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Takemasa Miyoshi, Yoshiaki Sato, and Takashi Kadowaki

independent. Miyoshi and Yamane (2007) distributed computations at each grid point to each computational node according to geographical regions as shown schematically in Fig. 4a . This parallelization is subject to significant loss of efficiency when the observing density is irregular in the horizontal, which is the case in the real world. In the case of Fig. 4a , node 7 over Europe, for example, contains many more observations than node 1 over Antarctica and the Southern Ocean, so that the

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Steven J. Greybush, Eugenia Kalnay, Takemasa Miyoshi, Kayo Ide, and Brian R. Hunt

distances, imbalance is smaller and spread over broader areas. This finding agrees with the Lorenc (2003) explanation using Fig. 1 in that imbalance can be introduced in the region where the impact of an observation moves toward zero. The circular patterns of imbalance surrounding the Southern Ocean islands in the case of L = 250 km demonstrate the detrimental impact of strong localization resulting from a sharp transition between a region with strong observation impact and a region with little

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Mark Buehner, P. L. Houtekamer, Cecilien Charette, Herschel L. Mitchell, and Bin He

forecast model and the operational observations, except without satellite radiances, the operational 3D-Var system at the National Centers for Environmental Prediction was compared against an EnKF. Medium-range forecasts initialized from the EnKF ensemble-mean analysis and the 3D-Var analysis (both at the same spatial resolution) showed that using the EnKF analyses led to large improvements in the Southern Hemisphere and more modest improvements in the Northern Hemisphere. In a similar experimental

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Zhiyong Meng and Fuqing Zhang

localization in ensemble data assimilation using a hierarchical ensemble filter . Physica D , 230 , 99 – 111 . Anderson , J. L. , 2009 : Spatially and temporally varying adaptive covariance inflation for ensemble filters . Tellus , 61A , 72 – 83 . Anderson , J. L. , and N. Collins , 2007 : Scalable implementations of ensemble filter algorithms for data assimilation . J. Atmos. Oceanic Technol. , 24 , 1452 – 1463 . Anderson , J. L. , B. Wyman , S. Zhang , and T. Hoar , 2005

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Loïk Berre and Gérald Desroziers

domain, which is represented in Fig. 9 . The top panel of Fig. 9 is a map of raw innovation standard deviations from this study, averaged over the whole year period, and normalized in such a way that the mean field is 1.0 over the continental European area. Relatively small values can be observed over data-dense regions such as Europe and North America. In contrast, larger values are observed over oceanic regions, where storm tracks are located, and where fewer observations are available. On the

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Takuya Kawabata, Tohru Kuroda, Hiromu Seko, and Kazuo Saito

2130 JST, L1 remains in the same region because new convection is generated at its southern tip, although each convective cell in L1 has moved northward. Thus, L1 seems to have a back-building formation mechanism. The intensity of L1 in ref is similar to the observation, but in ref, L1 is entering a decaying stage. After 2130 JST, the intensity and shape of L1 could not be maintained in the extended forecast. The horizontal distributions of the mixing ratio of q r and the winds at z * = 225 m in

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Craig H. Bishop and Daniel Hodyss

Lorenc (2003) , Buehner (2005) , Buehner et al. (2010a , b) , Wang et al. (2007) , Liu et al. (2009) , and others. Buehner et al. (2010a , b) found that an ensemble 4D-VAR scheme that used NECL but did not use a tangent linear model or adjoint, outperformed a version of the operational 4D-VAR scheme both in the tropics and Southern Hemisphere, but not in the northern extratropics. The promise of improving 4D-VAR with ensemble covariances is a particularly strong motivation for this study

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José A. Aravéquia, Istvan Szunyogh, Elana J. Fertig, Eugenia Kalnay, David Kuhl, and Eric J. Kostelich

and short-term forecasts in the Southern Hemisphere extratropics near the surface. We use this improved set of analyses as the baseline for the evaluation of the results obtained with the augmented observational dataset. Despite the aforementioned coding error, the former version of the LETKF provided analyses and short-term forecasts that in the SH, on average, were more accurate at the 99% significance level than those obtained with the then-operational SSI of NCEP at the same T62L28 resolution

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