Bulletin of Geophysics and Oceanography (2785339X)65(1)pp. 123-138
The study investigated wind-driven upwelling along the Makran coasts, utilising wind, temperature, and sea surface current data. Results revealed a seasonal coastal upwelling system along the eastern Makran coasts, primarily influenced by coastline orientation, and impacting sea surface dynamics. Trend analysis of sea surface temperature (SST) data indicated consistently negative, or near-zero, SST variations in the Makran upwelling system, in contrast to adjacent areas. Peak upwelling intensity occurred in May, spanning 62° to 66° E, encompassing over 300 km of Makran coasts. Temperature profile data validated the presence of a seasonal coastal upwelling system along the eastern Makran coasts. The examination of sea surface current components, in the northern Arabian Sea and the Gulf of Oman, highlighted the dominance of the seasonal upwelling system, driven by a decreased geostrophic current in May. In the northern Arabian Sea, the intensified geostrophic current, interacting with the Ekman current, diminished coastal upwelling intensity along the eastern Makran coasts. © 2024-OGS.
Marine Pollution Bulletin (0025326X)209
Advanced satellite technology and algorithms are making substantial progress in meeting the need for improved environmental monitoring of coastal waterways. Integrating high-resolution satellites with in-situ radiometric equipment is essential for effectively monitoring algal blooms and managing coastal resources. Our work has built a model to examine geographical and temporal fluctuations in chlorophyll-a concentration in Bushehr Bay, Persian Gulf, Iran, using radiometric data and high-resolution remote sensing. In this study, we used twenty-four bio-optical features for analysis. After evaluating and selecting the most important features, we used the top five features to estimate chlorophyll-a concentration using machine learning algorithms. Likewise, the model could effectively investigate our climatology of chlorophyll in the study area. Our findings provide a dependable approach to monitor the environmental effect of chlorophyll-a and enhance water quality and regional management of primary production in coastal waters. This proposed proxy may be implemented in comparable places globally. © 2024 Elsevier Ltd
European Physical Journal Plus (21905444)139(11)
Formation of a diurnal ocean mixed layer (OML) as one of the nonlinear dynamic processes has been investigated by using large eddy simulation (LES) in previous studies, but the effect of different terms of heat fluxes on the OML has not been discussed separately so far. In this paper, the effect of air–sea interaction on the OML was evaluated by large eddy simulation (LES) in the presence or absence of Langmuir circulation (LC), wave breaking (WB), sensible heat flux (SHF), long wave radiation (LWR), latent heat flux, and insolation or short wave radiation for the first time. We used average climatic parameters for the Arabian Sea during the summer monsoon to define the ideal case of simulation. The area was simulated for 33.5 h, and the results of the first 9.5 h were ignored. The variation of different simulated parameters was investigated during a 24-h period. The results of the present study showed that since the SHF and LWR values were omissible, the effects of these two fluxes on many OMD properties are negligible. We also observed that SHF had a reversible effect because of its positive and negative values during the defined timeframe of the simulation. In addition, the maximum impression of heat fluxes was seen in the presence of evaporation and insolation. However, the evaporation in the absence of LC and WB caused a slight decrease in velocity shear and shear production and an increase in the dissipation rate (approximately double), pressure transport, and TKE transport. Moreover, in the presence of evaporation, the presence or absence of LC and WB did not affect the profile of turbulent heat flux. Evaporation did not change the Stokes production as well. The results of this study show that the effect of solar insolation on OML is significant and even more effective than surface evaporation. It reduced TKE and causes most of the diurnal variation in TKE. Furthermore, significant changes in the TKE profile are controlled by the shear production profile. © The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2024.
Iranian Journal of Geophysics (20080336)17(2)pp. 105-125
The water environment is considered as a suitable conductor for sound waves propagation and the changes in the horizontal and vertical structures of physical parameters are effective on the speed and propagation of sound. One of the effective vertical processes in the water column is the double diffusion process with two structures of salt-fingering and diffusive convection, which are created due to the vertical gradient of temperature and salinity with different diffusion coefficients. Salt-fingering occurs when a layer of warm and salty water is located above cold and fresh water. In areas such as the Strait of Hormuz, with thermohaline exchange between the salty basin (Persian Gulf) and the open sea (Oman Sea), the conditions for the formation of salt fingers and their growth are significant. To determine double diffusion structures, the Turner angle (Tu) method is used in terms of density ratio (Rρ). Turner angle values (in degree) for the formation of double diffusion structures are defined in the range of -90 < Tu < 90. So that the diffusive convection structure is formed for the values of -90 < Tu < -45 and the salt finger structure is formed for the values of 45 < Tu < 90. With the increase of the warm water inflow entering from the Oman Sea into the Persian Gulf, in spring and summer and the increase of evaporation in late spring, the conditions for the formation of salt fingers are strengthened and salt fall occurs in all the eastern and middle stations of the Strait Hormuz. Also, in the southern stations, salt fingers extend from the surface to a depth of 65 m. The vertical gradients of temperature and salinity in the eastern cross-section of the Strait of Hormuz form a warm and salty surface layer (34 °C and 39 psu) over a cold and fresh water layer (29 °C and 37.5 psu) so that the warm and Salty water mass spreads on the surface and falls from the surface to a depth of 40-70 m as salt fingers. The fall of salt fingers causes the speed of sound waves to be not uniform along the channel so from the surface to the depth of salt finger fall, it has the highest value (1557 m/s). In this study, sound signal propagation at frequencies above 500 Hz (600 Hz and 60 kHz) is simulated using Ray theory and the Bellhop model. The results show that sound rays with a small propagation angle are scattered on the surface after passing through the salt fingers. But by increasing the depth of the sound source, the dissipative effect of the salt structure decreases while the deviation from the location of the strong structure is observed. In general, the propagation and transmission of the sound signal along the channel depend on the stratification leading to the salt finger structure, and the sound rays are propagated with significant deviation and 80-85 dB loss in transmission (10-15 dB increase in loss), while these salt fingers exist in water. © 2023 Iranian Geophyisical Society. All rights reserved.
