Smyth, P., K. Ide and M. Ghil 1999 Multiple Regimes in Northern Hemisphere Height Fields via Mixture Model Clustering. J. Atmos. Sci., 56, 3704--3723.  Home/Search   Document Details and Download   Summary   Related Articles   Check

.... for extended range prediction, we have isolated the dominant patterns of atmospheric LFV using an analysis of weather regimes [Ghil et al. 1991] Our analysis reproduces the NH and PAC regimes found in previous studies during the winter months [Kimoto and Ghil, 1993; Cheng and Wallace, 1993; Smyth et al. 1999]. The first and third hemispheric regimes, by frequency of occurrence, resemble contrasting phases of the AO, i.e. of NH EOF 2 (Figure 2b) NH mountain torque variations in the 15 30 day band contribute to the break up of both of these regimes. Over the PAC sector, we find that unfiltered torque ....

Smyth, P., Ide, K. and M. Ghil, Multiple regimes in northern hemisphere height fields via mixture model clustering, J. Atmos. Sci., 56, 3704-3723, 1999.

.... for extended range prediction, we have isolated the dominant patterns of atmospheric LFV using an analysis of weather regimes [Ghil et al. 1991] Our analysis reproduces the NH and PAC regimes found in previous studies during the winter months [Kimoto and Ghil, 1993; Cheng and Wallace, 1993; Smyth et al. 1999]. The first and third hemispheric regimes, by frequency of occurrence, resemble contrasting phases of the AO, i.e. of NH EOF 2 (Figure 2b) NH mountain torque variations in the 15 30 day band contribute to the break up of both of these regimes. Over the PAC sector, we find that unfiltered torque ....

Smyth, P., Ide, K. and M. Ghil, Multiple regimes in northern hemisphere height fields via mixture model clustering, J. Atmos. Sci., 56, 3704-3723, 1999.

.... time series of weather maps using empirical orthogonal functions (EOFs) Preisendorfer, 1988; Molteni et al. 1988] Observational studies show that, above a broad band background, midlatitude LFV is characterized by intermittent weather regimes [Cheng and Wallace, 1993; Kimoto and Ghil, 1993; Smyth et al. 1999], but also by intraseasonal oscillations [Branstator, 1987; Kushnir, 1987; Ghil et al. 1991] The latter are known to be modulated by tropical convection at the 30 60 day time scale of the Madden Julian Oscillation (MJO) Madden and Julian, 1994; Higgins and Mo, 1997] and the 2 6 year time ....

.... an east west dipole centered over the Rockies that resembles the PNA pattern [Wallace and Gutzler, 1981] its primary center of action, over the northeastern Pacific, describes an anomalous extension or contraction of the jet stream in this sector [Kimoto and Ghil, 1993; Cheng and Wallace, 1993; Smyth et al. 1999]. We project the individual 700 hPa height maps onto the three EOFs in Figure 2 to obtain the corresponding principal components (PCs) Preisendorfer, 1988] Each of their MTM power spectra (not shown) exhibits several significant peaks in the 15 30 day band. To quantify the correspondence ....

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Smyth, P., Ide, K. and M. Ghil, Multiple regimes in northern hemisphere height fields via mixture model clustering, J. Atmos. Sci., 56, 3704-3723, 1999.

.... time series of weather maps using empirical orthogonal functions (EOFs) Preisendorfer, 1988; Molteni et al. 1988] Observational studies show that, above a broad band background, midlatitude LFV is characterized by intermittent weather regimes [Cheng and Wallace, 1993; Kimoto and Ghil, 1993; Smyth et al. 1999], but also by intraseasonal oscillations [Branstator, 1987; Kushnir, 1987; Ghil et al. 1991] The latter are known to be modulated by tropical convection at the 30 60 day time scale [Legras and Ghil, 1985; Jin and Ghil, 1990; Strong et al. 1995] arising from the seminal work of Charney and ....

.... an east west dipole centered over the Rockies that resembles the PNA pattern [Wallace and Gutzler, 1981] its primary center of action, over the northeastern Pacific, describes an anomalous extension or contraction of the jet stream in this sector [Kimoto and Ghil, 1993; Cheng and Wallace, 1993; Smyth et al. 1999]. We project the individual 700 hPa height maps onto the three EOFs in Figure 2 to obtain the corresponding principal components (PCs) Preisendorfer, 1988] Each of their MTM power spectra (not shown) exhibits several significant peaks in the 15 30 day band. To quantify the correspondence ....

[Article contains additional citation context not shown here]

Smyth, P., Ide, K. and M. Ghil, Multiple regimes in northern hemisphere height fields via mixture model clustering, J. Atmos. Sci., 56, 3704-3723, 1999.

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Smyth, P., K. Ide and M. Ghil 1999 Multiple Regimes in Northern Hemisphere Height Fields via Mixture Model Clustering. J. Atmos. Sci., 56, 3704--3723.

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Smyth, P., K. Ide, and M. Ghil, 1999: Multiple regimes in northern hemisphere height fields via mixture model clustering. J. Atmos. Sci., 56, 3704--3723.

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Smyth, P. (1999a). Multiple regimes in Northern hemisphere height fields via mixture model clustering. Journal of the Atmospheric Sciences, 56:3704--3723.

