The pace of emerging issues in our global environment such as climate change and human technological advances are unprecedented. Decision makers are setting new policies and regulations at the regional, national and international levels to adapt to the changing environment with support of the current technological and scientific advances. The aim is to establish adaptive management capable of safeguarding our society, restoring natural resources, preserving biodiversity, understanding ocean-land-atmosphere connections and discovering future trends.
I believe this sets a new stage containing a variety of challenges and opportunities. My strategic research plan is to adapt to new directions and developments in environmental science and the demands to serve regional, national and international needs. Here I briefly describe some of my current and previous research projects.

Climate Change and Ecosystem Evaluation


The main research question is: How have the tidal river circulation and sediment dynamics changed over the last century under the influence of dredging, contaminant introduction, mean sea level rise, and climate change? 

This includes implementation of a stochastic modeling approach that more realistically incorporates uncertainties in future sea-level rise, extreme events, and climate variability. Also a Bayesian multi-modeling approach will be incorporated such that the errors and uncertainties in any individual model can be assessed and propagated realistically through the suite of linked hydrodynamic, sediment, and contaminant models.

Passaic River Conceptual model - 3D salinity iso-surfaces

a) PASSAIC RIVER CONCEPTUAL MODEL - 3D SALINITY ISO-SURFACES - WITHOUT DREDGING
 [choose HD quality]

Vorticity

b) PASSAIC RIVER CONCEPTUAL MODEL - 3D SALINITY ISO-SURFACES - WITH DREDGING
 [choose HD quality]

Numerical Models and Remote Observation Linkage


A multi-scale temporal and spatial data-assimilative modeling framework for improving bathymetry information was established. It utilizes remotely sensed observations and provides estimation of bathymetry in a nested tidal inlet, nearshore, and coastal region around the New River Inlet, NC. We employed ocean circulation and wave model components for the assimilative modeling framework. In the tidal inlet case, O(1 km), the data were surface velocity components derived from short-dwell airborne synthetic aperture radar (SAR) and wavenumber-frequency pairs derived from long-dwell tower-mounted X-band radar. Extension into the nearshore zone, O(10 km), involved assimilation of short-dwell satellite data to enhance bathymetry information in larger spatial scales. At the coastal ocean scale, O(100 km), experiments with assimilation of water surface elevation data derived from satellite altimeters will be presented, with the aim of reducing systematic slope errors in bathymetry.


Surface signature of the wave breaking
[Click to enlarge]
Iterative data assimilation
[Click to enlarge]

Nearshore Oil Pollution Transport

Boyant pollutants approaching the shore might reach the surf zone by first slowing down, sometimes not even reaching the shore (Slow, compared to time associated with shore-propagating tracers moving by advection).
A “red tide” event off the coast of Florida. Image courtesy of P. Schmidt, Charlotte  Sun [Click to enlarge]

The setup presented in bellow figure was initialized with oil only at the surface. 


The time evolution of oil pollution at the surface and in interior in terms of droplets with different sizes are presented hereafter.

Oil pollution transport only forced by incoming waves. interaction between surface oil and oil droplet class sizes controlled by wave dissipation as driving force (eddy)  [Click to enlarge]
Initial oil assumed only at the surface (slick) 800m away from the shoreline. The oil thickness at the slick are shown for hours after initial state [Click to enlarge]
[Click to enlarge]

Three Dimensional Ocean Modelling

My main case study is New River Inlet (NRI). Full 3D hydrodynamical modelling for this tidal inlet has been performed. Sample 3D output for temperature iso-surfaces and velocity vectors are given in Fig. a.
2D results for vorticity and surface layer temperature are presented in [Link: 2D results].

Conceptual model for parameter study of estuarine circulation [Links: Animation1 , Animation2].





a) 3D temperature and velocity field [choose HD quality]

Vorticity

b) 3D Vorticity field [choose HD quality]

Bathymetry Estimation in Variable Tidal Environments

I am currently working on bathymetry estimation of a typical variable tidal environment, e.g. tidal inlets, using surface wave and current current information. In this research a bathymetry estimation methodology using Kalman filter ensemble assimilation method using the wave
information, e.g. coherent frequency and wave numbers, and surface velocity current component observations a variable tidal inlet has been developed.  

Our results showed that Inclusion of both wave (wavenumber) and current velocity data enable us to improve our estimation of the depth in the entrance area. It  is also providing a smooth transition of the estimated bathymetry from offshore were only wave data is available to up-stream of the inlet where the current velocity measurements are the only available data (More ...) .

https://sites.google.com/site/moghimis/research/prior_true_flood_t.png
Left: Prior, middle: True and Right: assimilated results 
[Click to enlarge]



River Plume Response to Surface Waves

 

Our main questions aimed to be addressed during this modelling study is about
quantification of the wave effects on full three dimensional hydrodynamics of
inlets and shallow near-shore regions.

These questions could be listed as: 
How the waves-current interaction would affect temperature and salinity  distribution in and around surf-zone? 

How different wave forcing mechanisms could affect near-shore and plume dynamics in terms of:

  • The plume area and thickness
  • Enhancing vertical stratification due to enhancement of  eddy diffusivity
  • How inclusion of temperature and salinity interact with formation and location of near-shore rip-currents?
  • How much rip-current are contributing in lateral mixing of tracers in  near-shore area.
 

