GFDL-Type Typhoon Initialization in MM5

Kwon, Hyun-Han; Won, Seong Hee; Ahn, Myung Hwan; Suh, Ae Sook; Chung, Hyo-Sang

doi:10.1175/1520-0493(2002)130<2966:gttiim>2.0.co;2

Cited by 23 publications

(17 citation statements)

References 13 publications

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“…The Optimum Interpolation Sea Surface Temperature (OISST) version 2 [Reynolds et al, 2002], produced by the National Oceanic and Atmospheric Administration (NOAA), is used for the lower boundary condition over the ocean. For a more realistic simulation, the Geophysical Fluid Dynamics Laboratory (GFDL) bogussing algorithm [Kwon et al, 2002] is used. Physical parameterizations used in the simulation include the Grell convective scheme, a bulk aerodynamic formulation of the planetary boundary layer, horizontal and vertical diffusion, and dry convective adjustment.…”

Section: Experimental Frameworkmentioning

confidence: 99%

Adjoint‐based forecast sensitivities of Typhoon Rusa

Kim

Jung

2006

Geophysical Research Letters

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Sensitivities of the forecast to changes in the initial state are evaluated for Typhoon Rusa, which passed through the Korean Peninsula in 2002, to understand the impact of initial condition uncertainties on the forecast and thence to diagnose the sensitive regions for adaptive observations. To assess the forecast sensitivities, adjoint‐based sensitivities were used. Sensitive regions are located horizontally in the right half circle of the typhoon, and vertically in the lower and upper troposphere which coincide with the inflow and outflow regions near the typhoon. Forecast error is reduced around 18% by extracting properly weighted adjoint‐based forecast sensitivity perturbations from the initial state, and the correction occurs primarily in the lower to mid‐troposphere where the forecast error is the largest. In contrast to the improvement in the overall forecast, the track and intensity forecast are not improved much through the modification of the initial condition by adjoint‐based forecast sensitivities.

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Section: Experimental Frameworkmentioning

confidence: 99%

Adjoint‐based forecast sensitivities of Typhoon Rusa

Kim

Jung

2006

Geophysical Research Letters

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“…One is to implant the bogus vortices into the large-scale environment of the analysis (Ueno 1989(Ueno , 1995Leslie and Holland 1995;Trinh and Krishnamurti 1992;Kurihara et al 1993;Kurihara et al 1995;Peng et al 1993;Liu et al 1997). The other is to include the bogus in observations and put it in the analysis procedure (Lord 1991;Xiao et al 2000;Zou and Xiao 2000;Pu and Braun 2001;Kwon et al 2002). How to improve the typhoon bogus scheme for typhoon initialization is still an important issue in the near future (Liu et al 2000).…”

Section: Introductionmentioning

confidence: 99%

A Tropical Cyclone Bogus Data Assimilation Scheme in the MM5 3D-Var System and Numerical Experiments with Typhoon Rusa (2002) Near Landfall

Xiao

Kuo

Zhang

et al. 2006

Journal of the Meteorological Society of Japan

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A typhoon bogus data assimilation (BDA) scheme is built in the MM5 3D-Var system with mainly three components: a) An algorithm to specify the typhoon bogus sea-level pressure (SLP) and wind profiles is constructed in the MM5 3D-Var system based on the typhoon report issued by the regional typhoon center and the 3D-Var background; b) The errors of the bogus observations are empirically assigned according to our knowledge of the typhoon SLP and wind distributions; c) The MM5 3D-Var system includes typhoon bogus observation operators. Since typhoon bogus observations can have large differences from the 3D-Var background fields, special treatment is made to allow the typhoon bogus data retained in the minimization procedure.Numerical experiments are conducted using Typhoon Rusa (2002) case in the Northwestern Pacific Ocean near landfall to the Korean Peninsula. It is indicated that the 3D-Var bogus algorithm works well and can improve the prediction of typhoon track and intensity. With MM5 3D-Var BDA, the initial typhoon vortex is balanced with the dynamical and statistical balance embedded in the 3D-Var system. It can generate a well-defined warm core structure in the typhoon initialization. Compared with bogussing in the 3D-Var background fields, MM5 3D-Var BDA results in less spin-down/up problems in the subsequent typhoon forecast. Sensitivity experiments show that assimilation of the only bogus SLP data produces too strong a typhoon intensity, while assimilation of the only bogus wind data produces much weaker intensity prediction than the observations. Assimilation of both bogus SLP and wind data obtains the best initialization and prediction for this typhoon case. Its landfall location, time and intensity are very close to the observation in the experiment.

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“…This discrepancy is believed to result from a relatively stronger environmental steering current 1 of ϳ9 m s Ϫ1 from the modeled 1 The steering current is computed as follows. First, filter out the storm circulation using the methods of Kurihura et al (1993Kurihura et al ( , 1995 and Kwon et al (2002) and compute the averaged currents at each level by averaging over a 100-800-km radial band centered on the TC. Second, compute the layer mean value of the above currents with pressure weight as the value of the steering current associated with the TC.…”

Section: A Track and Intensitymentioning

confidence: 99%

A High-Resolution Simulation of Typhoon Rananim (2004) with MM5. Part I: Model Verification, Inner-Core Shear, and Asymmetric Convection

Li¹,

Duan²,

Yu³

et al. 2008

Monthly Weather Review

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In this study, the fifth-generation Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) Mesoscale Model (MM5) is used to simulate Typhoon Rananim (2004) at high resolution (2-km grid size). The simulation agrees well with a variety of observations, especially for intensification, maintenance, landfall, and inner-core structures, including the echo-free eye, the asymmetry in eyewall convection, and the slope of the eyewall during landfall. The asymmetric feature of surface winds is also captured reasonably well by the model, as well as changes in surface winds and pressure near the storm center.The shear-induced vortex tilt and storm-relative asymmetric winds are examined to investigate how vertical shear affects the asymmetric convection in the inner-core region. The inner-core vertical shear is found to be nonunidirectional, and to induce a nonunidirectional vortex tilt. The distribution of asymmetric convection is, however, inconsistent with the typical downshear-left pattern for a deep-layer shear. Qualitative agreement is found between the divergence pattern and the storm-relative flow, with convergence (divergence) generally associated with asymmetric inflow (outflow) in the eyewall. The collocation of the inflow-induced lower-level convergence in the boundary layer and the lower troposphere and the midlevel divergence causes shallow updrafts in the western and southern parts of the eyewall, while the deep and strong upward motion in the southeastern portion of the eyewall is due to the collocation of the net convergence associated with the strong asymmetric flow in the midtroposphere and the inflow near 400 hPa and its associated divergence in the outflow layer above 400 hPa.

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GFDL-Type Typhoon Initialization in MM5

Cited by 23 publications

References 13 publications

Adjoint‐based forecast sensitivities of Typhoon Rusa

Adjoint‐based forecast sensitivities of Typhoon Rusa

A Tropical Cyclone Bogus Data Assimilation Scheme in the MM5 3D-Var System and Numerical Experiments with Typhoon Rusa (2002) Near Landfall

A High-Resolution Simulation of Typhoon Rananim (2004) with MM5. Part I: Model Verification, Inner-Core Shear, and Asymmetric Convection

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