The mean meridional circulation and midlatitude ozone buildup

[摘要] The wintertime ozone buildup over the Northern Hemisphere (NH) midlatitudesand its connection with the mean meridional circulation in the stratosphereare examined statistically on a monthly basis from October to March(1980–2002). The ozone buildup begins locally in October with positive totalozone tendencies over the North Pacific, which spread eastward and westwardin November and finally cover all midlatitudes in December. The local onsetof the buildup in October is not evident in zonal mean ozone tendency, whichis close to zero. From November to March, zonal mean total ozone tendency(50°–60° N) shows a strong correlation (|r|=0.7) with several zonal meanparameters associated to the mean meridional circulation, namely: eddy heatflux, temperature tendency, the vertical residual velocity and the residualstreamfunction. At the same time, on the latitude-altitude cross section,correlation patterns between ozone tendency and widely used eddy heat fluxare not uniform during winter. The strongest correlations are locatedequatorward (almost throughout the stratosphere) or poleward (only in thelower stratosphere) of the edge of the polar vortex. Such distribution maydepend on the existence of the midlatitude and polar waveguides whichdefined refraction of upward propagating waves from the troposphere eitherto the midlatitude stratosphere or to the polar stratosphere. As aconsequence of the nonuniform correlation patterns, heat flux averaged overthe common region 45°–75° N, 100 hPa is not always an optimum proxyfor statistical models describing total ozone variability in midlatitudes.Other parameters approximating the strength of the mean meridionalcirculation have more uniform and stable correlation patterns with ozonetendency during winter. We show that the NH midlatitude ozone buildup has astable statistical relationship with the mean meridional circulation in allmonths from October to March and half of the interannual variability inmonthly ozone tendencies can be explained by applying different proxies ofthe mean meridional circulation.

[学科分类] 大气科学