جستجوی مقالات مرتبط با کلیدواژه "salinity" در نشریات گروه "فیزیک"

Mutation breeding has proven to be efficient for developing new cultivars adapted to normal and stress conditions, including salinity. Mutant populations developed through gamma irradiation of Tarom Mahalli, Hassani, and Anbarboo local rice varieties were evaluated and screened for agronomic traits for 10 years in saline paddy fields of Mazandaran. These traits included plant height, early maturity, yield, yield components, and relative tolerance to salinity stress. The salinity levels of both soil and irrigation water varied between 4-11 and 2-9 dS/m, respectively, in different years and locations. The tolerance indices of the mutants were either 3 or 5, with 13 mutants showing lower stress sensitivity indices than their respective parents. Most mutants reached 50% flowering in fewer days than their parents, with selected mutants (2310, 2212, and 133) flowering between 80 and 90 days after sowing. The average plant height of selected mutants (M5-M7) in the saline paddy fields of Mazandaran ranged between 110-130 cm. All selected mutants produced a higher number of panicles per hill compared to Tarom Mahalli. The average yield of rice mutants varied between 3000 and 4500 kg/ha in different locations and years, with mutants 2212 and 2310 showing the highest yields in Bahnamir and Fereydoonkenar. These mutants exhibited at least a 35% increase in yield compared to Tarom Mahalli. The amylose percentage of the mutants ranged between 18-23%. Based on these results, mutants 2212, 2310, and 133 were selected for cultivation in paddy fields with saline or brackish water.

The Persian Gulf is a semi-enclosed water basin that is utilized by various countries, and its territorial waters are not exclusive to Iran. Past studies have largely overlooked the distribution of temperature and salinity in the Iranian section of the Persian Gulf. This research investigates the characteristics of temperature and salinity in this region. The data used in this study consists of CTD temperature and salinity measurements collected during the Persian Gulf Explorer expedition in May 2019. Ten stations were selected, and the data were divided into two sections: eastern and western parts of Iran’s territorial waters, and then analyzed using ODV software. The results indicate that at stations perpendicular to the Iranian coast, the water column down to the deepest measured depth exhibits stratification and well-defined baroclinic conditions from the Iranian coast to the mid-waters of the Persian Gulf. This stratification is influenced by a counterclockwise eddy resulting from the inflow of Indian Ocean Surface Water (IOSW). The inflow velocity gradually decreases as it enters the Persian Gulf, leading to horizontal instability that can induce upwelling. Notably, upwelling is observed at station 7, where at depths exceeding 50 meters, the minimum temperature (20.57 °C) and salinity (approximately 40 psu) are recorded, indicating the rising of deeper water.

Eddies formation is an important oceanic phenomenon that plays a significant role in the transport of fluid in the ocean. The main eddy in the Persian Gulf is mainly due to factors such as wind, tide and density variations. This paper uses the HD model of MIKE3D packages to perform the simulations; first a large-scale flow model is implemented for the entire area of the Oman Sea and the Persian Gulf, and then the formation of mesoscale in the Persian Gulf and the Oman Sea is simulated by the output of Model 3 MIKE with a resolution of ten kilometers for 2013 in 30 layers of Sigma and Z coordinates. Almost all year round, a thermohaline stream enters the Oman Sea Persian Gulf and penetrates deeper areas, causing fluctuations in the temperature and salinity in the Oman Sea. This thermohaline flow that enters the Oman Sea causes temperature changes and these changes cause the formation of eddy in the Oman Sea. It was also seen that a coastal stream in the northwest direction from the north of the Strait of Hormuz enters the Persian Gulf and there is a southwest stream in the southern part of the strait. The main eddy in the Persian Gulf is clockwise and it was observed that the general shape of the eddy in the Persian Gulf is clockwise and the counterclockwise eddy in the center of the Persian Gulf becomes stronger from April to July and in August, it has the highest resolution. In this study, more attention was paid to the months when eddy has more clarity.

