scholarly journals Comparative assessment of validity of gradient wind models for a translating tropical cyclone

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Yuzuru Eguchi ◽  
Yasuo Hattori ◽  
Mitsuharu Nomura
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Wind Field ◽  
Comparative Assessment ◽  
Maximum Wind Speed ◽  
Observation Data ◽  
High Wind ◽  
Maximum Wind ◽  
Gradient Wind ◽  
The Difference

AbstractAccurate and conservative evaluations of the gradient wind in the free atmosphere are needed to account for high-wind hazards when designing wind resistance for critical infrastructure. This paper compared the validity of three existing gradient wind models to select an appropriate evaluation model, which enables us to accurately compute the asymmetric gradient wind field of a translating tropical cyclone under the condition of a symmetric pressure distribution and a constant translation velocity. The validity of the three models was assessed by evaluating the residuals in momentum conservation equations for the gradient wind under a specific tropical cyclone condition. The magnitude of the residuals was considered to be the measure of error in the gradient wind derived from each model. The results showed that the most frequently used model yielded the largest magnitude of residuals with the lowest maximum wind speed among the three models. The wind characteristics of the three models were validated using archived observation data of hurricanes. The physical reason for the difference in maximum wind speed among the three models was explained by the difference in the streamline feature of the gradient wind field. It was also revealed that the differences in maximum wind speed and magnitude of residuals became more pronounced as the translation speed and the intensity of a tropical cyclone increased. The comparative assessment of the three gradient wind models allowed us to identify the best model for use in conservative wind-resistant design and high-wind risk estimates.

scholarly journals A Novel Multiscale Intensity Metric for Evaluation of Tropical Cyclone Intensity Forecasts

2014 ◽  
Vol 71 (4) ◽  
pp. 1292-1304 ◽  
Author(s):  
Tomislava Vukicevic ◽  
Eric Uhlhorn ◽  
Paul Reasor ◽  
Bradley Klotz
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Microwave Radiometer ◽  
Maximum Speed ◽  
Forecast Errors ◽  
Cyclone Intensity ◽  
Maximum Wind ◽  
Tropical Cyclone Intensity Forecasts ◽  
The Difference ◽  
The Impact

Abstract In this study, a new multiscale intensity (MSI) metric for evaluating tropical cyclone (TC) intensity forecasts is presented. The metric consists of the resolvable and observable, low-wavenumber intensity represented by the sum of amplitudes of azimuthal wavenumbers 0 and 1 for wind speed within the TC vortex at the radius of maximum wind and a stochastic residual, all determined at 10-m elevation. The residual wind speed is defined as the difference between an estimate of maximum speed and the low-wavenumber intensity. The MSI metric is compared to the standard metric that includes only the maximum speed. Using stepped-frequency microwave radiometer wind speed observations from TC aircraft reconnaissance to estimate the low-wavenumber intensity and the National Hurricane Center’s best-track (BT) intensity for the maximum wind speed estimate, it is shown that the residual intensity is well represented as a stochastic quantity with small mean, standard deviation, and absolute norm values that are within the expected uncertainty of the BT estimates. The result strongly suggests that the practical predictability of TC intensity is determined by the observable and resolvable low-wavenumber intensity within the vortex. Verification of a set of high-resolution numerical forecasts using the MSI metric demonstrates that this metric provides more informative and more realistic estimates of the intensity forecast errors. It is also shown that the maximum speed metric allows for error compensation between the low-wavenumber and residual intensities, which could lead to forecast skill overestimation and inaccurate assessment of the impact of forecast system change on the skill.

Analysis of Boundary Layer Wind Field Statistical Characteristics and Reference Wind Pressure in Wenzhou District

2011 ◽  
Vol 368-373 ◽  
pp. 1424-1430
Author(s):  
Jian Jia Wu ◽  
Wen Hai Shi
Keyword(s):  
Wind Speed ◽  
Wind Field ◽  
Wind Pressure ◽  
Maximum Wind Speed ◽  
Statistical Characteristics ◽  
Annual Maximum ◽  
Maximum Wind ◽  
Wind Speed Maximum ◽  
Mean Wind Speed ◽  
Extreme Wind Speed

Based on large amount of meteorological wind field records observed in Wenzhou district, this paper analyzed the annual maximum wind speed (maximum 10 minute mean wind speed), annual extreme wind speed (maximum 3 seconds mean wind speed), reference wind pressure and wind field characteristics of typhoon in Wenzhou. The results shows that the annual maximum wind speed have a decreased trend on the whole in different areas of Wenzhou, and the trend in coastal area is more obvious than that in inland areas; the annual maximum wind speed in different areas of Wenzhou is unsteady and the typhoons have great effect on it; the value of reference wind pressure in Dongtou is greater than the value given by the design load code of China (GB50009-2001, 2002), but the values of other areas are less than the value of Code. Based on the wind field of three typhoon records, some significant results about the variation and routine characteristics of typhoon are also discussed.

