Simulating synthetic tropical cyclone tracks for statistically reliable wind and pressure estimations

Abstract. The design of coastal protection measures and the quantification of coastal risks at locations affected by tropical cyclones (TCs) are often based solely on the analysis of historical cyclone tracks. Due to data scarcity and the random nature of TCs, the assumption that a hypothetical TC could hit a neighboring area with equal likelihood to past events can potentially lead to over- and/or underestimations of extremes and associated risks. The simulation of numerous synthetic TC tracks based on (historical) data can overcome this limitation. In this paper, a new method for the generation of synthetic TC tracks is proposed. The method has been implemented in the highly flexible open-source Tropical Cyclone Wind Statistical Estimation Tool (TCWiSE). TCWiSE uses an empirical track model based on Markov chains and can simulate thousands of synthetic TC tracks and wind fields in any oceanic basin based on any (historical) data source. Moreover, the tool can be used to determine the wind extremes, and the output can be used for the reliable assessment of coastal hazards. Validation results for the Gulf of Mexico show that TC patterns and extreme wind speeds are well reproduced by TCWiSE.

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Simulating Synthetic Tropical Cyclone Tracks for Statistically Reliable Wind and Pressure Estimations

10.5194/nhess-2020-250 ◽

2020 ◽

Author(s):

Kees Nederhoff ◽

Jasper Hoek ◽

Tim Leijnse ◽

Maarten van Ormondt ◽

Sofia Caires ◽

...

Keyword(s):

Tropical Cyclone ◽

Historical Data ◽

Coastal Hazards ◽

Coastal Protection ◽

Wind Fields ◽

Protection Measures ◽

Wind Speeds ◽

Reliable Assessment ◽

Cyclone Tracks ◽

Extreme Wind Speeds

Abstract. The design of coastal protection measures and the quantification of coastal risks at locations affected by tropical cyclone (TC) are often based solely on the analysis of historical cyclone tracks. Due to data scarcity and the random nature of TCs, the assumption that future TCs could hit a neighboring area with equal likelihood than past events can potentially lead to over- and/or underestimations of extremes and associated risks. The simulation of numerous synthetic TC tracks based on (historical) data can overcome this limitation. In this paper, a new method for the generation of synthetic TC tracks is proposed. The method has been implemented in the highly flexible open-source Tropical Cyclone Wind Statistical Estimation Tool (TCWiSE). TCWiSE uses an Empirical Track Model based on Markov-chains and can simulate thousands of synthetic TC tracks and wind fields in any oceanic basin based on any (historical) data source. Moreover, the tool can be used to determine the wind extremes and the output can be used for the reliable assessment of coastal hazards. Validation results for the Gulf of Mexico show that TC patterns and extreme wind speeds are well reproduced by TCWiSE.

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Generating reliable estimates of tropical cyclone induced coastal hazards along the Bay of Bengal for current and future climates using synthetic tracks

10.5194/nhess-2021-181 ◽

2021 ◽

Author(s):

Tim Willem Bart Leijnse ◽

Alessio Giardino ◽

Kees Nederhoff ◽

Sofia Caires

Keyword(s):

