فصلنامه فیزیک زمین و فضا
سال چهل و هشتم شماره 3 (پاییز 1401)

Seismic isolators and structural control methods, such as the use of dampers, is one of the methods to create safety and relaxation after an earthquake, which has been studied since 1980s. In addition, soil-structure interaction is one of the key parameters in the analysis of structures. In recent decades, the use of seismic isolators and various types of passive control systems has received much attention worldwide. Hence, in this paper, the simultaneous use of LRB isolators in the soil-structure interface and viscous dampers at the height of the structure has been considered under the seismic load. For this purpose, four different types of 5-story steel buildings including moment frame, moment frame with viscous damper, moment frame with base isolator and moment frame with base isolators in the soil structure interface and viscous damper at the height of building were modeled using a software. After the nonlinear time history analysis, results were compared. The average of seven different earthquakes was selected for the purpose of understanding the input ground motion effect. In order to investigate the effect of soil-structure interaction, the 5 story base-isolated moment frame with damper at the height of building was studied with two different modeling approaches: the first one includes raft foundation, soil, and superstructure interaction (SSI model), while the second one considers superstructure based on the fixed base and rigid foundation condition (NSSI model). The results of these isolated moment frame structures with dampers at the height of buildings in the SSI and NSSI models were evaluated. Then the first three mode periods, the peak responses of base acceleration, the peak responses of roof acceleration, the peak responses of story shear, the input energy, the dissipated energy by dampers, the dissipated energy by base isolators, the hysteresis behavior of a damper and an isolator for different models in NSSI and SSI condition were analyzed. The comparison of the results of different NSSI models showed that the simultaneous use of base isolators in the soil structure interface and dampers at the height of moment frame building had a significant effect on structural responses. For example, the peak roof accelerations of base-isolated moment frame with dampers at the height of building were 39 %, 35 %, and 15 % less than the moment frame, the moment frame with dampers at the height of building, and the base-isolated moment frame building, respectively. In addition to the proper performance of isolator dampers, we also achieved the effect of the soil-structure interaction consideration as a key factor in modeling the isolated moment frame structure with dampers at the height of building.

Aeromagnetic data provide useful information for delineating magnetic basement, structural patterns, tectonics, and thermal status of the survey area. The current study presents the results of airborne magnetic studies in Basiran area (South Khorasan province) 100 km southwest of Birjand, that is well-known for its great mineral potential such as gold, copper, iron, manganese and silver. Appearance of Ghale-Zari, Bishe and the other active mines in the area indicate the promising mine potential of the region. Basiran area in the classification of the structural zones of Iran is located in the Lut Block. The Lut Block stretched over 900 km in the north-south direction and nearly 200 km in the east-west direction and bounded by the Nayband and Nehbandan faults. The lithology of the Lut Block is mainly lavas and pyroclastic rocks, as well as sub-volcanic rocks of Eocene-Oligocene ages eras. Volcanic rocks display a scattered pattern since they formed during the subduction to post-collisional stages between the Arabian and Asian plates. In 2005, a high-resolution airborne magnetic data collection (with flight line distances of 250 meters) was carried out in Basiran area of approximately 1500 km2 by the Geological Survey of Iran (GSI). The purpose of this survey is the study of the patterns of magnetic fields and their relationship with geological structures, especially iron bodies and to create a suitable exploration database for further investigations. The collected raw aeromagnetic data set are processed by applying Diurnal Variation correction and IGRF removal using Geosoft Oassis Montaj software. Processing of airborne data need applying other technical corrections such as lag compensation, topography and leveling in order to prepare the residual magnetic intensity data or TMA map (Total Magnetic Anomaly Map). In order to have a qualitative interpretation, we need to prepare all relevant maps to follow the anomaly variations. Then geophysical and mathematical filters are sequentially applied that routinely are the reduction-to-the pole (RTP) and upward continuation. The RTP map removes the latitude dependence of the magnetic fields and upward continuation maps bring and show the effect of the magnetic sources at depth. Based on the other studies results, in literature review, there are at least five main sources of anomalies in the Basiran area, which may be related to several magnetic and geological structures at depth. These sources are clearly at 300 m, 500 m and 1000 meters upward continuation maps. As the main results, this paper emphasizes on the key role of the aeromagnetic study to understand the relation between magnetic anomalies and the subsurface structures. Basiran area is a high potential area for mineral exploration that includes copper, gold, iron, and manganese that is made it valuable for many researchers that are active in mining exploration.

