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Hyun Mee Kim and Byoung-Joo Jung

Abstract

In this study, the structure and evolution of total energy singular vectors (SVs) of Typhoon Usagi (2007) are evaluated using the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) and its tangent linear and adjoint models with a Lanczos algorithm. Horizontal structures of the initial SVs following the tropical cyclone (TC) evolution suggest that, relatively far from the region of TC recurvature, SVs near the TC center have larger magnitudes than those in the midlatitude trough. The SVs in the midlatitude trough region become dominant as the TC passes by the region of recurvature. Increasing magnitude of the SVs over the midlatitude trough regions is associated with the extratropical transition of the TC. While the SV sensitivities near the TC center are mostly associated with warming in the midtroposphere and inflow toward the TC along the edge of the subtropical high, the SV sensitivities in the midlatitude are located under the upper trough with upshear-tilted structures and associated with strong baroclinicity and frontogenesis in the lower troposphere. Given the results in this study, sensitive regions for adaptive observations of TCs may be different following the TC development stage. Far from the TC recurvature, sensitive regions near TC center may be important. Closer to the TC recurvature, effects of the midlatitude trough become dominant and the vertical structures of the SVs in the midlatitude are basically similar to those of extratropical cyclones.

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Sim D. Aberson

statistics were incorporated and rawinsonde balloon drift in time and space were included in the system. By 2003, background errors were recomputed, and the divergence tendency constraint in tropics was removed. Other minor changes to the assimilation system were implemented in 2004. In 1997, the GFS horizontal resolution was spectral triangular 126 (T126) with a 284 × 190 Gaussian grid, or an approximately 1° latitude–longitude grid, and the vertical coordinate extended from the surface to about 2

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Matthieu Plu

different atmospheric features. Bengtsson and Hodges (2006) updated and extended L82 by applying the same method to extratropical 500-hPa height fields and to wind fields in the tropics, using the ECMWF model. Bengtsson et al. (2005) and Froude et al. (2007) applied the L82 method to cyclone tracks. They studied the predictability of extratropical cyclone tracks using the ECMWF global model, aiming to infer how much future observation and model improvements could reduce forecast error. An

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Kun-Hsuan Chou, Chun-Chieh Wu, Po-Hsiung Lin, Sim D. Aberson, Martin Weissmann, Florian Harnisch, and Tetsuo Nakazawa

tropics: An evaluation of model performance during the 1995 hurricane season . Mon. Wea. Rev. , 126 , 1287 – 1305 . Weissmann , M. , and Coauthors , 2011 : The influence of assimilating dropsonde data on typhoon track and midlatitude forecasts . Mon. Wea. Rev. , 139 , 908 – 920 . Woollen , J. R. , 1991 : New NMC operational OI quality control . Preprints, Ninth Conf. on Numerical Weather Prediction, Denver, CO, Amer. Meteor. Soc., 24–27 . Wu , C.-C. , and Coauthors , 2005

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Chun-Chieh Wu, Jan-Huey Chen, Sharanya J. Majumdar, Melinda S. Peng, Carolyn A. Reynolds, Sim D. Aberson, Roberto Buizza, Munehiko Yamaguchi, Shin-Gan Chen, Tetsuo Nakazawa, and Kun-Hsuan Chou

System (GEFS), specifically developed for the tropics ( Aberson 2003 ). Second is the ETKF ( Majumdar et al. 2002a ), which predicts the reduction in forecast error variance for feasible deployment of targeted observations based on a combination of NCEP, European Centre for Medium-Range Weather Forecasts (ECMWF), and Canadian Meteorological Center (CMC) ensembles. Third are the total-energy singular vectors (TESVs; Palmer et al. 1998 ; Buizza and Montani 1999 ; Peng and Reynolds 2006 ), which

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