Ozone trends deduced from combined Nimbus 7 SBUV and NOAA 11 SBUV/2 data

Abstract

The long‐term time series of global ozone from the Nimbus‐7 SBUV (Nov. 1978–June 1990) are extended through June 1994 by using measurements from the NOAA‐11 SBUV/2. The data sets are merged based upon comparisons during the 18‐month overlap period in which both instruments were operational. During this period, the average offset between the two time series is less than 2% in total ozone, and less than 6% in Umkehr layers 1–10. A linear‐regression trend model is applied to the extended time series to calculate updated trends as a function of latitude and altitude. Trends through June 1994 are 1.5‐2% per decade less negative than through June 1990 in the tropical middle stratosphere (35–40 km) and in the upper stratosphere (45–50 km) at mid‐latitudes. In the lower stratosphere, the trends are nearly 1.5% per decade more negative in the southern hemisphere tropical regions to 25°S, but remain relatively unchanged elsewhere. The seasonal structure of the total ozone trends is similar to past trend study results, but the magnitude of the seasonal trend can vary by 2% per decade depending on the length of the time series. Both TOMS (through April 1993) and SBUV total ozone time series show small negative trends in the equatorial region, though they are not statistically significant at the 2‐σ level.

Ozone climatology, trends, and substances that control ozone

“…There are seasonal differences in upper stratospheric ozone trends. Trends are largest in winter and smallest in summer (Hood et al, 1993;Hollandsworth et al, 1995b). Recent estimates from SBUV version 8 data for the 1979-97 period over northern mid-latitudes at 2-3 hPa show a decline of 5.7±2.8% per decade in winter and 3.1±1.5% per decade in summer (Rosenfield et al, 2005).…”

The dynamically driven long‐term trend in stratospheric ozone over northern middle latitudes

“…The monthly anomalies, the difference between the individual monthly means and their 20-year average, are plotted for the region between 30 • N and 60 • N in Fig. 4 for both ozone schemes and also for the total ozone data from the TOMS (McPeters et al 1996) and SBUV (Hollandsworth et al 1995). The anomalies have been smoothed by a 24-month running mean to average over both the annual cycle and the QBO, as in the earlier studies of Solomon et al (1996Solomon et al ( , 1998.…”

Comment on “New evidence for ozone depletion in the upper stratosphere,” by H. Claude, et al.

“…Hollandsworth et al (1995) found that the seasonal trends computed from the SBUV(/2) record varied by more than 0.2% per year when the length of the data set was extended from 11.5 years to 12.5 years.…”

“…We use the 15-year combined record of ozone profile measurements from the Nimbus 7 (N7) SBUV and NOAA 11 (Nll) SBUV/2 instruments employed by Hollandsworth et al (1995) and the linear regression statistical model described in Hood et al (1993) to examine trend differences due to: varying the time interval, selecting zonal average data as compared to station data, and including QBO and ll-year solar cycle terms.…”