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John E. Janowiak, Peter Bauer, Wanqiu Wang, Phillip A. Arkin, and Jon Gottschalck

climatological features of tropical rainfall, the temporal variations of these short-range rainfall predictions did a poor job of mimicking observed variations in the tropics. In fact, Janowiak et al. (1998) concluded that the correlation between observed precipitation (based in infrared satellite data) and the NCEP-1 reanalysis (representative of models around 1990) short-range precipitation forecasts were weak to nonexistent over much of the tropical Pacific. More specifically, Hendon et al. (2000

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Warren J. Tennant, Glenn J. Shutts, Alberto Arribas, and Simon A. Thompson

not affected. However, the assumed westward tilt with height ( Fig. 1b ) loosely matches the observed phase tilt of midlatitude baroclinic wave systems ( Ebisuzaki 1991 ) and equatorial, convectively coupled waves in the troposphere. The benefit of this vertical structure in the streamfunction forcing is to support baroclinic instability in the midlatitudes and to promote vertical motion in the tropics with near-surface convergence below upper-troposphere divergence and vice versa. Similar ideas

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Munehiko Yamaguchi and Sharanya J. Majumdar

areas and the norm. Moist SVs are targeted for the whole tropics (20°S–30°N), not each TC, while dry SVs are targeted for the Northern Hemisphere only (30°–90°N). The total energy norm includes the specific humidity term, and w q = 0.04 is used for both dry and moist SVs. In the initial norm, the vertical integration of the total energy is limited up to about 5 (700) hPa for wind and temperature (specific humidity) perturbations. Initial perturbations are created by linearly combining

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Sharanya J. Majumdar, Kathryn J. Sellwood, Daniel Hodyss, Zoltan Toth, and Yucheng Song

, in mid-March), sensitivity was exhibited in the tropics, with a clear propagation of the target area toward the verification region. Given that the ETKF commonly selects areas of large ensemble spread in its targets, it may not emphasize the sensitivity captured by initially tiny convective perturbations that modify a forecast in the midlatitudes ( Zhang et al. 2003 ; Hodyss and Majumdar 2007 ). The properties of the targets were also examined for different observing variables. The evolution of

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Thomas M. Hamill, Jeffrey S. Whitaker, Michael Fiorino, and Stanley G. Benjamin

that the background-error covariance model in variational systems may implicitly reflect balances between the mass and wind fields that are tuned for the midlatitudes and less appropriate in the tropics. Mass–wind balances in the EnKF covariances are set directly by the ensemble-estimated covariances. To date, however, no experiments have been performed with an EnKF applied in a high-resolution global forecast model with a full observational dataset. The combined application of a high

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