Estuarine, Coastal and Shelf Science (10960015)280
Structures caused by temperature and salinity gradients and their resulting mixing have a significant effect on sound propagation in shallow and deep waters. One of the vertical structures is salt-fingering (SF), which is formed by the vertical gradient of temperature and salinity, when warm and salty water is located above cold and fresh water. Quantification of double diffusion (DD) structures is done by the Turner (Tu) angle theory. Warm surface water from the Oman Sea, evaporation and salty surface water of the Persian Gulf provides the initial conditions for the formation of SF in the Strait of Hormuz. In depth less than 5 m, weak SF (45 < Tu ≤ 67.5) are formed and by dominating water buoyancy, salt fingers gradually grow and strong SF (67.5≤Tu < 90) extend from the surface to 25 m deep. This process causes mixing and changing the depth of the boundary layer. The diffusion structure in the SF plays a significant role in the deflection and energy loss of the sound signal. By passing through the SF structure on the surface, the sound signal is scattered, and its transmission is lost up to 80 dB (TLS), and the propagation of the sound along the channel is weakened. With increasing frequency and propagation angle, the deflection occurs from the location of the SF towards the cold and fresh water. But by passing through the place of the strong SF, the sound signal is propagated with a delay and 10–20 dB increase in TLS. © 2022 Elsevier Ltd
European Physical Journal Plus (21905444)137(7)
Aerodynamic impacts of two tree implant layout with different tree heights on air pollution distribution inside the street canyon, where the walls height and street width are equal, has been investigated using Parallelized Large Eddy simulation model (PALM). A reference tree-free case, six double-row, and center-row planted trees with 5 m, 10 m, and 15 m height cases were studied. The results of the modeling study reveal that the center-row planted trees have direct impacts on air ventilation inside the street canyon. In street canyons with center-row planted trees, taller trees worsen the air quality up to 10 %. In street canyons with double-row planted trees, trees higher than roof-top level improve air quality inside the street canyon by about 6%. The highest concentration values were modeled at the pedestrian level about 1.5 m to 2 m near the leeward wall. The center-row tree implant is more favorable for air quality improvement than the double-row tree implant. The trees increase air pollution around the roof level near the leeward wall. © 2022, The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.
Nivar (26453347)46(118-119)pp. 113-129
Double Diffusion Convection (DD) structures, in two types of Salt-Fingering (SF) and Diffusive Convection (DC), occur due to vertical temperature and salinity gradients with different diffusion coefficients. And thermohaline circulation in the Strait of Hormuz often causes the formation of SF on the surface and in the northern or middle parts of the strait and DC structure in the depth and southern parts of the Strait of Hormuz. In this study, the formation of DD investigated. This effect depends on the formation conditions of diffusion structures and the average structures and their role in temperature changes and thermal energy of water in the Strait of Hormuz have been temperature and thermal energy of the water mass. Due to the fluctuations resulting from the DD structures in the hot days of the year, a 2-5% change in the temperature and thermal energy of water is observed. So that the maximum changes up to 5% (change in energy) occur in the southern parts of the strait. The heat exchange during the DC process is higher than that of SF (more than 10 times). However, the thermal energy is minimal at the place of the cold mass and strong convection, and the DC structure is weakened due to the increased energy exchange with the environment,. This heat exchange causes the internal energy of water to decrease by about 250 J. While during the growth of SF, the temperature and thermal energy of the environment (on a small scale) increases. © 2022, Islamic Republic of Iran Meteorological Organisation. All rights reserved.
European Physical Journal Plus (21905444)137(3)
In this paper, Turbulent flow patterns inside and above a street canyon with an aspect ratio of 1 according to different thermal conditions are simulated using a large eddy simulation (LES) model. To investigate heat flux and temperature stratification effects on flow patterns, six simulation cases performed, including heat fluxes and thermal stratification. In the case with no heat flux and no thermal stratification (neutral condition), a primary vortex appears at the center of the street canyon. Introducing heat flux at upwind building-wall and bottom-street surface reinforces the primary vortex. However, heating of the downwind wall creates a secondary vortex close to the heated surface and the primary vortex is weakened and shrunk. Stable thermal stratification inside the street canyon can eliminate the primary vortex and replaces it with small eddies, while the primary vortex persists in the unstable thermal stratification condition. Heating the bottom surface of the street causes a large horizontal temperature gradient across the width of the street canyon. In contrast, where the walls are heated, it confined to the vicinity of the heated building wall at pedestrian level. The results imply that heat forcing can intensify the turbulence and improves air ventilation inside the street canyon. © 2022, The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.
Urban Climate (22120955)41
Using a parallelized LES model (PALM) the importance of additional transport terms generated by applying time and area averaging on the fluxes of resolved scale variables (i.e. dispersive momentum (scalar) fluxes) compared to conventional turbulent momentum (scalar) fluxes in different street canyons is investigated. It is shown that the role of dispersive fluxes in the total flux is much greater than considered before (even more than conventional turbulent fluxes); if the true effect of dispersive fluxes is not taken into account, a large amount of the total flux would be lost and there would be no consistency between the pollutants concentration and the rate of their production and exit. © 2021 Elsevier B.V.
In this study, a new method of condensation particle counting, CPC, using optical guiding of micro particles was developed. Optical forces (e.g., radiation pressure and photophoretic force) can guide particles in directions that are of the order of their diameter. Optical forces on micro particles by radiation of a donut shaped beams such as first order Laguerre- Gaussian, LG01, and single-charged Bessel-Gaussian, BG01, beams are investigated. The movement of aerosols that irradiated by these beams are simulated. In experiments, the microscopic aerosols are trapped along a BG01 beam axis and guided to the measuring space where a second beam is focused. Due to decrease in particle diffusivity, most of them can pass in focused light. As a result, the lights scattered by micro particles have sufficient intensity for detecting. This is even more important as the particles get smaller. Experimentally, by guiding aerosols less than 3.5 µm in a BG01 beam as an optical tube, about 18% increase in condensation counting of them was obtained. © 2021 Elsevier GmbH
Urban Climate (22120955)35
Effects of different ambient wind speeds and aspect ratios on turbulence and pollutant concentration in and above street canyons are numerically investigated and compared using parallelized LES model (PALM) and ((Transition Conditions)) are introduced for the first time. The results show that, increasing of ambient wind speed does not change the shape of streamlines but increases the magnitude of time- and area-averaged turbulent kinetic energy with the rate of square of speed ratios resulting in better ventilation of pollutants. As aspect ratio increases, the magnitude of turbulent kinetic energy and turbulent fluxes especially in lower depths of the canyon decrease sharply causing decreased pollution transport to higher levels. An applied case is between 2 and 4 aspect ratios in which there are two vortices along the depths of the canyon. As the width of the canyon increases, the rate of the upper vortex penetration increases and eventually at aspect ratio 2 makes a transition from two to one vortex; we call such conditions as transition conditions. In transition conditions increasing of less than half a meter of street canyon width will drastically decrease the pollution concentration inside the canyon; this is useful in optimizing canyon dimensions for better ventilation. © 2020 Elsevier B.V.