Tropical Cyclone ◽

Tropical Cyclones ◽

Storm Surge ◽

Bay Of Bengal ◽

Coastal Hazards ◽

Wind Fields ◽

Tropical Cyclone Frequency ◽

Wind Speeds ◽

Wave Heights ◽

Cyclone Frequency

Abstract. Deriving reliable estimates of design water levels and wave conditions resulting from tropical cyclones is a challenging problem of high relevance for, among others, coastal and offshore engineering projects and risk assessment studies. Tropical cyclone geometry and wind speeds have been recorded for the past few decades only, therefore resulting in poorly reliable estimates of the extremes, especially at regions characterized by a low number of past tropical cyclone events. In this paper, this challenge is overcome by using synthetic tropical cyclone tracks and wind fields generated by the open source tool TCWiSE (Tropical Cyclone Wind Statistical Estimation), to create thousands of realizations representative for 1,000 years of tropical cyclone activity for the Bay of Bengal. Each of these realizations is used to force coupled storm surge and wave simulations by means of the processed-based Delft3D Flexible Mesh Suite. It is shown that the use of synthetic tracks provides reliable estimates of the statistics of the first-order hazard (i.e. wind speed) compared to the statistics derived for historical tropical cyclones. Based on estimated wind fields, second-order hazards (i.e. storm surge and waves) are computed. The estimates of the extreme values derived for wind speed, wave height and storm surge are shown to converge within the 1,000 years of simulated cyclone tracks. Comparing second-order hazard estimates based on historical and synthetic tracks show that, for this case study, the use of historical tracks (a deterministic approach) leads to an underestimation of the mean computed storm surge up to −30 %. Differences between the use of synthetic versus historical tracks are characterized by a large spatial variability along the Bay of Bengal, where regions with a lower probability of occurrence of tropical cyclones show the largest difference in predicted storm surge and wave heights. In addition, the use of historical tracks leads to much larger uncertainty bands in the estimation of both storm surges and wave heights, with confidence intervals being +80 % larger compared to those estimated by using synthetic tracks (probabilistic approach). Based on the same tropical cyclone realizations, the effect that changes in tropical cyclone frequency and intensity, possibly resulting from climate change, may have on modelled storm surge and wave heights were computed. An increase in tropical cyclone frequency of +25.6 % and wind intensity of +1.6 %, based on literature values, could result in an increase of storm surge and wave heights of +11 % and +9 % respectively. This suggest that climate change could increase tropical cyclone induced coastal hazards more than just the actual increase in maximum wind speeds.

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A global historical data set of tropical cyclone exposure (TCE-DAT)

10.5194/essd-2017-78 ◽

2017 ◽

Cited By ~ 1

Author(s):

Tobias Geiger ◽

Katja Frieler ◽

David N. Bresch

Keyword(s):

Tropical Cyclone ◽

Tropical Cyclones ◽

The United States ◽

Long Term Effects ◽

Wind Fields ◽

Damage Functions ◽

Data Set ◽

Wind Field Model ◽

Wind Speeds ◽

The Difference

Abstract. Tropical cyclones pose a major risk to societies worldwide with about 22 million directly-affected people and damages of $29 billion on average per year over the last 20 years. While data on observed cyclones tracks (location of the center) and wind speeds is publically available these data sets do not contain information about the spatial extent of the storm and people or assets exposed. Here, we apply a simplified wind field model to estimate the areas exposed to wind speeds above 34, 64, and 96 knots. Based on available spatially-explicit data on population densities and Gross Domestic Product (GDP) we estimate 1) the number of people and 2) the sum of assets exposed to wind speeds above these thresholds accounting for temporal changes in historical distribution of population and assets (TCE-hist) and assuming fixed 2015 patterns (TCE-2015). The associated country-event level exposure data (TCE-DAT) covers the period 1950 to 2015 and is freely available at http://doi.org/10.5880/pik.2017.005. It is considered key information to 1) assess the contribution of climatological versus socio-economic drivers of changes in exposure to tropical cyclones, 2) estimate changes in vulnerability from the difference in exposure and reported damages and calibrate associated damage functions, and 3) build improved exposure-based predictors to estimate higher-level societal impacts such as long-term effects on GDP, employment, or migration. We validate the adequateness of our methodology by comparing our exposure estimate to estimated exposure obtained from reported wind fields available since 1988 for the United States. We expect that the free availability of the underlying model and TCE-DAT will make research on tropical cyclone risks more accessible to non-experts and stakeholders.

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Microphysics-Based Bulk Parameterizations of Enthalpy and Momentum Fluxes for Tropical Cyclones

10.5194/egusphere-egu2020-4383 ◽

2020 ◽

Author(s):

Sydney Sroka ◽

Kerry Emanuel

Keyword(s):

