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## Ensemble forecasting at NCEP and the breeding method (1997)

Venue: | Mon. Wea. Rev |

Citations: | 191 - 15 self |

### Citations

2922 | The NCEP/NCAR 40-Year Reanalysis Project - Kalnay, Coauthors - 1996 |

496 |
Atmospheric Data Analysis
- Daley
- 1991
(Show Context)
Citation Context ...hastic component. The similarity between the analysis and breeding cycles is stronger on the small scales and over data-poor regions where the analysis is based primarily on the first-guess forecast (=-=Daley 1991-=-). Over data-rich regions and on the larger scales the observations can better remove the growing errors from the first guess but since current operational analysis techniques do not have knowledge ab... |

454 | Determining lyapunov exponents from a time series
- Wolf, Swift, et al.
- 1985
(Show Context)
Citation Context ...mportantly, if a system has at least one positive global Lyapunov exponent, its behavior is chaotic, that is, arbitrarily close points on the attractor will eventually separate into unrelated points (=-=Wolf et al. 1985-=-). When the Lyapunov exponents are interpreted locally, each of them can be associated with a perturbation vector, I. The first of these vectors, with the largest exponent, can be uniquely determined:... |

282 | The ECMWF ensemble prediction system: methodology and validation - Molteni, Buizza, et al. - 1996 |

274 |
The national meteorological centers spectral statistical-interpolation analysis system, Monthly Weather Review 120 (8
- Parrish, Derber
- 1992
(Show Context)
Citation Context ...nation of possible analysis errors. a. Growing and nongrowing errors A typical operational analysis performed with optimal interpolation or spectral statistical interpolation (see, e.g., Lorenc 1981; =-=Parrish and Derber 1992-=-) is a weighted average of 1) observational measurements and 2) a short-range dynamical forecast (first guess), started from the preceeding analysis. It has been long recognized that the resulting ana... |

249 |
Ensemble forecasting at NMC: The generation of perturbations
- Toth, Kalnay
- 1993
(Show Context)
Citation Context ...he National Meteorological Center), the bred vectors, which represent a nonlinear extension of the Lyapunov vectors (the fastest growing perturbations on the attractor) are used for the same purpose (=-=Toth and Kalnay 1993-=-). In yet another approach, Houtekamer et al. (1996) use multiple analysis cycles (with perturbed observational data and different model formulations) for generating initial ensemble perturbations. Th... |

132 | A system simulation approach to ensemble prediction - Houtekamer, Lefaivre, et al. - 1996 |

127 | The singular-vector structure of the atmospheric global circulation - Buizza, Palmer - 1995 |

110 |
Theoretical skill of Monte Carlo forecast
- Leith
- 1974
(Show Context)
Citation Context ...een accepted that running an ensemble of numerical forecasts from slightly perturbed initial conditions can have a beneficial impact on the skill of the forecast by means of ensemble averaging (e.g., =-=Leith 1974-=-). Beyond providing a better estimate of the first * Additional affiliation: General Sciences Corporation, Laurel, Maryland. Corresponding author address: Dr. Zoltan Toth, Environmental Modeling Cente... |

106 |
A global three-dimensional multivariate statistical interpolation scheme
- Lorenc
- 1981
(Show Context)
Citation Context ...careful examination of possible analysis errors. a. Growing and nongrowing errors A typical operational analysis performed with optimal interpolation or spectral statistical interpolation (see, e.g., =-=Lorenc 1981-=-; Parrish and Derber 1992) is a weighted average of 1) observational measurements and 2) a short-range dynamical forecast (first guess), started from the preceeding analysis. It has been long recogniz... |

99 |
A study of the predictability of a 28-variable atmospheric model
- Lorenz
- 1965
(Show Context)
Citation Context ... a small number of vectors. 1 1 The fact that in the atmosphere all perturbations (and errors in a perfect model environment) tend to turn toward the leading Lyapunov vectors within a couple of days (=-=Lorenz 1965-=-; Szunyogh et al. 1997) ensures that even suboptimal ensemble perturbations, that do not appreciably project onto the actual error field, will have a positive impact beyond a few days lead time. 3. Er... |