On April 5, 2016, the Sefid-Sang earthquake with a magnitude of Mw~6 occurred about 30 km from Sefid-Sang and 80 km from Mashhad in Khorasan-Razavi province, Iran. Looking at the distribution of aftershocks reported by the Iranian Seismological Center (IRSC), due to the error in the locating of the earthquakes, it is not possible to attribute these events to the activity of any pre-mapped faults. In this study, we attempt to determine the relative location of earthquakes and improve the seismic phase readings on the data recorded in the seismic waveforms recorded by seismic stations of the IRSC to find the causative fault. To relocate the aftershocks of the Sefid-Sang earthquake of April 2016, 2136 data that were recorded in the period from April 2016 to May 2017 at IRSC, were obtained from this center. First, a spatial distribution was drawn for these data, and as said before it was very difficult to determine the causative fault. The data were relocated using the double difference method and also apply the cross-correlation on the waveforms to improve the reading of the seismic phases. In this research, the aftershocks relocated in four different cases. Once the entire data without improving seismic phases relocate with HypoDD together, the next step, first using cross-correlation on all waveforms, we improve the phase readings, and then HypoDD is used to relocate all aftershocks. Then we try to use this double difference method on the data with a better condition in the first reported location. We selected data with an azimuth gap less than 180 degrees, RMS less than 0.5 seconds, and magnitude less than 2.5. Again on selected data, HypoDD was run in two different ways, once only using the phases which read by IRSC experts, and the second, addition, of the cross-correlation output of the waveforms was used to improve the readings. By examining the depth sections on two profiles, first in the northwest-southeast direction and the second, perpendicular to the first profile, it was found that the dip of the fault plane is about 45 degrees towards the northeast, and accordingly, the fault direction is northwest-southeast. Using InSAR image processing, Ghayournajarkar and Fukushima, 2020, stated that aftershocks are more compatible with the fault model whose dip is northeast, and the dip of the fault model has a dip of 47.4 degrees. As can be seen, most of the studies conducted, such as the result of this study, consider a fault with a northwest-southeast strike and northeast dip as the fault that caused the 1396 SefidSang earthquake. According to the existing faults in the region, this fracture is the most consistent with the continuation of the Kashafroud fault. Considering the importance of the Kashafroud fault in determining the seismic hazard of Mashhad city, this shows the necessity of studies to better identify this fault zone and its parallel branches. Compared to the study of Einakchie et al. 2018, this study showed that to obtain favorable results in determining the relative location of earthquakes, efforts should be made to improve the seismic phase readings by any method such as waveforms cross-correlation. Also, despite not having the data of the temporary local dense network used by Khosravi et al. 2018, by choosing stricter conditions on data selection and also improving the reading of seismic phases, and determining the relative location to reduce the error caused by the velocity model, the results could improve a lot, of course, in this study the main advantage is the existence of the JRKH permanent station less than 10 km from the epicenter of the mainshock. The importance of the temporary seismographic network around the epicenter of the earthquake increases the number of records and increases the accuracy of earthquakes, but in cases in which we do not have access to such networks data, existing of the close station to epicenters and using double-difference method could help to get more accurate results.

Low-induction-number frequency-domain geoelectromagnetic (LIN-GeoFEM) instruments are ground conductivity meters that use a small coil transmitter (Tx) and one coil receiver (Rx). This coil–coil system is designed to propagate alternating electromagnetic fields through the earth at small Tx–Rx separations and low frequency and receive the EM field coupling in the shallow subsurface to provide direct measures of the apparent electrical conductivity. This measured property is a complicated average of spatially distributed localized electrical conductivities in the subsurface. Instruments capable of operating as LIN FEM instruments include the EM38, EM31, and EM34 (Geonics Ltd., Mississauga, ON), the DUALEM instruments series (DUALEM, Inc., Milton, ON), the GEM instrument series (Geophex Ltd., Raleigh, NC) and CMD series (GF Instruments, s.r.o.). The Tx and Rx coils can be oriented relative to each other and the earth's surface. Orientations considered in this study are horizontal coplanar (HCP) (both coils lie flat on the ground) and vertical coplanar (VCP) (coils are upright and coplanar). The range of LIN FEM instruments applications for environmental and hydrologic characterization and monitoring is large and increasing.The LIN-GeoFEM applications are industrially feasible as long as there is a reasonably fast algorithm that is accurate enough to invert the survey data. Furthermore, forward modeling plays a key role in the inversion procedure. The linear integral equation (IE) method is a powerful tool in EM forward modeling for geophysical applications, especially for simple background conductivity structures. The main advantage of the IE method in comparison with the finite difference (FD) and finite element (FE) methods is its fast and accurate simulation of the response for models with compact 2-D or 3-D bodies in a layered background. The main limitation of the IE method is that the background conductivity model must have a simple structure to allow for an efficient Green’s function calculation. Fortunately, the most widely used background models in LIN-GeoFEM explorations are those formed by horizontally homogeneous layers. A main issue is that the EM field integral equation is nonlinear. However, an approximate linear equation is obtained for the electromagnetic induction at low induction numbers using the Born approximation. A 2D forward modeling code for LIN-GeoFEM is developed based on the integral equation (IE) method. Here, a linear relation between model parameters and apparent conductivity values is proposed. The 2D problem is obtained from 3D using numerical integration along the y-axis (strike direction) from minus infinity to infinity. So, the linear approximation is applied to the 2D inversion of LIN measurements. We use a damped minimum length solution using depth weighting to solve this problem iteratively. Thus, we obtain a better estimate of conductivity in a few iterations. Using this 2D linear inversion or imaging technique, we can produce reasonably good results of inverting jointly and individually VCP and HCP for low and moderate conductivity contrasts.To validate the algorithm, we consider two 2D synthetic scenarios and field data acquired on a thick conductive dyke in the Bloemfontein Nature Reserve region in South Africa. The first synthetic scenario consists of one 3 W.m conductive horizontal or vertical prism immersed in a 100 W.m resistive host. In this example, the recovered models from the inversion of the HCP (VMD) and VCP (HMD) data show good results for the vertical and horizontal prism, respectively. The second scenario simulates four 20 W.m conductive vertical and horizontal prisms in a 100 W.m resistive background. The recovered conductivity from the inversion of the VCP data has the weakest results, especially in the case of vertical prisms. In the conductivity section from the inversion of HCP data, the existence of the four anomalous bodies is evident. However, the image obtained from the joint inversion of HCP and VCP data has generated useful information about the true model in all recovered models. The result of jointly inverting VCP and HCP field data confirms the presence of the dyke as a zone of low conductivities.

