The Sound of Tropical Cyclones

Abstract Underwater ambient sound levels beneath tropical cyclones were measured using hydrophones onboard Lagrangian floats, which were air deployed in the paths of Hurricane Gustav (2008) and Typhoons Megi (2010) and Fanapi (2010). The sound levels at 40 Hz–50 kHz from 1- to 50-m depth were measured at wind speeds up to 45 m s−1. The measurements reveal a complex dependence of the sound level on wind speed due to the competing effects of sound generation by breaking wind waves and sound attenuation by quiescent bubbles. Sound level increases monotonically with increasing wind speed only for low frequencies (<200 Hz). At higher frequencies (>200 Hz), sound level first increases and then decreases with increasing wind speed. There is a wind speed that produces a maximum sound level for each frequency; the wind speed of the maximum sound level decreases with frequency. Sound level at >20 kHz mostly decreases with wind speed over the wind range 15–45 m s−1. The sound field is nearly uniform with depth in the upper 50 m with nearly all sound attenuation limited to the upper 2 m at all measured frequencies. A simple model of bubble trajectories based on the measured float trajectories finds that resonant bubbles at the high-frequency end of the observations (25 kHz) could easily be advected deeper than 2 m during tropical cyclones. Thus, bubble rise velocity alone cannot explain the lack of sound attenuation at these depths.

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On the clouds of bubbles formed by breaking wind-waves in deep water, and their role in air-sea gas transfer

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1982.0011 ◽

1982 ◽

Vol 304 (1483) ◽

pp. 155-210 ◽

Cited By ~ 271

Keyword(s):

Wind Speed ◽

Air Temperature ◽

Deep Water ◽

Wind Waves ◽

Gas Transfer ◽

Convective Conditions ◽

Breaking Wind Waves ◽

Stable Conditions ◽

Natural Tendency ◽

Small Bubbles

Clouds of small bubbles generated by wind waves breaking and producing whitecaps in deep water have been observed below the surface by using an inverted echo sounder. The bubbles are diffused down to several metres below the surface by turbulence against their natural tendency to rise. Measurements have been made at two sites, one in fresh water at Loch Ness and the other in the sea near O ban, northwest Scotland. Sonagraph records show bubble clouds of two distinct types, ‘ columnar clouds’ which appear in unstable or convective conditions w hen the air temperature is less than the surface water temperature, and ‘ billow clouds ’ which appear in stable conditions w hen the air temperature exceeds that of the water. Clouds penetrate deeper as the wind speed increases, and deeper in convective conditions than in stable conditions at the same wind speed. The response to a change in w ind speed occurs in a period of only a few minutes.

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Assessment of the noise produced by wind farms with the acoustically analogous techniques without stopping the noise source

Wind Engineering ◽

10.1177/0309524x18780395 ◽

2018 ◽

Vol 43 (2) ◽

pp. 201-209

Author(s):

Gino Iannace ◽

Amelia Trematerra ◽

Umberto Berardi

Keyword(s):

Wind Speed ◽

Wind Turbine ◽

Wind Turbines ◽

Wind Farm ◽

Noise Source ◽

Sound Field ◽

Wind Farms ◽

Sound Level ◽

Acoustic Measurements ◽

Relative Contribution

In Italy, wind turbines with a nominal power below 1 MW can be installed following simplified authorization procedures and are therefore becoming the preferred choice for promoters. The assessment of the noise of wind farms is not easy, due to economic reasons, with it being difficult to stop and assess the relative contribution of each wind turbine. Several acoustic measurements were taken inside homes located near a wind farm consisting of three wind turbines, each with a nominal power of 1 MW. The acoustic measurements were taken by placing sound level meters inside the houses at different wind speed values and wind directions. The acoustic measurements were taken using the acoustically analogous place technique. For economic reasons, the plant cannot be switched off. In this case, the sound field generated by the operation of the wind turbines was measured by placing two sound level meters in a house.