Boundary Layer ◽

Tropical Cyclone ◽

State Of The Art ◽

Sea Spray ◽

Wind Speeds ◽

Extreme Wind ◽

Momentum Fluxes ◽

Forecast Models ◽

Extreme Wind Speeds ◽

Tropical Cyclone Boundary Layer

<p>Despite the powerful influence that sea spray has on air-sea enthalpy and momentum fluxes, most state-of-the-art tropical cyclone forecast models do not incorporate the microphysics of sea spray evaporation into their boundary layer flux schemes. Since the air-sea enthalpy and momentum fluxes control a tropical cyclone&#8217;s intensification rate, increasing the accuracy of the associated bulk parameterizations is crucially important for improving forecast skill. New microphysics-based bulk parameterizations for enthalpy and momentum flux through the tropical cyclone boundary layer are developed from a set of prognostic evaporation equations and numerical simulations of evaporating, multiphase flow subject to extreme wind speeds. The microphysics-based parameterizations are computationally inexpensive and are functions of the local environmental conditions; these features allow forecast models to efficiently vary the air-sea enthalpy and momentum fluxes in space and time. By developing microphysics-based bulk parameterizations, the influence that sea spray exerts on tropical cyclone intensification can be more accurately simulated and intensity forecasts could be improved.</p>

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Coastal Stability and Micro Morphology; Disturbances due to Human Interventions along West Coast of India

10.5194/egusphere-egu2020-7140 ◽

2020 ◽

Author(s):

Rafeeque Mk ◽

Akhil Thulasidharan ◽

Mintu E George ◽

Suresh Babu Ds ◽

Prasad Tk

Keyword(s):

Coastal Region ◽

Coastal Hazards ◽

Coastal Protection ◽

Peninsular India ◽

Coastal Morphology ◽

Protection Measures ◽

The World ◽

Human Interventions ◽

Kerala State ◽

Micro Morphology

<p>Coastal areas are known as cradles of civilization from the beginning of human settlements and the coastal belts in tropics experience high density of population all over the world. Indian coastal region is one of the most populated coastal belts of the world. Kerala coastal region of South West Peninsular India hosts 2931 person per sq. km. Stability of coastal zone helps to prevent the intensity of coastal hazards like extreme waves, coastal flooding and coastal erosion, which is quite noticeable in the northern part of Kerala state, when compared to the southern coastal region. The paleo-shoreline of Kozhikode coast in northern Kerala is identified as 2.5 to 5 km landward from the modern shoreline in the Beypur &#8211; Kallayi sector, 1 to 2 km in the Kallayi &#8211; Korapuzha Sector and 1 to 2.5 km in the Korapuzha &#8211; Quilandi Sector. This proves that the area is an accreting one over the recent geological history. The sediment discharge of Chaliyar, Korapuzha, Kadalundi and Kallayi rivers along with micro morphology leads to the evolution and development of this coastal plain for last few centuries. Paleo channels of this area changed its direction in many places during Holocene &#8211; Pleistocene period under the tidal influence. Nearshore bottom features of the area got diversified with parallel and transverse bars, reefs, exposed and buried rocks. The major nearshore features are demarcated as Kadalur Cape, Thoovappara, Elathur Cape, Thikkodi reef, Kadalur reef, Anchorage reef, Coote reef, Calicut reef, Rocky It, Gilham rocks, Rocky points, Black rock and Puthiyangadi bay. As a fast growing urbanised coastal city of the state, the Kozhikkode coast line is subjected to intense human interventions and thereby adversely affect sustainability of the coastline. Construction of two major fishing harbours, vis. Puthiyappa and Quilandi and Beypur port in 1990s re-defined the coastal morphology and nearshore bottom features of the sector. Shoreline towards the south of Puthiyappa harbour and Beypur breakwater is accreted and vast beach was developed while the Quilandi harbour doesn&#8217;t have much influence on sediment drift. Rocky coast, sand bed, seasonal sand bar and exposed and buried rocks have been properly documented in the paper. Along with those natural features, the artificial landforms and coastal protection measures have been analysed for understanding the disturbances in the coastal stability of the area. One-meter contour of the bathymetry line runs parallel to the coast except in the near shore of the Elathur and Kadalur headlands. Current investigations show that 48 percent of the total coastline can be considered as stable (Quilandi - Korapuzha and Korapuzha &#8211; Kallayi sectors), while 36 percent is erosion prone (Kallayi &#8211; Beypur Sector) and the rest is accreting.</p>

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Tropical Cyclone Wind Retrievals from the Advanced Microwave Sounding Unit: Application to Surface Wind Analysis

