Filed observations of spray production function during Tropical Cyclones Olwyn and Veronica

2020 ◽  
Author(s):  
Alexander Babanin ◽  
Hongyu Ma ◽  
Xingkun Xu ◽  
Fangli Qiao
Keyword(s):  
Tropical Cyclones ◽  
Heat Fluxes ◽  
Sea Spray ◽  
Laser Array ◽  
Cyclone Intensity ◽  
Wind Speeds ◽  
The Indian Ocean ◽  
The Waves ◽  
Wave Properties

<p>Spray produced in Tropical Cyclones affects the dynamic and heat fluxes between the atmosphere and ocean, and thus can influence the Cyclone intensity in a number of ways. Measurements of the Sea Spray Generation Function (SSGF) in situ, however, are extremely challenging and correspondingly rare, and uncertainties in quantifying SSGF reach 1000 times.</p><p>In the presentation, measurements of the total volume of spray by means of a laser array in Tropical Cyclones Olwyn (2015) and Veronica (2019) in the Indian Ocean will be reported. They are used to develop a parameterisation of SSGF at wind speeds ranging from light to extreme. It is argued that the spray is produced by wind-over-the-waves, and therefore wave properties are also accounted for in the parameterisation.</p>

scholarly journals A Review of Parameterizations for Enthalpy and Momentum Fluxes from Sea Spray in Tropical Cyclones

2021 ◽  
Author(s):  
Sydney Sroka ◽  
Kerry Emanuel
Keyword(s):  
Tropical Cyclones ◽  
Critical Role ◽  
Sea Spray ◽  
High Wind ◽  
High Wind Speed ◽  
Wind Speeds ◽  
Crucial Component ◽  
Momentum Fluxes ◽  
Interaction Scheme ◽  
Speed Regime

AbstractThe intensity of tropical cyclones is sensitive to the air-sea fluxes of enthalpy and momentum. Sea spray plays a critical role in mediating enthalpy and momentum fluxes over the ocean’s surface at high wind speeds, and parameterizing the influence of sea spray is a crucial component of any air-sea interaction scheme used for the high wind regime where sea spray is ubiquitous. Many studies have proposed parameterizations of air-sea flux that incorporate the microphysics of sea spray evaporation and the mechanics of sea spray stress. Unfortunately, there is not yet a consensus on which parameterization best represents air-sea exchange in tropical cyclones, and the different proposed parameterizations can yield substantially different tropical cyclone intensities. This paper seeks to review the developments in parameterizations of the sea spray-mediated enthalpy and momentum fluxes for the high wind speed regime and to synthesize key findings that are common across many investigations.

Fuel for Cyclones: Quantification of Ocean‐Atmosphere Energy Exchange during Tropical Cyclones in the Bay of Bengal Using Indian Ocean Moored Observatories

2020 ◽  
Vol 54 (4) ◽  
pp. 81-92
Author(s):  
Ramasamy Venkatesan ◽  
Narayanaswamy Vedachalam ◽  
Gopalakrishnan Vengatesan ◽  
Robert A. Weller ◽  
Amit Tandon ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Tropical Cyclones ◽  
Bay Of Bengal ◽  
Heat Content ◽  
Coupled Models ◽  
Wind Speeds ◽  
Ocean Atmosphere ◽  
Time Availability ◽  
Ocean Atmosphere Interaction

AbstractBased on the in-situ subsurface thermal and salinity measurements from the Ocean Moored Buoy Network for Northern Indian Ocean (OMNI) during the passage of very severe tropical cyclones (TCs) in the Bay of Bengal, we have identified that the depth of ocean‐atmosphere interaction is limited by the depth of the pycnocline. During the TC Vardha and Phailin with cyclone-period-averaged wind speeds of 8 and 21 m/s, respectively, the maximum possible rates of water-vapor generation during the cyclone period, computed based on the salinity changes and considering precipitation, are 1.0 and 9.3 kg/m2/h, respectively. For the same wind speeds, based on the ocean heat content (OHC) changes, it is quantified that ~78% and 89% of the OHC changes are in the form of latent heat. The real-time availability of the in-situ subsurface parameters can be used in the ocean-atmosphere coupled models and intensification studies.

