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Zonal asymmetries in SAMS stratospheric methane and nitrous oxide
Author(s) -
Ziemke J. R.,
Stanford J. L.
Publication year - 1995
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49712152409
Subject(s) - stratosphere , polar vortex , atmospheric sciences , sudden stratospheric warming , latitude , environmental science , mixing ratio , atmosphere (unit) , ozone layer , methane , polar , rossby wave , climatology , troposphere , ozone , greenhouse gas , ozone depletion , middle latitudes , geology , meteorology , chemistry , physics , oceanography , geodesy , organic chemistry , astronomy
Stratospheric and Mesospheric Sounder (SAMS) methane (CH 4 ) and nitrous oxide (N 2 O) constituent measurements were taken a decade before the Upper Atmosphere Research Satellite (UARS) observations and are generally of lesser quality. However, SAMS data are important because of the limited lifetime of the UARS and because they provide a unique, historical data series for these gases involved in greenhouse and ozone‐depletion effects. While most prior SAMS analyses focused on zonal means, this paper assesses the strengths and weaknesses of analysing zonally asymmetric perturbations in SAMS data. It is shown that wave‐1 perturbations can be successfully investigated, provided sufficient care is taken and aliasing considered. At the lowest SAMS level, 20 hPa (∼ 28 km altitude) zonal‐wave‐1 CH 4 and N 2 O data reveal similar features for latitudes 45°N–65°N during stratospheric warming events and break‐up of the polar vortex. Large wave‐1 anomalies in the upper stratosphere (2 and 0.6 hPa) were found to be out of phase with the corresponding anomalies at 20 hPa. In one episode in early 1981 (during stratospheric sudden warming) southward winds over North America transported air with low mixing ratios from polar latitudes, while northward winds over Siberia transported air with high mixing ratios from subtropical latitudes. the effect produced strong wave‐1 amplitudes in both CH 4 and N 2 O mixing ratios. Cross‐correlations between wave‐1 CH 4 and N 2 O are large and positive in middle and high latitudes (consistent with ideal tracer behaviour for both constituent gases) but weak over the tropics. the cause of the latter remains an open issue.