Determination of the overburden-bedrock interface with fine-grained sediments in a high-fold sedimentary environment is a challenging geophysical issue. Electrical Resistivity Tomography (ERT) is considered one of the most effective geophysical approaches for mapping subsurface layers based on the conductivity distribution of materials. The surveys are often performed in two dimensions to investigate lateral and depth variations of resistivity and chargeability values of subsurface layers. The resistivity method, influenced by the volumetric properties of empty spaces, is defined by the ability to transfer charge in subsurface medium, but the induced polarization method depends upon the geometric properties of the pore spaces (grain surface size). Despite the advantages of geo-electrical methods in imaging subsurface structures, due to the high dependency of resistivity and induced polarization parameters on the physical and hydrogeological conditions of the layers, it is not possible to fully match the geological and geo-electrical sections.One of the applications of geophysical studies is to determine the contact zone between overburden and bedrock in engineering structures such as embankment dams. In cases where the conductivity contrast between the overburden and the bedrock is low, the exact determination of this boundary with the help of geo-electrical methods confronts high uncertainty. In this study, the efficiency of electrical resistivity tomography and induced polarization is investigated by measuring several parallel profiles with the aim of imaging the boundary between overburden and bedrock and determining the possibility of a water escape zone at the left bank of the Ilam embankment dam. According to the results obtained from the inversion of the field measurements, rechargeable sections would be ascribed to the shale region as well as marl limestone containing pyrite particles.The main objectives of this study include determining the general condition of the overburden concerning the bedrock, geometric imaging of the bedrock, and identification of parts of the bedrock eroded over time. The significant challenge of this geophysical study is the low conductivity contrast between clay and silt overburden and limestone bedrock interbedded with shale and marl. Due to the size of the study area, the studies were performed based on tomographic measurements of electrical resistivity and induced polarization. The field surveys were conducted using four almost parallel profiles (according to the topographic conditions of the area) and with relatively different lengths and through a Pole-Dipole array in forward and reverse measurements.Geological data as well as borehole information are used to validate the geo-electrical sections to better interpret the models obtained from the collected data (i.e., geo-electrical measurements). Finally, due to the high topography of the area and to better show the trend of subsurface structures using two-dimensional models obtained from electrical resistivity tomography and induced polarization as well as drilled boreholes, a three-dimensional view of sections and boreholes has been prepared. Based on the models obtained from the geo-electrical data, it can be concluded that geophysical studies (electrical tomography) have been able to successfully determine the eroded region of the bedrock surface as well as the bedrock-overburden contact which correlates well with boreholes drilled in the area.