In this study, particle motion with low thermal conductivity, such as carbon nanoclasts aerosols, is simulated when irradiated by an optical tube such as Laguerre- Gaussian and Bessel-Gaussian beams. Opticall forces due to light radiation to the particle include the radiation and photophoretic forces that result from the transmission of the photon's momentum to the particle and its surroundings. Here, these forces are generally calculated for radiation an m-charge Laguerre-Gaussian beam, LG0m, on a spherical micro particle. Longitudinal and transverse component of radiation and photophoretic forces for radiation of LG0m with m = 0, 1 and 2 are derived. LG0m beams have a ring-shaped intensity profile when m > 0. The particles can be guided into these pipeline beams on the optical axis based on the particle's size and the beam properties. The optical guidance can be in the direction of the beam or opposite. Some particles are also trapped completely. © 2021 Elsevier GmbH
In this study, a new method of microscopic particle's size and condensation measurement by dual-beam methods is investigated. In this method microscopic particles in a turbulent fluid such as aerosols guide to the interfering fringes of two shifted frequency laser beams by an optical tube (e.g., single-charged Bessel-Gaussian laser beams) instead of mechanical guiding of them. Optical forces such as radiation and photophoretic forces on a particle in a fluid was obtained. It was shown theoretically the Signal-to-Noise Ratio, SNR, and the number of detected photons scattered from the particles cross the fringes will be significantly increased rather than mechanical guiding of them. In addition, the Doppler frequency broadening and angular uncertainty are decreased by new measurement. The condensation of aerosols in the lab was measured by counting the signal burst from particles which traverse light fringes after guided them into a single charge Bessel-Gaussian laser beam. Due to the lack of laboratory facilities, our group can't determine the frequency Doppler shifted of laser beam to determine the particle's dimensions. © 2020 Elsevier GmbH
Bollettino di Geofisica Teorica ed Applicata (00066729)61(2)pp. 249-270
Regional sea level changes were studied in the North-West Indian Ocean (NWIO). Basically, the processes affecting regional sea level changes can be divided into dynamic and quasi-static components. In the present study, dynamic sea level changes were evaluated by applying statistical methods such as Trend, Empirical Orthogonal Function (EOF), Spectral and Correlation analyses to the mean sea level anomaly, surface heat flux, and wind stress data. In addition, quasi-static sea level changes were examined by considering the inverted barometer effect. The results indicated that the maximum sea level rise is mostly observed in areas adjacent to the Gulf of Aden, and the minimum sea level rise is seen at the centre of the region, near the equator and oriented towards the SW. In general, in NWIO, the main factors affecting sea level changes are weakened and intensified with a one-year period. The correlation coefficients of heat flux and wind stress with the 2nd EOF of the sea level are larger than those of other modes so that the effect of internal factors, such as seasonal change, is, generally, smaller than the effect of external factors such as El-Nino-Southern Oscillation. The direction of prevailing winds in the region causes the positive sea level anomalies by Ekman suction and increasing the depth of the tropical thermocline. The inverted barometer effect on the sea level changes is significant in most of the months, except December, in such a way that it decreases in the cold months by moving towards high latitudes, while increases in warm months by moving to high latitudes. The distribution of non-barometric effects in the Arabian Sea indicates that they are caused by interactions with the Indian Ocean mostly from the southern areas of the Arabian Sea and the intensity of these effects decreases northwards and westwards during the year. © 2020 – OGS.
Laser Physics Letters (1612202X)16(6)
A fiber-optic Fabry-Pérot acoustic sensor with a ∼50 nm-thick multilayer graphene diaphragm is reported. In this paper, the results of the simulation and experimental investigation of the Fabry-Pérot acoustic sensor are primarily presented, and the main area of interest is studying the different algorithms for enhancement of the sensor sensitivity. The phase generated carrier (PGC) demodulation algorithm is presented, based on differential-cross-multiplying (DCM), the arctangent (ATAN) function and ATAN based on a coordinate rotation digital computer CORDIC algorithm. The simulation results reveal that the PGC demodulation method, based on the ATAN CORDIC algorithm, has a better result (signal-to-noise ratio) than the DCM and ATAN function without using the CORDIC algorithm. On this account, a PGC demodulation algorithm based on the ATAN method with a CORDIC algorithm is applied in the experimental investigation due to the simulation results and simpler digital implementation on a field programmable gate array. The acoustic sensor shows a high frequency response from 8-10 kHz and may be useful for highly sensitive acoustic sensing without temperature and pressure fluctuation. The results also show acoustic sensitivity in the order of -98 dB re rad µPa-1 at 1 kHz. © 2019 Astro Ltd.
Measurement: Journal of the International Measurement Confederation (02632241)137pp. 556-561
In this paper, the results of simulation and experimental investigation of interferometric optical fiber acoustic sensing are primarily presented, and the main area of interest is studying the different algorithms for enhancement of sensor sensitivity. In fact, when light propagates through optical fiber, in a Michelson interferometer, the phase of light changes due to effect of external perturbation as acoustic wave on optical path length and this phase change is detected by demodulation algorithm. It is strived to present the Phase Generated Carrier (PGC) demodulation algorithm based on Differential-Cross-Multiplying (DCM), Arctangentfunction (ATAN) and ATAN based on Coordinate Rotation Digital Computer CORDIC algorithm. Simulation results reveal that PGC demodulation method based on ATAN CORDIC algorithm has better result (signal to noise ratio) than DCM and ATAN without using CORDIC algorithm. On this account, PGC demodulation algorithm based on ATAN method with CORDIC algorithm is applied in the experimental investigation due to simulation results and simpler digital implementation on Field Programmable Gate Array (FPGA). Moreover, acoustic frequency is detected as sidebands of harmonics of phase modulator frequencies. The sensitivity of digital circuit is 5μradHz -0.5 and the minimum detectable phase is 50μrad Acoustic frequency is detected as sidebands of harmonics of phase modulator frequencies, and consequently, the system allows detecting the sinusoidal acoustic wave with different frequencies. It is also detected acoustic frequency by measurement of the reflected optical power. Moreover, in this part, it is packaged sensing arm of interferometer with polymer material (polyurethane) for investigation the effect of polymer on sensitivity enhancement of sensor. It is observed with applying of acoustic wave, the reflected optical power decreases and this reduction is more, when sensing arm is packaged with polymer. © 2019 Elsevier Ltd
In this study, the behavior of charged particles within a fluid is investigated when exposed to the radiation of a Laguerre-Gaussian beam as an optical tube. Optical forces (e.g., Photophoretic, Radiation pressure and Lorentz forces) and non-optical forces (e.g., Drag and gravitational forces) determine the trajectories of ions movement within these beams. Trapping of charged particles in the direction of the beam axis in an optical tubes depends on the superiority of the radial component of the photophoretic force on the electromagnetic force. The factors affecting this, such as the amount and type of electrostatic charge and the radius of the particle, and the shape and power of the beam are studied. As a result, the charged particle can be guided to various paths based on their electrostatic charge and particle diameter. This could be done in the study of ions within a fluid by optical methods. One of the applications proposed in this regard is that we can counted charged and uncharged particles within a fluid (e.g., liquid ions or aerosols) by separating them in an optical tube. © 2019
Iranian Journal of Science and Technology, Transaction A: Science (10286276)43(4)pp. 2035-2042
Numerical simulation of tidal current energy extraction has raised the knowledge about the issue of energy extraction from marine sources. A water channel in laboratory scale is simulated using FLUENT code. FLUENT is a state-of-the-art computer software for CFD analysis based on the finite volume method, and its applications have been over almost the entire fluid dynamic spectrum. FLUENT has been used for tidal energy extraction simulation in this study. A disk, which generates a pressure drop due to energy loss, drives the tidal stream turbine in the model. The fluid model, which can be freely deformed, has been used for the free water surface. Numerical results show that a wake is formed in the back of the tidal flow turbine and an accelerated flow around, especially below the energy generator device is created. It is supposed that the drop of the water surface due to the energy extraction in the model has an important effect on improving the wake of the turbine. © 2019, Shiraz University.