Estimating Tropical Cyclone Intensity from Infrared Image Data

2011 ◽  
Vol 26 (5) ◽  
pp. 690-698 ◽  
Author(s):  
Miguel F. Piñeros ◽  
Elizabeth A. Ritchie ◽  
J. Scott Tyo
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
North Atlantic Ocean ◽  
Infrared Image ◽  
Ocean Basin ◽  
Maximum Wind Speed ◽  
Tropical Cyclone Intensity ◽  
Cyclone Intensity ◽  
Maximum Wind

Abstract This paper describes results from a near-real-time objective technique for estimating the intensity of tropical cyclones from satellite infrared imagery in the North Atlantic Ocean basin. The technique quantifies the level of organization or axisymmetry of the infrared cloud signature of a tropical cyclone as an indirect measurement of its maximum wind speed. The final maximum wind speed calculated by the technique is an independent estimate of tropical cyclone intensity. Seventy-eight tropical cyclones from the 2004–09 seasons are used both to train and to test independently the intensity estimation technique. Two independent tests are performed to test the ability of the technique to estimate tropical cyclone intensity accurately. The best results from these tests have a root-mean-square intensity error of between 13 and 15 kt (where 1 kt ≈ 0.5 m s−1) for the two test sets.

scholarly journals Estimating the Key Parameter of a Tropical Cyclone Wind Field Model over the Northwest Pacific Ocean: A Comparison between Neural Networks and Statistical Models

2021 ◽  
Vol 13 (14) ◽  
pp. 2653
Author(s):  
Ziyao Sun ◽  
Biao Zhang ◽  
Jie Tang
Keyword(s):  
Wind Speed ◽  
Statistical Models ◽  
Pressure Difference ◽  
Wind Field ◽  
Field Model ◽  
Wind Pressure ◽  
Maximum Wind Speed ◽  
Maximum Wind ◽  
Wind Field Model ◽  
Key Parameter

Estimation of maximum wind speed associated with tropical cyclones (TCs) is crucial to evaluate potential wind destruction. The Holland B parameter is the key parameter of TC parametric wind field models. It plays an essential role in describing the radial distribution characteristics of a TC wind field and has been widely used in TC disaster risk evaluation. In this study, a backpropagation neural network (BPNN) is developed to estimate the Holland B parameter (Bs) in TC surface wind field model. The inputs of the BPNN include different combinations of TC minimum center pressure difference (Δp), latitude, radius of maximum wind speed, translation speed and intensity change rate from the best-track data of the Joint Typhoon Warning Center (JTWC). We find that the BPNN exhibits the best performance when only inputting TC central pressure difference. The Bs estimated from BPNN are compared with those calculated from previous statistical models. Results indicate that the proposed BPNN can describe well the nonlinear relation between Bs and Δp. It is also found that the combination of BPNN and Holland’s wind pressure model can significantly improve the maximum wind speed underestimation and overestimation of the two existing wind pressure models (AH77 and KZ07) for super typhoons.

scholarly journals A Study of the Effects of the Ice-Microphysics, Surface Friction, and Surface Heat Flux on Tropical Cyclone Formation§

2013 ◽  
Vol 7 (1) ◽  
pp. 110-118
Author(s):  
Masanori¶ Yamasaki
Keyword(s):  
Heat Flux ◽  
Wind Speed ◽  
Tropical Cyclone ◽  
Surface Heat Flux ◽  
Numerical Experiments ◽  
Surface Friction ◽  
Surface Heat ◽  
Maximum Wind Speed ◽  
Maximum Wind ◽  
Ice Microphysics

This paper describes results from numerical experiments which have been performed to understand the effects of the ice microphysics, surface friction, and surface heat flux on tropical cyclone (TC) formation. This study uses the author’s non-hydrostatic model that intends to resolve cumulus convection. However, the horizontal grid size is taken to be somewhat large; 2 km in an area of 600 km x 600 km. A non-uniform coarse grid is used in the surrounding area with 4,000-km square. Several buoyancy perturbations arranged in the west-east direction, and a weak vortex with the maximum wind speed of 5 m s–1 are given at the initial time of the numerical time integrations. It is confirmed from two numerical experiments with and without ice microphysics that the development of a vortex is slower, and TC formation is delayed, in the presence of ice microphysics. It is also confirmed that a vortex can develop even without surface friction. It is shown that a strong vortex with the maximum wind speed of 20~25 m s–1 can be obtained. As expected, however, no eye forms, and further development does not occur. That is, it is confirmed that surface friction is indispensable to eye formation and a very strong TC having an eye. As for the third concern of this study, it is shown that a vortex with the maximum wind speed of about 5 m s–1 does not develop in the absence of the surface heat flux. That is, the surface heat flux plays an important role even in a weak vortex. Important backgrounds and understandings that are concerned with these results are described, based on studies on TCs in the past 50 years.

