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Sim D. Aberson

previous 20–25 yr and suggested that operational missions would be effective in operational numerical forecast error reduction. In 1996, NOAA procured a Gulfstream IV-SP jet aircraft (G-IV), and put it to use in operational “synoptic surveillance” missions in the environments of tropical cyclones that threaten the continental United States, Puerto Rico, the U.S. Virgin Islands, and Hawaii. A new dropwindsonde, based on the Global Positioning System, was developed by the National Center for

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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

that affect the TC tracks in this basin. There are six types of guidance: three TESVs from different global models, the ETKF based on the multimodel ensemble members, the DLM wind variance, and the ADSSV (details are listed in Table 1 ). In the northwestern Pacific Ocean there are several interesting dynamical systems affecting the TC motion ( Wu 2006 ), such as the subtropical high, the midlatitude trough, the subtropical jet, and the southwesterly monsoon. The latter two systems appear to play

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Munehiko Yamaguchi, Takeshi Iriguchi, Tetsuo Nakazawa, and Chun-Chieh Wu

; Chou and Wu 2008 ). The Astra SPX jet, which cruises at about 750 km h −1 at up to about 14 km with a maximum flight range of about 6.5 h, is used in this field experiment. Dropwindsondes are released in and around a TC every 150–200 km close to the resolution of the traditional rawinsonde network. To maximize the possible improvement of numerical forecasts with the limited aircraft resources, targeted observation techniques are adopted. Three sensitivity analysis products were first taken into

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Carolyn A. Reynolds, Melinda S. Peng, and Jan-Huey Chen

et al. 2006 ; Reynolds et al. 2007 ), but puts more emphasis on the complicated dynamical systems affecting TC evolution, such as the midlatitude trough and the subtropical jet. In this study, SVs are used to examine TC sensitivity during recurvature, and the subsequent downstream impacts resulting from the interaction of the TC with the midlatitude environment. The leading SVs represent the fastest-growing perturbations to a particular forecast (in a tangent linear sense), and as such, have

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

field campaign was to address short-range TC dynamics and forecast skill in one region and the downstream impacts of TCs on medium-range dynamics and forecast skill in another region ( Elsberry and Harr 2008 ; Parsons et al. 2008 ). This was the first time that four aircraft [the DOTSTAR Astra jet, the German Aerospace Center (DLR) Falcon 20, a U.S. Navy P-3, and a U.S. Air Force C-130] were used simultaneously to observe typhoons. DOTSTAR Astra and DLR Falcon sampled the TC environment, especially

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Sim D. Aberson

aircraft ( Burpee et al. 1996 ). NOAA procured a Gulfstream IV-SP jet aircraft (G-IV) in 1996 and put it to use in operational “synoptic surveillance” missions in the environments of tropical cyclones that threaten the contiguous United States, U.S. Caribbean territories, and Hawaii. The missions led to 10%–15% reductions in GFS track forecast error during the critical watch and warning period before possible landfall (within the first 60 h), and small impacts in Geophysical Fluid Dynamics Laboratory

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

winds). Consequently the wind increment will have the effect of displacing toward the west the jet of strong northwesterly winds in the background state. For the third experiment ( Fig. 6 ), the time of the temperature observation coincides with the end of the assimilation time window. In all four results, the location of the maximum temperature increment is now upstream, that is to the northwest, of the observation location. The wind increment again forms a cell of cyclonic circulation

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Shin-Gan Chen, Chun-Chieh Wu, Jan-Huey Chen, and Kun-Hsuan Chou

on hurricane track and intensity forecasts of GPS dropwindsonde observations from the first-season flights of the NOAA Gulfstream-IV jet aircraft . Bull. Amer. Meteor. Soc. , 80 , 421 – 427 . Ancell , B. , and G. J. Hakim , 2007 : Comparing adjoint- and ensemble-sensitivity analysis with applications to observation targeting . Mon. Wea. Rev. , 135 , 4117 – 4134 . Bishop , C. H. , and Z. Toth , 1999 : Ensemble transformation and adaptive observations . J. Atmos. Sci. , 56

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