An Analysis of Tropopause Pressure and Total Ozone Correlations

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  • 1 Meteorology Department, University of Maryland, College Park, Maryland
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Abstract

The relationship between total ozone and tropopause pressure is analyzed using 4 years (1979–82) of Nimbus-7 total ozone data and NMC global analyses of tropopause on a 5° by 5° grid. The fields are separated into medium (synoptic) and large spatial scales via a spherical harmonic expansion. The global distribution of variability and correlation are presented for each season. The large-scale analysis is based primarily on data from 1979 due to pronounced temporal inhomogeneities in the tropical tropopause data.

The synoptic scales show strong correlations (>0.6) in the middle latitudes of both hemispheres with a rapid equatorward drop and a more gradual poleward decline: a similar dependence on latitude is found using tropopause values derived directly from station data. Within a season, the areas of highest correlation tend to be associated with the regions of maximum variance of the storm track regions. In contrast, the seasonal dependence is such that the summer hemispheres tend to have the most extensive regions of high correlation while the more energetic winter seasons have the smallest. A frequency analysis (limited to time scales longer than 3 days) of selected regions indicates that in middle latitudes synoptic-scale fluctuations of total ozone and tropopause pressure exhibit generally similar distributions in power and no significant phase differences: equatorward the coherence drops rapidly at all frequencies.

Nonseasonal fluctuations of the large-scale fields generally show weak correlations (<0.6) everywhere. A major exception is the springtime middle latitude South Pacific. The strongest correspondence between large-scale ozone and tropopause pressure fields involves long period (seasonal) fluctuations in high latitudes. Over Antarctica the coupling is strongest in middle and late spring in association with the spring warming while the decrease in total ozone in early spring shows no apparent relation to tropopause variations.

Abstract

The relationship between total ozone and tropopause pressure is analyzed using 4 years (1979–82) of Nimbus-7 total ozone data and NMC global analyses of tropopause on a 5° by 5° grid. The fields are separated into medium (synoptic) and large spatial scales via a spherical harmonic expansion. The global distribution of variability and correlation are presented for each season. The large-scale analysis is based primarily on data from 1979 due to pronounced temporal inhomogeneities in the tropical tropopause data.

The synoptic scales show strong correlations (>0.6) in the middle latitudes of both hemispheres with a rapid equatorward drop and a more gradual poleward decline: a similar dependence on latitude is found using tropopause values derived directly from station data. Within a season, the areas of highest correlation tend to be associated with the regions of maximum variance of the storm track regions. In contrast, the seasonal dependence is such that the summer hemispheres tend to have the most extensive regions of high correlation while the more energetic winter seasons have the smallest. A frequency analysis (limited to time scales longer than 3 days) of selected regions indicates that in middle latitudes synoptic-scale fluctuations of total ozone and tropopause pressure exhibit generally similar distributions in power and no significant phase differences: equatorward the coherence drops rapidly at all frequencies.

Nonseasonal fluctuations of the large-scale fields generally show weak correlations (<0.6) everywhere. A major exception is the springtime middle latitude South Pacific. The strongest correspondence between large-scale ozone and tropopause pressure fields involves long period (seasonal) fluctuations in high latitudes. Over Antarctica the coupling is strongest in middle and late spring in association with the spring warming while the decrease in total ozone in early spring shows no apparent relation to tropopause variations.

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