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Glejin, J., V. Sanil Kumar, T. N. Balakrishnan Nair, and J. Singh. "Influence of winds on temporally varying short and long period gravity waves in the near shore regions of Eastern Arabian Sea." Ocean Science Discussions 9, no. 5 (September 25, 2012): 3021–47. http://dx.doi.org/10.5194/osd-9-3021-2012.
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Abstract. Wave data collected off Ratnagiri, west coast of India during 1 May 2010 to 30 April 2012 is used in the study. Seasonal and annual variation in wave data controlled by the local wind system such as sea breeze and land breeze, and remote wind generated long period waves observed along the west coast of India, is studied. Sea breeze plays an important role in determining the sea state during pre and post monsoon seasons and the maximum wave height is observed during peak hours of sea breeze at 15:00 UTC. Long period waves (peak period over 13 s) are observed mainly during the pre and the post monsoon season. Maximum peak period observed during the study is 22 s and is in the month of October. Long period waves observed during the south west monsoon period of 2011 are identified as swell propagated from the Southern Ocean with an estimated travelling time of 5–6 days. The swells reaching the Arabian Sea from the South Indian Ocean and Southern Ocean, due to storms during the pre and post monsoon periods will modify the near surface winds, due to the dominant wave induced wind regime. Energy spectrum of observed waves indicates onset and decline of strong south west monsoon winds. Convergence of energy-containing frequency bands corresponding to short period waves (Tp < 8 s) and long period waves (Tp > 13 s) to intermediate period waves (8 < Tp < 13 s) are observed at the end of the pre monsoon season; divergence is observed during the start of the post monsoon period from intermediate period waves to short period waves and long period waves. South west monsoon period is characterized by the energy corresponding to the frequency band of intermediate period waves along the west coast of India.
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Glejin, J., V. Sanil Kumar, T. M. Balakrishnan Nair, and J. Singh. "Influence of winds on temporally varying short and long period gravity waves in the near shore regions of the eastern Arabian Sea." Ocean Science 9, no. 2 (March 20, 2013): 343–53. http://dx.doi.org/10.5194/os-9-343-2013.
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Abstract. Wave data collected off Ratnagiri, west coast of India, during 1 May 2010 to 30 April 2012 are used in this study. Seasonal and annual variations in wave data controlled by the local wind system such as sea breeze and land breeze, and remote wind generated long period waves are also studied. The role of sea breeze on the sea state during pre- and postmonsoon seasons is studied and it is found that the maximum wave height is observed at 15:00 UTC during the premonsoon season, with an estimated difference in time lag of 1–2 h in maximum wave height between premonsoon and postmonsoon seasons. Observed waves are classified in to (i) short waves (Tp < 8 s), (ii) intermediate waves (8 < Tp < 13 s), and (iii) long waves (Tp> 13 s) based on peak period (Tp) and the percentages of occurrence of each category are estimated. Long period waves are observed mainly during the pre- and the postmonsoon seasons. During the southwest monsoon period, the waves with period > 13 s are a minimum. An event during 2011 is identified as swells propagated from the Southern Ocean with an estimated travelling time of 5–6 days. The swells reaching the Arabian Sea from the south Indian Ocean and Southern Ocean, due to storms during the pre- and postmonsoon periods, modify the near surface winds due to higher phase wave celerity than the wind speed. Estimation of inverse wave age using large-scale winds such as NCEP (National Centers for Environmental Prediction) reflects the presence of cyclonic activity during pre- and postmonsoon seasons but not the effect of the local sea breeze/land breeze wind system.
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Poulose, Jismy, A. D. Rao, and Prasad K. Bhaskaran. "Role of continental shelf on non-linear interaction of storm surges, tides and wind waves: An idealized study representing the west coast of India." Estuarine, Coastal and Shelf Science 207 (July 2018): 457–70. http://dx.doi.org/10.1016/j.ecss.2017.06.007.
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DATTATRI, J., and P. VIJAYA KUMAR. "Wave Prediction for the east coast of India under storm conditions in the Bay of Bengal." MAUSAM 25, no. 2 (February 7, 2022): 211–22. http://dx.doi.org/10.54302/mausam.v25i2.5195.
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Cyclonic storms are frequent in the Bay of Bengal particularly during the NE monsoon period. Some of these storms are severe and generate high waves which cause havoc in the coastal regions. This paper presents an analysis of the cyclonic storm which hit coastal Andhra Pradesh on 7 November 1969.
Wave prediction under storm conditions involves an analysis of moving fetches and variable wind speeds. Wilson's graphical method incorporating the latest available wave prediction relations was used for wave predicted waves which are deep water waves, were modified to account for refraction, shoaling and bottom friction effects as they enter shallower waters. The predicted waves were compared with the waves observed by the Visakhapatnam outer harbour authorities.
The results of the analysis suggest that (i) Wilson's graphical method can be applied for wave prediction for Indian coasts under storm conditions, (ii) the recommended value of bottom friction factor appears to be low and (iii) waves of considerable height are experienced even in areas not in the direct path of the cyclone.
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Mehra, P., S. Mohan, P. Vethamony, K. Vijaykumar, T. M. Balakrishnan Nair, Y. Agarvadekar, K. Jyoti, et al. "Coastal sea level response to the tropical cyclonic forcing in the north Indian Ocean." Ocean Science Discussions 11, no. 1 (February 20, 2014): 575–611. http://dx.doi.org/10.5194/osd-11-575-2014.
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Abstract. The study examines the observed storm-generated sea-level variation due to deep depression (Event-E1) in the Arabian Sea from 26 November–1 December 2011 and a cyclonic storm "THANE" (Event-E2) over the Bay of Bengal during 25–31 December 2011. The sea-level and surface meteorological measurements collected during these extreme events exhibit strong synoptic disturbances leading to storm surge up to 43 cm on the west coast and 29 cm on the east coast of India due to E1 and E2. E1 generated sea level oscillations at the measuring stations on the west coast (Ratnagiri, Verem and Karwar) and east coast (Mandapam and Tuticorin) of India with significant energy bands centered at periods of 92, 43 and 23 min. The surge dome has a duration of 92.6, 84.5 and 74.8 h at Ratnagiri, Verem and Karwar, respectively. However, on the east coast, the sea level oscillations during Thane were similar to those during calm period except for more energy bands centred at periods of ~ 100, 42 and 24 min at Gopalpur, Gangavarm and Kakinada, respectively. Multi-linear regression analysis shows that the local surface meteorological data (daily-mean wind and atmospheric pressure) is able to account for ~ 57% and ~ 70% of daily-mean sea-level variability along the east and west coast of India. The remaining part of variability observed in the sea level may be attributed to local coastal currents and remote forcing.
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Cousineau, Julien, and Enda Murphy. "Numerical Investigation of Climate Change Effects on Storm Surges and Extreme Waves on Canada’s Pacific Coast." Atmosphere 13, no. 2 (February 12, 2022): 311. http://dx.doi.org/10.3390/atmos13020311.
