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1.
V. Sanil Kumar Glejin Johnson K. K. Dubhashi T. M. Balakrishnan Nair 《Natural Hazards》2013,69(1):509-522
We studied the wave characteristics during the very severe cyclonic storm THANE which crossed the east coast of India between Puducherry and Cuddalore based on waves measured at a location in Bay of Bengal at 14 m water depth. Objective of the paper is to document the highest wave height measured in the nearshore waters of east coast of India. On 29 December 2011, cyclone passed within 77–315 km of the wave measurement location with maximum wind speed of 46.3 m/s (90 knots) and resulted in maximum wave height of 8.1 m. Maximum wave height recorded is 0.54 times the water depth, and the ratio of crest height to wave height of the highest wave recorded is 0.65. Maximum value of significant wave height estimated using the parametric wave model for deep-water conditions is 6.4 m, whereas the measured value is 6 m indicating that parametric wave model estimates the wave height reasonably well (within 8 % error) during the cyclone period. 相似文献
2.
Spectral and statistical wave parameters obtained from the measured time series wave data off Paradip, east coast of India
during May 1996–January 1997 were analysed along with MIKE 21 spectral wave model (SW) results. Statistical wave parameters
and directional wave energy spectra distinctly separate out the wave conditions that prevailed off Paradip in the monsoon,
fair weather and extreme weather events during the above period. Frequency-energy spectra during extreme events are single
peaked, and the maximum energy distribution is in a narrow frequency band with an average directional spreading of 20°. Spectra
for other seasons are multi-peaked, and energy is distributed over a wide range of frequencies and directions. The NCEP re-analysis
winds were used in the model, and the results clearly bring out the wave features during depressions. The simulated wave parameters
reasonably show good match with the measurements. For example, the correlation coefficient between the measured and modelled
significant wave height is 0.87 and the bias −0.25. 相似文献
3.
Cyclone-generated surface waves are simulated using state-of-art SWAN (Simulating WAves Nearshore) model coupled with hydrodynamic
model inputs. A severe cyclonic storm passed over the Arabian Sea during 4–9th November 1982 is selected from UNISYS track
records. The cyclone lasted for nearly 6 days and subsided with a land fall at Gujarat coast, west coast of India. In this
study, cyclonic wind fields are generated using a well-established relationship suggested by Jelesnianski and Taylor (1973). The associated water level variations due to storm surge and surge generated currents are simulated using POM (Princeton
Ocean Model). The outputs are one-way coupled with the wave model SWAN for simulating wave parameters off Gujarat, north-east
basin of Arabian Sea. An extensive literature review is carried out on the progress and methodology adopted for storm wave
modelling and analysis. The results presented in this paper reveal the severity of the storm event and would be highly useful
for assessing the extreme wave event/climate especially for the south coast of Gujarat. 相似文献
4.
5.
基于多相孔隙介质弹性理论,给出了非饱和土中不同弹性波的传播方程。根据分界面上的边界条件,建立了各势函数波幅值之间的关系式,讨论了入射剪切波在不同饱和度土层分界面上的反射与透射问题。在无限空间非饱和土体中存在3种压缩波和1种剪切波,因此,当剪切波传播到不同饱和度的非饱和土层分界面上将分别在上、下土层激发产生4种反射波和4种透射波。推导出不同反射波和透射波的振幅比例系数和能量比例系数的理论表达式,并且在此基础上进行数值分析。在数值算例中分别研究了各反射波与透射波的能量比例系数（即能量反射率和能量透射率）受入射频率、入射角度以及上、下土层土体饱和度变化的影响情况。计算结果表明：各能量反射率和能量透射率不仅与入射角和入射频率有关,而且其受上、下土层饱和度变化的影响也同样不能忽视。 相似文献
6.