55 |
A numerical approach to ergodic problems of dissipative dynamical systems, Prog
- Shimada, Nagashima
- 1979
(Show Context)
Citation Context ...in the breeding method, has been applied. Rescaling in these linear methods, however, is used to avoid computer overflow, not to prevent/control nonlinear saturation (see, e.g., Benettin et al. 1976; =-=Shimada and Nagashima 1979-=-). New aspects of the breeding method proposed by Toth and Kalnay (1993) are that perturbations are developed for a 1) complex physical system, in a 2) nonlinear framework, at a 3) high horizontal and... |

53 | Optimal prediction of forecast error covariances through singular vectors - Ehrendorfer, Tribbia - 1997 |

50 |
Predictability and finite-time instability of the northern winter circulation
- Molteni, Palmer
- 1993
(Show Context)
Citation Context ... a full model to compute the initial perturbations that grow fastest over a specified period, measured with a given norm (Lorenz 1965). In its application to ensemble forecasting at ECMWF (see, e.g., =-=Molteni and Palmer 1993-=-; Buizza and Palmer 1995; Molteni et al. 1996), the fastest growing perturbations are determined for a 48-h forecast tra2 Correlation is the cosine of the angle between two directions in phase space. ... |

49 |
Kalnay,1993: Operational ensemble prediction at the National Meteorological Center: Practical aspects. Wea. Forecasting
- Tracton, E
(Show Context)
Citation Context ...al Meteorological Center), the bred vectors, which represent a nonlinear extension of the Lyapunov vectors (the fastest growing perturbations on the attractor) are used for the same purpose (Toth and =-=Kalnay 1993-=-). In yet another approach, Houtekamer et al. (1996) use multiple analysis cycles (with perturbed observational data and different model formulations) for generating initial ensemble perturbations. Th... |

45 | Estimating the covariance matrices of analysis and forecast error in variational data assimilation - Fisher, Courtier - 1995 |

45 |
Objective analysis of meteorological fields. Israel Program for Scientific Translation
- Gandin
- 1965
(Show Context)
Citation Context ...s, 4 which, as we discussed in section 3b, are assumed to be more important in ensemble forecasting. Optimal interpolation (OI) could also be used to estimate the distribution of the analysis errors (=-=Gandin 1965-=-), but such an estimate is very dependent on the assumed error covariances for the forecast and the observations. In addition, the OI estimate would not properly account for the growing component of t... |

42 | Extended-range prediction and the - Palmer - 1993 |

30 |
Kolmogorov entropy and numerical experiments, Phys. Rev. A14
- Benettin, Galgani, et al.
- 1976
(Show Context)
Citation Context ...turbations, also used in the breeding method, has been applied. Rescaling in these linear methods, however, is used to avoid computer overflow, not to prevent/control nonlinear saturation (see, e.g., =-=Benettin et al. 1976-=-; Shimada and Nagashima 1979). New aspects of the breeding method proposed by Toth and Kalnay (1993) are that perturbations are developed for a 1) complex physical system, in a 2) nonlinear framework,... |

28 |
Problems and promises of deterministic extended-range forecasting
- Smagorinsky
- 1969
(Show Context)
Citation Context ...fore projecting, after one or two days, onto growing directions of the evolving basic flow. Such an initial decay was apparent in early experiments in atmospheric predictability (see, e.g., Fig. 4 in =-=Smagorinsky 1969-=-). Even if the random errors are balanced, they will still initially grow very slowly or decay. By contrast, ‘‘growing errors’’ will, by definition, amplify, so that they are primarily responsible for... |

15 | Estimates of global analysis error from the global weather experiment observational network - Daley, Mayer - 1986 |

