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Third-generation models employ a host of parameterization schemes to consider the input wind forcing and the wave energy dissipation under different physical settings and environmental conditions. To evaluate the performance of such models in large-scale enclosed water bodies, WAVEWATCH-III model has been employed for the Caspian Sea which is a land-locked water body, located in the north of Iran. The Caspian Sea consists of three interconnected regions, called the northern, middle, and southern Caspian Sea. The division is based on the bathymetry and morphologic features, and the rapid variability in depth provides a unique modeling challenge. Recently implemented “ST6” physics in the WAVEWATCH-III model is calibrated and evaluated for the Caspian Sea. Moreover, both bottom friction methods, viz., JONSWAP and SHOWEX, in combination with calibrated ST6 were employed to fine-tune the model for this fetch-limited basin. Model performance was assessed using recent coastal measurements along the southern Caspian Sea as well as altimeter data via statistical parameters. Using ST6 calibration, the HH index for model performance against altimeter data was decreased by 7.7%. For the ADCP data, this improvement was ~17% at Noshahr station, and ~7% at Roudsar station, both along the southern boundary of the sea. The bias was decreased by 19.3% by calibrating the ST6 source term, specifically in the deeper areas. It should be noted that the bias against altimeter data has been improved by 19.5%. Due to the steep slope of the surf zone, the model was not so sensitive to the bottom friction formulation; however, the 1D propagation tests confirmed a slightly better performance of the SHOWEX formulation than that of the JONSWAP formulation.

Simulating hurricane-generated waves is a challenging task due to rapidly fluctuating wind speed and direction, simultaneous presence of swells propagating out of the previous location of the hurricane and following/opposing waves on either side of the hurricane track, and dissipation in wind speed radially from the center of the hurricane. Bulk wave parameters have been investigated using the source term packages ST3, ST4 and ST6 implemented in the WAVEWATCH-III model to determine the most appropriate formulation for simulating hurricane-generated waves in the Gulf of Mexico. Based on the comparisons between model results and in situ observations during the passage of Hurricane Ivan (2004), it is shown that ST3 is not as successful as other formulations for hurricane wave modeling. Calibrated ST6 variant, T12, has shown to be the best formulation for simulating bulk wave parameters at points within the range of hurricane wind forcing; however, for the area beyond, and also during fair weather conditions, calibrated ST4 formulation, T471-Ex4, is recommended. Although T471-EX4 and T12 packages outperformed other cases, they overestimated waves propagating in the oblique and opposing wind. Dependence of ST6 parameter a 0 on wind and wave direction is examined to improve the model performance.

The Caspian Sea is the largest closed basin on Earth, with unique physical characteristics and complex bathymetry. Sparse measurements and coarse resolution models have not yet provided a full picture of its dynamics. In this study, a high resolution (∼3.3 km) Regional Ocean Modeling System (ROMS) was used to study its annual and seasonal circulation patterns, and distributions of salinity and temperature. Temperature and salinity nudging were implemented which forced the model to follow in situ observations. This approach effectively limited the model error in predicting the temperature and salinity. The model successfully reproduced sea surface temperature and salinity over the entire basin. The simulated sea surface salinity showed three salinity fronts over the Caspian Sea. The salinity profile was vertically uniform in deep waters of the Caspian Sea. In contrast, the vertical thermal structure formed the seasonal thermocline at a depth of 15–40 m which was intensified in summer. In general, the seasonal variability of water temperature or salinity was confined to the upper 100 m of the water column. Simulations revealed an impermanent weak northward current along the eastern coasts of the Middle Caspian Sea, a persistent strong southward current along its western coasts and a permanent deep anticyclonic gyre over the Southern Caspian Sea. Using a high resolution model, this study also reports several mesoscale and small scale structures in the Caspian Sea which have not been reported before.