Estuarine, Coastal and Shelf Science (10960015)212pp. 372-386
Ekman transport is a key factor in the coastal upwelling regimes in the northern coastal region of the Persian Gulf. In this paper, the Ocean Module of Parallelized Large-Eddy Simulation Model (PALM) was utilized so as to investigate the Ekman layer and estimate the water mass transport in the Persian Gulf for the first time. In order to take into account the effect of the topography on the Ekman transport, three experiments with the same initial and boundary conditions and different topographies were carried out. The results indicated that, in the vicinity of the shoreline and in shallow waters Turbulent Kinetic Energy (TKE) is 10 times stronger than in the offshore area. It was concluded that in the presence of the shoreline the vertical velocity increases and in the onshore area, the upwelling speed is 3–4 times larger than in the offshore area. It was revealed that the Ekman transport reached a steady state at the end of the simulation, and reached a constant value of about 250 kg/ms. © 2018 Elsevier Ltd
Bollettino di Geofisica Teorica ed Applicata (00066729)59(2)pp. 179-192
Despite the great work on the propagation of vertical electrical dipole (VED), the effect of inhomogeneous soil texture on VED electromagnetic radiation above the soil is not understood. Using Fourier integral transform, the equations of the magnetic fields for each region is obtained. Also, the electrical permittivity and conductivity variation of soil texture with humidity is extracted. Having humidity dependency of soil to depth, the electrical permittivity and conductivity of soil texture in each depth can be calculated. The maximum changes of the value of integration will be 0.1% by doubling the number of semi-intervals, so the magnetic field is validated. In the cases of clay or sand, the magnetic fields inside and above the Earth are the same at the frequency of 1 MHz. But the magnetic field differences for clay and sand inside the Earth at the frequency of 50 MHz are significant. In the distances far from vertical electrical dipole in the air, the magnetic fields are the same in different heights because the distances to the points come closer in different heights and high radial distances. © 2018 - OGS.
Applied Physics B: Lasers and Optics (09462171)124(12)
In this study, the microscopic particle motion inside an optical pipeline, such as particle motion through a mechanical tube, is investigated. The photons in an optical tube guide the particles towards the center of the light beam by inducing photophoretic and radiation pressure forces. Laguerre–Gaussian- and Bessel-like beams are examples of such optical tubes. The Reynolds number of particle motion in optical tubes is investigated. The power of the light beam and the ratio of the particle radius to the light beam ring radius influence the turbulence of the particle flow and the value of the Reynolds number. The diffusion coefficient of particle movement in such pipelines is derived, which indicates that an optical tube is a good tool for guiding and trapping particles in micron- and nanometer-scale dimensions. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
Journal of the Earth and Space Physics (25383906)44(3)pp. 659-671
In this study, the turbulent properties of the bottom Ekman layer of the Persian Gulf is studied, using a Parallelized Large-Eddy Simulation Model (PALM). Three numerical experiments were carried out with emphasis on stratification effects. A reference experiments (EXP C) without vertical gradients of the potential temperature and salinity and two experiments with vertical gradient of the potential temperature and salinity. The initial values of the surface potential temperature and salinity and their vertical gradients, provided from in situ data, were chosen according to August (EXP A) and November (EXP N) condition of the Persian Gulf. The eastern part of the Iranian coastal area of the Persian Gulf near the Hormuz Strait was chosen because there is a considerable western current during the year in this area. Also, the sea is deep enough to observe a distinctive pycnocline layer which separates surface and bottom mixed layer. The domain size is 200m×200m×100m in x, y and z directions respectively. A pycnocline layer with 40m and 20m deep was considered for August and November, respectively. A Geostrophic current with 0.15m s^(-1) speed is supposed to flow in x direction over the rough sea bed. The bottom boundary condition of the momentum flux was set to Dirichlet in order to create a no-slip condition at the sea bed. The simulations were carried out for 48h to include at least two inertial periods and avoid inertial oscillations. The results showed that the stratification limits the bottom Ekman layer depth and it does not grow with time. While in EXP C, where the fluid is neutral, a rapid growth of the bottom Ekman layer is obvious during the first 20h and its maximum depth reaches 60m. The Ekman cross-stream current component cannot entrain into pycnocline layer and it vanished at the bottom of the pycnocline layer. In autumn in which the pycnocline layer is thinner, the Ekman spiral is broadened and the magnitude of the Ekman cross-stream current component is 25% larger in compare to summer. The maximum value of the Ekman cross-stream current component is about 0.04m s^(-1) in EXP C and EXP A while it is about 0.05m s^(-1) in EXP N. The hodograph of the horizontal velocity in EXP C is more similar to Ekman theoretical solution. The stream-wise component of the horizontal velocity decrease with the same rate near the sea bed in all experiments which implies that the stratification does not have much effect on bottom stress. It is concluded that when an intense pycnocline exists and the bottom mixed layer is thin, less time is needed to trigger the turbulence. The bulk turbulent kinetic energy in all experiments is the same. Since the bottom boundary is assumed adiabatic and there is no heat flux from the bottom, the heat budget in the neutral BBL is approximately conserved (molecular diffusion is not considerable compared). Then a pycnocline is necessary to maintain heat conservation after the formation of a mixed layer. These intensified pycnocline can be observed as distinctive peaks in vertical profiles of the buoyancy frequencies near the top and bottom of the stratified layer. The thickness of the intensified pycnocline grows with time and at the end of simulation reaches about few meters. These intensified pycnocline layers in November is thicker than that of August. Also at the bottom interface of the stratified, the shear stress increases. © 2018 Institute of Geophysics. All Rights Reserved.
Bollettino di Geofisica Teorica ed Applicata (00066729)59(3)pp. 301-312
Using the long-term wind time series, coastal upwelling was investigated in the northern Persian Gulf. The shoreline was divided into 34 segments from NW to SE and the daily Ekman transport components were computed. Based on the Ekman transport components, a coastal upwelling index was calculated. Starting from these, in this paper we present, for the first time in this region, the annual cycles of the coastal upwelling. The annual cycles revealed the most intense coastal upwelling in the central areas, located about 51° E - 53° E, including three peaks in June, November and February. In addition, a simple optimization procedure has been done to determine the best shoreline angle for the favourable conditions of coastal upwelling occurrence at each segment and month. To investigate the results, sea surface temperature (SST) and sea level anomalies (SLAs) were analysed. A cross-correlation analysis was done on the daily time series and indicated that the SST decreases more in the segments with more intense coastal upwelling along the northern shoreline. The linear temporal trend was also applied to SLA gridded time series; the results show the sea level anomaly responses to wind-driven coastal upwelling. © 2018 - OGS.