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Storm surges and waves are key climate-driven parameters affecting the design and operation of ports and other infrastructure on the coast. Reliable predictions of future storm surges and waves are not yet available for the west coast of Canada, and this data gap hinders effective climate risk assessment, planning and adaptation. This paper presents numerical simulations of storm surges and waves in British Columbia coastal waters under a future climate (Representative Concentration Pathway) scenario (RCP8.5). The numerical models were first forced by wind and surface pressure fields from the ERA-5 global reanalysis, and calibrated and validated using historical wave and water level records. The models were then driven by atmospheric data from four regional climate models (RCMs) to investigate potential changes in the frequency and magnitude of storm surges and extreme waves over the 21st century. The model outputs were analyzed to determine the potential impacts of climate change on storm surges and wave effects at key ports and transportation assets in western Canada. The study is the first of its kind to utilize unstructured, computational models to simulate storm surges and waves for the entire western Canada coastal region, while maintaining the high spatial resolution in coastal sub-basins needed to capture local dynamic responses.
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Eerkes-Medrano, Laura, David E. Atkinson, Hajo Eicken, Bill Nayokpuk, Harvey Sookiayak, Eddie Ungott, and Winton Weyapuk, Jr. "Slush-Ice Berm Formation on the West Coast of Alaska." ARCTIC 70, no. 2 (May 31, 2017): 190. http://dx.doi.org/10.14430/arctic4644.
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Some coastal communities in western Alaska have observed the occurrence of “slush-ice berms.” These features typically form during freeze-up, when ice crystal – laden water accumulates in piles on the shore. Slush-ice berms can protect towns from storm surge, and they can limit access to the water. Local observations from the communities of Gambell, Shaktoolik, Shishmaref, and Wales were synthesized to develop a taxonomy of slush-ice berm types and a conceptual process model that describes how they form and decay. Results indicated two types of slush-ice berm formation processes: in situ (forming in place) and advective (pushed in by storm winds). Several formation mechanisms were noted for the crystals that compose in situ berms. Cold air temperatures cool the surface of the water, and winds that translate surface cooling through a greater depth aid crystal formation. Snow landing in the water cools via melting of the snow and by contributing crystals directly to the water. A negative surge can expose the wet beach to cold air, allowing crystals to form on the beach, which are then picked up by waves. Slush crystals for advective berm events form offshore. Winds move the slush towards shore, where it accumulates, and wind-induced waves move it up onto the beach.
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Prince, Harshith Clifford, R. Nirmala, R. S. Mahendra, and P. L. N. Murty. "Storm Surge Hazard Assessment Along the East Coast of India using Geospatial Techniques." Asian Journal of Water, Environment and Pollution 19, no. 6 (November 14, 2022): 51–57. http://dx.doi.org/10.3233/ajw220088.
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The study aims to estimate the extent of inundation and depth due to a storm surge event by selecting a worst-case cyclone track scenario for Andhra Pradesh, Odisha and West Bengal on the basis of historic data. Storm surge model results for the Orissa cyclone suggest that over 2,150 km2 of land is inundated with an extent of 45 km from the shoreline and 1,100 km2 area submerged with 1-2 m from the ground. Andhra’s model suggests that about 450 km2 of the area is inundated due to which the majority of the area is submerged <1 m from the ground. The West Bengal model is carried out using a synthetic track with a wind speed of 155 knots based on the recent cyclonic storm in Bangladesh. The result shows 5,400 km2 of land submerged by <1 m about 2,700 km2 of the area was submerged by 1-2 m of water. The most affected areas were South 24 Parganas and parts of Bangladesh.
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Sanil Kumar, V., C. Sajiv Philip, and T. N. Balakrishnan Nair. "Waves in shallow water off west coast of India during the onset of summer monsoon." Annales Geophysicae 28, no. 3 (March 19, 2010): 817–24. http://dx.doi.org/10.5194/angeo-28-817-2010.
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Abstract. The wave growth characteristics during the onset of summer monsoon in a swell dominated open ocean at a location off the west coast of India at 14 m water depth are studied. 67% of the measured waves are due to the swells arriving from south and south-west and the balance was due to the seas from south-west to north-west. Wave age of the measured data indicates that the measured waves are young sea with presence of swells. Even when the wind speed reduced to less than 3 m/s, significant wave height more than 2 m is present due to the swells in the Arabian Sea. The maximum wave height increased from 2 to 8 m within 60 h. The mean wave directions at the high frequencies align with the westerly wind direction and gradually shift to south-westerly swell direction at low frequencies during the wave growth. The strong westerly winds present between longitude 72° and 72.5° at latitude 12.5° has created the high waves (Hm0 upto 5.65 m) during the measurement period.
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Mehra, P., M. Soumya, P. Vethamony, K. Vijaykumar, T. M. Balakrishnan Nair, Y. Agarvadekar, K. Jyoti, et al. "Coastal sea level response to the tropical cyclonic forcing in the northern Indian Ocean." Ocean Science 11, no. 1 (February 3, 2015): 159–73. http://dx.doi.org/10.5194/os-11-159-2015.
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Abstract. The study examines the observed storm-generated sea level variation due to deep depression (event 1: E1) in the Arabian Sea from 26 November to 1 December 2011 and a cyclonic storm "THANE" (event 2: E2) over the Bay of Bengal during 25–31 December 2011. The sea level and surface meteorological measurements collected during these extreme events exhibit strong synoptic disturbances leading to storm surges of up to 43 cm on the west coast and 29 cm on the east coast of India due to E1 and E2. E1 generated sea level oscillations at the measuring stations on the west coast (Ratnagiri, Verem and Karwar) and east coast (Mandapam and Tuticorin) of India with significant energy bands centred at periods of 92, 43 and 23 min. The storm surge is a well-defined peak with a half-amplitude width of 20, 28 and 26 h at Ratnagiri, Verem and Karwar, respectively. However, on the east coast, the sea level oscillations during Thane were similar to those during calm period except for more energy in bands centred at periods of ~ 100, 42 and 24 min at Gopalpur, Gangavaram and Kakinada, respectively. The residual sea levels from tide gauge stations in Arabian Sea have been identified as Kelvin-type surges propagating northwards at a speed of ~ 6.5 m s−1 with a surge peak of almost constant amplitude. Multi-linear regression analysis shows that the local surface meteorological data (daily mean wind and atmospheric pressure) is able to account for ~ 57 and ~ 69% of daily mean sea level variability along the east and west coasts of India. The remaining part of the variability observed in the sea level may be attributed to local coastal currents and remote forcing.
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BEHERA, S. K., and P. S. SALVEKAR. "Numerical investigation of coastal circulation around India." MAUSAM 49, no. 3 (December 17, 2021): 345–60. http://dx.doi.org/10.54302/mausam.v49i3.3640.
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A simple wind driven ocean circulation model with one active layer is used to simulate the coastal circulation around India. The close agreement of numerical results to that of the observed fields ind1cate the influence of wind on the coastal circulation. The northward currents along the west coast of India during winter months are dominated by remote forcing from Bay of Bengal; however the southward currents during summer months are less influenced by the remote forcing. The coastaly trapped Kelvin waves which give rise to the remote forcing response are found to be produced by the annual cycle in the local wind of the Bay of Bengal. Equatorial waves do not provide the correct phase of west coast circulation. The island chains of Maldive and Laccadive do not affect the model circulation significantly. But the exclusion of Sri Lanka from the model geometry significantly alters the circulation of southwestern Bay of Bengal during summer months. Some of these findings are already shown by sophisticated multilayer models, e.g., McCreary et al. 1993. However, some of these results are again reproduced here in order to highlight the significance of such simple model and hence the simple model is used for detail study.