The novel process consisted of two steps was established by combining all sidestreams lines (supernatant gravity thickener, underflow mechanical thickener, and centrate), treating them together away from the mainstream treatment plant, and returning treated sidestreams effluents to the plant outfall instead of plant head. The two steps novelty treatment combined degradation, nitrification, and dilution processes. To treat combined sidestreams, a novel pilot extended nutrient moving bed biofilm reactor was developed. The effects of sidestream elimination on a full-scale anaerobic/anoxic/oxic system were simulated using GPS-X7. The statistical results of R values greater than 0.8 and NMSE values near zero proved the calibrated model’s validation. The novel system successfully removed 98, 93, 100, 85, 98, 100, and 98% of BOD, COD, NH4, NO3, TSS, H2S, and PO4-P from sidestreams, respectively. Furthermore, the simulation results showed that eliminating sidestreams has reduced volumes of full-scale A2/O facilities, controlled hydraulic and pollutants shocks, and minimized cost and energy. The novel process proved successful in treating combined sidestreams and eliminating their impacts on the A/O2 system.

Changes in land cover have significant impacts on meteorological parameters of the area. The water level of the Lake Urmia has reduced considerably in recent years. Due to the very different characteristics of water and land, the desiccation of the Lake has a significant impact on atmospheric parameters close to the lake basin. In this study, four synoptic stations around the lake were investigated to study the anomalous changes of the meteorological parameters in a 33-year period from 1985 to 2017. Then, using the WRF-Lake model, the lake in two scenarios of high water (1998) and low water condition (2017) was simulated. The changes in the mean monthly temperature anomalies in all studied stations indicate an increase in period of sharp decrease in lake water depth compared to the average long-term regional temperature. The results also show that the average monthly wind speed at stations near the shore has decreased over the mentioned 33-year period. The anomaly study of the average monthly relative humidity shows its increase in waterlogged years and its decrease in years the water depth in the lake has decreased sharply. From 2006 onwards, despite the approximate decrease of two thirds of the lake water, the relative humidity is not affected by the continuous decrease of the lake depth. Small changes were observed in cumulative precipitation anomalies with changes in the lake water depth. The simulation results performed by the WRF-Lake model also show that in these two scenarios, the temperature of the cold season of the year (from December to February) on Lake Urmia and its shore decreased by 2.6 and 1.86°, respectively. In the warm season of the year (from June to August), it is increased by 1.20 and 1.40°. Also, the average wind speed on the lake in the cold and warm season of the year from 1998 to 2017 has decreased by 1.14 and 0.35 m/s, respectively. Simulation results for relative humidity and precipitation also show that these parameters are less affected by local climate conditions than temperature and wind speed parameters.

The aim of the present work is to evaluate wind dataset in generation of the wave characteristic along the southern basin of the Caspian Sea (SBC). To achieve this purpose, satellite altimetry data, numerical model results and field measurements were considered for 2011. The mixed re-analysis/forecast wind data from European Center for Medium Range Weather Forecast, ERAI_MIXED, are analyzed. Comparisons are made using altimetry data from CERSAT, mixed re-analysis/forecast GFS datasets (GFS_MIXED) and field observation from two buoys and one ADCP located in SBC. The modeling was carried out using the SWAN model over a composite-overlap nested grid system. The results showed that the ERAI_MIXED underestimated wind data in SBC, similar to other datasets from ECMWF and GFS. However, the simulation results implied that using the same configuration for the wave model, ERAI_MIXED led to superior results compared to GFS_MIXED and ERAI_MIXED-COR. Comparison with limited observation showed that ERAI_MIXED data slightly overestimated the wave height in the offshore station and underestimated it at the nearshore buoy. Finally, model results showed that moderate to low wind speed over the SBC might generate the waves up to 4 m wave height.

One of the indicators representing the permissible performance of a marine model is the capability of model in providing an accurate spatiotemporal distribution of the thermal structure of domain. Data assimilation is taken into account as an expedient platform in order to achieve this goal. In this paper, the ensemble Kalman filter (EnKF) was applied as a data assimilation scheme to enhance the sea surface temperature (SST) simulation and whereupon the underwater temperature of the Persian Gulf in the finite volume community ocean model (FVCOM). The daily satellite measured SST data that obtained from advanced very high-resolution radiometer pathfinder were considered as observational assimilation data. The comparisons between the results of both proposed models including FVCOM and SST measurements were carried out to evaluate the efficiency of data assimilation. The comparisons revealed a meaningful improvement in the assimilated simulation of the spatiotemporal SST variability in the whole domain, especially in the shallow parts and near the Hormuz Strait. The root-mean-square error reduced significantly in assimilation run. The statistical comparisons of the results bias denote a positive impact of the data assimilation.

