Normal mode Rossby waves and their effects on chemical composition in the late summer stratosphere D. Pendlebury1, T. G. Shepherd1, M. Pritchard1,2, and C. McLandress1 1University of Toronto, Toronto, Canada 2now at: University of California, San Diego, USA
Abstract. 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.
Zonal 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.
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- and 10-day waves between 30 and 60 km, although the nature of the correlations depend
strongly on altitude. Interannual variability of the waves is also examined.
Citation: Pendlebury, D., Shepherd, T. G., Pritchard, M., and McLandress, C.: Normal mode Rossby waves and their effects on chemical composition in the late summer stratosphere, Atmos. Chem. Phys., 8, 1925-1935, doi:10.5194/acp-8-1925-2008, 2008.