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Kettle, Anthony J. "Storm Anatol over Europe in December 1999: impacts on societal and energy infrastructure." Advances in Geosciences 56 (December 23, 2021): 141–53. http://dx.doi.org/10.5194/adgeo-56-141-2021.
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Abstract. Storm Anatol impacted the North Sea and northern Europe on 3–4 December 1999. It brought hurricane force winds to Denmark and northern Germany, and high winds also in Sweden and countries around the Baltic Sea. For many meteorological stations in Denmark, the wind speeds were the highest on record and the storm was ranked as a century event. The storm impacts included extensive forest damage, fatalities, hundreds of injuries, power outages, transportation interruptions, as well as storm surge flooding on the west coast of Denmark. Strongly committed to wind energy, Denmark lost 13 onshore wind turbines destroyed during the storm. An important industry insurer noted that this was a remarkably low number, considering the storm intensity and the large number of turbines (>3500) installed in the country. In 1999, offshore wind energy was just getting started in Europe, and the storm provided an important test of environmental extreme conditions impacting offshore infrastructure. This contribution takes a closer look at the regional met-ocean conditions during the storm. A brief overview is made of the wind field and available wave measurements from the North Sea. An examination is made of water level measurements from around the North Sea to characterize the storm surge and identify possible meteo-tsunamis and infragravity waves. Offshore accidents are briefly discussed to assess if there had been unusual wave strikes on shipping or platforms. At the time of the storm in 1999, there was a growing awareness in the scientific community of possible changes in ambient sea state conditions and the increasing threat of rogue waves. The offshore wind energy community had become aware from the impact of rogue waves from damage at the research platform FINO1 in the southern North Sea during severe storms in 2006, 2007, 2009, and 2013. Storm Anatol may have been another rogue wave storm at an earlier stage of offshore wind energy development.
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Abbasi, Esmaeil, Hana Etemadi, Joseph M. Smoak, Iman Rousta, Haraldur Olafsson, Piotr Baranowski, and Jaromir Krzyszczak. "Investigation of Atmospheric Conditions Associated with a Storm Surge in the South-West of Iran." Atmosphere 12, no. 11 (October 29, 2021): 1429. http://dx.doi.org/10.3390/atmos12111429.
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Severe thunderstorms are often accompanied by strong vertical air currents, temporary wind gusts, and heavy rainfall. The development of this atmospheric phenomenon over tropical shallow water zones, such as bays, can lead to intensification of atmospheric disturbances and produce a small-scale storm surge. Here, the storm surge that occurred on 19 March 2017 in the Persian Gulf coastal area has been investigated. Air temperature, precipitation, mean sea level pressure, wave height, wind direction, wind speed, geopotential height, zonal components, meridional winds, vertical velocity, relative humidity, and specific humidity obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF) and Global Forecast System (FNL) were used to implement the Weather Research and Forecasting (WRF) model. The results showed that the main cause of the storm surge was the occurrence of a supercell thunderstorm over the Persian Gulf. The formation of this destructive phenomenon resulted from a downburst under Cumulonimbus cloud and high-velocity air subsidence, after collision with the sea surface coinciding with the high tide. This caused a severe, yet temporary, gust, which in turn caused the creation of the four waves of 3.1 m height along the coast of Bandar Dayyer.
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Chen, Yongping, Shunqi Pan, Judith Wolf, and Yanliang Du. "DOWNSCALING EFFECTS ON MODELLING WAVES, TIDES AND STORM SURGE." Coastal Engineering Proceedings 1, no. 32 (February 1, 2011): 33. http://dx.doi.org/10.9753/icce.v32.waves.33.
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This paper presents the results of downscaling effects when modelling waves, tides and storm surge using a nested modelling system. In this study, the coupled POLCOMS/ProWAM models are used, with 3 nested computational domains, the largest of which covers part of north-eastern Atlantic Ocean with a coarse resolution grid and the smallest covers the surrounding waters of south-west Cornish coast of the UK with a finer resolution grid. Applying the identical surface wind forcing to all 3 computational domains and the wave and tide boundary conditions provided from the coarse to finer domains, the computed wave heights, tides and surge levels are examined at selected locations to study the downscaling effects. The results show that downscaling could considerably increase accuracy of model predictions in the local domain. For the particular test conditions used in the present study, 3-level and 2-level downscaling produces similar results in the local domain. The results also indicate that downscaling with reduction of grid resolution by 6 times is acceptable for the study site.
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Glejin, Johnson, V. Sanil Kumar, T. M. Balakrishnan Nair, Jai Singh, and Prakash Mehra. "Observational Evidence of Summer Shamal Swells along the West Coast of India*." Journal of Atmospheric and Oceanic Technology 30, no. 2 (February 1, 2013): 379–88. http://dx.doi.org/10.1175/jtech-d-12-00059.1.
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Abstract Wave data collected off Ratnagiri, which is on the west coast of India, in 2010 and 2011 are used to examine the presence of the summer shamal swells. This study also aims to understand variations in wave characteristics and associated modifications in wind sea propagation at Ratnagiri. Wind data collected using an autonomous weather station (AWS), along with Advanced Scatterometer (ASCAT) and NCEP data, are used to identify the presence of summer shamal winds along the west coast of the Indian subcontinent and on the Arabian Peninsula. NCEP and ASCAT data indicate the presence of summer shamal winds over the Arabian Peninsula and northwesterly winds at Ratnagiri. This study identifies the presence of swells from the northwest that originate from the summer shamal winds in the Persian Gulf and that reach Ratnagiri during 30% of the summer shamal period. AWS data show the presence of northwest winds during May and southwest winds during the strong southwest monsoon period (June–August). Another important factor identified at Ratnagiri that is associated with the summer shamal events is the direction of wind sea waves. During the onset of the southwest monsoon (May), the sea direction is in the direction of swell propagation (northwest); however, during the southwest monsoon (June–August), a major part of the wind sea direction is from the southwest. The average occurrence of summer shamal swells is approximately 22% during the southwest monsoon period. An increase in wave height is observed during June and July at Ratnagiri due to the strong summer shamal event.
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Rashmi, R., V. M. Aboobacker, P. Vethamony, and M. P. John. "Co-existence of wind seas and swells along the west coast of India during non-monsoon season." Ocean Science 9, no. 2 (March 8, 2013): 281–92. http://dx.doi.org/10.5194/os-9-281-2013.
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Abstract. An attempt has been made to understand the co-existence of wind seas and swells along the west coast of India during non-monsoon season. Wave data were collected in different years during non-monsoon season (off Goa during May 2005, off Ratnagiri during January–February 2008 and off Dwarka during December 2007–January 2008), which is fairly a calm weather season along these regions. Diurnal variation in wave parameters is noticeable along the central west coast of India (off Goa and Ratnagiri), which is due to the interaction of multidirectional waves (both wind seas and swells) of varying magnitudes and frequencies. Swells are predominantly mature (91%) and old (88%) during late pre-monsoon and post-monsoon seasons, respectively. Sea Swell Energy Ratio quantifies wind sea, swell and mixed seas prevailing in these regions during non-monsoon season. Intermodal distance (ID) between the energy peaks is moderately separated during non-monsoon season, whereas, during the shamal events, energy peaks are very close to each other (ID ∼ 0). However, pure wind seas (ID ∼ 1) are weakly present and found to co-exist with the swells almost all the time during non-monsoon season. Wind sea growth has been found while the swell propagates opposite to the direction of the wind and wind sea. Wind seas have minimum angular spreads in multimodal state. Under low winds, the interaction between wind sea and swell dominates and thereby the multimodal state reduces to unimodal state. The fetch available for the evolution of the wind sea spectrum has been estimated, and it is found to be less than 150 km. For the fetch limited condition, a non-dimensional empirical relation has been derived relating the significant wind sea height in terms of wind speed and peak wind sea period, and this relation fits for the west coast of India.