Desalination plants have become invaluable solutions especially where freshwater resources are scarce. However, the byproduct of their operation is an outflow which is more saline and heated than the ambient water body. This heated plume adversely affects the ecosystem if it is not treated properly. In this study, 3D finite volume coastal and ocean model is employed to address this issue close to Qeshm Island. In addition to calibrating the model, two alternatives are simulated and discussed to mitigate the adverse effects of the heated plume. It is shown that the plume tends to move in the upper layer of the water column due to its lower density than the ambient water. By moving the outfall to deeper parts of the sea—10-meter-deep—the negative effects of the plume significantly decreases and fulfilled the Iran national guidelines. Moreover, due to the mechanism of the Qeshm desalination plant, the spread of salinity is of the least importance compared to the increase in temperature.

This study investigates a rare situation at the Mond River Estuary in the Persian Gulf, in which the classical estuarine density gradient coincides with hypersaline runoff entering from saline soils upstream of the estuary after severe precipitation. This builds a unique estuarine setting, where two salt water masses, one originating from the coastal ocean and the other being discharged from upstream confine a range of almost freshwater in the middle of estuary. This “freshwater lens estuary” (FLE) situation includes two saltwater sources with opposing senses of estuarine circulation. Therefore, the tidal damping by the strong river flood can occur, especially during neap tide when high Unsteadiness number (∼0.04) signified ebb oriented condition which was induced by straining residual lateral circulation near the FLE mouth. Transition from well-mixed to weak strain induced periodic stratification regimes indicated the importance of the spring-neap tidal variations. Close to the mouth, a 13.66-day periodic tidal asymmetry from the triad K1-O1-M2 (ebb-dominance during spring tide and flood-dominance in neap tide) was overcome by higher harmonics.

This study evaluates the capability of the Simulating WAves Nearshore (SWAN) wave model (version 41.01) in predicting significant wave height and spectral peak energy content for swell waves in very shallow water of surf zone during depth-induced wave breaking and dissipation. The model results were compared with field measurements at five nearshore stations. The results demonstrated that some breaker index formulations were successful for significant wave height prediction in surf zones. However, an incorrect shape of the energy spectrum and overestimated near spectral peak energy content at shallow water stations were obtained using all of the embedded depth-induced wave breaking formulations in SWAN. The dependent breaker index on relative depth (Kpd) formulation, which was successful in predicting near spectral peak energy content, resulted in an average error of 30%. Finally, this formulation was modified to enhance the model performance in reproducing the spectral peak energy content.

In this paper, the impact of sea surface temperature (SST) data assimilation on the results of a finite volume community ocean model has been examined by using the nudging scheme. In this regard, the advanced very high-resolution radiometer satellite SST data were selected as the observational data for assimilation. The numerical modeling was performed over the Persian Gulf from 1998 to 2003 in two different modes: with and without SST data assimilation. The performance of data assimilation with the nudging scheme was evaluated by comparing the simulated SST with the in situ SST measurements and optimum interpolation SST data. Both the spatial and temporal comparisons show the efficiency of assimilation in correcting the model results. The spatial root mean square error in the assimilated run depicts meaningful improvements in the whole of the domain. Also, the temporal comparisons of the results show the capability of assimilation in lowering the model output errors. The simulated SST obtained by applying the data assimilation in the shallow parts of the Persian Gulf matched exactly with the measured ones, especially near the Hormuz Strait. Finally, the results show significant improvements in the SST simulated by using the nudging schemes.

