As assessment of the singular‐vector approach to targeted observing using the FASTEX dataset

Gelaro, Ronald; Langland, Rolf H.; Rohaly, G. D.; Rosmond, Thomas E.

doi:10.1002/qj.49712556109

Cited by 93 publications

(18 citation statements)

References 23 publications

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“…For example, Gelaro et al (1999) showed that the impact of the additional observations during the FASTEX campaign occurs primarily as a result of changes to the analysis in the subspace of the leading SVs. Similarly, Gelaro et al (2000), although they did not attempt to estimate that added value of targeted observations, concluded that most of the improvement induced by satellite data over the northern Pacific during the NORPEX campaign resulted from changes to the analysis that project onto the leading SVs at the initial time.…”

Section: Discussionmentioning

confidence: 99%

The value of observations. II: The value of observations located in singular‐vector‐based target areas

Buizza

Cardinali

Kelly

et al. 2007

Quart J Royal Meteoro Soc

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Data-assimilation experiments have been run in seven different configurations for two seasons to assess the value of observations taken in target regions identified either using singular vectors (SVs) or randomly, and located over the Pacific or the Atlantic Oceans. The value has been measured by the relative short-range forecast error reduction in downstream areas, specifically a North American region for observations taken in the Pacific Ocean, and a European region for observations taken in the Atlantic Ocean.Overall, results have indicated (1) that observations taken in SV-target areas are on average more valuable than observations taken in randomly selected areas, (2) that it is important that the daily set of singular vectors are used to compute the target areas, and (3) that the value of targeted observations depends on the region, the season and the baseline observing system. If the baseline observing system is data-void over the ocean, then the average value of observations taken in SV-target areas is very high. Considering for example winter 2004, SV-targeted observations over the Pacific (Atlantic) reduce the day-2 forecasts error of 500 hPa geopotential height forecasts in the verification region by 27.5% (19.1%), compared to 15.7% (14.9%) for observations taken in random areas. By contrast, if the baseline observing system is data-rich over the ocean, then the average value of observations taken in SV-target areas is rather small. Considering for example winter 2004, it has been estimated that adding SV-targeted observations over the Pacific (Atlantic) would reduce, on average, the day-2 forecasts error in the verification region by 4.0% (2.0%), compared to 0.5% (1.7%) for observations in random areas. These average results have been confirmed by single-case investigations, and by a careful examination of time series of forecast errors.These results indicate that more accurate assimilation systems that can exploit the potential value of localized observations are needed to increase the average return of investments in targeting field experiments. Copyright The value of targeted observationsIn the past decade, field experiments have been organized to assess the impact of extra observations, taken in some specific, case-dependent target areas identified using objective and subjective methods, on (mainly shortrange) forecast accuracy. These campaigns, organized following a proposal at a workshop in 1995 (Snyder, 1996) The general conclusions of these campaigns (see e.g. Langland (2005) for a review of issues in targeted observing) were that in most of the cases the impact of the targeted observations was positive, and that on average the impact was small, with maximum error reductions in some specific cases for variables such as mean-sea-level pressure of about 10-15%. For example, considering observations targeted using singular vectors in five cases of the FASTEX campaign, Montani et al. (1999) concluded that the forecast impact was more evident if the verification area coincided with the ...

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Section: Discussionmentioning

confidence: 99%

The value of observations. II: The value of observations located in singular‐vector‐based target areas

Buizza

Cardinali

Kelly

et al. 2007

Quart J Royal Meteoro Soc

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“…The prediction will be improved if these errors are reduced by adequate observations. The technique is, therefore, also useful for designing an appropriate observing system [e.g., Palmer et al, 1998;Buizza and Montani, 1999;Gelaro et al, 1999].…”

Section: Introductionmentioning

confidence: 99%

Application of singular vector analysis to the Kuroshio large meander

Fujii¹,

Tsujino²,

Usui³

et al. 2008

J. Geophys. Res.

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[1] Singular vector analysis is applied to the formation of the Kuroshio large meander south of Japan. We use a simulation run of an ocean general circulation model (OGCM), in which a large meander occurs, as the background state. Singular vectors are calculated by the Lanczos method in which the tangent linear and adjoint models of the OGCM are used. We apply an incremental correction approach for setting up the initial perturbation and averaging for the final norm in order to get modes reflecting nonlinear physics by filtering out high-frequency variations. The perturbation extracted as the leading right singular vector affects the formation of the large meander most if it is set to the background state two months before. When the perturbation is added, it enhances an anticyclonic eddy southeast of Kyushu in the upper layer, which induces downwelling north of it and develops an anticyclonic eddy in the deep layer. The anticyclonic eddy produces a cold anomaly at the downstream edge, and produces baroclinic instability there, resulting in further development of the large meander. In contrast, the anticyclonic eddy in the deep layer is weakened when the perturbation is subtracted, the development of the cold anomaly in the deep layer is delayed, and consequently the meander is not so well developed. Thus singular vector analysis reveals the role of the anticyclonic eddy approaching southeast of Kyushu in the upper layer, and indicates the importance of the anticyclonic eddy in the deep layer.Citation: Fujii, Y., H. Tsujino, N. Usui, H. Nakano, and M. Kamachi (2008), Application of singular vector analysis to the Kuroshio large meander,

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“…Also in the context of NWP [Buizza and Palmer 1995, Gelaro et al 1998, Buizza and Montani 1999, Gelaro et al 1999 and in the context of ENSO dynamics and prediction [Penland and Sardeshmukh 1995, Moore and Kleeman 1996, 1997a, singular vector methods have been successfully applied to derive non-normal modes which lead to optimal, transient growth of relevant norms.…”

Section: Overviewmentioning

confidence: 99%

Observational Requirements for Global-Scale Ocean Climate Analysis: Lessons from Ocean State Estimation

Heimbach¹,

Forget²,

Ponte³

et al. 2010

Proceedings of OceanObs'09: Sustained Ocean Observations and Information for Society

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As assessment of the singular‐vector approach to targeted observing using the FASTEX dataset

Cited by 93 publications

References 23 publications

The value of observations. II: The value of observations located in singular‐vector‐based target areas

The value of observations. II: The value of observations located in singular‐vector‐based target areas

Application of singular vector analysis to the Kuroshio large meander

Observational Requirements for Global-Scale Ocean Climate Analysis: Lessons from Ocean State Estimation

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