Over the last decade, extensive studies have been done to date rock surfaces using optical luminescence signals, and recently a model has been proposed showing that shows the rock surfaces using infrared-stimulated luminescence signal have been successfully dated. This method is based on the resetting of luminescence signal with depth into rock surfaces. When a rock surface is first exposed to sunlight, the luminescence signal that has been stored over time in its constituent minerals (particularly quartz and feldspar) starts to decrease. The longer the rock is exposed to sunlight, the depth of light penetration into the rock also increases and the luminescence signal in the rock decreases, however, the rate of luminescence resetting reduces with depth because of the attenuation of daylight into the rock surface. This differential change in bleaching rate with depth leads to the development of a sigmoidal shape luminescence-depth profile. Such profile provides an internal check on an inadequate daylight exposure, and therefore an incomplete resetting of the luminescence signal and allow us to identify the sample that are most likely to provide reliable OSL age. In this study, we investigated the potential of this method to date debris rocks of Fatalak landslide which were induced by Rudbar-Manjil earthquake in north of Iran in 1990. Cores of ~10 cm long and 1 cm diameter were extracted from the buried and exposed sides of the rock samples using a water-cooled, diamond-tipped drill. The cores were then cut into ~1.5 mm thick slices. The slices were gently broken into small chips and mounted in 10-mm diameter stainless steel cups for natural luminescence signal and dose response measurements. All sub-samples from each slice were stimulated by infrared radiation and the blue and ultraviolet luminescence signals were measured. To determine whether the luminescence signals at the buried surface of the rock were sufficiently bleached before the earthquake event, we measured the natural sensitivity-corrected IR50 and pIRIR225 signals (Ln/Tn) with depth into the core and the luminescence-depth profiles were plotted. Unexpectedly, weak or no IR50 and pIRIR225 signals and no suitable luminescence-depth profiles were observed. According to the experience of the second author, almost all sediment samples taken from Iran have generated IRSL signal, so it is necessary to investigate the cause of the lack of a suitable IRSL signal for rock samples in Fatalak. Due to the fact that with increasing depth, the bleaching rate decreases and the luminescence signal intensity increases and also the luminescence signal is generated by a small percentage (approximately 10%) of the grains of the dosimeter grains (mainly quartz and feldspar), it is possible to produce signals (response to the same dose) with different intensities and properties for different slices. Therefore, the potential of all slices to produce the signal and finally to prepare the luminescence-depth profile were investigated. Unfortunately, this profile did not match the profiles provided by previous studies.In order to analyze whether this observation is due to the nature of the samples taken from Iran or there was a defect in the luminescence signal measuring device or in the experiment process, we performed similar tests for a rock surface which was taken from another site. The same process was then carried out for two rock art paintings from Spain, which showed acceptable signals and the IR50 depth profile showed a sigmoidal shape where the luminescence signal was almost reset at the surface slice but increased with depth until it reached saturation, as expected from the model. Then, the luminescence-depth profiles from Fatalak and Spain sites were compared with two previous successful studies in Italy and Denmark. The IRSL luminescence-depth profile for rock art sample in Spain was in a good agreement with that of the two burial samples from Italy and Denmark. However, no such correlation was observed between the profiles of the Fatalak sample and the profiles of the two Italian and Danish samples. As the profiles derived for Fatalak sample were not consistent with the model and none of the previous studies, we could not determine the time of the landslide event in the conventional method.

One way of gridding two dimensional vector data is gridding each component separately. Alternatively, using Green’s functions we can grid two components simultaneously in a way that couples them through elastic deformation theory. This is particularly suited, though not exclusive, to data that represent elastic/semi-elastic deformation, like horizontal GPS velocity fields. Measurements made on the surface of the Earth are often sparse and unevenly distributed. For example, GPS displacement measurements are limited by the availability of ground stations and airborne geophysical measurements are highly sampled along flight lines but there is often a large gap between lines. Many data processing methods require data distributed on a uniform regular grid, particularly methods involving the Fourier transform or the computation of directional derivatives. Hence, the interpolation of sparse measurements onto a regular grid (known as gridding) is a prominent problem in the Earth Sciences.In this research, sparse two-dimensional vector data of the horizontal GPS velocity field are interpolated using Green’s functions derived from elastic constraints. The method is based on the Green’s functions of an elastic body subjected to in-plane forces. This approach ensures elastic coupling between the two components of the interpolation. Users may adjust the coupling by varying Poisson’s ratio. Smoothing can be achieved by ignoring the smallest eigenvalues in the matrix solution for the strengths of the unknown body forces. The study area is the oblique collision zone of Arabia-Eurasia tectonic plates, which has a GPS velocity field with sparse distribution.Since the Green’s functions developed for the half-space environment, the Mercator map projection used to create the half-space for interpolation and gridding. Data split into a training and testing set. We will fit the gridder on the training set and use the testing set to evaluate how well the gridder is performing. The vector gridding was done using the Poisson's ratio 0.5 to couple the two horizontal components. Then score on the testing data. The best possible score is 1, meaning a perfect prediction of the test data. By calculating the mean square deviation ratio (MSDR) to evaluate the gridding accuracy, the score of 0.86 obtained for this statistic.While this method is not new, it provides some insight into the behavior of the coupled interpolation for a wide range of Poisson’s ratio. This approach provides improved interpolation of sparse vector data when the physics of the deforming material follows elasticity equations.We interpolated our horizontal GPS velocities onto a regular geographic grid with 1 arc second spacing and masked the data that were far from the observation points and finally the residuals between the predictions and the original input data were calculated. Interpolation of horizontal GPS velocity fields of local geodynamic networks were proposed to obtain an estimate for Poisson's ratio values in the best case for gridding validation.In this study, two dimensional GPS data were interpolated. Three dimensional GPS data gridding can also be done using the Green’s functions provided by Uieda et al., (2018). It is also recommended to use different Green’s functions to grid different types of spatial data.