15 |
Forecasting forecast skill
- Kalnay, Dalcher
- 1987
(Show Context)
Citation Context ...t skill (or the reliability of forecasts) in the time domain. This has been a subject of considerable research because of its importance for mediumand extended-range forecasts (e.g., Branstator 1986; =-=Kalnay and Dalcher 1987-=-; Palmer and Tibaldi 1988). If we can determine a priori which forecasts are going to be most skillful, the utility of extended-range forecasts can be considerably enhanced (e.g., Tracton et al. 1989)... |

13 |
A dynamical estimation of forecast error covariances in an assimilation system
- Bouttier
- 1994
(Show Context)
Citation Context ...ons are not enough to determine the state of the atmosphere, these dynamically developing errors cannot be removed at the next analysis time: their amplitude can only be reduced (see, e.g., Fig. 9 of =-=Bouttier 1994-=-).3300 MONTHLY WEATHER REVIEW VOLUME 125 So at the start of the next short-range forecast in the analysis cycle, dynamically developed errors are already present in the initial conditions ready to am... |

12 |
The relationship between spread and forecast error in extended-range forecasts
- Barker
- 1991
(Show Context)
Citation Context ...le forecasts are displayed in Fig. 9. The fact that the spread/ error PAC is low at short lead times is due to the presence of random errors in the initial conditions and verifying analyses (see also =-=Barker 1991-=-; Wobus and Kalnay 1995). Since there is a strong zonally symmetric component in the error fields, we computed the PAC of the spread/error both with (not shown) and without the zonal mean included. Th... |

10 |
A comparison of Lyapunov and Optimal vectors in a low resolution GCM. Tellus 48A
- Szunyogh, Kalnay, et al.
- 1997
(Show Context)
Citation Context ...er of vectors. 1 1 The fact that in the atmosphere all perturbations (and errors in a perfect model environment) tend to turn toward the leading Lyapunov vectors within a couple of days (Lorenz 1965; =-=Szunyogh et al. 1997-=-) ensures that even suboptimal ensemble perturbations, that do not appreciably project onto the actual error field, will have a positive impact beyond a few days lead time. 3. Errors in the analysis I... |

10 |
1995] “Transient error growth and local predictability: A study in the Lorenz system,” Tellus A
- Trevisan, Legnani
(Show Context)
Citation Context ...rs, this removal process cannot be complete (see Iyengar et al. 1996). b. Lyapunov vectors Theoretically, the bred perturbations are related to the local Lyapunov vectors of the atmosphere (LLVs, see =-=Trevisan and Legnani 1995-=-). The Lyapunov exponents (�i) have been widely used for characterizing the behavior of simple dynamical systems: ] 2[ 1 p i(t) �i � lim log , (3) t p (0) t→� where p is a linear perturbation spanning... |

9 |
Localization of optimal perturbations using a projection operator
- Buizza
- 1994
(Show Context)
Citation Context ...er that has to be chosen to reflect the size of initial error in the analysis. An estimate of the analysis error can be derived from optimal interpolation analysis techniques (see, e.g., Gandin 1965; =-=Buizza 1994-=-). However, since these estimates are subject to the statistical approximations made within the analysis scheme, we attempted to optimize the overall perturbation size experimentally by verifying ense... |

9 | A synoptic evaluation of the NCEP ensemble - Toth, Kalnay, et al. - 1997 |

7 |
Using ensembles to identify observations likely to improve forecasts
- Bishop, Toth
- 1996
(Show Context)
Citation Context ...ve side of the SV methodology is 3 A cheap alternative to using a traditional linear adjoint algorithm for targeting is a singular value decomposition in the subspace of an already existing ensemble (=-=Bishop and Toth 1996-=-).3306 MONTHLY WEATHER REVIEW VOLUME 125 FIG. 6. Relative regional uncertainty (for 500-hPa streamfunction) present in the control analysis as determined from the rms difference between two analyses ... |

