SEASONAL CYCLES AND QBO VARIATIONS IN STRATOSPHERIC CH4 AND H2O OBSERVED IN UARS HALOE DATA

Measurements of stratospheric methane (CH4) and water vapor (H2O) are used to investigate seasonal and interannual variability in stratosphe ric transport. Data are from the Halogen Occultation Experiment (HALOE ) on the Upper Atmosphere Research Satellite (UARS) spanning 1991-97. Profile measurements are binned according to analyzed potential vortic ity fields (equivalent latitude mapping), and seasonal cycles are fit using harmonic regression analysis. Methane data from the UARS Cryogen ic Limb Array Etalon Spectrometer and water vapor from the Microwave L imb Sounder are also used to fill in winter polar latitudes (where HAL OE measurements are unavailable), yielding complete global seasonal cy cles. These data reveal well-known seasonal variations with novel deta il, including 1) the presence of enhanced latitudinal gradients (mixin g barriers) in the subtropics and across the polar vortices, 2) strong descent inside the polar vortices during winter and spring, and 3) vi gorous seasonality in the tropical upper stratosphere, related to seas onal upwelling and the semiannual oscillation. The observed variations are in agreement with aspects of the mean meridional circulation deri ved from stratospheric meteorological analyses. Interannual variations are also investigated, and a majority of the variance is found to be coherent with the equatorial quasibiennial oscillation (QBO). Strong Q BO influence is found in the tropical upper stratosphere: the double-p eaked ''rabbit ears'' structure occurs primarily during QBO westerlies . The PBO also modulates the latitudinal position of the tropical ''re servoir'' in the middle stratosphere.