scholarly journals The Impact of Variational Assimilation of SSM/I and QuikSCAT Satellite Observations on the Numerical Simulation of Indian Ocean Tropical Cyclones

2008 ◽  
Vol 23 (3) ◽  
pp. 460-476 ◽  
Author(s):  
Randhir Singh ◽  
P. K. Pal ◽  
C. M. Kishtawal ◽  
P. C. Joshi
Keyword(s):  
Indian Ocean ◽  
Bay Of Bengal ◽  
Mesoscale Model ◽  
Initial Conditions ◽  
Lower Troposphere ◽  
Heat Fluxes ◽  
Cyclone Intensity ◽  
Wind Speeds ◽  
The Impact ◽  
Quikscat Winds

Abstract In this study, the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) with three-dimensional variational data assimilation (3DVAR) is utilized to investigate the influence of Special Sensor Microwave Imager (SSM/I) and Quick Scatterometer (QuikSCAT) observations on the prediction of an Indian Ocean tropical cyclone. The 3DVAR sensitivity runs were conducted separately with QuikSCAT wind vectors, SSM/I wind speeds, and total precipitable water (TPW) to investigate their individual impact on cyclone intensity and track. The Orissa supercyclone over the Bay of Bengal during October 1999 was used for simulation and assimilation experiments. Assimilation of the QuikSCAT wind vector improves the initial position of the cyclone’s center with a position error of 33 km, which was 163 km in the background analysis. Incorporation of QuikSCAT winds was found to increase the air–sea heat fluxes over the cyclonic region, which resulted in the improved simulated intensity when compared with the simulation made without QuikSCAT winds in the initial conditions. The cyclone track improved significantly with assimilation of QuikSCAT wind vectors. The track improvement resulted from relocation of the initial cyclonic vortex after assimilation of QuikSCAT wind vectors. Like QuikSCAT, assimilation of SSM/I wind speeds strengthened the cyclonic circulation in the initial conditions. This increase in the low-level wind speeds enhanced the air–sea exchange processes and improved the simulated intensity of the cyclone. The lack of information about the wind direction from SSM/I prevented it from making much of an impact on track prediction. As compared to the first guess, assimilation of the SSM/I TPW shows a moistening of the lower troposphere over most of the Bay of Bengal except over the central region of the cyclone, where the assimilation of SSM/I TPW reduces the lower-tropospheric moisture. This decrease of moisture in the TPW assimilation experiment resulted in a weak cyclone intensity.

scholarly journals The Use of a Spiral Band Model to Estimate Tropical Cyclone Intensity

2020 ◽  
Author(s):  
Boris Yurchak
Keyword(s):  
Tropical Cyclones ◽  
Radar Data ◽  
Physical Parameters ◽  
Band Model ◽  
Approximation Techniques ◽  
Cyclone Intensity ◽  
Wind Speeds ◽  
Radar Images ◽  
Logarithmic Spirals ◽  
Theoretical Finding

Spiral cloud-rain bands (SCRBs) are some of the most distinguishing features inherent in satellite and radar images of tropical cyclones (TC). The subject of the proposed research is the finding of a physically substantiated method for estimation of the TC’s intensity using SCRBs’ configuration parameters. To connect a rainband pattern to a physical process that conditions the spiraling feature of a rainband, it is assumed that the rainband’s configuration near the core of a TC is governed primarily by a streamline. In turn, based on the distribution of primarily forces in a TC, an analytical expression as a combination of hyperbolic and logarithmic spirals (HLS) for the description of TC spiral streamline (rainband) is retrieved. Parameters of the HLS are determined by the physical parameters of a TC, particularly, by the maximal wind speed (MWS). To apply this theoretical finding to practical estimation of the TC’s intensity, several approximation techniques are developed to “convert” rainband configuration to the estimation of the MWS. The developed techniques have been tested by exploring satellite infrared imageries and airborne and coastal radar data, and the outcomes were compared with in situ measurements of wind speeds and the best track data of tropical cyclones.

scholarly journals A Wind–Wave-Dependent Sea Spray Volume Flux Model Based on Field Experiments

