A Nonhomogeneous Hidden Markov Model for Precipitation
نویسندگان
چکیده
A stochastic model for relating precipitation occurrences at multiple rain gauge stations to broad-scale atmospheric circulation patterns (the so-called \downscaling problem") is proposed. The model is an example of a nonhomogeneous hidden Markov model and generalizes existing downscaling models in the literature. The model assumes that atmospheric circulation can be classi ed into a small number of (unobserved) discrete patterns (called \weather states"). The weather states are assumed to follow a Markov chain in which the transition probabilities depend on observable characteristics of the atmosphere (e.g. mean sea-level pressure). Precipitation is assumed to be conditionally temporally independent given the weather state. An autologistic model for multivariate binary data is used to model rainfall occurrences and capture local spatial dependencies. A modi ed EM algorithm based on Markov chain maximum likelihood procedures is developed for estimation. This approach is used to model a 15 year sequence of winter data from 30 rain stations in southwestern Australia. The rst 10 years of data are used for model development and the remaining 5 years are used for model evaluation. The tted model is able to accurately reproduce the observed rainfall statistics in the reserved data, even in the face of a non-stationary shift in atmospheric circulation (and, consequently, rainfall) between the two periods. The tted model also provides some useful insights into the processes driving rainfall in this region. We discuss the role that models such as this might play in assessing the impact of climate change.
منابع مشابه
A Nonhomogeneous Hidden Markov Model for Precipitation Occurrence
A nonhomogeneous hidden Markov model is proposed for relating precipitation occurrences at multiple rain gauge stations to broad-scale atmospheric circulation patterns (the so-called \downscaling problem"). We model a 15 year sequence of winter data from 30 rain stations in southwestern Australia. The rst 10 years of data are used for model development and the remaining 5 years are used for mod...
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