K. R. Muraleedharan P. K. Dinesh Kumar S. Prasanna Kumar Sebin John B. Srijith K. Anil Kumar K. Naveen Kumar S. Gautham V. Samiksha 《Estuaries and Coasts》2018,41(4):1021-1035
Mud bank formation during the southwest monsoon along the southwest coast of India remains an enigma to the researchers and coastal community in spite of several earlier studies. The present study attempts to unravel the mystery through a high-frequency, season-long time-series observation at Alappuzha, located at the southern part of the west coast of India, a region of frequent occurrence of mud bank. Using 7-month-long weekly time-series observation, we identified strong winds and high waves associated with onset of the southwest monsoon and subsequent three episodic atmospheric low-pressure events (LPEs).With the help of in situ time-series data, we show that the strong winds and high waves associated with southwest monsoon pre-conditions the near shore bottom sediment to bring it into suspension. The high amplitude waves associated with the southwest monsoon, while propagating from the deep water to shallow water region, interact with the bottom initiating bottom-sediment movement and its suspension due to wave refraction and shoaling. The sporadic occurrence of the atmospheric LPEs enhances the process of suspension of bottom sediment in the near shore region leading to the formation of fluid mud. Simulations with a cohesive sediment transport model yielded realistic estimates of sediment transport, in the presence of an onshore current, a pre-requisite for transporting the fluid mud toward the coast. The prevailing onshore upwelling current during the southwest monsoon provides the favorable pre-requisite conditions for transporting the fluid mud through depression channel network towards the coast. Once sufficient quantity and thickness of fluid mud is accumulated in the near shore region, it acts as a wave damper for subsequent high monsoon waves, as indicated by the time-series wave data, leading to the formation of tranquil mud bank region. Depression channel networks extending from the shelf to the coast off Alappuzha, Kochi, Ponnani, Beypore, and Ullal were found in the bathymetric charts, thus explaining why mud banks occur only at few locations in spite of the prevalence of similar monsoon conditions. 相似文献
7.
Trends in seasonal temperatures over the Indian region 总被引：1，自引：0，他引：1
Nilesh K Wagholikar K C Sinha Ray P N Sen P Pradeep Kumar 《Journal of Earth System Science》2014,123(4):673-687
An investigation has been carried out to identify the trends in maximum, minimum and mean temperatures and temperature range over the Indian land mass during the winter (January, and February), pre-monsoon (March–May), southwest monsoon (June–September) and post-monsoon (October–December) seasons by using high resolution daily gridded data set prepared by India Meteorological Department for the period of 1969–2005. It has been observed that the maximum temperatures over the west coast of India show rising trend in winter, southwest monsoon and post-monsoon seasons but the maximum temperatures do not show any significant trend over the other parts of the country. Minimum temperatures show increasing trend over the North Indian states in all seasons and they show an increasing trend over the west coast of India in winter and southwest monsoon seasons. Mean temperature shows an increasing trend over the west coast of India during winter and southwest monsoon seasons. Decreasing trend is observed in the temperature range over North India in all seasons due to increasing trend in minimum temperature. 相似文献
8.
A three-dimensional numerical model is described to study theresponse of a coastal ocean excited by a tropical cyclone in the Bay of Bengal. The numericalexperiments have been carried out using the model to understand the dynamics and thermodynamics ofthe ocean due to different cyclonic systems approaching in different directions. In the firstexperiment, the model is used to simulate the vertical thermal structure of the ocean as a response ofpassage of the less intensified 1997 cyclone, which was skirting the east coast of India before crossingthe Bangladesh coast. The simulations are compared with the buoy data available during the storm period.In the next experiment, it is considered an idealized cyclone with hurricane winds movingnormal to the east coast of India crossing between Visakhapatnam and Kakinada to evolve thermalstructure and currents of the ocean. A net decrease of the SST of 6–7 °C is simulated whenthe severe cyclonic storm moved over the coastal ocean. 相似文献
9.
N. P. Kurian K. Rajith T. S. Shahul Hameed L. Sheela Nair M. V. Ramana Murthy S. Arjun V. R. Shamji 《Natural Hazards》2009,49(2):325-345
Wind waves in the innershelf of the south-central Kerala coast, south-west India were measured at four locations during different
seasons. Simultaneously, numerical models were developed to simulate the wave and sediment transport regime of the innershelf.