Vessel-mounted ADCP measurements were conducted to describe the transverse structure of flow between the two headland tips in Khuran Channel, south of Iran (26° 45′ N), where the highest tidal velocities in spring tides were ~ 1.8 m/s. Current profiles were obtained using a 614.4 kHz TRDI WorkHorse Broadband ADCP over nine repetitions of three cross-channel transects during one semidiurnal tidal cycle. The 2.2-km-long transects ran north/south across the channel. A least-square fit to semidiurnal, quarter-diurnal, and sixth diurnal harmonics was used to separate the tidal signals from the observed flow. Spatial gradients showed that the greatest lateral shears and convergences were found over the northern channel and near the northern headland tip due to very sharp bathymetric changes in this area. Contrary to the historical assumption, the across-channel momentum balance in the Khuran Channel was ageostrophic. The current study represents one of the few examples reported where the lateral friction influences the across-channel momentum balance.

This study experimentally investigates the development and decay of bound energy fractions due to positive and negative interactions (b2p and b2n, respectively) applying bispectral analysis. It was revealed that the Ursell number is the most successful parameter to estimate the variation patterns of b2p and b2n. The experimental waves included 27 waves with three offshore wave heights, three periods, and three offshore water depths propagating over a mild slope of 1:30. A wide variety of wave nonlinearity and bound coupling intensities were observed across the experimental dissipative surf zone. For a wave propagating toward the shore, the corresponding Ursell numbers for the relative maximum values of b2p and b2n are 0.27 and 0.22, respectively. The ratio of significant wave height to water depth corresponding to these extreme values for positive and negative triads are ~0.4 and ~0.32, respectively. The highest values of b2p and b2n for a progressive wave can be predicted as a function of the Ursell number using two new proposed experimental formulations. The sub-harmonics are more persistent during wave-breaking conditions than super-harmonics due to lower wave steepness. The biphase values of self-coupling of the spectral peak are attained negative for waves with Ursell numbers greater than 0.35.

Soil erosion due to surface water is a standout among the serious threat land degradation problem and an hazard environmental destruction. The first stage for every kind of soil conservation planning is recognition of soil erosion status. In this research, the usability of two new techniques remote sensing and geographical information system was assessed to estimate the average annual specific sediments production and the intensity erosion map at two sub-basins of DEZ watershed, southwest of Lorestan Province, Iran, namely Absorkh and Keshvar sub-basins with 19,920 ha, using Modified Pacific Southwest Inter-Agency Committee (MPSIAC) soil erosion model. At the stage of imagery data processing of IRS-P6 satellite, the result showed that an overall accuracy and kappa coefficient were 90.3% and 0.901, respectively, which were considered acceptable or good for imagery data. According to our investigation, the study area can be categorized into three level of severity of erosion: moderate, high, and very high erosion zones. The amount of specific sediments and soil erosion predicted by MPSIAC model was 1374.656 and 2396.574 m3 km−2 year−1, respectively. The areas situated at the center and south parts of the watershed were subjected to significant erosion because of the geology formation and ground cover, while the area at the north parts was relatively less eroded due to intensive land cover. Based on effective of nine factors, the driving factors from high to low impact included: Topography > Land use > Upland erosion > Channel erosion > Climate > Ground cover > Soil > Runoff > Surface geology. The measured sediment yield of the watershed in the hydrometric station (Keshvar station) was approximately 2223.178 m3 km−2 year−1 and comparison of the amount of total sediment yield predicted by model with the measured sediment yield indicated that the MPSIAC model 38% underestimated the observed value of the watershed.

The third-generation wave model, WAVEWATCH III, was employed to simulate bulk wave parameters in the Persian Gulf using three different wind sources: ERA-Interim, CCMP, and GFS-Analysis. Different formulations for whitecapping term and the energy transfer from wind to wave were used, namely the Tolman and Chalikov (J Phys Oceanogr 26:497–518, 1996), WAM cycle 4 (BJA and WAM4), and Ardhuin et al. (J Phys Oceanogr 40(9):1917–1941, 2010) (TEST405 and TEST451 parameterizations) source term packages. The obtained results from numerical simulations were compared to altimeter-derived significant wave heights and measured wave parameters at two stations in the northern part of the Persian Gulf through statistical indicators and the Taylor diagram. Comparison of the bulk wave parameters with measured values showed underestimation of wave height using all wind sources. However, the performance of the model was best when GFS-Analysis wind data were used. In general, when wind veering from southeast to northwest occurred, and wind speed was high during the rotation, the model underestimation of wave height was severe. Except for the Tolman and Chalikov (J Phys Oceanogr 26:497–518, 1996) source term package, which severely underestimated the bulk wave parameters during stormy condition, the performances of other formulations were practically similar. However, in terms of statistics, the Ardhuin et al. (J Phys Oceanogr 40(9):1917–1941, 2010) source terms with TEST405 parameterization were the most successful formulation in the Persian Gulf when compared to in situ and altimeter-derived observations.