7 |
Removing growing errors in the analysis
- Kalnay, Toth
- 1994
(Show Context)
Citation Context ...ervations. Recently, it was also pointed out that the repeated use of a model forecast as a first guess has a profound dynamical effect on the errors in the analysis (Toth and Kalnay 1993; Kalnay and =-=Toth 1994-=-). The analysis cycle can be considered as the running of a nonlinear perturbation model upon the true state of the atmosphere. The perturbation amplitude (i.e., the analysis error) is kept small by p... |

7 |
Three years of operational prediction of forecast skill at NMC Mon
- Wobus, Kalnay
- 1995
(Show Context)
Citation Context ...are displayed in Fig. 9. The fact that the spread/ error PAC is low at short lead times is due to the presence of random errors in the initial conditions and verifying analyses (see also Barker 1991; =-=Wobus and Kalnay 1995-=-). Since there is a strong zonally symmetric component in the error fields, we computed the PAC of the spread/error both with (not shown) and without the zonal mean included. The spread/skill spatial ... |

7 |
Objective evaluation of the NCEP global ensemble forecasting system
- Zhu, Iyengar, et al.
- 1996
(Show Context)
Citation Context ...relationship, an objective evaluation of the NCEP ensemble during the 1995/96 winter season strongly indicates that the system can effectively distinguish between cases with high and low uncertainty (=-=Zhu et al. 1996-=-). g. Size of the ensemble It was Leith (1974) who first considered the question of how many ensemble members are needed to improve the skill of the control forecast by ensemble averaging. Using a sim... |

6 |
On the prediction of forecast skill
- Palmer, Tibaldi
- 1988
(Show Context)
Citation Context ...ty of forecasts) in the time domain. This has been a subject of considerable research because of its importance for mediumand extended-range forecasts (e.g., Branstator 1986; Kalnay and Dalcher 1987; =-=Palmer and Tibaldi 1988-=-). If we can determine a priori which forecasts are going to be most skillful, the utility of extended-range forecasts can be considerably enhanced (e.g., Tracton et al. 1989). Here we will demonstrat... |

5 |
Prediction Experiments with Two-Member Ensembles
- Houtekamer, Derome
- 1994
(Show Context)
Citation Context ...control forecast, as long as the ensemble perturbations are representative of the initial probability distribution of the basic flow around the control analysis. Earlier studies (e.g., Houtekamer and =-=Derome 1994-=-; Toth and Kalnay 1993) using models of different sophistication confirmed Leith’s results. In this section we illustrate why this is the case by means of a very simple error growth example. Though th... |

4 | Lyapunov characteristic exponents for smooth dynamical systems and for Hamiltonian systems; a method for computing them - Giorgilli, Strelcyn - 1980 |

4 | Dynamical extended range forecasting (DERF) at the National Meteorological - Tracton, Mo, et al. - 1989 |

3 |
Ensemble experiments with a new lagged analysis forecasting scheme. Research Activities in Atmospheric and Oceanic Modelling
- Ebisuzaki, Kalnay
- 1991
(Show Context)
Citation Context ... that the growth rate in a breeding cycle depends on the amplitude of perturbations but is always larger than that obtained with other perturbation methods such as scaled lagged averaged forecasting (=-=Ebisuzaki and Kalnay 1991-=-, not shown), difference fields between short-range forecasts verifying at the same time (Toth and Kalnay 1993), or Monte Carlo perturbations (which have a wider range of growth rate values than the d... |

3 |
Medium–range ensembles using both the ECMWF T63 and unified models—An initial report
- Harrison, Richardson, et al.
- 1995
(Show Context)
Citation Context ...parison of experimental results. We conclude by noting that a combination of ensemble forecasts from different numerical prediction centers may give further improvement to the quality of an ensemble (=-=Harrison et al. 1995-=-). The benefits from having a larger number of forecasts, and using different analysis schemes, forecast models, and perturbation techniques may all contribute to the success of numerical weather pred... |