2021 ◽  
Vol 9 (11) ◽  
pp. 1168
Author(s):  
Xingkun Xu ◽  
Joey J. Voermans ◽  
Hongyu Ma ◽  
Changlong Guan ◽  
Alexander V. Babanin
Keyword(s):  
Field Experiments ◽  
Wind Wave ◽  
Weather Forecasting ◽  
Sea Spray ◽  
Volume Flux ◽  
Laser Altimeter ◽  
Flux Model ◽  
Spray Volume ◽  
Wave Properties

Sea spray can contribute significantly to the exchanges of heat and momentum across the air–sea interface. However, while critical, sea spray physics are typically not included in operational atmospheric and oceanic models due to large uncertainties in their parameterizations. In large part, this is because of the scarcity of in-situ sea spray observations which prevent rigorous validation of existing sea spray models. Moreover, while sea spray is critically produced through the fundamental interactions between wind and waves, traditionally, sea spray models are parameterized in terms of wind properties only. In this study, we present novel in-situ observations of sea spray derived from a laser altimeter through the adoption of the Beer–Lambert law. Observations of sea spray cover a broad range of wind and wave properties and are used to develop a wind–wave-dependent sea spray volume flux model. Improved performance of the model is observed when wave properties are included, in contrast to a parameterization based on wind properties alone. The novel in-situ sea spray observations and the predictive model derived here are consistent with the classic spray model in both trend and magnitude. Our model and novel observations provide opportunities to improve the prediction of air–sea fluxes in operational weather forecasting models.

An Evaluation of Dvorak Technique–Based Tropical Cyclone Intensity Estimates

2010 ◽  
Vol 25 (5) ◽  
pp. 1362-1379 ◽  
Author(s):  
John A. Knaff ◽  
Daniel P. Brown ◽  
Joe Courtney ◽  
Gregory M. Gallina ◽  
John L. Beven
Keyword(s):  
Tropical Cyclone ◽  
Affect Intensity ◽  
Translation Speed ◽  
Atlantic Basin ◽  
Cyclone Intensity ◽  
Wind Speeds ◽  
Uniform Manner ◽  
Mean Square Errors ◽  
Practical Accuracy

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.

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

2008 ◽  
Vol 38 (6) ◽  
pp. 1313-1326 ◽  
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).

scholarly journals A sea spray aerosol flux parameterization encapsulating wave state

2014 ◽  
Vol 14 (4) ◽  
pp. 1837-1852 ◽  
Author(s):  
J. Ovadnevaite ◽  
A. Manders ◽  
G. de Leeuw ◽  
D. Ceburnis ◽  
C. Monahan ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Source Function ◽  
Eddy Correlation ◽  
Sea Spray ◽  
Physical Parameters ◽  
Wave State ◽  
Coastal Station ◽  
Wind Speeds ◽  
Sea Spray Aerosol

Abstract. A new sea spray source function (SSSF), termed Oceanflux Sea Spray Aerosol or OSSA, was derived based on in-situ sea spray aerosol measurements along with meteorological/physical parameters. Submicron sea spray aerosol fluxes derived from particle number concentration measurements at the Mace Head coastal station, on the west coast of Ireland, were used together with open-ocean eddy correlation flux measurements from the Eastern Atlantic Sea Spray, Gas Flux, and Whitecap (SEASAW) project cruise. In the overlapping size range, the data for Mace Head and SEASAW were found to be in a good agreement, which allowed deriving the new SSSF from the combined dataset spanning the dry diameter range from 15 nm to 6 μm. The OSSA source function has been parameterized in terms of five lognormal modes and the Reynolds number instead of the more commonly used wind speed, thereby encapsulating important influences of wave height, wind history, friction velocity, and viscosity. This formulation accounts for the different flux relationships associated with rising and waning wind speeds since these are included in the Reynolds number. Furthermore, the Reynolds number incorporates the kinematic viscosity of water, thus the SSSF inherently includes dependences on sea surface temperature and salinity. The temperature dependence of the resulting SSSF is similar to that of other in-situ derived source functions and results in lower production fluxes for cold waters and enhanced fluxes from warm waters as compared with SSSF formulations that do not include temperature effects.

scholarly journals Air-Sea Interactions over Eddies in the Brazil-Malvinas Confluence