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Li, Yuanyi, Huan Feng, Guillaume Vigouroux, Dekui Yuan, Guangyu Zhang, Xiaodi Ma, and Kun Lei. "Storm Surges in the Bohai Sea: The Role of Waves and Tides." Water 12, no. 5 (May 25, 2020): 1509. http://dx.doi.org/10.3390/w12051509.
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A storm surge is a complex phenomenon in which waves, tide and current interact. Even though wind is the predominant force driving the surge, waves and tidal phase are also important factors that influence the mass and momentum transport during the surge. Devastating storm surges often occur in the Bohai Sea, a semi-enclosed shallow sea in North China, due to extreme storms. However, the effects of waves on storm surges in the Bohai Sea have not been quantified and the mechanisms responsible for the higher surges that affect part of the Bohai Sea have not been thoroughly studied. In this study, we set up a storm surge model, considering coupled effects of tides and waves on the surges. Validation against measured data shows that the coupled model is capable of simulating storm surges in the Bohai Sea. The simulation results indicate that the longshore currents, which are induced by the large gradient of radiation stress due to wave deformation, are one of the main contributors to the higher surges occurring in some coastal regions. The gently varying bathymetry is another factor contributing to these surges. With such bathymetry, the wave force direction is nearly uniform, and pushes a large amount of water in that direction. Under these conditions, the water accumulates in some parts of the coast, leading to higher surges in nearby coastal regions such as the south coast of the Bohai Bay and the west and south coasts of the Laizhou Bay. Results analysis also shows that the tidal phase at which the surge occurs influences the wave–current interactions, and these interactions are more evident in shallow waters. Neglecting these interactions can lead to inaccurate predictions of the storm surges due to overestimation or underestimation of wave-induced set-up.
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Kharitonova, Lyudmila, Dmitrii Alekseev, and Vladimir Fomin. "Mathematical simulation of the Ay-Todor bay wave regime." InterCarto. InterGIS 27, no. 3 (2021): 16–31. http://dx.doi.org/10.35595/2414-9179-2021-3-27-16-31.
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Investigation of wave regime of coastal water areas is practically important for safe shipping, constructing and using of coastal infrastructure objects. At the present paper statistical characteristics and space distribution of parameters of wind waves in the Ay-Todor Bay region placed on the Crimea South Coast of the Black Sea are obtained on the basis of mathematical simulation. Analysis of the wind wave parameters for the year diapason of 1979–2017 has shown that waves running from the east and having 0.5 m heights and 3.0–3.5 s mean periods are the most repeatable. The most durable storms are formed by waves coming from East–South-South-West sector in the period from December to January. The multiannual calm duration is equal to ~11 days. Estimation of extremal characteristics (height, period and length) of wind waves of different probability, which possible one time in a year, 5, 10, 25, 50 and 100 years are made. For the storm probable one time in 25 years the mean wave height near the boundary of the Ay-Todor Bay is equal to 4.5 m. For this storm the wave height of 1% probability reaches 9.6 m. For the directions of winds of 4 % regime probability which causes the most dangerous waves calculations of wave characteristics with high space resolution (~1.5 m) are carried out by using of SWAN model and nested grid technology. Fields of significant wave height, mean wave length, bottom wave orbital velocities and space distribution of wave breaking zones are analyzed. It is found that most intensive waves are generated by wind having south-east, east and south directions. Maximal bottom orbital velocities of wave current reaches of 2.5–3.5 m/s and occurs along the coast till 10 m depth. Model calculation of wave currents by using of SWASH model allowed obtained presence in the coastal zone near beach of local cyclonic eddy, which transport suspended sediments along its south edge from beach towards the sea.
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Sinha, Mourani, Ravi Kumar Yadav, and Paromita Chakraborty. "Island Modeling Using Unstructured Grid during a Tropical Storm." International Journal of Oceanography 2016 (February 15, 2016): 1–8. http://dx.doi.org/10.1155/2016/5834572.
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The coastal wave dynamics of Agatti island situated on a coral atoll in Lakshadweep, India, having a notable topographic feature of steeper eastern shore over the western shore, is analysed in this study. A multinested model setup is generated using the global third-generation models WAM (Wave Modeling) and SWAN (Simulating Waves Nearshore). A high resolution unstructured grid is generated for the domain containing the island using SMS (Surface-Water Modeling System) interpolated with merged GEBCO (General Bathymetric Chart of the Oceans) and SRTM (Shuttle Radar Topography Mission) bathymetry. The SWAN model is integrated with a fine resolution of one minute by one minute during the tropical storm 01A (05–10 June 2004) which passed near the island. Model simulated significant wave height data when validated against satellite observations exhibited high accuracy. SWH (significant wave height) is observed to be greater for the west coast than that over the east coast of the island due to steeper eastern shore and there is widespread wave energy dissipation along the southwest direction of wave propagation during normal conditions. The one-dimensional energy density spectra generated during the storm period exhibit multimodality with structured and unstructured grids.
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Caillouët, Kevin A., and Suzanne L. Robertson. "Temporal and Spatial Impacts of Hurricane Damage on West Nile Virus Transmission and Human Risk." Journal of the American Mosquito Control Association 36, no. 2s (June 1, 2020): 106–19. http://dx.doi.org/10.2987/19-6887.1.
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ABSTRACT Hurricanes have profound impacts on zoonotic pathogen ecosystems that exhibit spatial and temporal waves in both distance from and time since the event. Wind, rain, and storm surge directly affect mosquito vectors and animal hosts of these pathogens. In this analysis, we apply a West Nile virus transmission model parameterized for the Northern coast of the Gulf of Mexico to explore the effect of event timing of hurricane landfall, time since the event, and damage extent on human West Nile virus neuro-invasive disease (WNV-NID) risk. Early-season hurricanes, which make landfall prior to the peak of baseline WNV transmission activity, increase the average total WNV-infectious mosquitoes for the year by 7.8% and human WNV-NID incidence by 94.3% across all areas with hurricane damage. The indirect effects on human exposure to mosquito bites in the immediate aftermath and long-term recovery from the event have strong impacts on the risk of infection. The resultant interactive direct and indirect storm effects on the pathogen system are spatially and temporally heterogenous among the generalized time and space categories modeled.
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Dietrich, J. C., J. J. Westerink, A. B. Kennedy, J. M. Smith, R. E. Jensen, M. Zijlema, L. H. Holthuijsen, et al. "Hurricane Gustav (2008) Waves and Storm Surge: Hindcast, Synoptic Analysis, and Validation in Southern Louisiana." Monthly Weather Review 139, no. 8 (August 2011): 2488–522. http://dx.doi.org/10.1175/2011mwr3611.1.