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An Examination of Wind Decay, Sustained Wind Speed Forecasts, and Gust Factors for Recent Tropical Cyclones in the Mid-Atlantic Region of the United States

Weather and Forecasting ◽

10.1175/waf-d-13-00125.1 ◽

2015 ◽

Vol 30 (1) ◽

pp. 153-176 ◽

Cited By ~ 6

Author(s):

Bryce Tyner ◽

Anantha Aiyyer ◽

Jonathan Blaes ◽

Donald Reid Hawkins

Keyword(s):

Surface Roughness ◽

Wind Speed ◽

Tropical Cyclones ◽

Surface Wind ◽

Software Tool ◽

Weather Forecast ◽

The United States ◽

Atlantic Region ◽

Wind Speeds ◽

Gust Factors

Abstract In this study, several analyses were conducted that were aimed at improving sustained wind speed and gust forecasts for tropical cyclones (TCs) affecting coastal regions. An objective wind speed forecast analysis of recent TCs affecting the mid-Atlantic region was first conducted to set a benchmark for improvement. Forecasts from the National Digital Forecast Database were compared to observations and surface wind analyses in the region. The analysis suggests a general overprediction of sustained wind speeds, especially for areas affected by the strongest winds. Currently, National Weather Service Weather Forecast Offices use a software tool known as the Tropical Cyclone Forecast/Advisory (TCM) wind tool (TCMWindTool) to develop their wind forecast grids. The tool assumes linear decay in the sustained wind speeds when interpolating the National Hurricane Center 12–24-hourly TCM product to hourly grids. An analysis of postlandfall wind decay for recent TCs was conducted to evaluate this assumption. Results indicate that large errors in the forecasted wind speeds can emerge, especially for stronger storms. Finally, an analysis of gust factors for recent TCs affecting the region was conducted. Gust factors associated with weak sustained wind speeds are shown to be highly variable but average around 1.5. The gust factors decrease to values around 1.2 for wind speeds above 40 knots (kt; 1 kt = 0.51 m s−1) and are in general insensitive to the wind direction, suggesting local rather than upstream surface roughness largely dictates the gust factor at a given location. Forecasters are encouraged to increase land reduction factors used in the TCMWindTool and to modify gust factors to account for factors including the sustained wind speed and local surface roughness.

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Calculating Dropwindsonde Location and Time from TEMP-DROP Messages for Accurate Assimilation and Analysis

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-17-0023.1 ◽

2017 ◽

Vol 34 (8) ◽

pp. 1673-1678 ◽

Cited By ~ 4

Author(s):

Sim D. Aberson ◽

Kathryn J. Sellwood ◽

Paul A. Leighton

Keyword(s):

Wind Speed ◽

Tropical Cyclones ◽

Current Practice ◽

Wind Speeds ◽

The Mean ◽

Fall Speed ◽

Mean Differences ◽

Release Location

AbstractCurrent practice is to transmit dropwindsonde data from aircraft using the TEMP-DROP format, which provides only the release location and time with 0.1° latitude × 0.1° longitude (about 11 km) and 1-h resolutions, respectively. The current dropwindsonde has a fall speed of approximately 15 m s−1, so the instrument will be advected faster horizontally than it will descend if the wind speed exceeds this value. Where wind speeds are greatest, such as in tropical cyclones, this will introduce large errors in the location of the observations, especially near the surface. A technique to calculate the correct time and location of each observation in the TEMP-DROP message is introduced. The mean differences between the calculated and reported locations are about 0.5 km for distance and 15 s for time, or <1% of the error size for distance and <10% for time.

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The impact of atmosphere-ocean-wave coupling on extreme surface wind forecasts

10.5194/egusphere-egu21-1273 ◽

2021 ◽

Author(s):

Emanuele Silvio Gentile ◽

Suzanne L. Gray ◽

Janet F. Barlow ◽

Huw W. Lewis ◽

John M. Edwards

Keyword(s):

Wind Speed ◽

Wind Waves ◽

Surface Wind ◽

Computational Cost ◽

Sea Surface ◽

Model Systems ◽

Sea State ◽

Extreme Surface ◽

Wind Speeds ◽

The Impact

Accurate modelling of air-sea surface exchanges is crucial for reliable extreme surface wind forecasts.&#160; While atmosphere-only weather forecast models represent ocean and wave effects through sea-state independent parametrizations, coupled multi-model systems capture sea-state dynamics by integrating feedbacks between atmosphere, ocean and wave model components.Here, we present the results of studying the sensitivity of extreme surface wind speeds to air-sea exchanges at kilometre scale using coupled and uncoupled configurations of the Met Office's UK Regional Coupled Environmental Prediction (UKC4) system. The case period includes the passage of extra-tropical cyclones Helen, Ali, and Bronagh, which brought maximum gusts of 36 ms-1 over the UK.Compared to the atmosphere-only results, coupling to ocean decreases the domain-average sea surface temperature by up to 0.5 K. Inclusion of coupling to waves decreases the 98th percentile 10-m wind speed by up to 2 ms-1 as young, growing wind waves decrease wind speed by increasing the sea aerodynamic roughness. Impacts on gusts are more modest, with local reductions of up to 1ms -1, due to enhanced boundary-layer turbulence which partially offsets air-sea momentum transfer.Using a new drag parametrization based on the COARE~4.0 scheme, with a cap on the neutral drag coefficient and decrease for wind speeds exceeding 27 ms-1 , the atmosphere-only model achieves equivalent impacts on 10-m wind speeds and gusts as from coupling to waves. Overall, the new drag parametrization achieves the same 20% improvement in forecast 10-m wind skill as coupling to waves, with&#160; the&#160; advantage&#160; of saving the computational cost of the ocean and wave models.&#160;

