An Evaluation of Dvorak Technique–Based Tropical Cyclone Intensity Estimates
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Abstract The satellite-based Dvorak technique (DVKT) is the most widely available and readily used tool for operationally estimating the maximum wind speeds associated with tropical cyclones. The DVKT itself produces internally consistent results, is reproducible, and has shown practical accuracy given the high cost of in situ or airborne observations. For these reasons, the DVKT has been used in a reasonably uniform manner globally for approximately 20 years. Despite the nearly universal use of this technique, relatively few systematic verifications of the DVKT have been conducted. This study, which makes use of 20 yr of subjectively determined DVKT-based intensity estimates and best-track intensity estimates influenced by aircraft observations (i.e., ±2 h) in the Atlantic basin, seeks to 1) identify the factors (intensity, intensity trends, radius of outer closed isobar, storm speed, and latitude) that bias the DVKT-based intensity estimates, 2) quantify those biases as well as the general error characteristics associated with this technique, and 3) provide guidance for better use of the operational DVKT intensity estimates. Results show that the biases associated with the DVKT-based intensity estimates are a function of intensity (i.e., maximum sustained wind speed), 12-h intensity trend, latitude, and translation speed and size measured by the radius of the outer closed isobar. Root-mean-square errors (RMSE), however, are shown to be primarily a function of intensity, with the best signal-to-noise (intensity to RMSE) ratio occurring in an intensity range of 90–125 kt (46–64 m s−1). The knowledge of how these factors affect intensity estimates, which is quantified in this paper, can be used to better calibrate Dvorak intensity estimates for tropical cyclone forecast operations, postseason best-track analysis, and climatological reanalysis efforts. As a demonstration of this capability, the bias corrections developed in the Atlantic basin are also tested using a limited east Pacific basin sample, showing that biases and errors can be significantly reduced.Keywords:
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"Reply to “Comments on ‘Nonlinear Response of a Tropical Cyclone Vortex to Prescribed Eyewall Heating with and without Surface Friction in TCM4: Implications for Tropical Cyclone Intensification’”" published on Dec 2016 by American Meteorological Society.
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Tropical cyclone scales
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"Comments on “Nonlinear Response of a Tropical Cyclone Vortex to Prescribed Eyewall Heating with and without Surface Friction in TCM4: Implications for Tropical Cyclone Intensification”" published on Dec 2016 by American Meteorological Society.
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長期の再現期間を想定した台風被害予測を行うために,少数の観測台風資料の統計特性から多数の台風資料を作成することが可能な時系列相関型の全球確率台風モデル(GSTM)を作成した.確率台風モデルの精度は台風特性値とその時間変化率に関する結合PDFの近似方法に依存しており,主成分分析とクラスター分析を用いた近似法により,中心気圧や進行方位といった台風特性値の再現性が向上することを明らかにした.また,新しく開発したGSTMを観測結果と比較して,その精度検証を行った.GSTMにより得られた台風資料から作成した各台風特性値の確率分布は,北西太平洋において観測資料のそれとよく一致しており,本確率台風モデルの有用性が示された.
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A barotropic prirnitive equation model is used to simulate the tropical cyclone motion.Tropical cyclonemovements under different environmental flow backgrounds were examined and sensitivity of tropical cyclonetracks were discussed.Conclusions of practical significance have been obtained in this paper.
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Abstract : The overarching objective of this project is to identify impacts to tropical cyclone structure and intensity throughout the tropical cyclone lifetime. A common factor is the impact of mid- and upper-level environmental conditions that affects formation and intensification of a tropical cyclone. It is hypothesized that during the formation process, the environmental interaction has maximum impact on the vertical alignment of the fledgling circulation and as a mature tropical cyclone impacts on upper-level outflow control periods of intensification or decay. Observational data of the tropical cyclone-environment at upper levels are used in conjunction with numerical simulations to examine the spatial and temporal sensitivities that result in tropical cyclone intensification versus decay, and the mechanisms via which the environmental interaction influences the tropical cyclone primary swirling wind circulation at various stages of intensification.
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