Advances in Space Research (02731177)60(9)pp. 1949-1957
In this paper, the effect of atmospheric electrical conductivity on the electromagnetic waves radiated by a vertical electric dipole located in the earth, near the surface of the earth, is investigated. As far as electrical conductivity is concerned, the atmosphere is divided into three areas, in which the electrical conductivity changes with altitude. The Maxwell equations in these areas are investigated as well. Using the differential transform method, the differential equation is solved in a way that atmospheric electrical conductivity is variable. Solving the problem in these areas indicates that electrical conductivity in the middle and lower areas of atmosphere may be ignored. However, in the upper areas of atmosphere, the magnitude of the magnetic field in the ionosphere at a frequency of 10 kHz at night is five times smaller when electrical conductivity is considered compared to when it is neglected. © 2017 COSPAR
Environmental Modeling and Assessment (14202026)21(6)pp. 721-730
The Persian Gulf ecosystem is facing a variety of stresses as a result of being located within the richest oil province in the world, which hosts more than 67 % of the world oil reserve. In this paper, the distribution of oil pollution on the surface layer of the Persian Gulf is predicted for the different months after the release, based on the Coupled Hydrodynamical Ecological model for Regional Shelf seas (COHERENS). An Eulerian model for the Persian Gulf is set up using the Cartesian coordinate in the horizontal direction, and the sigma coordinate in the vertical direction. Based on this model, our analysis and simulation results indicate that the winds lead to diffusion of the contaminant concentration in the direction of the Arabian coast from the initial position of the spill. The results of this study can be used to provide appropriate solutions for preventing oil from spreading further in the region. © 2016, Springer International Publishing Switzerland.
Meteorological Applications (13504827)21(2)pp. 271-277
The most prominent features of the annual and seasonal atmospheric flow have been recognized over the eight coastal sites in the north east of the Persian Gulf. Six to 10 year hourly recorded data of wind vectors from eight synoptic stations, located in Hormozgan Province in Iran, were analysed. The wind rose diagrams have been plotted to show the distribution of wind direction experienced at each station during the available data period. The results of the study showed that all through the year the wind direction in the west part of the area was predominately westerly. However, there were also some significant differences and exceptions, which have been investigated and discussed in this article. In the spring and summer, Bandar Abbas had a southerly prevailing wind. The considerable difference between summer wind pattern in Jask and other stations showed that Jask was much more influenced by monsoon than other stations. Investigation of diurnal wind properties indicated formation of reversing flow during the daytime in Lengeh, Bandar Abbas and Jask. Among all stations, diurnal changes of wind direction and, thus, presence of the sea and land breeze, were observed only in Lengeh, Bandar Abbas and Jask. The spatial configurations, diurnal reversal of wind and variation of wind speed frequency distribution over those three sites accorded well with the theory of the sea and land breeze circulation. © 2012 Royal Meteorological Society.
Journal of the Earth and Space Physics (25383906)40(4)pp. 169-180
In this study, the dispersion mechanisms of aerosols suspended in a turbulent plane channel flow is investigated using a novel numerical approach. A turbulent channel flow is simulated by a Direct Numerical Simulation (DNS) method, for which no-slip boundary conditions are assumed at the top and bottom walls, while periodicity conditions are applied on the other sides. DNS, in particular, allows a detailed analysis of the near wall region, where most of the particle transfer mechanisms take place. Hence, it is found the best simulating method for detailed analyzing the dispersion mechanisms compared to the other available methods. The simulation procedure of the turbulent flow is continued as along as enough, 14000 time units, when fully developed turbulent condition are achieved. The aerosols with two Stokes number, 15 and 25, are then introduced in the simulated turbulent channel flow, and tracked by a Lagrangian approach. The drag force compared to the effect of Brownian motion is a dominant force due to the aerosols size. The initial concentration of suspended aerosols is also assumed considerably low, so that the simulations conducted under the one-way coupling condition. Besides, the collisions of aerosols with the walls are assumed elastically. The particle tracking was continued throughout the fluid simulation time to obtain the all reliable interesting statistics. Comparison of the particle flux intensities indicates that turbophoretic and turbulent diffusion fluxes are the dominant dispersion mechanisms. In other words, the free-flight flux can be neglected in comparison with the other fluxes in the wall region. The steadystate concentration distribution is not uniform across the channel, primarily due to the opposing actions of the turbophoretic and turbulent diffusion flux. Turbulent diffusion flux separated the aerosols from the core and gathered them in the near wall region, while the turbophoretic flux migrate the particles from the near wall to the wall region. It was also observed that the turbophoretic flux for smaller aerosols is more efficient than that of larger ones. However, the opposite was observed for the turbulent diffusions flux. The smaller particles were less gathered in the near wall region due to a stronger turbulent diffusion flux and more migrated to the wall region due to stronger turbophoretic flux. We also investigated the cross channel fluid and particles velocity profiles. It was shown that the aerosol velocity components lag the fluid velocities in the near wall, but lead it in the core region. This is due to the transverse migration of aerosols across the channel.
Applied Mathematical Modelling (0307904X)37(4)pp. 2417-2429
Inertial particle transfer in a turbulent plane Couette flow (C flow) was studied using Direct Numerical Simulation (DNS) of the flow combined with a Lagrangian particle tracking approach for particles with Stokes numbers (St) 5, 25 and 125. The particle concentration was assumed low enough, so that the simulations were done under one-way coupling condition. Our numerical simulations show that the particles suspended in a C flow (C particles) have velocities respectively smaller and larger than the carrier fluid velocities in the near-wall and core region. The C particles in comparison to the same sized particles suspended in a Poiseuille flow (P particles) with a same Reynolds number (Re), have larger fluctuating activities in the core, while the opposite was observed in the near-wall region. This fact is due to the Large Scale Structures (LSSs) existing in the core region of the C flows. The LSSs also strengthen the near-wall accumulation of C particles, so that these particles respect to the same sized P particles have more accumulation in the near-wall region. Moreover, the LSSs affect the deposition velocity of particles whereby among the P and C particles with smallest Stokes number (St= 5), the C particles have larger deposition velocity while among the those ones with larger Stokes numbers (St= 25, 125) the opposite was the case. Finally, it was found that although the diffusional deposition mechanism for the C particles is less efficient than for the P ones, the number of deposited C particles during the time is greater than the number of deposited P particles. © 2012 Elsevier Inc.