Journal of Applied Meteorology and Climatology ◽

10.1175/jam2352.1 ◽

2006 ◽

Vol 45 (3) ◽

pp. 399-415 ◽

Cited By ~ 32

Author(s):

Kotaro Bessho ◽

Mark DeMaria ◽

John A. Knaff

Keyword(s):

Tropical Cyclone ◽

Wind Direction ◽

Surface Wind ◽

Wind Fields ◽

Directional Bias ◽

Wind Speeds ◽

Research Division ◽

Microwave Sounding Unit ◽

Microwave Sounding ◽

Advanced Microwave Sounding Unit

Abstract Horizontal winds at 850 hPa from tropical cyclones retrieved using the nonlinear balance equation, where the mass field was determined from Advanced Microwave Sounding Unit (AMSU) temperature soundings, are compared with the surface wind fields derived from NASA's Quick Scatterometer (QuikSCAT) and Hurricane Research Division H*Wind analyses. It was found that the AMSU-derived wind speeds at 850 hPa have linear relations with the surface wind speeds from QuikSCAT or H*Wind. There are also characteristic biases of wind direction between AMSU and QuikSCAT or H*Wind. Using this information to adjust the speed and correct for the directional bias, a new algorithm was developed for estimation of the tropical cyclone surface wind field from the AMSU-derived 850-hPa winds. The algorithm was evaluated in two independent cases from Hurricanes Floyd (1999) and Michelle (2001), which were observed simultaneously by AMSU, QuikSCAT, and H*Wind. In this evaluation the AMSU adjustment algorithm for wind speed worked well. Results also showed that the bias correction algorithm for wind direction has room for improvement.

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Estimates of tropical cyclone geometry parameters based on best track data

10.5194/nhess-2019-119 ◽

2019 ◽

Author(s):

Kees Nederhoff ◽

Alessio Giardino ◽

Maarten van Ormondt ◽

Deepak Vatvani

Keyword(s):

Wind Speed ◽

Tropical Cyclone ◽

Wind Profile ◽

Wind Fields ◽

Engineering Applications ◽

Wind Speeds ◽

Pressure Fields ◽

Ne Pacific ◽

Wind Profiles

Abstract. Parametric wind profiles are commonly applied in a number of engineering applications for the generation of tropical cyclone (TC) wind and pressure fields. Nevertheless, existing formulations for computing wind fields often lack the required accuracy when the TC geometry is not known. This may affect the accuracy of the computed impacts generated by these winds. In this paper, empirical stochastic relationships are derived to describe two important parameters affecting the TC geometry: radius of maximum winds (RMW) and the radius of gale force winds (∆AR35). These relationships are formulated using best track data (BTD) for all seven ocean basins (Atlantic, S/NW/NE Pacific, N/SW/SE Indian Oceans). This makes it possible to a) estimate RMW and ∆AR35 when these properties are not known and b) generate improved parametric wind fields for all oceanic basins. Validation results show how the proposed relationships allow the TC geometry to be represented with higher accuracy than when using relationships available from the literature. Outer wind speeds can be well reproduced by the commonly used Holland wind profile when calibrated using information either from best-track-data or from the proposed relationships. The scripts to compute the TC geometry and the outer wind speed are freely available via Delft Dashboard.

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Estimates of tropical cyclone geometry parameters based on best-track data

Natural Hazards and Earth System Science ◽

10.5194/nhess-19-2359-2019 ◽

2019 ◽

Vol 19 (11) ◽

pp. 2359-2370 ◽

Cited By ~ 1

Author(s):

Kees Nederhoff ◽

Alessio Giardino ◽

Maarten van Ormondt ◽

Deepak Vatvani

Keyword(s):