According to the complexity of planetary-scale mechanisms affecting extreme snowfall events, the necessity of recognizing and studying the effective components of these climatic mechanisms are presented. Due to the role of the polar vortex of northern hemisphere in tropospheric variability in winter and also, in variability of the structure of the teleconnection patterns on intensity and weakness of the polar vortex, revealing the mechanism of impact of the two mentioned components on synoptic patterns leading to extreme snowfall events in Iran was considered in this study. According to the environmental approach in this study, first the snowfall days were identified and the atmospheric circulation patterns related to these days were investigated. For this purpose, daily data on rainfall and winter temperature (December-March) of fifty Iranian synchronous stations in the statistical period 1951-2016 were received from the Meteorological Organization of Iran. Atmospheric data and teleconnection indices were also obtained from the NCEP / NCAR. Finally, five periods were identified, during which snowfall was recorded in at least six stations and their average snowfall reached more than 20 mm. Of these event periods, which were in January and February, three periods related to January were examined in this study, which occurred in 1972, 1988 and 2008. In the second stage, atmospheric patterns were drawn in combination and for the average of the event periods, in three scales of hemisphere, synoptic and expanse of Iran, in the GrADS system Then, the amount and status of the teleconnection indices including: NAM, AO, NAO and PNA were analyzed in the period of extreme snowfall events. The emphasis of this study is on the effect of mid-tropospheric conditions in terms of altitude, temperature and altitude on snowfall events in Iran, while the patterns of pressure and temperature of the earth's surface and the humidity of the lower troposphere have also been considered. In hemispheric-scale combined patterns, the emphasis has been on showing the status of the tropospheric polar vortex in relation to teleconnection indices. In the third step, by doing a combined analysis, the effect of polar vortex on the change in teleconnection indices and their effectiveness on the formation of synoptic patterns leading to extreme snowfall events in Iran was revealed. According to the research findings, the NAM index, the strength of the center of the polar vortex and the AO index have shown the shape of the vortex in terms of its concentration or elongation. The PNA index has also been associated with the strength of northwestern Europe and the North Pacific anticyclones, which have contributed to the formation of blocking systems due to the northward deflection of the extending trough of polar vortex from their axial direction. The NAO index also represents the emergence of systems in the Euro-Atlantic section. The results showed that the necessary dynamic conditions for all three events have provided the emergence of blocking patterns due to weakening and distortion of the polar vortex. These events are often associated with disconnection of jet stream in the Eastern Hemisphere, especially in the Euro-Atlantic area. Hence, NAO and PNA indices, directly and NAM and AO indices indirectly affected the conditions required for extremesnowfall events in Iran.

In arid environments, extreme wet and dry periods are considered a serious threat to human societies. These periods affect the agricultural sector, transportation networks, vegetation, the environment, water resources, and the sustainability of human societies. Extra-arid and arid regions of southeastern Iran are good examples of an area affected by extreme climate events hazards, such as, floods and droughts. This study, to better understanding the causes and processes leading to extremely dry and wet episodes in southeastern Iran, investigates the space and time variability of winter dry/wet events and their associated large-scale atmospheric driving circulations. The data of this research are of two categories. Monthly gridded data from 1-month standardized precipitation-evapotranspiration index (SPEI01) and daily average geopotential field data of 500 hPa (HGT500) retrieved from NCEP/NCAR Reanalysis data over a period of 55 years (1960-2015) have been used to evaluate the dry and wet spells and circulation types (CTs) of winter atmosphere, respectively. December to March (DJFM) are selected as winter months and data for 55 winters are extracted through MATLAB programming facilities in the southeastern part of Iran. 168 gridpoints cover the southeastern part of Iran. The western and northern boundaries of the study area are bounded by the meridian 55 degrees east and 32 degrees north. Finally, a new database with the arrangement  was formed and became the basis for further processing. Of course, the database of the variable height of geopotential is different and has a matrix with dimensions . Extreme wet and dry periods have been identified based on SPEI01 values outside the range [+1.5, -1.5], respectively. By applying the Principal Component Analysis (PCA) with Varimax rotation on S-mode analysis and correlation matrix of the SPEI01 field, three sub-regions of independent climatic variability are identified. Large-scale daily atmospheric circulation patterns are then classified into twelve circulation types (CTs) by applying PCA to the 500 hPa geopotential height fields and non-iterative K-means clustering technique to the retained PCA scores, followed by Esteban et al. (2005). The linkage between daily CTs and winter, dry/wet spells in the region are investigated by applying the performance index (PI) to the daily precipitation data of three representative stations of the identified sub-regions. Results show a significant relationship between the frequencies of occurrence of the identified CTs and of dry/wet spells at the three representative stations, in extra-arid and arid regions of southeastern Iran. 6 circulation patterns (CT) were identified for the study area, each of which has a negative phase and a positive phase, and a total of 12 patterns were identified. According to the results of the performance index, CT1+ pattern with deep Trough and ridge pattern on the Mediterranean Sea and the Caspian Sea, respectively, has a large share in providing above-average rainfall (P1> 1) in the east and southeast (Zahedan station). But this phase is related to the dry periods of the study area. Unlike the second type (CT2), its positive phase (+CT2) is associated with dry periods and its negative phase (-CT2) is associated with wet periods.