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AbstractHurricane Gustav (2008) made landfall in southern Louisiana on 1 September 2008 with its eye never closer than 75 km to New Orleans, but its waves and storm surge threatened to flood the city. Easterly tropical-storm-strength winds impacted the region east of the Mississippi River for 12–15 h, allowing for early surge to develop up to 3.5 m there and enter the river and the city’s navigation canals. During landfall, winds shifted from easterly to southerly, resulting in late surge development and propagation over more than 70 km of marshes on the river’s west bank, over more than 40 km of Caernarvon marsh on the east bank, and into Lake Pontchartrain to the north. Wind waves with estimated significant heights of 15 m developed in the deep Gulf of Mexico but were reduced in size once they reached the continental shelf. The barrier islands further dissipated the waves, and locally generated seas existed behind these effective breaking zones.The hardening and innovative deployment of gauges since Hurricane Katrina (2005) resulted in a wealth of measured data for Gustav. A total of 39 wind wave time histories, 362 water level time histories, and 82 high water marks were available to describe the event. Computational models—including a structured-mesh deepwater wave model (WAM) and a nearshore steady-state wave (STWAVE) model, as well as an unstructured-mesh “simulating waves nearshore” (SWAN) wave model and an advanced circulation (ADCIRC) model—resolve the region with unprecedented levels of detail, with an unstructured mesh spacing of 100–200 m in the wave-breaking zones and 20–50 m in the small-scale channels. Data-assimilated winds were applied using NOAA’s Hurricane Research Division Wind Analysis System (H*Wind) and Interactive Objective Kinematic Analysis (IOKA) procedures. Wave and surge computations from these models are validated comprehensively at the measurement locations ranging from the deep Gulf of Mexico and along the coast to the rivers and floodplains of southern Louisiana and are described and quantified within the context of the evolution of the storm.
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Samiksha, Volvaiker, Ponnumony Vethamony, Charls Antony, Prasad Bhaskaran, and Balakrishnan Nair. "Wave–current interaction during Hudhud cyclone in the Bay of Bengal." Natural Hazards and Earth System Sciences 17, no. 12 (November 29, 2017): 2059–74. http://dx.doi.org/10.5194/nhess-17-2059-2017.
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Abstract. The present work describes the interaction between waves and currents utilizing a coupled ADCIRC+SWAN model for the very severe cyclonic storm Hudhud, which made landfall at Visakhapatnam on the east coast of India in October 2014. Model-computed wave and surge heights were validated with measurements near the landfall point. The Holland model reproduced the maximum wind speed of ≈ 54 m s−1 with the minimum pressure of 950 hPa. The modelled maximum surge of 1.2 m matches with the maximum surge of 1.4 m measured off Visakhapatnam. The two-way coupling with SWAN showed that waves contributed ≈ 0.25 m to the total water level during the Hudhud event. At the landfall point near Visakhapatnam, the East India Coastal Current speed increased from 0.5 to 1.8 m s−1 for a short duration ( ≈ 6 h) with net flow towards the south, and thereafter reversed towards the north. An increase of ≈ 0.2 m in Hs was observed with the inclusion of model currents. It was also observed that when waves travelled perpendicular to the coast after crossing the shelf area, with current towards the southwest, wave heights were reduced due to wave–current interaction; however, an increase in wave height was observed on the left side of the track, when waves and currents opposed each other.
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Vizy, Edward K., and Kerry H. Cook. "Tropical Storm Development from African Easterly Waves in the Eastern Atlantic: A Comparison of Two Successive Waves Using a Regional Model as Part of NASA AMMA 2006." Journal of the Atmospheric Sciences 66, no. 11 (November 1, 2009): 3313–34. http://dx.doi.org/10.1175/2009jas3064.1.
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Abstract Two successive African easterly waves (AEWs) from August 2006 are analyzed utilizing observational data, the European Centre for Medium-Range Weather Forecasts reanalysis, and output from the National Center for Atmospheric Research–National Oceanic and Atmospheric Administration Weather Research and Forecasting model (WRF) to understand why the first wave does not develop over the eastern Atlantic while the second wave does. The first AEW eventually forms Hurricane Ernesto over the Caribbean Sea, but genesis does not occur over the eastern Atlantic. The second wave, although weaker than the first over land, leaves the West African coast and quickly intensifies into Tropical Storm Debby west of the Cape Verde islands. This study shows that the environmental conditions associated with the first AEW’s passage inhibited development. These conditions include strong low- and midtropospheric vertical wind shear owing to a stronger than normal African easterly jet, lower than normal relative humidity, and increased atmospheric stability. All of these are characteristics of an intensification of the Saharan air layer (SAL), or SAL outbreak, over the eastern Atlantic. The environmental conditions were more favorable for genesis 2½ days later when the second wave left the African coast. Additionally, a strong low-level southwesterly surge develops over the eastern North Atlantic in the wake of the passage of the first wave. This westerly surge is associated with an enhancement of the low-level westerly flow, low-level cyclonic vorticity, large-scale low-level wind convergence, and vertical motion conducive for development over the region. While the initial westerly surge is likely associated with the passage of the first wave, over time (i.e., by 1600 UTC 20 August 2006) the development of the second wave becomes influential in maintaining the low-level westerly surge. Although SAL outbreaks are also associated with the addition of dust, the different cyclogenesis histories of the two systems are simulated without including dust in the regional model.
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Vinayachandran, Puthenveettil Narayana Menon, Yukio Masumoto, Michael J. Roberts, Jenny A. Huggett, Issufo Halo, Abhisek Chatterjee, Prakash Amol, et al. "Reviews and syntheses: Physical and biogeochemical processes associated with upwelling in the Indian Ocean." Biogeosciences 18, no. 22 (November 23, 2021): 5967–6029. http://dx.doi.org/10.5194/bg-18-5967-2021.