Strong monsoonal influence is seen in the wave characteristics with greater amplitudes, lower periods and switch-over from
SW to SWW–W direction. The net annual longshore sediment transport is southerly in the innershelf and northerly in the surf
zone. These counter-directional transports are linked by seasonally reversing the cross-shore transports. In the locations
where the transports in the longshore and cross-shore directions are balanced, stable beaches prevail. Erosion/accretion tendency
prevails in locations where these transports are not balanced. The southern and northern parts of the coast where onshore
transports are predominant could be accreting zones. The erosion/accretion pattern deduced from the sediment transport model
corresponds well with the long-term erosion/accretion trend for this coast. 相似文献
10.
This study analyzes fatalities caused by rip currents in important locations along east and west coasts of India for the period 2000–2010. Results include the frequency of fatalities from rip currents, their cause, and their spatial distributions. Rip current fatalities are most common in the southeastern India, with a non-uniform spatial distribution. August and October are identified as most favorable for rip current generation. In India, rip current-related drowning is estimated as 39 per year during the last decade. East coast of India averaged 30–40 drownings, and west coast of India averaged 5–10 drownings per year. In coastal Andhra Pradesh, more than 350 people had been drowned due to rip currents and only 10 people were rescued. Visakhapatnam recorded highest drowning (293); R. K. beach is the most vulnerable potential rip current zones. From 2007 onward, rip current deaths increased at an alarming rate. The frequency of rip current drownings increased markedly during shore-normal wave incidence and mid-low tidal stages. A new empirical forecasting technique has been developed for prediction of rip current risk in India for the first time. FORTRAN-based software was developed to generate automatic rip current forecast report for any given location. The scale’s performance was tested with field data and by using different statistical methods. The new predictive scale is predicting rip current occurrences reasonably well. 相似文献
11.
The crustal depth section obtained from deep seismic soundings along the Koyna II (Kelsi-Loni) profile, which lies near latitude 18°N roughly in the east-west direction in that part of the Deccan Trap Maharashtra State, India, shows a number of reflection segments below the Deccan Traps down to the Moho discontinuity. A deep fault below the Deccan Traps 13 km east of Mahad divides the entire cross-section including the Moho boundary into two crustal blocks. The reflection segments show updip towards the west coast in the western block. The Moho discontinuity which is at a depth of 39 km near the deep fault starts rising towards the coast, reaching a depth of 31.5 km at the west coast. The eastern block is thrown up by 1.5 km with respect to the western block along the deep fault. A structural contour map of the Moho discontinuity for the Koyna reservoir area has been prepared from the present results and the crustal information obtained along the Koyna I profile (Kaila et al., 1979a), shows that the deep fault in the Koyna area is aligned in the NNW-SSE direction.Refraction seismic data analysis by the wave front method reveals that the thickness of the Deccan Trap increases towards the west coast. The Deccan Trap is 600–700 m thick in the eastern region between Nira (SP 130) and Loni (SP 200) and attains a thickness of 1500 m at 10 km east of the west coast. The longitudinal wave velocity in the Deccan Traps along the profile varies from 4.8 to 5.0 km/sec and in the crystalline basement from 6.0 to 6.15 km/sec. A tentative isopach contour map of the Deccan Traps and a tentative structural contour map of the Pre-Deccan Trap contact have been prepared for the Koyna reservoir area from the results along the Koyna II and Koyna I profiles. A flexure aligned in a NNW-SSE direction, in the Pre-Deccan Trap contact, which is an expression of the deep fault into the basement, has been clearly brought out. The flexure coincides in general with the orientation of the Deccan volcanic scarp in this area. 相似文献
12.
Monthly-mean winds and currents have been used to identify the driving mechanisms of seasonal coastal circulation in the North
Indian Ocean. The main conclusions are: (i) the surface circulation off Arabia is typical of a wind-driven system with similar
patterns of longshore current and wind stress; (ii) circulation off the west coast of India is consistent with the dynamics
of a wind-driven eastern boundary current only during the southwest monsoon. During the northeast monsoon it is possible that
the influence of the interior flow is important. (iii) There are at least three mechanisms that influence the surface circulation
off the east coast of India: wind-stress, influence of fresh-water run off and contribution of the interior flow. It is difficult
at present to assess the relative importance of these three processes. 相似文献
13.
