Normal mode Rossby waves and their effects on chemical composition in the late summer stratosphere

D. Pendlebury (1) , T. G. Shepherd (1) , M. Pritchard (2) , C. Mclandress (1)

1 University of Toronto
2 University of California

During past MANTRA campaigns, ground-based measurements of several long-lived chemical species have revealed quasi-periodic fluctuations on time scales of several days. These fluctuations could confound efforts to detect long-term trends from MANTRA, and need to be understood and accounted for. Using the Canadian Middle Atmosphere Model, we investigate the role of dynamical variability in the late summer stratosphere due to normal mode Rossby waves and the impact of this variability on fluctuations in chemical species. Wavenumber~1, westward travelling waves are considered with average periods of 5, 10 and 16 days. Time-lagged correlations between the temperature and nitrous oxide, methane and ozone fields are calculated in order to assess the possible impact of these waves on the chemical species, although transport may be the dominant effect. Using Fourier-wavelet decomposition and correlating the fluctuations between the temperature and chemical fields, we determine that variations in the chemical species are well-correlated with the 5-day wave and the 10-day wave between 30 and 60 km. Interannual variability of the waves is also examined.

Domaines: Océan, Atmosphère

D. Pendlebury, T. G. Shepherd, M. Pritchard, C. Mclandress. Normal mode Rossby waves and their effects on chemical composition in the late summer stratosphere. Atmospheric Chemistry and Physics Discussions, 2007, 7 (4), pp.12011-12033. ⟨hal-00303052⟩