Profiles of salinity and temperature were measured in the strait of Hormuz (SH) during the winter of 2012, spring and summer of 2013. To investigate the double diffusion (DD) processes, Turner (TU) angle values are calculated in all the stations in the SH. Different TU angle values correspond to salt fingering (SF), diffusive convection (DC) and stable stratification. The distributions of the two forms of DD were plotted vertically along transects in the eastern, central and western part of the SH, and corresponding DD processes were described. The results show that both SF and DC occurred in most part of the study area. Two different water masses (the Indian Ocean surface water and the Persian Gulf water) were evident at the SH, and SF and DC were evident at the interface of two water masses. Due to evaporation, SF occurred in the surface layer of most Stations throughout the year. In the eastern part of the SH, occurrences of DC were more feasible in wintertime. SF was the main phenomenon at the end of hot season. For central part, SF occurred throughout the year in water column. In the western part, water column was stable in summer and DC happened in most part of water column in winter.

In this study, seasonal variation of different atmospheric and oceanic parameters is discussed based on recent comprehensive in situ observations from monthly cruises and two new permanents in Lake Urmia. Due to increasing water demand in the watershed of the Lake and low rivers’ inflow in recent years, the Lake water elevation has decreased. As a result, salinity has increased in the Lake to more than 500 g/L in 2017 based on field observations. Such a high value of salinity significantly suppresses the evaporation from the Lake. The evaporation rate was estimated for Lake Urmia using the modified Dalton and modified Penman bulk formulations for a hypersaline environment, as well as a theoretical model based on conservation laws of water mass, salt mass, and heat budget. The dedicated equation of state recently developed for Lake Urmia was used in all models. A good agreement was achieved between the modified Penman equation and the theoretical model. High mean wind speed and air temperature, as well as low air humidity and pressure, are shown to be responsible for high values of evaporation during summer. On the other hand, high values of salinity resulted from a high rate of evaporation in summer, and low river inflow in autumn decreases the water activity coefficient and results in a negligible evaporation rate during winter. The annual evaporation was in the range of 730–970 mm in 2017 based on in situ measurements and using a different model. The annual evaporation might be increased more than twofold if salinity returns to average values of the last decade.

The wind energy input and whitecap dissipation terms in the third generation wave models have been improved over the time. In this research, the well-known WAM-Cycle4, known as ST3, and the newest ST6 package in WAVEWATCH-III model were employed combined with ERA5 wind data over the Persian Gulf and Gulf of Oman. In order to model the wave height appropriately over the study area in comparison with both in-situ and satellite observations, new combined error parameters were introduced leading to two major calibration values: (1) the local calibration values relating to either Persian Gulf (PGc) or Gulf of Oman (GOc); (2) the global calibration values over the entire computational domain (PGGOc). Considerably different model performance was appeared in the Persian Gulf (PG) compared to either the Gulf of Oman (GO) or entire computational domain (PGGO) when ST3 package was employed, while obtained results using ST6 package showed negligible sensitivity to the domain. Both ST3 and ST6 packages with default tuning values significantly underestimated the wave height and peak period in PG; however, slight underestimation (~0.03 m) for wave height and overestimation (~0.1 s) for mean wave period were obtained in GO. During the time period the cyclone Phet has traversed across the study area, the model overestimated the wave height in comparison with altimeter dataset. Mean bias distribution over the study area indicates that calibrated ST6 outperforms calibrated ST3 over GO; however, both packages provide similar results over PG. Considering different methods for nonlinear interaction term led to similar directional wave spectrums over the study area and negligible changes in bulk wave parameters.

