A statistical trend analysis of revised Dobson total ozone data over the northern hemisphere

Abstract

A seasonal trend analysis of Dobson total ozone data that have been critically reevaluated and revised is performed for 29 northern hemisphere stations located between 19°N and 64°N latitude using data through 1986. The trend model considered for these data allows for a different linear trend for each month of the year, so that the seasonal as well as the latitudinal and regional nature of the total ozone trend behavior can be examined. The trend model also incorporates the 10.7‐cm solar flux series and the 50‐hPa equatorial zonal wind series as additional explanatory factors for solar and quasi‐biennial oscillation induced ozone variations. Regression random effects models are then used for the individual station seasonal trend estimates to obtain trend estimates as a function of latitude for different seasons of the year. The results of this seasonal trend analysis indicate significantly more negative trends during the winter months (December‐March) than during the summer months (May–August), notably at higher latitudes, with the trends in winter becoming more negative with increasing latitude. The trends in the winter are estimated to be of the order of −1.2%, −2.1%, and −3.0% per decade for latitudes 35°N, 45°N, and 55°N, respectively, while trends during the summer are of the order of −0.6% per decade with no distinct pattern as a function of latitude. The year‐round or annual trend over all latitudes is estimated to be about −0.84±0.82% per decade. The trends are found to display some regional variation, with trends in Japan being considerably less negative than those in North America and Europe. Sensitivity studies are also performed to investigate the effects on ozone trend estimates due to certain factors such as abnormal ozone behavior in 1983 and 1985, the use of ozone data prior to 1965, and nuclear weapons testing in the early 1960s. The seasonal trend analysis is also performed using published (unrevised) Dobson data. Trend results based on published data are on average less negative than trends from revised Dobson data for European stations, by about 1.0% per decade across all seasons, with only small average differences for stations in North America and Japan.

Global distribution of total ozone and lower stratospheric temperature variations

“…This has become standard practice (Bojkov et al, 1990;SPARC, 1998;WMO, 2003), but here more predictors are used, in particular meteorological parameters. Anomaly time series Y of total ozone or 50 hPa temperature are described as a linear combination of predictor time series (=explanatory variables), each of which accounts for a different contribution to total ozone or temperature variations:…”

“…(1) is typically a first-order autocorrelated noise series (Bojkov et al, 1990;SPARC, 1998). However, since seasonal mean data are used, and since the regression usually describes a very large part of the observed variance, autocorrelation was found to be negligible.…”

“…This includes trends (Bojkov et al, 1990;Staehelin et al, 2001;Ramaswamy et al, 2001), as well as variations associated with the QBO (Yang and Tung, 1995;Baldwin et al, 2001), the 11-year solar cycle (Zerefos et al, 1997;Hood, 1997;Labitzke and van Loon, 2000;Lee and Smith, 2003), the El Niño/Southern Oscillation (ENSO) (Shiotani, 1992;Zerefos et al, 1992;Reid, 1994), or meteorological factors (Hood et al, 1999;Appenzeller et al, 2000;Steinbrecht et al, 2001). …”

Daily distribution of UV-Index in Belo Horizonte (Brazil) and the shadow rule

“…Some authors (Downham, 1998;Sliney & Wengraitis, 2006) have proposed the shadow length to be equal to the body's height (SZA = 45 • or ratio 1) for the SR application. Maybe this works well for the typical ozone column (O3) amounts in the middle and high latitudes of Northern Hemisphere (Bojkov et al, 1990). But it fails if applied to the low latitudes (equatorial and tropical zones) of Southern Hemisphere because much lower O3 amounts are found in that region, producing an increment in the solar UVR incidence.…”

MANTRA ‐ A Balloon Mission to Study the Odd‐Nitrogen Budget of the Stratosphere

“…Changes to the mid-latitude ozone layer which started in the 1980s (Bojkov et al, 1990;Stolarski et al, 1991Stolarski et al, , 1992Kerr and McElroy, 1993;Hofmann et al, 1994) followed shortly after the end of the Stratoprobe flight series. The Stratoprobe results are notable because they: (1) predate the onset of ozone decline, (2) connect to the Arctic through flights made using the same equipment in 1978 and 1979, and (3) have been compared to satellite results from lower latitudes (e.g., Limb Infrared Monitor of the Stratosphere (LIMS) - Gille and Russell (1984)).…”