Environmental Forensics (15275930)14(4)pp. 312-323
In this paper, the distribution of pollution in various conditions is simulated by a hydrodynamic model to determine the behavior of the oil pollution spill into the sea and the effect of the physical processes such as wind, heat fluxes and wind stress on the distribution of these contaminants. Four scenarios are designed to examine the impact of these physical processes in the transport and diffusion of the oil pollution released within the surface layer. COHERENS model was used to simulate the oil pollution transport and diffusion, which coupled with contaminant and biological modules, has the ability to solve transport equation using sigma coordinate in the vertical direction and Cartesian coordinate in horizontal. The results of this numerical simulation can be used in providing appropriate solutions to prevent oil from spreading further in the region. © 2013 Copyright Taylor and Francis Group, LLC.
IEEE Photonics Journal (19430655)4(5)pp. 1484-1494
The authors propose a tunable slow-light slotted photonic crystal (PhC) waveguide, without nanoscale variation of structure parameters, applicable in on-chip absorption spectroscopy. The main feature of this structure is that the enhanced electrical field is strongly localized in an air slot with nanometer width due to slow-light properties of a slot mode. In the proposed structure, the slow-light region of the slot mode can be controlled using a selective infiltration of a PhC waveguide. The numerical calculation reveals that an enhancement factor, γ, of 20 can be achieved. © 2012 IEEE.
Applied Optics (21553165)51(5)pp. 568-576
The authors propose a biosensor architecture based on the selective infiltration of photonic crystal (PhC) structures. The proposed sensor consists of a ring cavity coupled to an optofluidic slow-light waveguide in a PhC platform. A high potential sensitivity of 293 nm?refractive index unit is numerically demonstrated, while maintaining an ultracompact footprint.© 2012 Optical Society of America.
Ghaffarpasand o., O.,
Drewnick, F.,
Hosseinibalam, F.,
Gallavardin, S.,
Fachinger, J.,
Hassanzadeh, I.,
Borrmann, S. Journal of Aerosol Science (18791964)50pp. 11-25
In order to quantify losses of nanometer-sized particles in turbulent flows through tubes, their penetration efficiencies were measured as a function of the particle size, Stokes number and Reynolds number. The penetration efficiency of tungsten oxide and ammonium nitrate particles with diameters between 3 and 17. nm was investigated in turbulent flow conditions with Reynolds numbers (. Re) extending from 4500 to 10,500.The measured penetration efficiencies in straight tubes were found to deviate from the empirical correlation of . Lee and Gieseke (1994). In contrast, the empirical equation of . Fan and Ahmadi (1993) agrees better with our experimental results, also in comparison with the corresponding . Wells and Chamberlain (1967) and . Wood (1981) empirical correlation.Additional experiments were conducted to quantify the penetration efficiency of nanoparticles in tubes having 90° bends for Dean numbers between 1426 and 2885. Penetration efficiencies of particles through 90° bends were found to increase with increasing curvature ratios. The influence of Reynolds number (when varied between 4500 and 10,500) on the penetration efficiencies was found to be insignificant within the uncertainty of the measurements. We compared our experimental results of the penetration efficiencies through 90° bends as a function of the Stokes number with the . Pui et al. (1987) parameterization which was validated for particles larger than 100. nm. For particles larger than 12. nm our data agree with the . Pui et al. (1987) parameterization. However, for smaller particles the measured penetration efficiencies increased with the Stokes number while their parameterization predicts the opposite. © 2012 Elsevier Ltd.
Environmental Forensics (15275930)13(1)pp. 55-67
In this study, the trends of Pollution Standard Index (PSI) and the levels of related air pollutants are analyzed based on the database monitored at two selected roadside air quality monitoring stations: Aghdasieh and Fatemi in Tehran during 2000-2006. The original measured pollutant data and the resultant PSIs are statistically analyzed in different time series, including daily, monthly and seasonal patterns. The daily mean PSIs in seasonal period can be regarded as nonstationary time series. The autoregressive integrated moving average (ARIMA) method implemented by the Box-Jenkins model is used to forecast the PSI time series. The performance evaluations of the adopted models are also carried out and discussed according to Akaike Information Criterion (AIC) and Bayesian information criteria (BIC). The results indicate that both ARIMA (1, 1, 1) and ARIMA (2, 1, 1) models can provide reliable satisfactory predictions for both time series. © 2012 Copyright Taylor and Francis Group, LLC.
Oceanological and Hydrobiological Studies (18973191)41(1)pp. 85-98
In this study, the Navier-Stokes equations that embrace conservation equations of momentum, volume, heat and salt are solved by using a 3-D numerical model. Then, based on the values obtained, the structure and variability of the outflow/inflow between the Persian Gulf and the Gulf of Oman is investigated. The basic equations are cast in a bottom-following, sigma coordinate system which greatly simplifies the numerical solution. Conservative finite difference methods are used to discretise the mathematical model in space. The model results, which are in agreement with limited direct measurements in the Strait, show a volume transport of deep outflow and a near-surface outflow from the Persian Gulf to the Gulf of Oman through the southern part of the Strait. About 65% of total outflow occurs in the bottom layer (40 m to the bottom) and 35% in the upper layer (from the surface to 40 m deep) during the year. The annual mean of surface inflow from the Gulf of Oman to the Persian Gulf, which occurs within the northern part of the Strait is about 0.2 Sv. The net volume transport annual mean through the Strait into the Persian Gulf is about 0.03 Sv. Strong temperature and density contrasts between bottom and surface layer waters are established in spring and summer. These are more pronounced in the southern part of the Strait. In the northern part of the Strait, the salinity contrast is nearly constant, but in the southern half it varies significantly during the year. Copyright © of Institute of Oceanography, University of Gdansk, Poland.
Applied Mathematical Modelling (0307904X)35(3)pp. 1512-1537
Salinity is an important component of the marine system. Due to shallow nature of the Persian Gulf, the salinity has been influenced by both wind driven and surface thermohaline fluxes (heat and moisture fluxes). In this study, the seasonal distribution of salinity and its variations due to wind stress and thermohaline forcing are investigated by using a three-dimensional hydrodynamic model, Coupled Hydrodynamical-Ecological Model for Regional and Shelf Seas (COHERENS). The simulation results show that the salinity in the Persian Gulf experiences dramatic spatial and temporal variations. The influence of the thermohaline forcing is considerably more than the wind stress on the salinity. The effect of the surface thermohaline fluxes over the salinity field is generally to increase the salinity for almost all the water column during the year. This effect is high during September-November where the evaporative surface salinity flux dominates over inflow of low-salinity values of Indian Ocean Surface Water. The wind forcing at the most regions of the Persian Gulf, in particular at the United Arab Emirate (UAE) coast and Bahrain-Qatar shelf, freshens the water all the year round. The wind and thermohaline forcing in March-June have strong potential to generate stratification in salinity structure. The model predictions, which are successful in simulating many features of observed pattern, indicate that the surface water of the Gulf is saltier in winter than that in spring and early summer. Both heat fluxes and wind stress play an important role for this seasonal cycle of the surface salinity. © 2010 Elsevier Inc.