2 | Examination of actual analysis differences for use in Monte Carlo forecasting - Augustine, Mullen, et al. - 1991 |

2 |
Numerical extended-range prediction: Forecast skill using a low-resolution climate
- Baumhefner
- 1996
(Show Context)
Citation Context ...rbations, random analysis errors are also well represented in a statistical sense. In addition to the above sites, ensemble forecast experiments are under way at several other places, including NCAR (=-=Baumhefner 1996-=-). The different perturbation techniques have various potential advantages. Their impact on the quality of ensemble forecasts can be evaluated only after a careful comparison of experimental results. ... |

2 |
The variability in skill of 72-hour global-scale NMC forecasts
- Branstator
- 1986
(Show Context)
Citation Context ...ations of forecast skill (or the reliability of forecasts) in the time domain. This has been a subject of considerable research because of its importance for mediumand extended-range forecasts (e.g., =-=Branstator 1986-=-; Kalnay and Dalcher 1987; Palmer and Tibaldi 1988). If we can determine a priori which forecasts are going to be most skillful, the utility of extended-range forecasts can be considerably enhanced (e... |

2 | Available from ECMWF, Shinfield Park - Memo - 1963 |

2 |
Are the bred vectors representative of analysis error
- Iyengar, Toth, et al.
- 1996
(Show Context)
Citation Context ...ed (from random errors introduced in earlier analyses) by the repeated use of the forecast first guess. Adjoint-based sensitivity calculations (Langland and Rohaly 1996) and analysis error estimates (=-=Iyengar et al. 1996-=-) also point out the flow-dependent, dynamically conditioned nature of important analysis errors. b. Which type of error is important? If we could decompose and follow the development of the errors pr... |

2 |
The ensemble forecast system (EFS). Models Department Tech. Note 2-95, Fleet Numerical Meteorology and Oceanography Center, 19 pp. [Available from Models Department
- Rennick
- 1995
(Show Context)
Citation Context ...ion of a medium-range ensemble (Takano 1996, personal communication). At FNMOC and at the South3318 MONTHLY WEATHER REVIEW VOLUME 125 African Weather Bureau a breeding-based ensemble is operational (=-=Rennick 1995-=-; W. Tennant 1995, personal communication), while at the National Center for Medium Range Weather Forecasting in India a breedingbased ensemble system is being prepared to be implemented (G. Iyengar 1... |

2 | Singular, Lyapunov and bred vectors in ensemble forecasting - Szunyogh, Kalnay - 1996 |

1 | Short-range ensemble forecasting (SREF): Report from a workshop - Toth - 1995 |

1 | Recent changes in the global forecast system at NMC - Kanamitsu, Coauthors - 1991 |

1 |
Analysis error and adjoint sensitivity in prediction of a North Atlantic frontal cyclone
- Langland, Rohaly
- 1996
(Show Context)
Citation Context ... instabilities of the evolving flow, dynamically generated (from random errors introduced in earlier analyses) by the repeated use of the forecast first guess. Adjoint-based sensitivity calculations (=-=Langland and Rohaly 1996-=-) and analysis error estimates (Iyengar et al. 1996) also point out the flow-dependent, dynamically conditioned nature of important analysis errors. b. Which type of error is important? If we could de... |

1 |
Operational ensemble prediction—The NMC experience
- Tracton
- 1994
(Show Context)
Citation Context ... ensemble members every day. When the forecasts from the last two days are also considered for the extended range, the total number of ensemble members valid for two weeks is 46 (see Fig. 12 and also =-=Tracton 1994-=-). Based on the results of section 6b, the size of the initial perturbations is set at 12.5% and 25% of the total rms variance in the NH and SH, respectively. (During SH summer, the perturbation size ... |