Kimoto, M., and M. Ghil 1993b Multiple flow regimes in the Northern Hemisphere winter. Part II: Sectorial regimes and preferred transitions, J. Atmos. Sci., 50, 2645--2673.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....circulation patterns is a problem which has attracted a significant amount of attention in atmospheric science. As defined in the atmospheric science literature, regimes are recurrent and persistent spatial patterns which can be identified from atmospheric data sets (Cheng and Wallace, 1993; Kimoto and Ghil, 1993). The most widely used data set for these studies consists of daily measurements since 1947 of geopotential height on a spatial grid of over 500 points in the Northern Hemisphere (NH) Geopotential height is the height in meters at which the atmosphere attains a certain pressure (e.g. one has ....

....flow fields is difficult. This has motivated the use of a variety of cluster analysis algorithms to objectively classify observed geophysical fields into a small set of preferred regimes or categories, e.g. fuzzy clustering (Mo and Ghil, 1988) kernel density estimation and bump hunting (Kimoto and Ghil, 1993), hierarchical clustering (Cheng and Wallace, 1993) and least squares (or k means) clustering (Michelangeli, Vautard, and Legras (1995) While these approaches have produced useful and repeatable results (in terms of significant cluster patterns) there is nonetheless a degree of subjectivity ....

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Kimoto, M., and Ghil, M., `Multiple flow regimes in the Northern hemisphere winter: Part I: methodology and hemispheric regimes,' J. Atmos. Sci., 50(16), pp.2625--2643, 1993.

....1988; Vautard et al. 1990; Kimoto and Ghil, 1993b) On longer time scales, there is evidence that SST anomalies, especially in the tropics, bias the quasi stationary statistics and transition probabilities of observed weather regimes (Ghil and Childress, 1987, Sec. 6. 5; Horel and Mechoso, 1988; Kimoto, 1989, Fig. 64 there; Palmer, 1993) 8 Since there is no unique or optimal definition of planetary flow regimes (Legras and Ghil, 1985) or weather regimes (Rheinhold and Pierrehumbert, 1982) we apply two independent methods to derive them: the probability density function (PDF) bump hunting ....

....of the atmospheric response to mid latitude SST anomalies. Indeed, Legras and Ghil (1985) Ghil and Childress (1987, Sec. 6. 5) and Palmer (1993) suggested a shift in the frequency of occurrence of Northern Hemisphere weather regimes as a result of changes in tropical SST anomalies, while Kimoto (1989, Fig. 64 there) and Horel and Mechoso (1988) found observational and GCM evidence for such a shift. 15 Conventionally, the difference between time means of a control and an anomaly experiment has been used to measure the response of an atmospheric GCM to an SST anomaly. The SST anomaly ....

Kimoto, M., 1989: Multiple Flow Regimes in the Northern Hemisphere Winter. Ph.D. thesis, University of California, Los Angeles, CA, 210pp.

.... these constraints, we present a cluster analysis of daily low pass filtered geopotential height data (using a filter with a halfpower point at 10 days, Blackmon and Lau, 1980) Here we select the 700 mb level for ease of comparison with previous observational studies of weather regimes (e.g. Kimoto and Ghil, 1993; Michelangeli et al. 1995) The aim of this analysis is to assign daily maps of intraseasonal fluctuations into clusters that describe the structure of the model atmosphere s 11 probability density function (PDF) Our guiding paradigm is the hypothesis that the relatively small amplitudes of ....

....were concatenated into a single 60 winter series, from which the mean seasonal cycle of CTRL was subtracted on a daily basis. The resulting time series was then truncated spatially by projecting onto its leading 4 EOFs, thereby retaining 74 of the variance. The PDF bump hunting method of Kimoto and Ghil (1993) was applied to the (daily) points in this EOF subspace. The kernel method was used to estimate the PDF as in Robertson et al. 1997) with the smoothing parameter set to 35 o . Regimes are defined within a 30 o radius of the bump centers; the latter corresponds to including all (lowpass ....