The study of sound propagation and its affective factors seems to be necessary due to the increasing applications of sound in various sciences. One of the environmental factors that influence the speed of sound is the change of current. Throughout the year, the flow of thermohaline enters the Oman Sea from the shallow inlet of the Persian Gulf, penetrating deeper into regions, causing fluctuations in temperature and salinity, resulting in reversal of sound velocity and consequently changes in characteristics. The sound in the Oman Sea extends from the Strait of Hormuz to the Indian Ocean, which varies in different years and seasons. In this study, a mathematical model was used to evaluate the effect of current change on sound propagation, and by combining the mechanical effects of eddies motion and sound propagation, a new mathematical relation was obtained to deviate sound velocity relative to angle within eddy. The path deviation of the acoustic rays is obtained after passing through the mesoscale eddies. It should be noted that for convenience, other environmental factors affecting sound propagation, including internal waves, have been overlooked. The result of the calculations shows that according to the location of sound input to the eddy range, the amount of deviation will vary with the angular velocity of the eddy and the amount of variation of the sound velocity relative to the deviation angle is obtained.

The vertical structures of the temperature, salinity and density are studied based on the measured data during fall, spring and summer 2016-2017 in Alashtrood and Lavijrood regions in the Southern Caspian Sea of Mazandaran. The results show a dominant role of the temperature in density determination. This can be attributed to the small range of salinity variations encountered in the studied regions. This can also be explained based on the fact that the temperature is the dominant factor to determine the density in tropical and subtropical regions. However, the role of the salinity is still important and cannot be ignored. Despite the similarity between the vertical structures of temperature in both regions during the fall, different vertical structures of the salinity have led to different structures for the density. During the spring in Lavijrood area, intrusion of the warm and fresh water at distance of 4-8 km from the coast, has led to a shallow mixed layer depth. The mixed layer depth has its maximum and minimum values during the fall and spring, respectively. Despite the fact that during the summer, the shallowest mixed layer depth is expected due to the strong stratification, we witnessed a deeper mixed layer depth in this season comparing with the spring profiles. This result is because of the high evaporation rate causing an increase in the surface salinity, which results in higher convection and consequently a deeper mixed layer. Finally, it is found that the vertical structures of the physical properties are comparable in both transects during the summer.

In this research, the variability in temperature and salinity field of the Caspian Sea was studied using POM model. In this model, temperature and salinity field’s data and wind field and the flux of atmospheric data were collected from WOA and ECMWF, respectively, with a resolution of 7.5 minutes and the time step of 6 hours and for Bathymetry data from GEBCO08 with an spatial resolution of 30 seconds is used. Initially, the model for ten years (1988-1997) was carried out. After examining the stability of the output with observation data available (1996) were compared, that good agreement between their temperature and salinity changes observed. The results showed, the maximum monthly average surface temperature difference of the Caspian Sea in February, May, August and November are 18 °C, 13 °C, 11 °C, 20 °C, respectively and the maximum monthly average surface salinity difference are, 2.8 psu, 3.2 psu, 5.2 psu and 4.8 psu, respectively. Salinity gradient in depth in February and August in the western part of the Caspian Sea to the eastern part has been stronger. Surface temperature difference between the eastern and western part of the middle basin, in August, and its temperature profile indicates the upwelling phenomena in this part of the Caspian Sea

This paper investigates the spatial and temporal changes of water physical parameters in the Strait of Hormuz. Temperature, salinity, and density measured and investigated for winter 2012, spring and summer 2013 by using CTD probe. Moreover, different water masses and layers were studied. The whole water column thermally, at most stations were completely mixed in the winter. Surface layer, namely mixed layer, is completely homogeneous in summer. Spring time is a transition state of water properties between winter and summer. Maximum changes of water column density were 2.0, 4.25, and 5.0 for winter, spring and summer, respectively. Water volume of Persian Gulf outflow change seasonally and sometimes Persian Gulf outflow was traceable near Iranian coast in spring. Based on this research, it seems that Persian Gulf outflow water volume was maxima in the spring time. Study of water masses in different parts of the Strait of Hormuz shows two different water masses in the eastern part of the strait. In summer, only two separate water masses were traceable in the central and western part of the Strait. It was also evident that, there were three-layers in the water column in summer. At the interface of water masses, fronts of different strengths depending on temperature and salinity gradients were formed. Salinity and sigma-t of Persian Gulf outflow in summer were more than those of winter