To quantify wave attenuation by (introduced) Spartina alterniflora vegetation at an exposed macrotidal coast in the Yangtze Estuary, China, wave parameters and water depth were measured during
13 consecutive tides at nine locations ranging from 10 m seaward to 50 m landward of the low marsh edge. During this period,
the incident wave height ranged from <0.1 to 1.5 m, the maximum of which is much higher than observed in other marsh areas
around the world. Our measurements and calculations showed that the wave attenuation rate per unit distance was 1 to 2 magnitudes
higher over the marsh than over an adjacent mudflat. Although the elevation gradient of the marsh margin was significantly
higher than that of the adjacent mudflat, more than 80% of wave attenuation was ascribed to the presence of vegetation, suggesting
that shoaling effects were of minor importance. On average, waves reaching the marsh were eliminated over a distance of ∼80 m,
although a marsh distance of ≥100 m was needed before the maximum height waves were fully attenuated during high tides. These
attenuation distances were longer than those previously found in American salt marshes, mainly due to the macrotidal and exposed
conditions at the present site. The ratio of water depth to plant height showed an inverse correlation with wave attenuation
rate, indicating that plant height is a crucial factor determining the efficiency of wave attenuation. Consequently, the tall
shoots of the introduced S. alterniflora makes this species much more efficient at attenuating waves than the shorter, native pioneer species in the Yangtze Estuary,
and should therefore be considered as a factor in coastal management during the present era of sea-level rise and global change.
We also found that wave attenuation across the salt marsh can be predicted using published models when a suitable coefficient
is incorporated to account for drag, which varies in place and time due to differences in plant characteristics and abiotic
conditions (i.e., bed gradient, initial water depth, and wave action). 相似文献
14.
Antony Joseph R. G. Prabhudesai Prakash Mehra V. Sanil Kumar K. V. Radhakrishnan Vijay Kumar K. Ashok Kumar Yogesh Agarwadekar U. G. Bhat Ryan Luis Pradhan Rivankar Blossom Viegas 《Natural Hazards》2011,57(2):293-312
Response of the coastal regions of eastern Arabian Sea (AS) and Kavaratti Island lagoon in the AS to the tropical cyclonic storm `Phyan??, which developed in winter in the south-eastern AS and swept northward along the eastern AS during 9?C12 November 2009 until its landfall at the northwest coast of India, is examined based on in situ and satellite-derived measurements. Wind was predominantly south/south-westerly and the maximum wind speed (U10) of ~16 m/s occurred at Kavaratti Island region followed by ~8 m/s at Dwarka (Gujarat) and ~7 m/s at Diu (located south of Dwarka) as well as two southwest Indian coastal locations (Mangalore and Malpe). All other west Indian coastal sites recorded maximum wind speed of ~5?C6 m/s. Gust factor (i.e., gust-to-speed ratio) during peak storm event was highly variable with respect to topography, with steep hilly stations (Karwar and Ratnagiri) and proximate thick and tall vegetation-rich site (Kochi) exhibiting large values (~6), whereas Island station (Kavaratti) exhibiting ~1 (indicating consistently steady wind). Rainfall in association with Phyan was temporally scattered, with the highest 24-h accumulated precipitation (~60 mm) at Karwar and ~45 mm at several other west Indian coastal sites. Impact of Phyan on the west Indian coastal regions was manifested in terms of intensified significant waves (~2.2 m at Karwar and Panaji), sea surface cooling (~5°C at Calicut), and moderate surge (~50 cm at Verem, Goa). The surface waves were south-westerly and the peak wave period (T p) shortened from ~10?C17 s to ~5?C10 s during Phyan, indicating their transition from the long-period `swell?? to the short-period `sea??. Reduction in the spread of the mean wave period (T z) from ~5?C10 s to a steady period of ~6 s was another manifestation of the influence of the cyclone on the surface wave field. Several factors such as (1) water piling-up at the coast supported by south/south-westerly wind and seaward flow of the excess water in the rivers due to heavy rains, (2) reduction of piling-up at the coast, supported by the upstream penetration of seawater into the rivers, and (3) possible interaction of upstream flow with river run-off, together resulted in the observed moderate surge at the west Indian coast. Despite the intense wind forcing, Kavaratti Island lagoon experienced insignificantly weak surge (~7 cm) because of lack of river influx and absence of a sufficiently large land boundary required for the generation and sustenance of wave/wind-driven water mass piling-up at the land?Csea interface. 相似文献
15.
