24 May 2023
 | 24 May 2023
Status: this preprint is open for discussion and under review for Atmospheric Measurement Techniques (AMT).

Total Column Ozone Trends from the NASA Merged Ozone Time Series 1979 to 2021 Showing Limited Recovery to 1979 Amounts after Declining into the Mid 1990s

Jay Herman, Jerald Ziemke, and Richard McPeters

Abstract. Monthly averaged total column ozone data ΩMOD from the Merged Ozone Data set (MOD) were examined to show that the latitude-dependent ozone depletion turnaround dates TA(θ) range from 1994 to 1998. ΩMOD used in this study was created by combining data from Solar Backscattered Ultraviolet instruments (SBUV/SBUV-2) and the Ozone Mapping and Profiler Suite (OMPS-NP) from 1979 to 2021. TA(θ) is defined as the date when the zonally average ozone ceased decreasing. The new calculated systematic latitude-dependent TA(θ) shape should appear in atmospheric models that combine the effects of photochemistry and dynamics in their estimate of ozone recovery. Trends of zonally averaged total column ozone in percent per decade were computed before and after TA(θ) using two different trend estimate methods that closely agree, Fourier Series Multivariate Linear Regression and linear regression on annual averages. During the period 1979 to TA(θ) the most dramatic rates of SH ozone loss were PD = −10.9 ± 3 % per decade at 77.5° S and −8.5 ± 0.9 % per decade at 65° S, which is about double the NH rate of loss of PD = −5.6 ± 4 %/decade at 77.5° N and 4.4 ± 1 %/decade at 65° N for the period 1979 toTA(θ). After TA(θ), there has been an increase at 65° S of PD = 1.6 ± 1.4% per decade with smaller increases from 55° S to 25° S and a small decrease at 35° N of −0.4 ± 0.3 %/decade. Except for the Antarctic region, there only has been a small recovery in the Southern Hemisphere toward 1979 ozone values and almost none in the Northern Hemisphere.

Jay Herman et al.

Status: open (until 29 Jun 2023)

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Jay Herman et al.

Jay Herman et al.


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Short summary
Fourier Series Multivariate Linear Regression trends (Percent/Decade) in ozone were estimated from the Merged Monthly averaged total column Ozone Data MOD from 1979 to 2021 in two different regimes, from 1979 to TA, and TA to 2021. The derived TA is the latitude-dependent date when ozone stopped decreasing ranging from 1994 to 1998. TA(Latitude) is a marker for photochemistry-dynamics models attempting to represent ozone change over the past 42 years.