Data Assimilation Meetings at Reading

Date Meeting type Speakers
30 Jan 2013 Invited speaker Laure Zanna (University of Oxford)
Modelling & predicting climate with dice.
The ocean contains a vigorous mesoscale eddy field with spatial scales of approximately 10 to 100km, evolving over time scales from weeks to months. These eddies are important in establishing the ocean's circulation and tracer properties. Grid spacing of roughly 10 km and smaller are necessary to properly simulate the eddy field, therefore ocean climate models are unlikely to routinely resolve geostrophic eddies and their effect needs to be parametrized. The goal of our study is to construct a stochastic parameterization of ocean mesoscale eddies using the output of high resolution model in order to replace or improve current deterministic closure schemes.
A quasi-geostrophic (QG) model in a double-gyre configuration is run at resolution of 7.5 km (eddy-resolving). The output of the high-resolution model is coarse-grained and used to calculate probability distribution functions for the eddy forcing conditioned on the model state. The parametrization is then derived using the evaluated conditional probability distribution functions and implemented into a coarse resolution run of the QG model. The dynamics of the mean flow, its variability and eddy-mean flow interaction with the new parametrization are examined and compared with deterministic closures of geostrophic eddies in a set of preliminary numerical experiments, all showing some promising results.

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