scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Assimilation of Earth Orientation Parameters to Constrain Natural Variability in an
Atmospheric Model
Neef Lisa , Matthes Katja
GFZ German Research Centre For Geosciences
It has been known for some time that global-scale atmospheric modes of variability, such as
ENSO, affect the global atmospheric angular mometum (AAM). The vector components of
AAM can furthermore be inferred from the parameters which define the earth's rotational rate
and axis. These earth orientation parameters (EOPs) are regularly observed by a variety of
methods and intruments, and provide a new constraint for the simulation of natural climate
signals in earth system models.
Here we discuss the problem of formally assimilating observed EOPs, most notably the rate of
rotation of the Earth (i.e. the length of day) into the global atmosphere model
ECHAM5/MESSy. Using a conceptual model, we illustrate and discuss the problem of
assimilating a global integral quantity in order to infer information about individual
components of a model state. We also present a full diagnosis of the representation of AAM
in the ECHAM/MESSy atmosphere, as well as a discussion of our progress towards an
operational assimilation system.