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Abstract. The Indian Ocean presents two distinct climate regimes. The north Indian Ocean is dominated by the monsoons, whereas the seasonal reversal is less pronounced in the south. The prevailing wind pattern produces upwelling along different parts of the coast in both hemispheres during different times of the year. Additionally, dynamical processes and eddies either cause or enhance upwelling. This paper reviews the phenomena of upwelling along the coast of the Indian Ocean extending from the tip of South Africa to the southern tip of the west coast of Australia. Observed features, underlying mechanisms, and the impact of upwelling on the ecosystem are presented. In the Agulhas Current region, cyclonic eddies associated with Natal pulses drive slope upwelling and enhance chlorophyll concentrations along the continental margin. The Durban break-away eddy spun up by the Agulhas upwells cold nutrient-rich water. Additionally, topographically induced upwelling occurs along the inshore edges of the Agulhas Current. Wind-driven coastal upwelling occurs along the south coast of Africa and augments the dynamical upwelling in the Agulhas Current. Upwelling hotspots along the Mozambique coast are present in the northern and southern sectors of the channel and are ascribed to dynamical effects of ocean circulation in addition to wind forcing. Interaction of mesoscale eddies with the western boundary, dipole eddy pair interactions, and passage of cyclonic eddies cause upwelling. Upwelling along the southern coast of Madagascar is caused by the Ekman wind-driven mechanism and by eddy generation and is inhibited by the Southwest Madagascar Coastal Current. Seasonal upwelling along the East African coast is primarily driven by the northeast monsoon winds and enhanced by topographically induced shelf breaking and shear instability between the East African Coastal Current and the island chains. The Somali coast presents a strong case for the classical Ekman type of upwelling; such upwelling can be inhibited by the arrival of deeper thermocline signals generated in the offshore region by wind stress curl. Upwelling is nearly uniform along the coast of Arabia, caused by the alongshore component of the summer monsoon winds and modulated by the arrival of Rossby waves generated in the offshore region by cyclonic wind stress curl. Along the west coast of India, upwelling is driven by coastally trapped waves together with the alongshore component of the monsoon winds. Along the southern tip of India and Sri Lanka, the strong Ekman transport drives upwelling. Upwelling along the east coast of India is weak and occurs during summer, caused by alongshore winds. In addition, mesoscale eddies lead to upwelling, but the arrival of river water plumes inhibits upwelling along this coast. Southeasterly winds drive upwelling along the coast of Sumatra and Java during summer, with Kelvin wave propagation originating from the equatorial Indian Ocean affecting the magnitude and extent of the upwelling. Both El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) events cause large variability in upwelling here. Along the west coast of Australia, which is characterized by the anomalous Leeuwin Current, southerly winds can cause sporadic upwelling, which is prominent along the southwest, central, and Gascoyne coasts during summer. Open-ocean upwelling in the southern tropical Indian Ocean and within the Sri Lanka Dome is driven primarily by the wind stress curl but is also impacted by Rossby wave propagations. Upwelling is a key driver enhancing biological productivity in all sectors of the coast, as indicated by enhanced sea surface chlorophyll concentrations. Additional knowledge at varying levels has been gained through in situ observations and model simulations. In the Mozambique Channel, upwelling simulates new production and circulation redistributes the production generated by upwelling and mesoscale eddies, leading to observations of higher ecosystem impacts along the edges of eddies. Similarly, along the southern Madagascar coast, biological connectivity is influenced by the transport of phytoplankton from upwelling zones. Along the coast of Kenya, both productivity rates and zooplankton biomass are higher during the upwelling season. Along the Somali coast, accumulation of upwelled nutrients in the northern part of the coast leads to spatial heterogeneity in productivity. In contrast, productivity is more uniform along the coasts of Yemen and Oman. Upwelling along the west coast of India has several biogeochemical implications, including oxygen depletion, denitrification, and high production of CH4 and dimethyl sulfide. Although weak, wind-driven upwelling leads to significant enhancement of phytoplankton in the northwest Bay of Bengal during the summer monsoon. Along the Sumatra and Java coasts, upwelling affects the phytoplankton composition and assemblages. Dissimilarities in copepod assemblages occur during the upwelling periods along the west coast of Australia. Phytoplankton abundance characterizes inshore edges of the slope during upwelling season, and upwelling eddies are associated with krill abundance. The review identifies the northern coast of the Arabian Sea and eastern coasts of the Bay of Bengal as the least observed sectors. Additionally, sustained long-term observations with high temporal and spatial resolutions along with high-resolution modelling efforts are recommended for a deeper understanding of upwelling, its variability, and its impact on the ecosystem.
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Amrutha, M. M., V. Sanil Kumar, and J. Singh. "Changes in nearshore waves during the active sea/land breeze period off Vengurla, central west coast of India." Annales Geophysicae 34, no. 2 (February 12, 2016): 215–26. http://dx.doi.org/10.5194/angeo-34-215-2016.
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Abstract. A unique feature observed in the tropical and subtropical coastal area is the diurnal sea-breeze/land-breeze cycle. We examined the nearshore waves at 5 and 15 m water depth during the active sea/land breeze period (January–April) in the year 2015 based on the data measured using the waverider buoys moored in the eastern Arabian sea off Vengurla, central west coast of India. Temporal variability of diurnal wave response is examined. Numerical model Delft3D is used to study the nearshore wave transformation. The wave height increased due to the sea breeze and reached its peak at ∼ 13:00 UTC at 15 m water depth, whereas the peak significant wave height is at 12:00 UTC at 5 m water depth. Due to the influence of the land/sea breeze system, the range of the peak wave period in 1 day varied up to 8 s. Reduction in the wave height of wind-sea is around 20 % and that of the swell is around 10 % from 15 to 5 m water depth.
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Vallivattathillam, Parvathi, Suresh Iyyappan, Matthieu Lengaigne, Christian Ethé, Jérôme Vialard, Marina Levy, Neetu Suresh, et al. "Positive Indian Ocean Dipole events prevent anoxia off the west coast of India." Biogeosciences 14, no. 6 (March 27, 2017): 1541–59. http://dx.doi.org/10.5194/bg-14-1541-2017.
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Abstract. The seasonal upwelling along the west coast of India (WCI) brings nutrient-rich, oxygen-poor subsurface waters to the continental shelf, favoring very low oxygen concentrations in the surface waters during late boreal summer and fall. This yearly-recurring coastal hypoxia is more severe during some years, leading to coastal anoxia that has strong impacts on the living resources. In the present study, we analyze a 1/4° resolution coupled physical–biogeochemical regional oceanic simulation over the 1960–2012 period to investigate the physical processes influencing the oxycline interannual variability off the WCI, that being a proxy for the variability on the shelf in our model. Our analysis indicates a tight relationship between the oxycline and thermocline variations in this region on both seasonal and interannual timescales, thereby revealing a strong physical control of the oxycline variability. As in observations, our model exhibits a shallow oxycline and thermocline during fall that combines with interannual variations to create a window of opportunity for coastal anoxic events. We further demonstrate that the boreal fall oxycline fluctuations off the WCI are strongly related to the Indian Ocean Dipole (IOD), with an asymmetric influence of its positive and negative phases. Positive IODs are associated with easterly wind anomalies near the southern tip of India. These winds force downwelling coastal Kelvin waves that propagate along the WCI and deepen the thermocline and oxycline there, thus preventing the occurrence of coastal anoxia. On the other hand, negative IODs are associated with WCI thermocline and oxycline anomalies of opposite sign but of smaller amplitude, so that the negative or neutral IOD phases are necessary but not the sufficient condition for coastal anoxia. As the IODs generally start developing in summer, these findings suggest some predictability to the occurrence of coastal anoxia off the WCI a couple of months ahead.
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Verhagen, Henk Jan. "Financial Benefits of Mangroves for Surge Prone High-Value Areas." Water 11, no. 11 (November 13, 2019): 2374. http://dx.doi.org/10.3390/w11112374.
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In this paper, protection options for a high-value, industrial area along the coast of West Bengal (India) are investigated. The options are designed to protect against cyclone surges with a probability of 1/100 per year. Two alternatives are compared, a classical solution of a dike with a revetment and a solution with a mangrove belt in front of the dike. The results reveal that from a pure infrastructural cash-flow point-of-view, the mangrove solution is at least 25% cheaper than the classical solution with a rock revetment. An important finding is that this conclusion does not need the financial evaluation of the obvious additional ecological advantages that mangroves offer. It is postulated that these results are generally valid for high-value coastal areas under the attack of waves during storm surges.
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Lai, R. J., and S. L. Bales. "EFFECTS OF THE GULF STREAM ON NEARSHORE WAVE CLIMATE." Coastal Engineering Proceedings 1, no. 20 (January 29, 1986): 35. http://dx.doi.org/10.9753/icce.v20.35.
