Impact of energetic particle precipitation on stratospheric polar constituents: an assessment using monitoring and assimilation of operational MIPAS data 1Atmospheric Science and Technology Directorate, Environment Canada, 2121 Trans-Canada Highway, H9P 1J3, Dorval (Québec), Canada
2Belgium Institute for Space Aeronomy, Avenue Circulaire 3, 1180, Bruxelles, Belgium
3Atmospheric Science and Technology Directorate, Environment Canada, 4905 Dufferin Street, M3H 5T4, Toronto, Ontario, Canada
Received: 23 September 2009 – Published in Atmos. Chem. Phys. Discuss.: 23 October 2009 Abstract. In 2003, strong energetic particle precipitation (EPP) events occurred
producing massive amounts
of ionization which affected the polar region significantly perturbing
its chemical state down to the middle stratosphere.
These events and their effects are generally left unaccounted for in current
models of stratospheric chemistry and large differences between observations
and models are then noted. In this study, we use a coupled 3-D stratospheric
dynamical-chemical model and assimilation system to ingest MIPAS temperature
and chemical observations. The goal is to gain further understanding of
assimilation and monitoring processes during EPP events and their
impacts on the stratospheric polar chemistry.
Moreover, we investigate the feasibility of assimilating valid "outlier"
observations associated with such events. We use OmF (Observation minus
Forecast) residuals as they filter out phenomena well reproduced by the
model (such as gas phase chemistry, transport, diurnal and seasonal cycles)
thus revealing a clear trace of the EPP. Inspection of OmF statistics in both
passive (without chemical assimilation) and active (with chemical
assimilation) cases altogether provides a powerful diagnostic tool to assess
the model and assimilation system. We also show that passive OmF can permit a
satisfactory evaluation of the ozone partial column loss due to EPP effects.
Results suggest a small but significant loss of 5–6 DU (Dobson Units) during
an EPP-IE (EPP Indirect Effects) event in the Antarctic winter of 2003, and
about only 1 DU for the SPE (Solar Proton Event) of October/November 2003.
Despite large differences between the model and MIPAS chemical observations
(NO2, HNO3, CH4 and O3), we demonstrate that a careful
assimilation with only gas phase chemistry included in the model (i.e. no
provision for EPP) and with relaxed quality control nearly eliminated the
short-term bias and significantly reduced the standard deviation error of
the constituents below 1 hPa.
Revised: 28 January 2010 – Accepted: 04 February 2010 – Published: 16 February 2010
Citation: Robichaud, A., Ménard, R., Chabrillat, S., de Grandpré, J., Rochon, Y. J., Yang, Y., and Charette, C.: Impact of energetic particle precipitation on stratospheric polar constituents: an assessment using monitoring and assimilation of operational MIPAS data, Atmos. Chem. Phys., 10, 1739-1757, doi:10.5194/acp-10-1739-2010, 2010.