In central Wisconsin, Cambrian strata of the Elk Mound Group record deposition on open‐coast, wave‐dominated tidal flats. Mature, medium‐grained quartz arenite is dominated by parallel‐bedding with upper‐flow regime parallel‐lamination, deposited during high‐energy storms that also produced three‐dimensional bedforms on the flats. Abundant wave ripples were produced as storms waned or during fair weather, in water depths ≤2 m. Indicators of variably shallow water (washout structures and stranded cnidarian medusae) and subaerial exposure (adhesion marks, rain‐drop impressions and desiccation cracks, including cracked medusae) are abundant. Parallel‐bedded facies preserve a Cruziana ichnofacies, similar to other Cambrian tidal‐flat deposits. Flats were dissected by small, mainly straight channels, the floors of which were grazed intensely by molluscs. Most channels were ephemeral but some developed low levées, point bars and cut‐banks, probably reflecting stabilization by abundant microbial mats and biofilms. Channels were filled with trough cross‐bedding that is interpreted to have been produced mainly during storm runoff. The strata resemble deposits of open‐coast, wave‐dominated tidal flats on the east coast of India and west coast of Korea. Ancient wave‐dominated and open‐coast tidal flats documented to date appear to have been limited to mud‐rich strata with ‘classic’ tidal indicators such as flaser bedding and tidal bundles. The Cambrian (Miaolingian to early Furongian) Elk Mound Group demonstrates that sandy, wave‐dominated tidal flats also can be recognized in the stratigraphic record. 相似文献
16.
Gegar Prasetya Jose Borrero Willem de Lange Kerry Black Terry Healy 《Natural Hazards》2011,58(3):1029-1055
The tsunami inundation flows on Banda Aceh, Indonesia reached 5 km inland during the December 26, 2004, event and devastated
most of the houses, buildings, and infrastructure along the coast and killed more than 167,000 people. The overland flows
from the northwest coast and the west coast collided at Lampisang village approximately 3.7 km from Ulee Lheue (northwest
coast) and 6.8 km from Lhok Nga (west coast) as reported by survivors. Inundation modeling based on the nonlinear shallow-water
wave equations reproduces the inundation pattern and demonstrates a colliding of the overland flows. The model suggests that
wave characteristics on the northwest coast of Banda Aceh were different from those on the waves that impacted upon the west
coast. The areas, which experienced higher inundation levels, did not always experience greatest overland flow speeds, and
the damage areas mostly coincide with the flow speed distribution rather than the runup and inundation depth. 相似文献
17.
P Amol D Shankar V Fernando A Mukherjee S G Aparna R Fernandes G S Michael S T Khalap N P Satelkar Y Agarvadekar M G Gaonkar A P Tari A Kankonkar S P Vernekar 《Journal of Earth System Science》2014,123(5):1045-1074
We present current data from acoustic Doppler current profilers (ADCPs) moored on the continental slope off the west coast of India. The data were collected at four locations (roughly at Kanyakumari, Kollam, Goa, and Mumbai) extending from ～ 7° to ～ 20°N during 2008–2012. The observations show that a seasonal cycle, including an annual cycle, is present in the West India Coastal Current (WICC); this seasonal cycle, which strengthens northward, shows considerable interannual variability and is not as strongly correlated along the coast as in climatologies based on ship drifts or the altimeter. The alongshore decorrelation of the WICC is much stronger at intraseasonal periods, which are evident during the winter monsoon all along the coast. This intraseasonal variability is stronger in the south. A striking feature of the WICC is upward phase propagation, which implies an undercurrent whose depth becomes shallower as the season progresses. There are also instances when the phase propagates downward. At the two southern mooring locations off Kollam and Kanyakumari, the cross-shore current, which is usually associated with eddy-like circulations, is comparable to the alongshore current on occasions. A comparison with data from the OSCAR (Ocean Surface Currents Analyses Real-time) data product shows not only similarities, but also significant differences, particularly in the phase. One possible reason for this phase mismatch between the ADCP current at 48 m and the OSCAR current, which represents the current in the 0–30 m depth range, is the vertical phase propagation. Current products based on Ocean General Circulation Models like ECCO2 (Estimating the Circulation and Climate of the Ocean, Phase II) and GODAS (Global Ocean Data Assimilation System) show a weaker correlation with the ADCP current, and ECCO2 does capture some of the observed variability. 相似文献
18.