Applied Mathematical Modelling (0307904X)35(12)pp. 5884-5902
The Persian Gulf circulation is investigated with respect to the relevant forcing mechanism including wind stress and thermohaline surface fluxes by using a three-dimensional numerical hydrodynamic model. The model results show a correlation between the strength of the bottom layer outflow of the Persian Gulf and that of the Indian Ocean Surface Water (IOSW) inflow into the Gulf. The inflow of IOSW into the Gulf attain maximum values in May-June in conjunction with peak bottom outflow through the Hormuz Strait. The results of sensitivity experiment indicate that circulation is dominated by thermohaline flows at almost all parts of the Gulf. The heat fluxes play an essential role on the general circulation of the Persian Gulf. In spring and summer, the wind stress generates southeast-flowing surface currents of magnitude about 5. cm/s along the Saudi Arabia and Iranian coasts on the northern Gulf. In winter and autumn, due to weak static stability, the wind produces mesoscale eddies in most parts of the Gulf. In winter and spring the wind stress acts to reinforce the thermohaline circulation of deep outflow. Conversely, in summer and autumn the wind forcing acts in opposition to the thermohaline forcing and causes a bottom inflow from Oman Sea into the Gulf. © 2011 Elsevier Inc.
Environmental Monitoring And Assessment (01676369)165(1-4)pp. 275-281
In this study, variations of ambient ozone level are thoroughly analysed according to the monitored data in a mixed residential, commercial and industrial city, Tehran, based on considering the meteorological factors. Ozone as a pollutant shows typical annual, weekly and diurnal cycles. This analysis has shown that the ozone level concentrations were below the WHO guidelines in Tehran during 2000-2003. The relation between ozone level at two different stations (Aghdasieh and Fatemi) is found (r=0.51). The ozone level response to meteorological parameters is investigated. The results suggest that the ozone level is affected (positively or negatively) by meteorological conditions, e.g. relative humidity, solar radiation, air temperature, wind speed and wind direction. © 2009 Springer Science+Business Media B.V.
Marine Pollution Bulletin (0025326X)58(5)pp. 658-662
The determination of activity concentrations of the radioactive elements 238U, 232Th, 40K and 137Cs was performed on grab samples taken from a polluted environment. The samples were sliced into strata from 5 cm depth, dried and ground to sieved through a 170 mesh size prior to the analysis. Activity concentration was quantified using gamma spectroscopy. The results showed that the concentrations of activity in the sediment samples are 177 ± 12.4, 117 ± 11.5, 1085 ± 101.6 and 131 ± 4.8 Bq kg-1 for 238U, 232Th, 40K and 137Cs, respectively. In general, the distribution of activity concentrations along the southern coast of the Caspian Sea area exceeded international limits. The hazard index of the samples was 0.19-0.88, with an average of 0.49. The mean values of radium equivalent activity and dose rate are 176 Bq kg-1 and 63 nGy h-1, respectively. © 2009 Elsevier Ltd. All rights reserved.
Saghafifar, H.,
Kurten, A.,
Curtius, J.,
Von der weiden, S.,
Hassanzadeh, I.,
Borrmann, S. Aerosol Science and Technology (15217388)43(8)pp. 767-780
A newly developed condensation particle counter provides measurements of aerosol particle number densities for size diameters as low as 3 nm. This Expansion Condensation Particle Counter (ECPC) operates based on fast adiabatic expansion with specialized detection and evaluation of the temporal development of light scattered by the ensemble of growing droplets. In its new configuration the ECPC has been modified such that a previously needed calibration factor became obsolete. In this article the new design is described which now includes a fast pressure sensor for monitoring the pressure drop inside the measurement chamber. Extensive laboratory experiments for characterizing the ECPC are described where sulfuric acid droplets with diameters between 2.5 nm and 23 nm have been utilized. Water as well as butanol are demonstrated to be suitable working fluids. One experiment using tungsten oxide (WOx) particles shows that a 50% cut-off size diameter as low as 2.5 nm can be reached for this ECPC with a detection efficiency of several percent for particles as small as 1.4 nm. High and low supersaturations are experimentally examined and the corresponding different cut-off sizes are obtained. Measurements of ambient urban air in Mainz (Germany) obtained by this ECPC are juxtaposed to those from a TSI UCPC 3025A with satisfactory agreement. Similarly, in-situ data recorded with two ECPC units in the city of Isfahan (Iran) are shown to demonstrate the suitability of the technique for traffic related pollution measurements. Also, in future applications coarse information on the chemical nature of nucleated particles can be obtained by simultaneously using various condensing liquids in different channels of the ECPC setup.
Environmental Monitoring And Assessment (01676369)155(1-4)pp. 149-155
This study performed a time-series analysis, frequency distribution and prediction of SO2 levels for five stations (Pardisan, Vila, Azadi, Gholhak and Bahman) in Tehran for the period of 2000-2005. Most sites show a quite similar characteristic with highest pollution in autumn-winter time and least pollution in spring-summer. The frequency distributions show higher peaks at two residential sites. The potential for SO2 problems is high because of high emissions and the close geographical proximity of the major industrial and urban centers. The ACF and PACF are nonzero for several lags, indicating a mixed (ARMA) model, then at Bahman station an ARMA model was used for forecasting SO2. The partial autocorrelations become close to 0 after about 5 lags while the autocorrelations remain strong through all the lags shown. The results proved that ARMA (2,2) model can provides reliable, satisfactory predictions for time series. © Springer Science+Business Media B.V. 2008.
Physica A: Statistical Mechanics and its Applications (03784371)387(10)pp. 2317-2327
Data of seven meteorological variables (relative humidity, wet temperature, dry temperature, maximum temperature, minimum temperature, ground temperature and sun radiation time) and ozone values have been used for statistical analysis. Meteorological variables and ozone values were analyzed using both multiple linear regression and principal component methods. Data for the period 1999-2004 are analyzed jointly using both methods. For all periods, temperature dependent variables were highly correlated, but were all negatively correlated with relative humidity. Multiple regression analysis was used to fit the meteorological variables using the meteorological variables as predictors. A variable selection method based on high loading of varimax rotated principal components was used to obtain subsets of the predictor variables to be included in the linear regression model of the meteorological variables. In 1999, 2001 and 2002 one of the meteorological variables was weakly influenced predominantly by the ozone concentrations. However, the model did not predict that the meteorological variables for the year 2000 were not influenced predominantly by the ozone concentrations that point to variation in sun radiation. This could be due to other factors that were not explicitly considered in this study. © 2008 Elsevier Ltd. All rights reserved.
Physica A: Statistical Mechanics and its Applications (03784371)387(16-17)pp. 4393-4403
Time series analysis used to investigate the stratospheric ozone formation and decomposition processes. Different time series methods are applied to detect the reason for extreme high ozone concentrations for each season. Data was convert into seasonal component and frequency domain, the latter has been evaluated by using the Fast Fourier Transform (FFT), spectral analysis. The power density spectrum estimated from the ozone data showed peaks at cycle duration of 22, 20, 36, 186, 365 and 40 days. According to seasonal component analysis most fluctuation was in 1999 and 2000, but the least fluctuation was in 2003. The best correlation between ozone and sun radiation was found in 2000. Other variables which are not available cause to this fluctuation in the 1999 and 2001. The trend of ozone is increasing in 1999 and is decreasing in other years. © 2008 Elsevier Ltd. All rights reserved.