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Level dependence of spatial processing in the primate auditory cortex

Journal of Neurophysiology ◽

10.1152/jn.00500.2011 ◽

2012 ◽

Vol 108 (3) ◽

pp. 810-826 ◽

Cited By ~ 25

Author(s):

Yi Zhou ◽

Xiaoqin Wang

Keyword(s):

Auditory Cortex ◽

Sound Field ◽

Primary Auditory Cortex ◽

Neural Mechanism ◽

Stimulus Level ◽

Sound Level ◽

Broadband Noise ◽

Spatial Tuning ◽

Sound Levels ◽

Tuning Width

Sound localization in both humans and monkeys is tolerant to changes in sound levels. The underlying neural mechanism, however, is not well understood. This study reports the level dependence of individual neurons' spatial receptive fields (SRFs) in the primary auditory cortex (A1) and the adjacent caudal field in awake marmoset monkeys. We found that most neurons' excitatory SRF components were spatially confined in response to broadband noise stimuli delivered from the upper frontal sound field. Approximately half the recorded neurons exhibited little change in spatial tuning width over a ∼20-dB change in sound level, whereas the remaining neurons showed either expansion or contraction in their tuning widths. Increased sound levels did not alter the percent distribution of tuning width for neurons collected in either cortical field. The population-averaged responses remained tuned between 30- and 80-dB sound pressure levels for neuronal groups preferring contralateral, midline, and ipsilateral locations. We further investigated the spatial extent and level dependence of the suppressive component of SRFs using a pair of sequentially presented stimuli. Forward suppression was observed when the stimuli were delivered from “far” locations, distant to the excitatory center of an SRF. In contrast to spatially confined excitation, the strength of suppression typically increased with stimulus level at both the excitatory center and far regions of an SRF. These findings indicate that although the spatial tuning of individual neurons varied with stimulus levels, their ensemble responses were level tolerant. Widespread spatial suppression may play an important role in limiting the sizes of SRFs at high sound levels in the auditory cortex.

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A Comparison of ASOS Near-Surface Winds and WSR-88D-Derived Wind Speed Profiles Measured in Landfalling Tropical Cyclones

Weather and Forecasting ◽

10.1175/waf-d-15-0162.1 ◽

2016 ◽

Vol 31 (4) ◽

pp. 1343-1361 ◽

Cited By ~ 3

Author(s):

Richard J. Krupar ◽

John L. Schroeder ◽

Douglas A. Smith ◽

Song-Lak Kang ◽

Sylvie Lorsolo

Keyword(s):

Boundary Layer ◽

Wind Speed ◽

Linear Regression ◽

Tropical Cyclones ◽

Estimation Methods ◽

Speed Ratio ◽

Near Surface ◽

Site Specific ◽

Wind Speeds ◽

Landfalling Tropical Cyclones

Abstract A set of velocity–azimuth display (VAD) wind speed profiles derived from coastal Weather Surveillance Radar-1988 Doppler (WSR-88D) systems was paired with Automated Surface Observing System (ASOS) 10-m standardized mean and nonstandardized gust wind speeds measured within 10 km of nearby WSR-88Ds. The goal was to formulate an appropriate methodology and empirical relationships to estimate overland near-surface wind conditions in landfalling tropical cyclones (TCs) using VAD tropical cyclone boundary layer (TCBL) lower-tropospheric wind measurements. A total of 17 TCs and seven ASOS/WSR-88D sites were used to construct a unique comparative dataset. Four estimation methods including the log and power laws, mean and gust wind speed ratio (WSR) methods, and curve fitting with linear regression and polynomial fits were evaluated. Results from the evaluation show that WSR-88D site-specific linear regression equations using a VAD 0–200-m layer average wind speed and nonzero intercepts provided the most accurate predictions of the ASOS 10-m standardized mean wind speed. Results also show that a non-site-specific linear regression model using a VAD 0–500-m mean boundary layer (MBL) wind speed and nonzero intercept is 1.07% more accurate than using a single-gust WSR to predict ASOS 10-m nonstandardized gust wind speeds. Only 2.15% of the ASOS 10-m nonstandardized maximum 3-s gust wind speeds were found to exceed the VAD 0–500-m MBL wind speed, indicating that the VAD 0–500-m MBL wind speed represents a viable source of momentum available for transport to the surface in the form of a gust.

