A Local Formulation of the Ensemble Transform (ET) Analysis Perturbation Scheme

McLay, Justin; Bishop, Craig H.; Reynolds, C. A.

doi:10.1175/2010waf2222359.1

Cited by 40 publications

(20 citation statements)

References 23 publications

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“…Initial conditions for the NOGAPS forecast ensemble are generated using a nine-banded local ensemble transform (ET) scheme (McLay et al 2010). In this methodology, short-term ensemble forecasts are linearly combined, under the constraint of an estimate of the analysis error variance, to produce a set of perturbations to the analysis from the Naval Research Laboratory Atmospheric Variational Data Assimilation System-Accelerated Representer (NAVDAS-AR) (Rosmond and Xu 2006;Chua et al 2009).…”

Section: Nogapsmentioning

confidence: 99%

Examining the Predictability of the Stratospheric Sudden Warming of January 2013 Using Multiple NWP Systems

et al. 2016

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The first multimodel study to estimate the predictability of a boreal sudden stratospheric warming (SSW) is performed using five NWP systems. During the 2012/13 boreal winter, anomalous upward propagating planetary wave activity was observed toward the end of December, which was followed by a rapid deceleration of the westerly circulation around 2 January 2013, and on 7 January 2013 the zonal-mean zonal wind at 608N and 10 hPa reversed to easterly. This stratospheric dynamical activity was followed by an equatorward shift of the tropospheric jet stream and by a high pressure anomaly over the North Atlantic, which resulted in severe cold conditions in the United Kingdom and northern Europe. In most of the five models, the SSW event was predicted 10 days in advance. However, only some ensemble members in most of the models predicted weakening of westerly wind when the models were initialized 15 days in advance of the SSW. Further dynamical analysis of the SSW shows that this event was characterized by the anomalous planetary wavenumber-1 amplification followed by the anomalous wavenumber-2 amplification in the stratosphere, which resulted in a split vortex occurring between 6 and 8 January 2013. The models have some success in reproducing wavenumber-1 activity when initialized 15 days in advance, but they generally failed to produce the wavenumber-2 activity during the final days of the event. Detailed analysis shows that models have reasonably good skill in forecasting tropospheric blocking features that stimulate wavenumber-2 amplification in the troposphere, but they have limited skill in reproducing wavenumber-2 amplification in the stratosphere.

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Section: Nogapsmentioning

confidence: 99%

Examining the Predictability of the Stratospheric Sudden Warming of January 2013 Using Multiple NWP Systems

et al. 2016

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“…Given these promising results, the present study investigates the incorporation of a variant of the Takaya et al [2010b] diurnal SST scheme into the NWP component of the U.S. Navy's global EPS. In addition, this study investigates the adaptation of the local ensemble transform (ET) ensemble generation scheme of McLay et al [2010] to generate SST analysis perturbations. Hence, the EPS design for the present study is distinct from those of Takaya et al [2010a] and Tennant and Beare [2011]in that it takes account of both SST diurnal variation and SST initial‐state uncertainty.…”

Section: Introductionmentioning

confidence: 99%

Inclusion of sea‐surface temperature variation in the U.S. Navy ensemble‐transform global ensemble prediction system

et al. 2012

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[1] The local ensemble transform (ET) analysis perturbation scheme is adapted to generate perturbations to both atmospheric variables and sea-surface temperature (SST). The adapted local ET scheme is used in conjunction with a prognostic model of SST diurnal variation and the Navy Operational Global Atmospheric Prediction System (NOGAPS) global spectral model to generate a medium-range forecast ensemble. When compared to a control ensemble, the new forecast ensemble with SST variation exhibits notable differences in various physical properties including the spatial patterns of surface fluxes, outgoing longwave radiation (OLR), cloud radiative forcing, near-surface air temperature and wind speed, and 24-h accumulated precipitation. The structure of the daily cycle of precipitation also is substantially changed, generally exhibiting a more realistic midday peak of precipitation. Diagnostics of ensemble performance indicate that the inclusion of SST variation is very favorable to forecasts in the Tropics. The forecast ensemble with SST variation outscores the control ensemble in the Tropics across a broad set of metrics and variables. The SST variation has much less impact in the Midlatitudes. Further comparison shows that SST diurnal variation and the SST analysis perturbations are each individually beneficial to the forecast from an overall standpoint. The SST analysis perturbations have broader benefit in the Tropics than the SST diurnal variation, and inclusion of the SST analysis perturbations together with the SST diurnal variation is essential to realize the greatest gains in forecast performance.

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“…In its purest form, only one set of transformation coefficients is used for the entire state. However, McLay et al (2010) have shown that smoothly blending the transformation coefficients relevant to large regions such as the tropics and extra-tropics can lead to performance advantages. In this first study, we approximate Eq.…”

Section: Description Of the Ensemble Transform Techniquementioning

confidence: 99%

“…Each member now creates unique atmospheric lateral BC from 28 members of the global NOGAPS ensemble (step 3). The members of the global ensemble are produced using perturbation methodology based on the banded ET as described in McLay et al (2008McLay et al ( , 2010. The banded ET produces initial perturbations by transforming 6-h ensemble forecast perturbations to be consistent with analysis error estimates.…”

Section: Implementation Of the Mesoscale Ensemble Systemmentioning

confidence: 99%

Development and testing of a coupled ocean–atmosphere mesoscale ensemble prediction system

et al. 2011

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A coupled ocean-atmosphere mesoscale ensemble prediction system has been developed by the Naval Research Laboratory. This paper describes the components and implementation of the system and presents baseline results from coupled ensemble simulations for two tropical cyclones. The system is designed to take into account major sources of uncertainty in: (1) non-deterministic dynamics, (2) model error, and (3) initial states. The purpose of the system is to provide mesoscale ensemble forecasts for use in probabilistic products, such as reliability and frequency of occurrence, and in risk management applications. The system components include COAMPS® (Coupled Ocean/ Atmosphere Mesoscale Prediction System) and NCOM (Navy Coastal Ocean Model) for atmosphere and ocean forecasting and NAVDAS (NRL Atmospheric Variational Data Assimilation System) and NCODA (Navy Coupled Ocean Data Assimilation) for atmosphere and ocean data assimilation. NAVDAS and NCODA are 3D-variational (3DVAR) analysis schemes. The ensembles are generated using separate applications of the Ensemble Transform (ET) technique in both the atmosphere (for moving or nonmoving nests) and the ocean. The atmospheric ET is computed using wind, temperature, and moisture variables, while the oceanographic ET is derived from ocean current, temperature, and salinity variables. Estimates of analysis error covariance, which is used as a constraint in the ET, are provided by the ocean and atmosphere 3DVAR assimilation systems. The newly developed system has been successfully tested for a variety of configurations, including differing model resolution, number of members, forecast length, and moving and fixed nest options. Results from relatively coarse resolution (∼27-km) ensemble simulations of Hurricanes Hanna and Ike demonstrate that the ensemble can provide valuable uncertainty information about the storm track and intensity, though the ensemble mean provides only a small amount of improved predictive skill compared to the deterministic control member.

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A Local Formulation of the Ensemble Transform (ET) Analysis Perturbation Scheme

Cited by 40 publications

References 23 publications

Examining the Predictability of the Stratospheric Sudden Warming of January 2013 Using Multiple NWP Systems

Examining the Predictability of the Stratospheric Sudden Warming of January 2013 Using Multiple NWP Systems

Inclusion of sea‐surface temperature variation in the U.S. Navy ensemble‐transform global ensemble prediction system

Development and testing of a coupled ocean–atmosphere mesoscale ensemble prediction system

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