Spicules are intermittently rising above the surface of the Sun eruptions; EUV jets are now also reported immediately above surface layers. The orientation of spicules is a valuable parameter in the absence of direct magnetic field measurements with a sufficient spatial resolution in the chromospheric region because it is presumably determined by the confined flow of plasma, which should occur along the magnetic field lines, especially where the solar magnetic field pressure dominates the gas pressure. Of course, all these measurements suffer from the overlapping effect of spicules seen along each line of sight, the effect of which will be more critical when we look near the solar limb. In the case of macrospicules as well imaged by AIA of the SDO mission using the 304 filter recording the emissions of the HeII, resonance line, an additional effect arises due to the optical thickness of the line, especially on disk and also above the limb in the inner chromospheric shell.The primary purpose of this paper is to determine automatically and objectively the apparent tilt angle of spicules, using the best available highly processed observations, from the Solar Optical Telescope (SOT) limb imaging experiment by using an H CaII line, onboard Hinode mission. Furthermore, the Hough transform is applied to the resulting images for making a statistical analysis of spicule orientations in different regions around the solar limb, from the pole to the equator. A technique for the automatic detection off-limb spicules was implemented, and statistical measurements were conducted to determine the tilt angle for spicules at different heliocentric angles.We apply and develop a method with the following steps: (1) To increase the visibility of spicules, a radial logarithmic scale is applied; (2) To enhance linear features, while the Madmax operator is used. We investigated in more detail the apparent inclination of spicules and found the statistically average values for different locations around the solar limb for tilt angle. The results show a large difference of spicule apparent tilt angles in (i) the solar pole regions, (ii) the equatorial regions, (iii) the active regions, and (iv) the coronal hole regions. Analytically, during the minimum solar magnetically activity, from the equator to the poles, the inclination angles of the spicules are getting smaller and their lengths increase. As a result, the chromosphere thickness in this case is thicker than that of the solar maximum activities. When the spicules in the polar coronal holes are significantly inclined, the chromosphere and even transition regions thickness is thinner. Numerically, spicules are visible in a radial direction in the polar regions with a tilt angle <200. The tilt angle is even reduced to 10 degrees inside the coronal hole with open magnetic field lines and at the lower latitude, the tilt angle reaches values over 50 degrees. Usually, around an active region, they show a wide range of apparent angle variations from -60 to +60 degrees, which is in close resemblance to the rosettes that are made of dark mottles and fibrils in projection on the solar disk. However, large-scale activities with short life-time do not play a significant role in the thickness of the chromosphere, and they are removed for long term measurements by averaging. Therefore, this study considers the most statistical population of spicules in the minimum (and maximum) solar activity in the polar regions, and in lower latitude, to be considered as their inclination angles. While at the maximum laps of solar cycle, the opposite result will be expected, and fully confirmed, and give us a topological reason for the chromospheric prolateness at minimum activities.

Near surface zone (O3surf), or tropospheric ozone at the ground level, is a secondary air pollutant that deteriorates human health and plants via damaging respiratory systems. This species is also one of the main greenhouse gases associated with global warming and climate change. Despite many efforts to study and to make policy control program, this gas is still increasing and is a recent serious threat for human. So, a comprehensive understating of its variation and controlling factors is necessary for having a precise plan for its regulation.Here, a measured time series of O3surf at one of the air quality monitoring sites in Iran, i.e. Geophysics Institute of the University of Tehran, is selected to assess the O3surf variation in more detail. Although this time series has been measured since 2007, there are many gaps in the data and a few years without data. Nevertheless, the data possess a high quality which is discussed in this paper. The series was prepared for the period of four years, i.e. 2007-2008 and 2019-2020. The data series was decomposed in to five spectral components, i.e. intraday (ID), diurnal (DU), synoptic (SY), seasonal (SE), and baseline (BL), by applying Kolmogorov-Zurbenko (KZ) filter. This filter was introduced by Kolmogorov and later was formalized by Zurbenko in 1997. Theoretically, the KZ filter is a technique consists of iterative running moving average (MA), in which a simple MA of m points is computed by: where ORG and t represent the original time series and its time steps, respectively, and S is the input for each iteration. Therefore, the filter can be express as:Here m and k are window length and number of iterations, respectively. R and J represent iteration and running window, respectively, and wi is defined as: Wi = Li – m +1 where Li is the length of S(ti). KZm,k is a low pass filter in which high frequency (short time period) variation are removed from the time series. The band of frequency and the level of suppression in this filter are controlled by m and k, respectively. Here, the ozone time series is decomposed to five spectral components as:ORG(t) = ID(t<12h) + DU(t12h-2.5d) + SY(t2.5d-21d) + SE(t21d-365d) + BL(t>365d)The results indicate that the contribution of each component to the O3surf variability is different as such that the DU component constitutes more than 50% of the ozone variability. In fact, this component makes most of the ozone variability which attributes to light variation (daytime-nighttime). The SE component has the second largest contribution to the O3surf variability. The contribution of the SY component is different and that depends on the year in which it is considered. As an example, the relative contribution of this component in 2007 is 8.93% and in 2019 is 4.84%. Only 5% of the total O3surf variability makes by the variation of the ID component. This implies that the contribution of each component to the total O3surf variability is different and such finding should be considered in ozone control strategies.