Deep-Sea Research Part I: Oceanographic Research Papers (09670637)54(9)pp. 1474-1485
In an attempt to understand the causes of the sea-level seasonal cycle in the Persian Gulf, we investigated the relationships of sea-level data from 11 stations with atmospheric pressure and thermosteric level. Sea level is significantly correlated among all stations. The mean trend in sea level for the Persian Gulf is about 2.34 mm/year. The thermosteric sea-level variability is estimated from temperature profiles at one-degree grid points. Contour maps of thermosteric level show that the height due to thermal expansion is high in summer and autumn, and low during winter and spring. The monthly mean thermostric height ranges from +2.2 cm in July to -2.1 cm in February. The major change in sea level due to the thermosteric level seems to be associated with the large change of the thermohaline circulation in the Persian Gulf. The maximum expansion occurs in summer, and the maximum contraction occurs in winter. Results of the regression analysis demonstrate that from 62% to 90.2% of the variance in the seasonal cycle is due to atmospheric pressure. The inclusion of the thermosteric sea level as a secondary forcing in the regression model improves the variance explained to 78.1-90.7%. The remaining change should be due to the halosteric effect and upwelling. Tide-gauge stations located at the Gulf's head show high correlation with Ekman vertical velocity. There are two distinct tide gauge stations in the Persian Gulf. One is found in the first cyclonic gyre and the other in the second gyre. The inclusion of Ekman upwelling to the model, improves significantly the variations explained as well, from 82.3% to 91.9%. © 2007 Elsevier Ltd. All rights reserved.
Meteorology and Atmospheric Physics (01777971)95(3-4)pp. 223-237
Data from tide gauges (1990-1999) at Bandar Abbas and Bushehr combined with atmospheric data at both stations are utilized to investigate the mean sea-level (MSL) response to meteorological forcing functions along the north coast of the Persian Gulf. The relations between MSL and forces due to air pressure, air temperature and local wind are examined. The characteristics of variability of each field are analyzed using the spectral analysis method. The annual cycle is dominant in the sea-level, atmospheric pressure, air temperature and wind spectra. The influence of local meteorological functions are quantified using forward stepwise regression techniques. The results suggest that 71.5% and 71.2% variations in the MSL of Bandar Abbas and Bushehr stations are due to meteorological forces at each stations. The model indicates that the most significant influence on the observed variation of MSL at Bandar Abbas is air pressure, while at Bushehr is air temperature. The results of multivariate and simple regression show that these parameters are highly intercorrelated. The sea-level is not significantly correlated with the monthly and winter NAO and Monsoon in the Persian Gulf. The remaining variations are due to density of sea water (steric effect), which has considerable influence on the sea-level variations, and coastal upwelling. © Springer-Verlag 2006.
Physica A: Statistical Mechanics and its Applications (03784371)382(2)pp. 586-596
Thirty-four years of data (1967-2000) are used to investigate the variability pattern relevant to air-sea interaction in the Persian Gulf. The patterns are derived using statistical techniques, such as empirical orthogonal function (EOF) and singular value decomposition (SVD). Statistical analysis methods are applied to determine the coupled modes of variability of monthly sea surface temperature (SST) and sea level pressure (SLP). The significant of the air-sea interaction is found by a strong resemblance between EOF and SVD eigenvectors and expansion coefficients of SST and SLP. We find that the four leading EOF patterns of SST together account for 99.8% of the total monthly SST variance and 94.4% of the SLP variance. The zero contour in the first SST EOF identified the front which separates the Persian Gulf cyclonic gyres. The SVD modes provide more information on the coupling between the fields than the modes obtained by EOF methods. Lagged correlation analysis between SVD1(SLP) and SVD1(SST) indicates that the coupling is strongest when SLP leads SST by -12, -6, 6 and 12 months. Therefore, the first mode of the SVD analysis seems to depict an air-to-sea forcing, in which the sea response to the atmospheric changes appears with an semiannual and interannual time lag. The two leading SVD modes of variability of the coupled SST and SLP fields account for 99.6% of the total variance. The main patterns of both variables of variability of both variables independently provide considerable information on the coupling, but only one of the two variables dominates each of the two first coupled modes. The first coupled mode of variability between the SST and atmospheric pressure can be described as a strengthening and weakening of the cyclonic gyres, which seems to force fluctuations in a north-south dipole structure in the SST by Ekman upwelling which is a wind-related process. The atmospheric forcing of the SST changes is detectable in the sea with a lag of 1 and 6 months. © 2007 Elsevier B.V. All rights reserved.
Journal of Radioanalytical and Nuclear Chemistry (15882780)268(3)pp. 539-544
A nonlinear function was applied in combination with the method of mixing activity calibration for fitting the experimental peak efficiency of HPGe spectrometers in the 50-2614 keV energy range. The preparation of Marinelli beaker standards of mixed gamma- and RG-Set at secular equilibrium with its daughter radionucliedes was studied. Self-absorption was measured for the activity calculation of the gamma-ray lines for daughters of 238U series, 232Th series, as well as 137Cs and 40K in soil samples. Self-absorption in the sample depends on a number of factors including sample composition, density, sample size and gamma-ray energy. Seven Marinelli beaker standards were prepared in different degrees of compaction with bulk density (ρ) of 1.000 to 1.600 g·cm-3. The detection efficiency versus density was obtained and the equation of self-absorption correction factors was calculated for soil samples. © 2006 Akadémiai Kiadó.
Annales Geophysicae (14320576)23(6)pp. 2031-2038
In this study we have analysed wind and wave time series data resulting from hourly measurements on the sea surface in Bushehr, the northern part of the Persian Gulf, from 15 July to 4 August 2000. Wind speed (U10) ranged from 0.34 to 10.38 m/s as alternating sea and land breezes. The lowest wind speed occurs at about midnight and the highest at around noon. The calculated autocorrelation of wind speed data shows that when the sea-land breeze is strong, the land-sea breeze is weak and vice versa. The significant wave height (Hs) varies between 0.10 to 1.02 m. The data of the present study reflects mostly the local waves or the sea waves. The calculated correlation between wind and wave parameters is rather weak, due to the continuous change in the wind direction. Wave height distribution follows the well-known Rayleigh distribution law. The cross correlation analyses between U10 and Hs reveal a time lag of 4 h. Finally, we have shown that the time series of U10, Hs, and wave period are stationary. We have modeled these parameters by an auto regressive moving average (ARMA) and auto regressive integrated moving average (ARIMA) models. © European Geosciences Union 2005.