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Smyth, P., M. Ghil, and K. Ide, `Multiple regimes in Northern hemisphere height fields via mixture model clustering,' Technical Report UCI-ICS 98--08, Information and Computer Science, University of California, Irvine, 1998.

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P. Smyth, K. Ide, and M. Ghil, Multiple regimes in Northern Hemisphere height fields via mixture model clustering, J. Atmos. Sci. 56:3704--3723 (1999).

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Smyth, P. (1999a). Multiple regimes in northern hemisphere height fields via mixture model clustering. Journal of the Atmospheric Sciences, 56:3704--3723.

....(e.g. Kimoto and Ghil (1993) namely, daily observations of the NH 700 mb geopotential heights on a 10 o Theta 10 o diamond grid (with 541 grid points) compiled at NOAA s Climate Analysis Center. The data are subject to a number of specific preprocessing steps (full details are provided in Smyth, Ghil and Ide (1998)) For the purposes of this paper it is sufficient to know that the daily 541 spatial grid points (or maps) are treated as 541 dimensional data vectors and then projected into a subspace defined by a few leading principal component directions for this 541 dimensional space. We will use the ....

....BIC 1923.6 1869.7 1853.3 1878.7 1906.6 1931.2 CV Likelihood 982.7 967.7 949.1 963.2 967.8 972.8 BIC datapoint 0.486 0.472 0.468 0.474 0.481 0.489 CV Likelihood datapoint 0.496 0.489 0.479 0.486 0.489 0. 491 results, and various extensions, are described in more detail in Smyth, Ghil, and Ide (1998)) In all experiments the number of cross validation partitions was M = 100 and the fraction of data fi contained in each test partition was set to 0.5. The number of clusters (mixture components) was varied from k = 1 to k = 15. The log likelihoods for k 6 were invariably much lower than those ....

[Article contains additional citation context not shown here]

Smyth, P., M. Ghil, and K. Ide, `Multiple regimes in Northern hemisphere height fields via mixture model clustering,' Technical Report UCI-ICS 98--08, Information and Computer Science, University of California, Irvine, 1998.

....we will use mixtures of regression models as the basis for clustering. Mixtures of multivariate (vector based) distributions and densities have been widely used for probabilistic clustering in the past (e.g. McLachlan and Basford (1988) Banfield and Raftery (1993) Cheeseman and Stutz (1996) Smyth et al. (1997), Fraley and Raftery (1998) and Smyth, Ide, and Ghil (in press) However, none of this work extends directly to trajectory clustering unless one uses a vector representation for the data. The work of Stanford and Raftery (1997) on mixture models for finding clusters in two dimensional spatial ....

Smyth, P., M. Ghil, and K. Ide, `Multiple regimes in Northern hemisphere height fields via mixture model clustering,' Journal of Atmospheric Science, in press. Stanford, D. and Raftery, A. E., `Principal curve clustering with noise,' Technical Report No. 317, Department of Statistics, University of Washington, February 1997.

....It is important to keep in mind that this technique is model based, i.e. we are hypothesizing a data generating mechanism (in the form of the density function f) for the observed data. Probabilistic model based clustering (e.g. see McLachlan and Basford (1988) Stutz and Cheeseman (1996) Smyth (1996) and Fraley and Raftery (1998)) builds on this idea by hypothesizing that the data are being generated by K different models. These K models correspond to the K clusters of interest. A particularly useful model of this form is the finite mixture model, which has the general form: f(x) K X k=1 f k (xj k )ff k (1) where ....

Smyth, P., M. Ghil, and K. Ide, `Multiple regimes in Northern hemisphere height fields via mixture model clustering,' Journal of Atmospheric Science, accepted for publication, December 1998.

....(e.g. Kimoto and Ghil (1993) namely, daily observations of the NH 700 mb geopotential heights on a 10 o Theta10 o diamond grid (with 541 grid points) compiled at NOAA s Climate Analysis Center. The data are subject to a number of specific preprocessing steps (full details are provided in Smyth, Ghil and Ide (1998)) For the purposes of this paper it is sufficient to know that the daily 541 spatial grid points (or maps) are treated as 541 dimensional data vectors and then projected into a subspace defined by a few leading principal component directions for this 541 dimensional space. We will use the ....

....the means. 4.2 Application of Mixture Model Clustering We applied the mixture model cross validation methodology to the data described in Section 4.1, using Gaussian components with unconstrained (full) covariance matrices. These results, and various extensions, are described in more detail in Smyth, Ghil, and Ide (1998)) In all experiments the number of cross validation partitions was M = 20 and the fraction of data fi contained in each test partition was set to 0.5. The number of clusters (mixture components) was varied from k = 1; 15. The log likelihoods for k 6 were invariably much lower than those ....

[Article contains additional citation context not shown here]

Smyth, P., M. Ghil, and K. Ide, `Multiple regimes in Northern hemisphere height fields via mixture model clustering,' Technical Report UCI-ICS 98--08, Information and Computer Science, University of California, Irvine, 1998.

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Padhraic Smyth, K. Ide, and M. Ghil, "Multiple Regimes in Northern Hemisphere Height Fields via Mixture Model Clustering," Journal of Atmospheric Science, 56, 37043723 (1999).

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