Precipitation is one of the most important meteorological quantities that its decrease compared to normal amounts in a period of time causes drought. In this study, statistical microscale methods were used to project and simulate climatic quantities to determine future drought indices of Hormozgan province using the LARS-WG model. For this study, climatic data of synoptic stations of Hormozgan province as well as 5 models of general atmospheric circulation including CanESM2, HadGEM-ES2, MPI-ESM-MR, GFDL-CM3 and MIROC5 with RCP2.6, RCP4.5 and RCP8.5 scenarios were used. The capability of the fifth report models was evaluated using coefficient of determination, mean square error (MSE) and Root-Mean-Square Error (RMSE). The results of evaluating the data generated in the LARS-WG model with climatic data showed that the highest coefficients of determination were related to the parameters of minimum and maximum temperatures (99%) and precipitation (94%), respectively. The results of studies of changes in climate parameters with the models of the fifth report in all periods indicate an increase in minimum and maximum temperatures in all these models in different climatic scenarios in future periods, and as we move away from the base period 2040-2021, the rate of temperature changes increases. The rate of increase in minimum temperature in most models is higher than the annual maximum temperature over the next 20 to 80 years and indicates that the increase in temperature in Hormozgan province will be more affected by the increase in minimum temperature. Examination of the results of different climatic scenarios shows that according to the optimistic scenario, precipitation changes in Hormozgan province are increasing and this increase in precipitation in the east and northeast will be more than the base period. Accordingly, the largest increase will occur in the period 2060-2041, which will be greater in the east and northeast (especially the city of Rudan). In this scenario, the least amount of rainfall occurs in the central areas and islands and part of the west of the province. According to the optimistic and moderate scenarios, precipitation changes in Hormozgan province are increasing and this increase in precipitation in the east and northeast is more than yhat of the base period. Also in the center and north of the province the precipitation will be less. The highest increase in precipitation in the period 2060-2041 by 4-64 mm varies in the stations of the province and this increase is in the east and northeast (Rudan city) by 64 mm. In this scenario, the least amount of rain will occur in the central and northern areas and part of the west of the province in Parsian city. According to the pessimistic scenario, the precipitation changes in Hormozgan province are increasing and this increase in precipitation in the east and northeast will be more than that of the base period. Accordingly, the highest rain increase in the period 2080-2061 is 13-90 mm in the stations of the province and this increase is 90 mm in the east and northeast (Rudan city). In this scenario, the least amount of rain will occur in Bandar Khamir city and the islands and part of the west of the province. In this scenario, the amount of rainfall in Bastak city increases significantly. In general, most of the models show an increase in rainfall in all three periods, so that the average of all models in each of the three scenarios of increased rainfall, especially in the east and north of Hormozgan province (highlands). In most meteorological stations of Hormozgan province, the highest increase in rainfall is predicted by CanESM2 model with RCP8.5 scenario and in the period 2080-2061.

Weather forecasting and monitoring systems based on numerical weather forecasting models have been increasingly used to manage issues related to meteorology and agriculture. Using more accurate daily average wind speed (10m) and relative humidity forecasts can be helpful in this regard. But systematic and random errors in the model affect the accuracy of forecasts. In this study, the model errors during the 5 and 14 days training period in the same climate areas on the points of the network where the observations are available were calculated. Then the errors were generalized on all points of the network using the cokriging interpolation method. This preserves the model forecasts for other points of the network and only error values are applied to them. To better evaluate the model, the spatial and temporal distribution of daily average wind speed (10m) and relative humidity forecast errors were also investigated over Iran. Observed daily wind speed and relative humidity data from 560 meteorological stations for the period 1/11/2019 to 1/2/2021 were used to evaluate the WRF model performance. The WRF model was run daily at 12UTC, with a forecast time of 120 hours, and first 12 hours of each run was consider as the model spin-up time and was not used in errors calculation. In order to correct wind speed and relative humidity forecast errors for next three days (forecasts of 36, 60 and 84 hours), the forecasts for each day in the period of 11/1/ 2019 to 1/2/2021, was extracted from the model outputs. In order to evaluate the error correction method, the skill score index was used. The validation results of the error correction method showed that the absolute mean error value, correlation coefficient and RMSE improved after the error correction compared to results that were before the error correction, which showed that the error correction method can be used for other network points that did not contain observational data. In general after correction, the RMSE for wind speed and relative humidity forecasts could decrease by 13% and 18%, and the skill score could increase to a maximum of 160% and 308%, respectively. Value of correlation coefficient, after correcting the model error, was significantly increased, compared to the raw model output. In general skill score for the raw wind speed and relative humidity forecast for more than 50% of the days was more than -0.5 and -0.3, but after corrections were  increased to 0.2, 0.4 respectively. Without exception, all climatic regions after error correction have higher skill scores than before error correction, so that the model skill score for most climatic regions after error correction was reached above zero for more than 75% of the days. The results showed that errors of the model in different months, places and climatic zones did not have a uniform distribution. In general, the model underestimated the wind speed and overestimated the relative humidity in most areas. In general, the lowest skill scores for relative humidity forecasts occurred in the colder months of November to February in most climatic zones. The 14-day error correction method did not improve the modeling skill score much compared to the 5-day error correction method, and they acted almost similarly. Knowing the spatial and temporal distribution of model forecast error can be helpful for researchers to have an overview of the areas (and months) where the model forecast error can be high or low.