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A Global Climatology of Tropical Cyclone Eyes

Monthly Weather Review ◽

10.1175/mwr-d-17-0343.1 ◽

2018 ◽

Vol 146 (7) ◽

pp. 2089-2101 ◽

Cited By ~ 8

Author(s):

Kenneth R. Knapp ◽

Christopher S. Velden ◽

Anthony J. Wimmers

Keyword(s):

Wind Speed ◽

Tropical Cyclones ◽

Objective Measure ◽

Infrared Images ◽

Area At Risk ◽

Wind Speeds ◽

Time Period ◽

Agency Practices ◽

Eye Location ◽

The Western Pacific

Abstract Intense tropical cyclones (TCs) generally produce a cloud-free center with calm winds, called the eye. The Automated Rotational Center Hurricane Eye Retrieval (ARCHER) algorithm is used to analyze Hurricane Satellite (HURSAT) B1 infrared satellite imagery data for storms occurring globally from 1982 to 2015. HURSAT B1 data provide 3-hourly observations of TCs. The result is a 34-yr climatology of eye location and size. During that time period, eyes are identified in about 13% of all infrared images and slightly more than half of all storms produced an eye. Those that produce an eye have (on average) 30 h of eye scenes. Hurricane Ioke (1992) had the most eye images (98, which is 12 complete days with an eye). The median wind speed of a system with an eye is 97 kt (50 m s−1) [cf. 35 kt (18 m s−1) for those without an eye]. Eyes are much more frequent in the Northern Hemisphere (particularly in the western Pacific) but eyes are larger in the Southern Hemisphere. The regions where eyes occur are expanding poleward, thus expanding the area at risk of TC-related damage. Also, eye scene occurrence can provide an objective measure of TC activity in place of those based on maximum wind speeds, which can be affected by available observations and forecast agency practices.

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Estimation of Surface Wind Speeds in Tropical Cyclones

Bulletin of the American Meteorological Society ◽

10.1175/1520-0477-41.1.9 ◽

1960 ◽

Vol 41 (1) ◽

pp. 9-13

Author(s):

C. L. Jordan ◽

Limon E. Fortner

Keyword(s):

Wind Speed ◽

Tropical Cyclones ◽

Surface Wind ◽

Surface Wind Speed ◽

Wind Speeds

The surface wind-speed reports in tropical cyclones given by aircraft-reconnaissance observers are based almost exclusively on state-of-sea observations. The reliability of wind estimates prepared in this manner is considered along with some of the practical difficulties involved in making observations from reconnaissance aircraft.

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A Model for Air–Sea Interaction Bulk Coefficient over a Warm Mature Sea under Strong Wind

Journal of Physical Oceanography ◽

10.1175/2007jpo3828.1 ◽

2008 ◽

Vol 38 (6) ◽

pp. 1313-1326 ◽

Cited By ~ 3

Author(s):

Naoto Kihara ◽

Hiromaru Hirakuchi

Keyword(s):

Wind Speed ◽

Tropical Cyclones ◽

Present Model ◽

Heat Fluxes ◽

Strong Wind ◽

Exchange Coefficient ◽

Total Enthalpy ◽

Wind Speeds ◽

A Value ◽

Strong Winds

Abstract A boundary layer model for evaluating sensible and latent heat fluxes over a mature sea accounting for sea spray effects at wind speeds of up to 28 m s−1 is presented. Heat exchange across the ocean surface controls the development of tropical cyclones, and Emanuel’s theory suggests that the ratio of the exchange coefficient of total enthalpy to the drag coefficient should be greater than 0.75 to maintain the intensity of tropical cyclones. However, traditional bulk algorithms predict a monotonic decrease in this ratio with increasing wind speed, giving a value of less than 0.5 under tropical cyclone conditions. The present model describes a decrease in the ratio with increasing wind speed under weak to moderate winds (<20 m s−1), and a plateau at approximately 0.7 under strong winds (>20 m s−1).

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