Abstract
Motivated by the mid-latitude atmospheric circulation, we develop a system that uses observations from a differentially heated rotating annulus experiment to constrain a numerical simulation in real-time. The coupled physical-numerical system provides a tool to rapidly prototype new methods for state and parameter estimation, and facilitates the study of prediction, predictability, and transport of geophysical fluids where observations or numerical simulations would not independently suffice. A computer vision system is used to extract measurements from the physical simulation, which constrain the model-state of the MIT general circulation model in a hybrid data assimilation approach. Using a combination of parallelism, domain decomposition and an efficient scheme to select ensembles of model-states, we show that estimates that effectively track the fluid-state can be produced. To the best of our knowledge, this is the first realtime coupled system for this laboratory analog of planetary circulation.
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Notes
The state for assimilation consists of the horizontal velocities and temperature. Vertical velocity is implicit, pressure is diagnostic and salinity is unrepresented.
This formulation is discussed for its simplicity. Other variations, e.g. explicit inverse, will be useful for small state sizes.
\({\bar{\mathbf{V}}}^{\rm f} = \frac{1}{S}\sum_{i=1}^S {\mathbf V}^{\rm f}[:,i]\)
Except near annulus boundaries, where the window is off-center.
A large number of matrices C ij are identical, thus saving storage costs.
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Acknowledgments
This work is funded by CNS-0540259 and NSF Grant CNS-0540248. The authors thank Ryan Abernathy for helping with the hardware platform development.
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Ravela, S., Marshall, J., Hill, C. et al. A realtime observatory for laboratory simulation of planetary flows. Exp Fluids 48, 915–925 (2010). https://doi.org/10.1007/s00348-009-0752-0
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DOI: https://doi.org/10.1007/s00348-009-0752-0