Spatial measurements of conductivity, temperature and depth were used to study salinity variations along the principal channels of the tidal hypersaline creek network in the vicinity of Bushehr Port, Persian Gulf during three 25- tidal cycles in both warm and cold months. Salinity variations and tidal fluctuations were out of phase throughout the short inverse estuary. The salinity values inside the creek were higher during the warm month (August 2014) than the corresponding values during the cold month (December 2014) due to the change in evaporation rates. The salinity values, also, were linearly increased longitudinally from the inlet to the head especially during warm season. Observed evaporation rates in August and December periods and the corresponding salinity differences between hypersaline water of the creek and the incoming seawater were used to determine the Residence Time (RT). The longitudinal variation of RT showed almost linear increase from the inlet to the head. The maximum temporal distribution of RT represented an increase from ~10 days in winter to ~30 days in summer due to the change in the longitudinal salinity gradient.

Quantifying the current in the Strait of Hormuz (SH) is vital for understanding the circulation in the Persian Gulf. To measure the current in the strait, four subsurface moorings were deployed at four different stations close to SH from early November 2012 to the end of January 2013. Tidal current were dominant in the SH. The tides in the SH were complex partially standing waves and the dominant pattern varied from being primarily semi-diurnal to diurnal. The phase difference between tidal constituents of current and sea level elevation time series was used as an index to show the partially progressive wave pattern inside the study area. At mooring positions 3 and 4, located to the left of SH, the phase differences were close to 160° and 100°, respectively. It indicates partially progressive waves in opposite direction at these stations. K 1 and M 2 were the two main constituents at all stations inside the study area. At surface, the magnitude of semi-major axis of ellipses for M 2 constituent was larger than corresponding value for K 1 whereas at the bottom layer, the opposite pattern was observed. The M 2 rotary coefficients at mooring 1 illustrated that current vector at the bottom layer rotated in opposite direction compared to current vectors at the middle and surface layers. The rotation was counterclockwise in the bottom layer, while it was clockwise in the surface and middle layers.

In this study, a series of field measurements were carried out to investigate triad interactions of spectral peak in near shore. The water level fluctuations were recorded at 5 stations with depths varying from 0.8 to 5 m along a shore-perpendicular transect at sandy coasts of Nowshahr, located in the southern Caspian Sea coast. Two storms with significant wave height of approximately 1.4 m were observed during the measurement period. Using bispectral analysis, a new quantitative index is proposed to investigate temporal and spatial intensity of nonlinear interaction between spectral peak and other harmonics. The proposed index was evaluated for time series of water level data and compared with the bicoherence value of self-spectral peak triad interaction (SSPT); b 2 ( f p , f p ) . Comparing to SSPT, the proposed new index includes all positive and negative triad interactions with spectral peak. The relative depth, k p d , of non-breaking waves varied from 0.25 to 2.00 along the transect during the study period, where k p is the wave-number and d is the water depth. In general, SSPT increased by decreasing k p d ; however, the results showed that in two shallow stations the maximum SSPT did not correspond to the lowest values of k p d . A considerable time lag was observed between occurrence of the most intensive triad interactions and termination of wave breaking in post storm condition. Furthermore, the intensive triad interactions happened several hours after the largest Ursell numbers of non-breaking waves.

This study investigated the tidal asymmetry imposed by both the interaction of principal tides and the higher harmonics generated by distortions within a tidal creek network with mixed mainly semidiurnal tide in the Bushehr Port, Persian Gulf. Since velocity and water-level imposed by principal triad tides K1-O1-M2 are in quadrature, duration asymmetries during a tidal period in this short, shallow inverse estuary should be manifest as skewed velocities. The principal tides produce periodic asymmetries including a strong ebb-dominance and a weak flood-dominance condition during spring and neap tides respectively. The higher harmonics induced by nonlinearities engender a flood-dominance condition where the convergence effects are higher than frictional effects, and an ebbdominance condition where intertidal storage are extended. Since the triad K1-O1-M2 driven asymmetry is not overcome by higher harmonics close to the mouth, the periodic asymmetry dominates within the creek in which higher harmonics reinforce the weak flood-dominance (strong ebb-dominance) condition in the convergent channel (divergent area). Also, the maximum flood and the maximum ebb from all harmonic constituents occurred close to high water slack time during both spring and neap tides in this short creek. Since occational wetting of intertidal areas happened close to the high water (HW) time during spring tide, the water level flooded slowly close to the HW time of the spring tide.