2021 ◽  
Vol 13 (7) ◽  
pp. 1335
Author(s):  
Ronald Souza ◽  
Luciano Pezzi ◽  
Sebastiaan Swart ◽  
Fabrício Oliveira ◽  
Marcelo Santini
Keyword(s):  
Latent Heat ◽  
Large Scale ◽  
Surface Wind ◽  
Heat Fluxes ◽  
Lower Atmosphere ◽  
Meteorological Variables ◽  
Global Ocean ◽  
Study Region ◽  
Cold Core

The Brazil–Malvinas Confluence (BMC) is one of the most dynamical regions of the global ocean. Its variability is dominated by the mesoscale, mainly expressed by the presence of meanders and eddies, which are understood to be local regulators of air-sea interaction processes. The objective of this work is to study the local modulation of air-sea interaction variables by the presence of either a warm (ED1) and a cold core (ED2) eddy, present in the BMC, during September to November 2013. The translation and lifespans of both eddies were determined using satellite-derived sea level anomaly (SLA) data. Time series of satellite-derived surface wind data, as well as these and other meteorological variables, retrieved from ERA5 reanalysis at the eddies’ successive positions in time, allowed us to investigate the temporal modulation of the lower atmosphere by the eddies’ presence along their translation and lifespan. The reanalysis data indicate a mean increase of 78% in sensible and 55% in latent heat fluxes along the warm eddy trajectory in comparison to the surrounding ocean of the study region. Over the cold core eddy, on the other hand, we noticed a mean reduction of 49% and 25% in sensible and latent heat fluxes, respectively, compared to the adjacent ocean. Additionally, a field campaign observed both eddies and the lower atmosphere from ship-borne observations before, during and after crossing both eddies in the study region during October 2013. The presence of the eddies was imprinted on several surface meteorological variables depending on the sea surface temperature (SST) in the eddy cores. In situ oceanographic and meteorological data, together with high frequency micrometeorological data, were also used here to demonstrate that the local, rather than the large scale forcing of the eddies on the atmosphere above, is, as expected, the principal driver of air-sea interaction when transient atmospheric systems are stable (not actively varying) in the study region. We also make use of the in situ data to show the differences (biases) between bulk heat flux estimates (used on atmospheric reanalysis products) and eddy covariance measurements (taken as “sea truth”) of both sensible and latent heat fluxes. The findings demonstrate the importance of short-term changes (minutes to hours) in both the atmosphere and the ocean in contributing to these biases. We conclude by emphasizing the importance of the mesoscale oceanographic structures in the BMC on impacting local air-sea heat fluxes and the marine atmospheric boundary layer stability, especially under large scale, high-pressure atmospheric conditions.

scholarly journals A Hypothesis for the Redevelopment of Warm-Core Cyclones over Northern Australia

2008 ◽  
Vol 136 (10) ◽  
pp. 3863-3872 ◽  
Author(s):  
Kerry Emanuel ◽  
Jeff Callaghan ◽  
Peter Otto
Keyword(s):  
Heat Transfer ◽  
Thermal Diffusivity ◽  
Tropical Cyclones ◽  
Deep Layer ◽  
Heat Fluxes ◽  
Northern Australia ◽  
One Dimensional ◽  
Warm Core ◽  
Vertical Heat ◽  
Underlying Soil

Tropical cyclones moving inland over northern Australia are occasionally observed to reintensify, even in the absence of well-defined extratropical systems. Unlike cases of classical extratropical rejuvenation, such reintensifying storms retain their warm-core structure, often redeveloping such features as eyes. It is here hypothesized that the intensification or reintensification of these systems, christened agukabams, is made possible by large vertical heat fluxes from a deep layer of very hot, sandy soil that has been wetted by the first rains of the approaching systems, significantly increasing its thermal diffusivity. To test this hypothesis, simulations are performed with a simple tropical cyclone model coupled to a one-dimensional soil model. These simulations suggest that warm-core cyclones can indeed intensify when the underlying soil is sufficiently warm and wet and are maintained by heat transfer from the soil. The simulations also suggest that when the storms are sufficiently isolated from their oceanic source of moisture, the rainfall they produce is insufficient to keep the soil wet enough to transfer significant quantities of heat, and the storms then decay rapidly.

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