The time evolution of atmospheric parameters on intraseasonal time scale in the eastern Arabian Sea (EAS) is studied during
the summer monsoon seasons of 1998–2003 using Tropical Rainfall Measuring Mission Microwave Imager (TMI) data. This is done
using the spectral and wavelet analysis. Analysis shows that over EAS, total precipitable water vapour (TWV) and sea surface
wind speed (SWS) have a periodicity of 8–15 days, 15–30 days and 30–60 days during the monsoon season. Significant power is
seen in the 8–15-day time scale in TWV during onset and retreat of the summer monsoon. Analysis indicates that the timings
of the intensification of 8–15, 15–30, and 30–60 days oscillations have a profound effect on the evolution of the daily rainfall
over west coast of India. The positive and negative phases of these oscillations are directly related to the active and dry
spells of rainfall along the west coast of India. The spectral analysis shows interannual variation of TWV and SWS. Heavy
rainfall events generally occur over the west coast of India when positive phases of both 30–60 days and 15–30 days modes
of TWV and SWS are simultaneously present. 相似文献
19.
During 23–30 September 1997, a rare cyclonic storm has developed close to the Andhra coast, and it has later travelled parallel to coastline northward and finally crossed the land at Chittagong (22°N, 91°E) on 27 September. While translating along the east coast of India, it has produced heavy to very heavy rainfall on the coastal stations causing devastating floods. In this study, we made an attempt to understand the salient causes of this unique cyclone movement. We have analyzed daily fields of wind and relative humidity for 850, 700, 500 hPa and mean daily OLR data to understand the plausible reasons for its movement. The buoy data deployed by National Institute of Ocean Technology, Chennai, Viz. DS5 (15°N, 81°E), DS4 (19°N, 88°E) and SW7 (20°N, 86°E) were analyzed to understand the ocean–atmosphere interaction processes in the west Bay of Bengal during formation of the system. Analysis of OLR over the cyclonic storm region has revealed that the heavy rainfall areas coincide with low OLR (120–180 W m?2). The persistent southward movement of 500 hPa ridge on the eastern wedge of the system along with the steering current at 200 hPa has helped in maintaining the movement of the system parallel to the east coast of India during its life cycle. 相似文献
20.
R. Tatavarti A. C. Narayana P. Manoj Kumar Shyam Chand 《Journal of Earth System Science》1999,108(1):57-68
Field experiments conducted in the nearshore ocean to understand the dynamics of mudbank off Kerala, south-west coast of India,
are highlighted. Real time monitoring of the nearshore ocean off Purakkad, Kerala was accomplished using pressure transducers
for nearshore surface wave measurements, and current sensors for nearshore velocity measurements. Comprehensive information
on the spatial structure of mudbank was obtained from aerial surveys. Extensive data collected on surface waves and currents
in the nearshore ocean, indicate that the infra-gravity (IG) waves (leaky modes and trapped edge wave modes), and far infra-gravity
(FIG) waves coupled with strong shoreline reflections and undertow play an important role in the dynamics associated with
the mudbanks off Kerala during the monsoon season. During the non-monsoon season evidence for progressive edge waves in the
infragravity frequency band, an energetic gravity wave band and a strong undertow with weak reflections was observed. 相似文献