Abstract:
As part of an effort to build an integrated observation and modeling system for the
New York Bight, this study explores observing system design using a representer-based
method. The Representer of a single observation describes the covariance between the
observed quantity and ocean state at all locations at any time. It is related closely to the
influence of the observation on control variable correction in a 4D Variational data
assimilation system. We prove that these properties hold for the combination of
representers that is associated with an arithmetic function of model variables or a group
of observations. The representer-based method is used here to identify which of a set of
proposed tracks for an autonomous coastal glider is better for predicting horizontal salt
flux within the Hudson Shelf Valley in a 2-day forecast period. Twin experiments
confirm the result. The system is also used to compare different observation strategies.
We show that a glider that traverses a regular transect influences a larger area than a
continuously profiling mooring, but the mooring carries stronger influence at the
observation location. The representer analysis shows how the information provided by
observations extends toward the dynamically upstream and how increasing the duration
of the analysis window captures more dynamical connections and expands the area of
influence of the observations in data assimilation. Overall, the study demonstrates that the
representer methodology can quantitatively contrast different observational strategies and
determine spatial patterns and temporal extent of the influence of observations, both of
which are helpful for evaluating the design of observation networks.
Description:
Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Ocean Modelling 35 (2010): 134-145, doi:10.1016/j.ocemod.2010.06.006.