YouTube Video

[choose HD quality]

YouTube Video

[choose HD quality]

Wave Current Interaction

Wave current interaction at the entrance of NRI has been studied. Vortex generation due to wave forcing terms (VF) are reproduced. Dynamical effects of wave induced pressure gradient in inlet hydraulics also investigated (Animations and more...).





 
vorticity May 15,2012
[Click to enlarge]

Wave Enhanced Turbulence Quantities

Modification of turbulence quantities by dissipating surface waves  enhances the vertical mixing and directly affects hydrodynaimcs and sediment transport in the vicinity of the breaking event which also modifies beach evolution processes. Several studies show the importance of inclusion of wave generated turbulence and its effects on sediment re-suspention on increasing of total sediment transport. Here we mainly focused on turbulence quantity enhancement due to active wave breaking inside surf zone.  we have implemented several methods originally developed for deep water and improved them for shallow water wave breaking applications.
Turbulence dissipation, up: Surface flux of wave dissipation, bottom: no wave effects [Click to enlarge].

Dynamical Wave and 3D Ocean Models Coupling

To investigate wave-current interaction, coupled modeling system including GETM and SWAN models using MCT toolkit has been developed as first part of my fellowship. To this end both 3D radiation stress method (Mellor,2003,2008,2011) and Vortex force (VF) approach (Ardhuin,2008) have been implemented. Both methods are be able to use physical component in between e.g. rollers evolution model, wave generated turbulence, bottom boundary layer and so on. 
Hereafter results of VF method for one of the test cases for a specific set of parameters such as inclusion of wave generated turbulence using k-epsilon turbulence scheme, assuming 50 percent of broken waves turn to roller and … has been presented [Read more ...].

I have completed this research during my stay in Germany [ Link ]. 

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LIP1D experiment: Case 1A (Hrms=0.6 m; T=5 s)
[Click to enlarge]

Environmental Impact of Wastewater on Inland Waters


we conducted several field observation campaigns to measure water quality and hydraulics parameters of the water body of the wetland. We used remote-sensing and field surveys to generate an updated hydrographic map and finally employed water quality numerical models to perform water quality simulation for different climate and future scenarios to study effects and levels of pollution enters into the wetland. 
Our field observation and numerical modeling results showed that the wetland situation is getting worse during summer time. Because while amount of the pollution entering the wetland stays almost the same throughout the year, there are higher evaporation rate and less precipitation during summer.
Undergraduate students trapped in the mud.
Taking samples from a leakage at a Mine Plant adjacent to the wetland (Scary! They did not like this).
ETM+ image of the Wetland region used for bathymetry improvement [Click to enlarge].
Model domain and final bathymetry 
[Click to enlarge].

Operational Wave Forecasting System

An operational real time wind and wave prediction system for Caspian Sea and Oman Sea region has been developed as the first phase of the Iranian Meteo-Ocean System.  
As an accurate wind field plays an important role in wave prediction, we took advantage of a high resolution numerical weather prediction model HRM, which is developed by German Weather Service (DWD). The model receives boundary conditions from DWD four times a day and runs at 7km grid size. This system uses WAM4.5 wave model. Whole system was set up at Iranian Meteorological Organization Linux cluster. The output of both models is accessible to every client, from forecasters to engineers, by using a well developed and efficient website.
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Snapshot of the website of the project [Click to enlarge]
Caspian Sea wave prediction sample output [Click to enlarge]

Environmental Impact of Thermal Pollution

In Mobin petrochemical complex thermal pollution study, a comprehensive chain of modeling steps including near- and far-field studies were conducted to investigate the thermal effluent effects of a huge outflow jet (discharge of 105 [m3/s]) on adjacent coastal environment.  This project was part of an EPC project for design and construction of intakes and storm water channels by SADRA company ($200M).  
Near-field analysis: Velocity vectors colored by velocity magnitude [Click to enlarge].

Far-field analysis forced by tidal currant [Click to enlarge]

Environmental Impact of Causeway Construction on Lake's Natural Circulation

After construction of the causeway, the pattern of current and water circulation in the lake has been disturbed considerably. Sediments were deposited in the Urmia City side along the Southern and Eastern part of the causeway. The reason for this is that the causeway separates the lake to two parts. The southern part of the lake receives almost 90% of the freshwater from rivers, while the evaporation is dominated in the Northern part. 
Numerical simulations of hydraulics and hydrodynamics of the causeway have been performed for: a) Determining design parameters of effective phenomena such as waves, storm surge, currents and rivers flood for: the stability study of the embankment body, design of its protection layer, design of the proposed bridge and associated structures. b) Investigation of salinity pattern in both side of the causeway and evaluation of required extra opening(s). c) Consideration of sedimentation around the causeway and suggestion of solution(s) for decreasing such sedimentation.


Causeway from a Landsat-TM image.
Salinity distribution for causeway without (left) and with new opening (right).
Adding 500m opening from kilometer 4 to kilometer 4.5 with two 450m openings on either side of the causeway shows closest correlation with natural condition (maximum r-square).

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