On the extraction of wind information from the assimilation of ozone profiles in Météo–France 4-D-Var operational NWP suite 1CNRM-GAME, Météo-France and CNRS URA 1357, Toulouse, France
2CNRM, Direction de la Météorologie Nationale, Casablanca, Morocco
3CERFACS, Toulouse, France
4DP, Météo–France, Toulouse, France
Received: 24 Jun 2008 – Published in Atmos. Chem. Phys. Discuss.: 28 Aug 2008 – Published: 22 Jul 2009Abstract. By applying four-dimensional variational data-assimilation
(4-D-Var) to a combined ozone and dynamics Numerical Weather
Prediction model (NWP), ozone observations generate wind
increments through the ozone-dynamics coupling. The dynamical
impact of Aura/MLS satellite ozone profiles is investigated using
Météo-France operational ARPEGE NWP 4-D-Var assimilation
system for a period of 3 months. A data-assimilation procedure has
been designed and run on 6-h windows. The procedure includes: (1)
4-D-Var assimilating both ozone and operational NWP standard
observations, (2) ARPEGE transporting ozone as a
passive-tracer, (3) MOCAGE, the Météo–France chemistry
and transport model re-initializing the ARPEGE ozone
background at the beginning time of the assimilation window. Using
observation minus forecast statistics, it is found that the ozone
assimilation reduces the wind bias in the lower stratosphere.
Moreover, the Degrees of Freedom for Signal diagnostics show that
the MLS data covering the 68.1–31.6 hPa vertical pressure range
are the most informative and their information content is nearly
of the same order as tropospheric humidity-sensitive radiances.
Furthermore, with the help of error variance reduction
diagnostics, the ozone contribution to the reduction of the
horizontal divergence background-error variance is shown to be
better than tropospheric humidity-sensitive radiances.
Citation: Semane, N., Peuch, V.-H., Pradier, S., Desroziers, G., El Amraoui, L., Brousseau, P., Massart, S., Chapnik, B., and Peuch, A.: On the extraction of wind information from the assimilation of ozone profiles in Météo–France 4-D-Var operational NWP suite, Atmos. Chem. Phys., 9, 4855-4867, doi:10.5194/acp-9-4855-2009, 2009.