Wind Speed ◽

Tropical Cyclone ◽

Wind Profile ◽

Wind Fields ◽

Engineering Applications ◽

Wind Speeds ◽

Pressure Fields ◽

Ne Pacific ◽

Wind Profiles

Abstract. Parametric wind profiles are commonly applied in a number of engineering applications for the generation of tropical cyclone (TC) wind and pressure fields. Nevertheless, existing formulations for computing wind fields often lack the required accuracy when the TC geometry is not known. This may affect the accuracy of the computed impacts generated by these winds. In this paper, empirical stochastic relationships are derived to describe two important parameters affecting the TC geometry: radius of maximum winds (RMW) and the radius of gale-force winds (ΔAR35). These relationships are formulated using best-track data (BTD) for all seven ocean basins (Atlantic; S, NW, and NE Pacific; and N, SW, and SE Indian oceans). This makes it possible to (a) estimate RMW and ΔAR35 when these properties are not known and (b) generate improved parametric wind fields for all oceanic basins. Validation results show how the proposed relationships allow the TC geometry to be represented with higher accuracy than when using relationships available from literature. Outer wind speeds can be reproduced well by the commonly used Holland wind profile when calibrated using information either from best-track data or from the proposed relationships. The scripts to compute the TC geometry and the outer wind speed are freely available via the following URL: https://bit.ly/2k9py1J (last access: October 2019).

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A Study of the Intensity of Tropical Cyclone Idai Using Dual-Polarization Sentinel-1 Data

Remote Sensing ◽

10.3390/rs11232837 ◽

2019 ◽

Vol 11 (23) ◽

pp. 2837 ◽

Cited By ~ 2

Author(s):

Peng Yu ◽

Johnny A. Johannessen ◽

Xiao-Hai Yan ◽

Xupu Geng ◽

Xiaojing Zhong ◽

...

Keyword(s):

Wind Speed ◽

Tropical Cyclone ◽

Band Model ◽

Strong Wind ◽

Cross Polarization ◽

Dual Polarization ◽

Wind Fields ◽

Polarization Model ◽

Wind Speeds ◽

Intense Storm

Monitoring the intensity and size of a tropical cyclone (TC) is a challenging task, and is important for reducing losses of lives and property. In this study, we use Idai, one of the deadliest TCs on record in the Southern Hemisphere, as an example. Dual-polarization synthetic aperture radar (SAR) measurements from the Copernicus Sentinel-1 mission are used to examine the TC structure and intensity. The wind speed is estimated and compared using well known C-band model functions based on calibrated cross-polarization SAR images. Because of the relatively high noise floor of the Sentinel-1 data, wind speeds under 20 m/s from cross-polarization models are ignored and replaced by low to moderate wind speeds retrieved from co-polarization radar signals. Wind fields retrieved from the co- and cross-polarization model results are then merged together to estimate the TC size and the TC fullness scale, a concept related to the wind structure of a storm. Idai has a very strong wind speed and fullness structure, indicating that it was indeed a very intense storm. The approach demonstrates that open and freely available Sentinel-1 SAR data is a unique dataset to estimate the potential destructiveness of similar natural disasters like Idai.

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A probabilistic model for estimating ocean-spray distribution in extreme tropical cyclone winds

MAUSAM ◽

10.54302/mausam.v48i4.4316 ◽

2021 ◽

Vol 48 (4) ◽

pp. 489-498

Author(s):

JAMES LIGHT HILL

Keyword(s):

Tropical Cyclone ◽

Initial Temperature ◽

Mechanical Energy ◽

Spray Cooling ◽

Wind Speeds ◽

Extreme Wind ◽

Future Global Warming ◽

Ocean Spray ◽

Spray Distribution ◽

Extreme Wind Speeds

ABSTRACT. Serious gaps in knowledge about ocean spray at wind speeds over 28 m/s remain difficult to fill by observation or experiment; yet refined study of the thermodynamics of Tropical Cyclones (including typhoons and hurricanes) requires assessment of the hypothesis that ‘spray cooling’ at extreme wind speeds may act to reduce (i) the initial temperature of saturated air rising in the eyewall and so also (ii) the input of mechanical energy into the airflow as a whole. Such progressive reductions at higher speeds could, for example, make any possible influence, of future global warming on Tropical Cyclone intensification largely se1f-limiting. In order to help in extrapolation of knowledge on ocean spray to extreme wind speeds, a probabilistic analysis is introduced which allows for the effects of gusts, gravity and evaporation on droplet distributions yet all other respect is as simple as possible. Preliminary indications from this simplified analysis appear to confirm the potential importance of spray cooling.

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