This paper presents the results of bound infragravity observation at the Nowshahr beach located in the southern part of the Caspian Sea. The water level data were measured at 6 stations along a transect perpendicular to the coastline. The bispectral method was utilized to show that the extreme values for the bound infragravity energy fraction (bii) were occurring when dimensionless values of wave height to depth ratio, relative depth, and wave steepness were in the range of 0.18‒0.22, 0.4‒0.5 and 0.015‒0.017, respectively. These detailed results could be equivalently summarized with the condition of having the Ursell number of peak waves within the range of 30‒40. The corresponding short wave groupiness factor (G.F.) values for waves with high values of bii were between 0.5 and 0.55. Also, it was revealed that the wave groupiness envelope had a positive correlation with infragravity wave energy level, but its correlation with the bound infragravity wave was negative when G.F. > 0.55. On the other hand, the low values of bii against the spectrum peakedness parameter for breaking waves followed an exponential relationship. The correlation of bound and free infragravity waves with wind waves was also studied. For non-breaking condition, the correlations of bound infragravity waves with swell and sea waves were considerable. The correlation of free waves with swells was also significant. In contrast, for breaking waves, a negligible correlation was observed between bound infragravity waves and wind waves.

Numerous wind force data with different temporal and spatial resolution have been released over the last decades which can be utilized in a wave model to simulate wave spectrum and its dynamics. On the other hand, diverse packages are available for computing sink and source terms in the wave model. In this study, the third generation wave model, SWAN, was employed to assess the performance of different formulation packages (KOMEN, JANSSEN, WST and ST6) in the Red Sea when ERA-Interim, CCMP and ERA5 wind data were employed. In situ measurements and altimeter data were used for skill assessments. Results showed that the SWAN with either JANSSEN or KOMEN formulation was more accurate when ERA5 wind data were used instead of ERA-Interim or CCMP. Combination of ERA5 wind data and JANSSEN outperformed other combination of wind data and model formulations. The model underestimated the significant wave height when either ST6 or WST package was employed. The worse performance at the study area was obtained when WST package was used in SWAN.

The Atchafalaya Shelf off the Louisiana coast in the United States is characterized by fine grained sediments dispersing into the shelf from the lower Atchafalaya River and Wax Lake outlets. Rapid seaward flushing of the sediment-laden river plumes, due to water level set-down during cold front passages forms a fluid mud layer close to the bottom, which effectively dampens the wave energy. In this study, the performance of a phase-averaged spectral wave model was skill assessed based on the wave data recorded close to the southern periphery of the mud zone during several days in March 2009. Separation of wave spectra into sea and swell partitions showed that the wave model overestimated the sea waves generated by northerly wind during the cold front passage. A non-stationary scheme was needed to solve the wave action balance equation to include the wind dynamics during the cold front passages over the study area. A recently developed mud-induced dissipation term was improved by modifying its algorithm for solving the implicit dispersion equation. The modified model became efficient enough to be used for non-stationary calculations. The thickness, density, kinematic viscosity of the mud layer, and its offshore extent were determined by trial and error. The mud-induced energy dissipation term enabled the model to reproduce the energy attenuation of short waves by the fluid mud. A high value of mud viscosity (0.01–0.1 m2/s) was required to obtain good agreement with in situ measurements when the maximum wave height occurred. However, the model using lower values of mud viscosity (0.001–0.01 m2/s) was more successful in reproducing the measured wave spectra from a few hours after the maximum wave activity. The simulation results also showed that presence of fluid mud with high value of mud viscosity hindered the wave growth in shallow water due to suppression of high frequency waves.