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HOME > Stratosphere Home > Winter Bulletins > Northern Hemisphere Winter 1994-1995 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.
  • Lienesch, J. NESDIS/Satellite Research Laboratory
  • 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
  • Stowe, L. NESDIS/Satellite Research Laboratory

Concerns of possible global ozone depletion (e.g., WMO/UNEP, 1992) 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


Ozone measurements during the winter of 1994-1995 indicate that total column ozone was unusually low over regions of the Northern Hemisphere. For middle and high latitudes, ozone values were 10 to 20 percent lower than typical values observed during these months in 1979 and the early 1980's. Over some high latitude regions, such as Siberia, total ozone in 1994-95 had decreased by up to 35 percent from 1979 values. Total ozone has decreased since 1979 over 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 daily minimum temperatures over the north polar region in December 1994 and January 1995 reached record low values. Temperatures observed were sufficiently low for chemical ozone destruction on polar stratospheric clouds within the polar vortex to go during the 1994-95 winter-spring period. A stratospheric warming during February 1995 interrupted the period of record low minimum temperatures, but record low minimum temperatures returned in the polar region during March 1995.


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, temperature and aerosols.

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
Aerosols NOAA/AVHRR Long & Stowe, 1993

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. The orbital characteristics of the NOAA polar orbiting satellites are such that the equatorial crossing times, over several years, are later in the day. For the SBUV/2 instruments, the extremely high solar azimuth angles eventually exceed the diffuser's calibrated range. This happened to the NOAA-11 SBUV/2 in late 1994. Fortunately, the NOAA-9 instrument had migrated back into the preferred solar azimuth angle range. After extensive comparisons with available ground-based observations and with NOAA-11 (Crosby, personal communication), it was determined that the NOAA-9 data are, on average, within two to four percent of Dobson total ozone data. Consequently, we use the data from the NOAA-9 SBUV/2 beginning in September 1994.


Figure 1 shows monthly average anomalies of zonal mean total column ozone, as a function of latitude and time, from January 1979 to March 1995. Certain aspects of long-term global ozone changes may be readily seen. In the extra-tropics and polar regions, ozone is substantially lower in recent years than in earlier years. The anomalies (percent difference) are derived relative to each month's long-term average. No adjustments have been made to the data from the three different satellite instruments, and it is very encouraging that the transitions, between the NIMBUS-7 SBUV and the NOAA-11 data sets in January 1989, and the NOAA-11 and the NOAA-9 data in September 1994, are very smooth. Stolarski et al. (1992), and more recently Hollandsworth et al. (1994) and Miller et al. (1994) have indicated that total ozone trends in the mid-latitudes are statistically significant and are about -2 to -4 % per decade, and that little or no significant trend exists over the equatorial region. 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. The anomalies decreased in 1994 along with the diminishing aerosol loading. However, large negative anomalies again developed in 1994-95 over the north polar region, with substantial negative ozone anomalies extending to the northern extra-tropics. In the tropical region, a weak high anomaly is seen in 1994-95, as part of the quasi-biennial oscillation of total ozone.

Geographical distributions of ozone and ozone changes are illustrated in the next four figures. Monthly mean total ozone amounts for March 1995 are shown in Figure 2. A region of high ozone (yellow and red colors) is located over middle to high northern latitudes. Low values are shown over the north polar region, and extending over Siberia to northern Greenland. These low total ozone values (green and blue, 300 to 220 DU), are typical for tropical values, in all months of the year, but are unusually low for the polar region. Figure 3 shows the percent difference in monthly mean total ozone, between March 1995 and March 1979. The 1979 base period is chosen because these values are typical for the early data record. Decreases since 1979 in total ozone of more than 40 percent, shown by the blue colors, extend over the north polar region to northern Siberia. Decreases of greater than 20 percent (green) cover a very large area of Siberia, northern Greenland and northern Canada. Over most of the United States, March 1995 values were lower than those for March 1979 by 15 to 20 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 changes of ozone.

The region of low total ozone over northern Siberia and the north polar region developed and grew during the months of January, February and March 1995. Figures 3, 4 and 5 show that the large region of relatively low ozone over Siberia (difference of the 1995 monthly mean from 1979 values) persisted for several months, but the locations of other positive and negative ozone differences from their 1979 values changed during the first three months of 1995. A region of persisting negative total ozone anomalies may be seen around the international dateline, near Hawaii.

On two days in December 1994, total ozone measured at the NOAA/CMDL, Mauna Loa observatory (MLO), Hawaii, dropped below 200 Dobson Units (DU), for the first time since measurements began at this site (1963). Minimum annual total ozone occurs at MLO at the end of December and the beginning of January in each year, with some fluctuation in the minimum values from year to year.

In Figure 6, ozone anomalies (percent difference from the monthly averages for the period 1964 to 1981) are shown for the 31 year record at MLO. The anomalies show a long-term downward trend of about 1.2 percent per decade, with an uncertainty of .38 percent for 95 percent confidence. The record low winter ozone of 1994-95 at MLO, Hawaii was thus the result of an unusually large


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National Centers for Environmental Prediction
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