J4.4
A Bayesian framework for storm tracking using a hidden-state representation
Lucas Scharenbroich, University of California, Irvine, CA; and C. C. Wang, H. Stern, P. Smyth, and G. Magnusdottir
The problem of tracking is of fundamental interest in many scientific disciplines, especially the atmospheric sciences where it is natural to study objects of interest – storms, hurricanes and other coherent phenomena – by tracking their evolution over time. We propose a Bayesian tracking methodology which is built on a hidden state representation of an object's temporal behavior that obeys a Linear Dynamic Model (LDM). The dynamic model may either be constructed "by hand" from consideration of an underlying physical model, or trained from a representative set of storm tracks. We address the data association problem using a combination of systematic search (the A* algorithm) and Monte Carlo sampling to extract tracks from a set of feature detections. We efficiently marginalize over the possible associations to obtain posterior distributions over the genesis and lysis times of storms.
Our methodology is different from the well-known Hodges tracking algorithm, TRACK[1]. The data association process is formulated to be independent of any specific dynamic model which allows different models to be plugged into the same tracking framework, and the use of a hidden state model automatically produces smoothed tracks from noisy or grid-aligned feature detections. Our method provides numerical estimates of the strength of individual track segments, as well as rankings of tracks based on their likelihood under the chosen LDM.
We apply the Bayesian methodology to a multi-year set of vorticity fields from the NCEP Final Analysis and ERA40 data sets to generate tracks of Westward Propagating Disturbances (WPDs) in the tropical Pacific region. The set of tracks compare well with the Tropical Prediction Center best track data set and contain fewer irrelevant tracks than those produced by the TRACK algorithm.
[1] Kevin I. Hodges. A general method for tracking analysis and its application to meteorological data. Monthly Weather Review, 122(11):2573–2586, Nov. 1994
Joint Session 4, Bridging the Gap between Artificial Intelligence and Statistics in Applications to Environmental Science-II
Wednesday, 23 January 2008, 10:30 AM-12:00 PM, 219
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