Dropsonde Observations of Intense Typhoons in 2017 and 2018 in the T-PARCII Project

2020 ◽  
Author(s):  
Kazuhisa Tsuboki ◽  
Hiroyuki Yamada ◽  
Tadayasu Ohigashi ◽  
Taro Shinoda ◽  
Kosuke Ito ◽  
...  
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Maximum Wind Speed ◽  
Central Pressure ◽  
The South ◽  
Main Island ◽  
Maximum Wind ◽  
Typhoon Intensity

<p>Typhoon is a tropical cyclone in the western North Pacific and the South China Sea. It is the most devastating weather system in East Asia. Strong winds and heavy rainfalls associated with a typhoon often cause severe disasters in these regions. There are many cases of typhoon disasters even in the recent decades in these regions. Furthermore, future projections of typhoon activity in the western North Pacific show that its maximum intensity will increase with the climate change. However, the historical data of typhoon (best track data) include large uncertainty after the US aircraft reconnaissance of typhoon was terminated in 1987. Another problem is that prediction of typhoon intensity has not been improved for the last few decades. To improve these problems, in situ observations of typhoon using an aircraft are indispensable. The T-PARCII (Tropical cyclone-Pacific Asian Research Campaign for Improvement of Intensity estimations/forecasts) project is aiming to improve estimations and forecasts of typhoon intensity as well as storm track forecasts.</p><p>In 2017, the T-PARCII team performed dropsonde observations of intense Typhoon Lan in collaboration with Taiwan DOTSTAR, which was the most intense typhoon in 2017 and caused huge disaster over the central Japan. It was categorized as a supertyphoon by JTWC and as a very intense and huge typhoon by JMA. Typhoon Lan moved northeastward to the east of the Okinawa main island and it was located around 23 N on 21 and 28 N on 22 October. In these two days, we made dropsonde observations at the center of the eye and in the surrounding area of the eyewall. The observations showed that the central pressure of Lan slightly increases from 926 hPa on 21 to 928 hPa on 22 October with the northward movement. On the other hand, The JMA best track data indicate that the central pressure decreases from 935 hPa on 21 to 915 hPa on 22 October. The observations also showed a significant double warm core structure in the eye and the maximum wind speed along the eyewall. The dropsonde data were used for forecast experiments. The result shows an improvement of typhoon track prediction.</p><p>The T-PARCII team also made aircraft observations of Typhoon Trami during the period from 25 to 28 September 2018 in collaboration with the SATREPS ULAT group and DOTSTAR. Trami was almost stationary during the period to the south of the Okinawa main island. Then, it moved northward and finally made a landfall over the central part of Japan. This also caused a big disaster and electricity was shut down for several days in the central part of Japan. Typhoon Trami showed a drastic change of intensity from 25 to 26 September with a large change of eye size from about a diameter of 60 km to 200 km. Dropsonde observations showed the change of central pressure and maximum wind speed as well as the thermodynamic structure of the eye.</p>

Uncertainty of Tropical Cyclone Best-Track Information

2012 ◽  
Vol 27 (3) ◽  
pp. 715-729 ◽  
Author(s):  
Ryan D. Torn ◽  
Chris Snyder
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Maximum Wind Speed ◽  
Sea Level Pressure ◽  
Position Uncertainty ◽  
Maximum Wind ◽  
Intensity Information ◽  
Weather And Climate ◽  
The Mean ◽  
National Hurricane Center