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Kimoto, M., and M. Ghil, 1993: Multiple flow regimes in the Northern Hemisphere winter.

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Kimoto, M. and M. Ghil, 1993: Multiple flow regimes in the northern hemisphere winter. Part II: Sectorial regimes and preferred transitions. J. Atmos. Sci., 16, 2645--2673.

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M. Kimoto and M. Ghil, Multiple flow regimes in the Northern Hemisphere winter. Part II: Sectorial regimes and preferred transitions, J. Atmos. Sci. 50:2645--2673 (1993).

....onsets of weather regimes over the Pacific, as well as the break ups of hemispheric scale regimes. Introduction Observational studies show that, above a broad band background, midlatitude low frequency variability (LFV) is characterized by intermittent weather regimes [Cheng and Wallace, 1993; Kimoto and Ghil, 1993], and 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 scale ....

.... To check the potential significance of our findings 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 ....

Kimoto, M. and M. Ghil, Multiple flow regimes in the Northern Hemisphere winter, J. Atmos. Sci., 50, 2625-2673, 1993.

....of weather regimes over the Pacific, as well as the break ups of hemispheric scale regimes. 3 Introduction Observational studies show that, above a broad band background, midlatitude low frequency variability (LFV) is characterized by intermittent weather regimes [Cheng and Wallace, 1993; Kimoto and Ghil, 1993], and 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 scale ....

.... To check the potential significance of our findings 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 ....

Kimoto, M. and M. Ghil, Multiple flow regimes in the Northern Hemisphere winter, J. Atmos. Sci., 50, 2625-2673, 1993.

.... effectively extracted from 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 third PAC EOF (Figure 2c) corresponds to 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 ....

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Kimoto, M. and M. Ghil, Multiple flow regimes in the Northern Hemisphere winter, J. Atmos. Sci., 50, 2625-2673, 1993.

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--194. Kimoto, M. and M. Ghil, 1993a: Multiple flow regimes in the Northern Hemisphere winter. Part I: Methodology and hemispheric regimes. J. Atmos. Sci., 50, 2625--2643.

.... effectively extracted from 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 ....

.... The third PAC EOF (Figure 2c) corresponds to 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 ....

[Article contains additional citation context not shown here]

Kimoto, M. and M. Ghil, Multiple flow regimes in the Northern Hemisphere winter, J. Atmos. Sci., 50, 2625-2673, 1993.

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Kimoto, M., and M. Ghil 1993b Multiple flow regimes in the Northern Hemisphere winter. Part II: Sectorial regimes and preferred transitions, J. Atmos. Sci., 50, 2645--2673.

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Kimoto, M., and M. Ghil 1993a Multiple flow regimes in the Northern Hemisphere winter. Part I: Methodology and hemispheric regimes, J. Atmos. Sci., 50, 2625--2643.

No context found.

Kimoto, M., and Ghil, M., `Multiple flow regimes in the Northern hemisphere winter: Part I: methodology and hemispheric regimes,' J. Atmos. Sci., 50(16), pp.2625--2643, 1993.

No context found.

Kimoto, M., and M. Ghil, 1993b: Multiple flow regimes in the Northern Hemisphere winter: Part II: Sectorial regimes and preferred transitions. J. Atmos. Sci., 50, 2645--2673.

No context found.

Kimoto, M., and M. Ghil, 1993a: Multiple flow regimes in the Northern Hemisphere winter: Part I: Methodology and hemispheric regimes. J. Atmos. Sci., 50, 2625--2643.

No context found.

Kimoto, M., and M. Ghil, 1993b: Multiple flow regimes in the Northern Hemisphere winter: Part II: Sectorial regimes and preferred transitions. J. Atmos. Sci., 50, 2645--2673.

No context found.

Kimoto, M., and M. Ghil, 1993a: Multiple flow regimes in the Northern Hemisphere winter: Part I: Methodology and hemispheric regimes. J. Atmos. Sci., 50, 2625--2643.

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