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Large scale ocean currents, such as the Gulf Stream, Kuroshlo, Peru Current, Agulhaus Current, etc., strongly modify the surrounding wave characteristics. As the Gulf Stream moves along the Continental Shelf of the southeast coast of the United States, the local ocean environment is divided into three wave climatic regimes. They are the offshore, the Gulf Stream, and the nearshore regimes. The nearshore zone is bounded by the land to the west and the Gulf Stream to the east. The distance between land and the Gulf Stream varies from 10 to 60 miles. Most of the waves in this regime are generated offshore and cross the Gulf Stream. The correlation of local wind and waves in the nearshore regime is poor except in the presence of a persistent onshore storm. A semi-empirical approach has been developed to compute the nearshore wave climate. The hindcast/forecast directional waves from the Spectral Ocean Wave Model (SOWM) of the Navy Fleet Numerical Oceanography Center have been used as the source of the initial offshore wave conditions. After crossing the Gulf Stream, which is assumed to be a uniform current with a velocity of 2 m/s, the waves are either refracted to the nearshore regime or reflected to the offshore regime following ray theory. The onshore waves in the nearshore zone are confined to the sector from 30 to 150 degrees. The computed results are then compared with measured data with good agreement. In summary, the Gulf Stream acts as a barrier to damp long waves and to regroup short waves. The refraction of long waves can be predicted by using ray theory. Further field experiments are needed to quantify the variation of the Gulf Stream and to investigate the interaction with approaching long waves and local wind generated short waves.
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Li, Xiuzhen, Zhiping Wen, and Wan-Ru Huang. "Modulation of South Asian Jet Wave Train on the Extreme Winter Precipitation over Southeast China: Comparison between 2015/16 and 2018/19." Journal of Climate 33, no. 10 (May 15, 2020): 4065–81. http://dx.doi.org/10.1175/jcli-d-19-0678.1.
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AbstractTwo extremely wet winters in 2015/16 and 2018/19 over Southeast China are compared in this study. South-to-north discrepancies appear in the spatial distribution of precipitation, with anomalous precipitation centered over the southeast coast in 2015/16 and the lower reaches of Yangtze River valley in 2018/19, respectively. Both instances of enhanced precipitation are ascribed mainly to warm and moist advection from the south, with transport in 2015/16 partly by a deepened India–Burma trough to the west, whereas with transport in 2018/19 mainly by a subtropical western North Pacific anticyclone (WNPAC). Both the India–Burma trough and WNPAC are maintained by the wave trains propagating along the South Asian jet, which are zonally offset by a quarter-wavelength. Further study of the wave train sources in 2015/16 and 2018/19 shows that they both tend to originate from extremely strong storm-track activity over the North Atlantic but have different displacement. The former is located more northeastward than the mean storm track and is modulated by a strong positive NAO, whereas the latter lies over the midlatitude central North Atlantic along with a circumglobal teleconnection. These differences further result in a quarter-wavelength offset in the Rossby wave source near the entrance of the South Asian jet by the convergence of upper-level divergent wind.
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Mehra, P., R. G. Prabhudesai, A. Joseph, V. Kumar, Y. Agarvadekar, R. Luis, and B. Viegas. "A study of meteorologically and seismically induced water level and water temperature oscillations in an estuary located on the west coast of India (Arabian Sea)." Natural Hazards and Earth System Sciences 12, no. 5 (May 21, 2012): 1607–20. http://dx.doi.org/10.5194/nhess-12-1607-2012.
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Abstract. The study examines the observed storm-generated sea-level oscillations (June 2007 and November 2009) along with the Sumatra geophysical tsunami (September 2007), indicating similarities in the sea-level response in the Mandovi estuary of Goa in the eastern Arabian Sea. Sea-level and surface meteorological measurements collected during storms exhibit strong synoptic disturbances leading to the coherent oscillations in the estuary with significant energy bands centred at periods of 24, 45, and 80 min. In particular, during the sporadic atmospheric event of June 2007, the atmospheric pressure dipped by ~12 mb, the wind direction stabilized to ~249° with peak wind speed up to 16 m s−1 and the positive sea-level surge swelled up by ~40 cm. Also, the water temperature cooled down by ~4.5 °C. Approximately 3 days prior to the 12 September 2007 Sumatra earthquake, the water temperature at Verem station started exhibiting a distinctly stronger semidiurnal oscillation (with a relatively larger variance of ~17.9 °C2 in contrast to a lesser variance of ~12 °C2 during the preceding normal days) and these well-defined oscillations continued to manifest for a week after the earthquake. The pre-earthquake enhanced seawater temperature oscillations observed at this tropical estuary provides an indication that routine monitoring of seawater temperature from tropical estuaries with fine temporal resolution may provide early information about impending coastal earthquakes.
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Li, Yanping, and R. E. Carbone. "Offshore Propagation of Coastal Precipitation." Journal of the Atmospheric Sciences 72, no. 12 (November 19, 2015): 4553–68. http://dx.doi.org/10.1175/jas-d-15-0104.1.
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Abstract This work focuses on the seaward propagation of coastal precipitation with and without mountainous terrain nearby. Offshore of India, diurnal propagation of precipitation is observed over the Bay of Bengal. On the eastern side of the bay, a diurnal but nonpropagating signal is observed near the west coast of Burma. This asymmetry is consistent with the inertio-gravity wave mechanism. Perturbations generated by diurnal heating over the coastal mountains of India propagate offshore, amplify in the upwind direction, and dissipate in the downwind direction relative to the steering wind, owing to critical-level considerations. A linear model is applied to evaluate sensitivity to gravity waves, as these affect deep moist convection and propagation. Analyses are performed for various heating depths, mountain widths, stability, Coriolis effect, background mean wind, and friction. Calculations reveal how these factors affect the amplitude, dissipation, initiation phase, and propagation speed of the diurnal disturbance. The propagation of precipitation triggered by land–sea breezes is distinguishable from that triggered by a mountain–plains circulation. Convection resulting purely from mountain heating begins earlier, propagates slower, and damps faster than that of the land–sea breeze. For mountains near a coast, slower propagation and stronger earlier convection result from a resonance-like combination of two dynamical mechanisms. The propagation of precipitation is initially triggered by the mountain breeze near the coastal mountain. Over the open ocean, the dominant signal propagates as that of the land breeze but with stronger convection.
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PRADHAN, D., and U. K. DE. "Doppler Weather Radar analysis of short term cyclonic storm." MAUSAM 63, no. 3 (January 1, 2022): 459–68. http://dx.doi.org/10.54302/mausam.v63i3.1242.
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On the east coast of India, during South-West monsoon period severe cyclonic storms are very rare and if they are short term cyclones then their prediction becomes very difficult due to rapid change in the intensity of the system. Though synoptic observations failed and satellite observations also cannot give decisive picture about such systems, in that case timely warning can not be issued by the weather agencies. Such a system was formed on 19 September, 2006 at about 250 km South-East of Kolkata (India). Very heavy rainfall associated with the system caused several human casualties and extensive damage to the property. According to news agencies, more than 100 people died and a million people became homeless due to heavy rainfall and strong winds associated with the cyclone during 19 September -21, 2006. At 0600 UTC, Doppler Weather radar (DWR) at Kolkata observed initial signatures of the system like a depression. Subsequently at 0900 UTC the observations indicated that the intensification of the system has taken place to a higher stage of deep depression and at about 1200 UTC clear spiral bands with a circular eye recorded by DWR confirmed for a fully developed severe cyclonic storm. The system weakened in to a deep depression at 1630 UTC after the landfall but again became a cyclonic storm at 2100 UTC of 19 September, 2006. Present study establishes that DWR is very useful for prediction of this short term cyclonic storm, its direction of movement and heavy rainfall associated. The maximum radial winds of the magnitude 32 m/s (64 knots/115 km/h) were also recorded by DWR at an altitude of 2.5 km in the eye wall region of the system. The high wind speed and the well defined structure of the cyclone observed by DWR confirmed that the system was a Severe Cyclonic Storm of T number 3.5. Records are available with surface observatories in the region for strong winds of the order of 110 km/h. This study also revealed that an early warning for strong winds and heavy rainfall could have been issued for development of such a short duration tropical cyclone using DWR data well in advance.