Abstract With the growing use of tropical cyclone (TC) best-track information for weather and climate applications, it is important to understand the uncertainties that are contained in the TC position and intensity information. Here, an attempt is made to quantify the position uncertainty using National Hurricane Center (NHC) advisory information, as well as intensity uncertainty during times without aircraft data, by verifying Dvorak minimum sea level pressure (SLP) and maximum wind speed estimates during times with aircraft reconnaissance information during 2000–09. In a climatological sense, TC position uncertainty decreases for more intense TCs, while the uncertainty of intensity, measured by minimum SLP or maximum wind speed, increases with intensity. The standard deviation of satellite-based TC intensity estimates can be used as a predictor of the consensus intensity error when that consensus includes both Dvorak and microwave-based estimates, but not when it contains only Dvorak-based values. Whereas there has been a steady decrease in seasonal TC position uncertainty over the past 10 yr, which is likely due to additional data available to NHC forecasters, the seasonal TC minimum SLP and maximum wind speed values are fairly constant, with year-to-year variability due to the mean intensity of all TCs during that season and the frequency of aircraft reconnaissance.

scholarly journals An Observational Study of a Coastal Barrier Jet Induced by a Landfalling Typhoon

2019 ◽  
Vol 147 (12) ◽  
pp. 4589-4609
Author(s):  
Yu-Cheng Kao ◽  
Ben Jong-Dao Jou ◽  
Johnny C. L. Chan ◽  
Wen-Chau Lee
Keyword(s):  
Wind Speed ◽  
Blocking Effect ◽  
Maximum Wind Speed ◽  
Doppler Velocity ◽  
Maximum Wind ◽  
Coastal Barrier ◽  
Southern Branch ◽  
The Difference ◽  
Landfalling Typhoon ◽  
Northern Branch

Abstract In this study, the structure and evolution of a coastal barrier jet (CBJ) along the east coast of Taiwan is documented using operational Doppler radars. The formation of the CBJ was controlled by the flow regime associated with the approaching Typhoon Haitang (2005). The CBJ persisted for 6 h and was approximately 140 km long and 25 km wide. The northern branch of the CBJ had stronger winds with maximum wind speed 49–52 m s−1, a greater vertical extent with jet core between 1.0 and 2.5 km in height, and a more persistent jet signal than the southern branch with maximum wind speed 43–46 m s−1 and jet core between 1.0 and 2.0 km. We investigated the terrain blocking effect leading to the CBJ formation using an idealized simulation. A vortex resembling Haitang is constructed based on circulation retrieved from generalized velocity track display (GVTD) technique. The result of a no-terrain simulation reveals wind speed 10–22 m s−1 lower than the observed Doppler velocity. The difference suggests the enhanced wind speed along the coast was most likely due to the terrain blocking effect.

scholarly journals Dependence of tropical cyclone damage on maximum wind speed and socioeconomic factors

2020 ◽  
Vol 15 (9) ◽  
pp. 094061
Author(s):  
Mengqi Ye ◽  
Jidong Wu ◽  
Wenhui Liu ◽  
Xin He ◽  
Cailin Wang
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Socioeconomic Factors ◽  
Maximum Wind Speed ◽  
Maximum Wind

Consistent Impacts of Surface Enthalpy and Drag Coefficient Uncertainty between an Analytical Model and Simulated Tropical Cyclone Maximum Intensity and Storm Structure

2020 ◽  
Vol 77 (9) ◽  
pp. 3059-3080
Author(s):  
Robert G. Nystrom ◽  
Richard Rotunno ◽  
Chris A. Davis ◽  
Fuqing Zhang
Keyword(s):  
Steady State ◽  
Wind Speed ◽  
Tropical Cyclone ◽  
Analytical Model ◽  
Maximum Intensity ◽  
Maximum Wind Speed ◽  
State Structure ◽  
Surface Exchange ◽  
Maximum Wind ◽  
Peak Intensity

Abstract Several previous studies have demonstrated the significant sensitivity of simulated tropical cyclone structure and intensity to variations in surface-exchange coefficients for enthalpy (Ck) and momentum (Cd), respectively. In this study we investigate the consistency of the estimated peak intensity, intensification rate, and steady-state structure between an analytical model and idealized axisymmetric numerical simulations for both constant Ck and Cd values and various wind speed–dependent representations of Ck and Cd. The present analysis with constant Ck and Cd values demonstrates that the maximum wind speed is similar for identical Ck/Cd values less than 1, regardless of whether changes were made to Ck or Cd. However, for a given Ck/Cd greater than 1, the simulated and theoretical maximum wind speed are both greater if Cd is decreased compared to Ck increased. This behavior results because of a smaller enthalpy disequilibrium at the radius of maximum winds for larger Ck. Additionally, the intensification rate is shown to increase with Ck and Cd and the steady-state normalized wind speed beyond the radius of maximum winds is shown to increase with increasing Cd. Experiments with wind speed–dependent Ck and Cd were found to be generally consistent, in terms of the intensification rate and the simulated and analytical-model-estimated maximum wind speed, with the experiments with constant Ck and Cd.

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