Nagatani, J.J. DeLuisi, C.L. Mateer , M.E. Gelman, S.Oltmans, W.G. Planet, and R. McPeters, 1994: Consideration of the 1994 Antarctic ozone hole and an update of stratospheric ozone trends, Proceedings of the Nineteenth Annual Climate Diagnostic Workshop, U.S. Department of Commerce NOAA, 13-17.

OFCM, 1988: National Plan for Stratospheric Monitoring 1988-1997. FCM-P17-1988. Federal Coordinator for Meteorological Services and Supporting Research, U.S. Dept. Commerce, 124pp.

Planet, W. G., J. H. Lienesch, A. J. Miller, R. Nagatani, R, D. McPeters, E. Hilsenrath, R. P. Cebula, M. T. DeLand, C. G. Wellemeyer, and K. M. Horvath, 1994: Northern hemisphere total ozone values from 1989-1993 determined with the NOAA-11 Solar Backscatter Ultraviolet (SBUV/2) instrument. Geophys. Res. Lett. 21, 205-208.

Solomon, S., R.W. Portmann, R.R. Garcia, L.W. Thomason, L.R. Poole, and M.P. McCormick, 1996a: The role of aerosol variations in anthropogenic ozone depletion at northern midlatitudes, J. Geophys. Res., 6713-6727.

Solomon, S., R.W. Portmann, R.R. Garcia, L.W. Thomason, L.R. Poole, M.P. McCormick, and R. Nagatani, 1996b: Recovery of northern hemisphere ozone from Pinatubo, submitted for publication.

Stolarski, R., R. Bojkov, L. Bishop, C. Zerefos, J. Staehelin and J Zawodny, 1992: Measured trends in stratospheric ozone, Science, 256, 342-349.

WMO/UNEP, 1994: Scientific assessment of ozone depletion: 1994. Report No. 37, WMO.

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