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Han, Weiqing, Julian P. McCreary, Yukio Masumoto, Jérôme Vialard, and Benét Duncan. "Basin Resonances in the Equatorial Indian Ocean." Journal of Physical Oceanography 41, no. 6 (June 1, 2011): 1252–70. http://dx.doi.org/10.1175/2011jpo4591.1.
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Abstract Previous studies have investigated how second-baroclinic-mode (n = 2) Kelvin and Rossby waves in the equatorial Indian Ocean (IO) interact to form basin resonances at the semiannual (180 day) and 90-day periods. This paper examines unresolved issues about these resonances, including the reason the 90-day resonance is concentrated in the eastern ocean, the time scale for their establishment, and the impact of complex basin geometry. A hierarchy of ocean models is used: an idealized one-dimensional (1D) model, a linear continuously stratified ocean model (LCSM), and an ocean general circulation model (OGCM) forced by Quick Scatterometer (QuikSCAT) wind during 2000–08. Results indicate that the eastern-basin concentration of the 90-day resonance happens because the westward-propagating Rossby wave is slower, and thus is damped more than the eastward-propagating Kelvin wave. Results also indicate that superposition with other baroclinic modes further enhances the eastern maximum and weakens sea level variability near the western boundary. Without resonance, although there is still significant power at 90 and 180 days, solutions have no spectral peaks at these periods. The key time scale for the establishment of all resonances is the time it takes a Kelvin wave to cross the basin and a first-meridional-mode (ℓ = 1) Rossby wave to return; thus, even though the amplitude of the 90-day winds vary significantly, the 90-day resonance can be frequently excited in the real IO, as evidenced by satellite-observed and OGCM-simulated sea level. The presence of the Indian subcontinent enhances the influence of equatorial variability in the north IO, especially along the west coast of India. The Maldives Islands weaken the 180-day resonance amplitude but have little effect on the 90-day resonance, because they fall in its “node” region. Additionally, resonance at the 120-day period for the n = 1 mode is noted.
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Mohanty, Shravani, and Rajendra Kumar. "Review Paper on Beach Evolution of the Indian Coasts." International Journal of Ocean and Coastal Engineering 04, no. 03n04 (September 2022). http://dx.doi.org/10.1142/s2529807022300010.
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Beaches provide protection to residents living near the ocean by acting as a buffer against the high winds and waves of powerful storms or rough seas. It also helps the government to increase revenue and the development of infrastructure. Because beaches are very accessible to humans, it is very important to go through the demerits that are causing changes in the beaches and what steps can be taken to prevent the beaches from evolving. There are several studies indicating that there is an increase in the wave heights and wave periods along the Indian coasts, with maximum wave heights increasing by more than 30% in some of the locations. It is also found that at most of the locations along the east coast, wave periods are expected to increase by almost 20% whereas along the west coast, they are expected to increase by around 10% [ Chowdhury et al. [ 2019 ] “Wave climate projections along the Indian coast,” Int. J. Climatol. https://doi.org/10.1002/joc.6096 .]. This will alter the distribution of wave energy at the shoreline, swash-aligned beaches and additionally the design of coastal structures. It is particularly important to evaluate the wave characteristics and sediment transport which leads to erosion and/or siltation problems along the Indian coasts. In this paper, an extensive review on wave hydrodynamics, sediment transport and coastal erosion is compiled along the Indian coasts.
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Rabinovich, Alexander B., Jadranka Šepić, and Richard E. Thomson. "Strength in numbers: The tail-end of Typhoon Songda combines with local cyclones to generate extreme sea level oscillations on the British Columbia and Washington coasts during mid-October 2016." Journal of Physical Oceanography, October 5, 2022. http://dx.doi.org/10.1175/jpo-d-22-0096.1.
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Abstract From 12 to 16 October 2016, a series of three major low-pressure systems, including the tail-end of Typhoon Songda, crossed the coasts of British Columbia (BC) and Washington State (WA). Songda was generated on 2 October and, after travelling northward along the coast of Japan, turned eastward toward North America. Once there, it merged with two extratropical cyclones moving along the coast of Vancouver Island. The combined lows generated pronounced storm surges, seiches and infragravity waves off southern BC and northern WA. Here, we examine the event in terms of sea levels measured by tide gauges and offshore bottom pressure recorders, together with high-altitude meteorological data, reanalysis data, and high-resolution air pressure and wind measurements from 182 meteorological stations. Surge heights during the event typically exceeded 80 cm, with maximum heights of over 100 cm observed at La Push (WA) and New Westminster (BC). At Tofino, on the west coast of Vancouver Island, there was a sharp 40-cm increase in sea level on 14 October in response to a marked air pressure disturbance; slightly lower sea level peaks were also observed at other outer coast locations. In all cases, the sea level response was 1.5-2.5 times greater than that expected from the inverted barometer effect, consistent with local topographic amplification. The sea level oscillations at Tofino had the form of a forced solitary wave (“meteorological tsunami”), whereas those on the southwestern shelf off Vancouver Island are well described by classical standing-wave theory. A numerical model closely reproduces the observed meteotsunami peaks and standing wave oscillations.
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Koiting, Russel Felix, Ejria Saleh, and Md Nizam Ismail. "Beach Morphology Changes during the Northeast and Southwest Monsoons at Mantanani Besar Island, Sabah (Malaysia)." Journal of Tropical Biology & Conservation (JTBC) 14 (October 15, 2017). http://dx.doi.org/10.51200/jtbc.v14i0.890.
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Mantanani Besar Island is a tourism and island that also has communities and is located in the west coast of Sabah. The island coastline is dominated by sandy beaches that tend to change due to direct exposure from natural phenomenon (waves, wind, current and periodic storm) and anthropogenic activities. The seasonal monsoon (NEM and SWM) is an important factor that intensifies the natural phenomenon leading to major beach changes in a short period of time. Therefore, this study aims to determine the beach morphology changes (profile, width, angle and volume) and to identify short-term beach changes trends at different seasonal monsoons. This study was conducted annually between 2013 and 2015. Beach profiling and field measurements were done in May and November 2013, March and September 2014 and January and May 2015 at 5 selected stations around Mantanani Besar Island. Further analysis of beach width, angle and volume were calculated based on beach profile data. The result of beach profile shows St. 1, St. 2 and St. 5 undergoing erosion while St. 3 and St. 4 are experiencing accretion. Averages of beach morphology were higher during the NEM than in SWM indicating more sediment accumulation on the beach of Mantanani Besar Island during the NEM and vice versa in SWM. The findings of this study are useful for local communities, tourist operators and the local government as a guide for any development and to produce shoreline management plans for Mantanani Besar Island.