A sudden stratospheric warming (SSW) represent large scale perturbations of the polar winter stratosphere, which substantively influence the temperature and circulation of the middle atmosphere and also the contents of atmospheric species. SSW occurs mostly in middle and late winter and almost exclusively in the Northern Hemisphere. During an event, the polar stratospheric temperature increases by several tens of degree Celsius within a few days and eventually becomes warmer than that of the mid latitudes, reversing the climatological temperature gradient. At the same time, the prevailing westerly wind speed decreases rapidly and becomes easterly.The tropopause is a transition layer between the troposphere and the stratosphere. The occasional exchange of air, water vapor, trace gases, and energy between the troposphere and the stratosphere occurs in this layer. Based on some concepts; two different tropopause in the name of thermal tropopause and dynamical tropopause are defined. The conventional definition is the thermal tropopause which is detected based on the mark disruption of the vertical temperature lapse rate. The thermal tropopause definition is based on the fact that the stratosphere is more stably stratified than the troposphere. The thermal tropopause is defined as the lowest level at which the lapse rate decreases to 2 K/km or less, provided that also the average lapse rate between this level and all higher levels within 2 km does not exceed 2 K/km. The original concept of the dynamical tropopause was based on the isentropic gradient of potential vorticity. The dynamical tropopause is typically determined in a thin layer with absolute PV values within 1 pvu and 4 pvu.The vertical temperature stratification of the atmosphere plays a basic role in atmospheric motions. In this paper, the Brunt–Väisälä frequency (N2) value is used to detect the change of stratospheric static stability. In this work the NCEP/NCAR reanalysis daily data including temperature at different pressure levels (1000hPa-10hPa), the tropopuse temperature and pressure from 1th of January 1961 to 31th of December 2020 in northern hemisphere are used. The study region covers 0° to 357.5° geographical longitudes and 0°N to 90°N geographical latitudes. The northern hemisphere is divide into three 30° none overlapping latitudinal band width called as the tropical bands (0°N-27.5°N), the middle latitude bands (30°N-57.5°N) and polar bands (60°N-90°N) regions. First of all the potential temperature and Brunt-Väisälä frequency (N2) at different pressure levels are calculated; then the average zonal mean temperatures at 10hPa, the tropopause temperatures, the tropopuse pressures and the values of N2 in three former introduced regions are obtained. To represent the tropopuse's height variations during the sudden stratospheric warming, the daily anomaly of these parameters in the regions are calculated and analyzed.The daily average mean zonal tropopause temperatures and pressure changes in the three meridian divided regions during eighteen major and one minor sudden stratospheric warming (SSW) events are analyzed in this study. The results show that all 19 SSW events in the statistical period of 1979-1920 are associated with positive anomaly of the zonal mean temperature and pressure of tropopuse along with increase of the tropopuse temperature and lowering its height which causes downward development of the stratosphere and thinning the depth of the troposphere. In addition, the tropopuse height reduction in the polar band region is greater than in the middle latitude band. It was also shown that, the static stability (positive anomaly) increment in the stratosphere started before the SSW and decreases during SSW (negative). These changes are greater in the polar cap band with respect to the middle latitudes band. This result reveals that the static stability structure in the lower stratosphere and upper troposphere in the polar cap are more affected by SSW with respect to other regions.

In this paper, a spectral approach to the origin and propagation of magnetoacoustic oscillations in the network and internetwork areas of solar granules is performed. The data used in this study are mostly from Interface Region Imaging Spectrometer (IRIS). Slit Jaw Images (SJIs) data of IRIS at wavelengths of 1400 angstroms related to Si IV and 2796 angstroms related to Mg II h / k and 2832 angstroms related to Mg II w s, are used to select network and internetwork areas. The data of the Mg II k spectrum with a wavelength of 2796 angstroms and a temperature of 10,000 Kelvin have been used to construct the temporal profile of the intensity at the peaks of h3, k3, h2r, h2v, k2r and k2v, and the prospective profile of intensity temperature. One of the common methods for temporal and frequential characteristics analysis is the use of wavelet analysis. This method seems to be a practical method due to the variety and flexibility of wavelet types for different types of analysis. Wavelets and their convolution with waves lead to the extraction of time, frequency and power data. It should be noted that due to the uncertainty principle, resolution of time and frequency interact and its need to select optimum limit of the time and frequency resolution. One of the reasons for choosing Morlet Wavelet for the analysis of this study is the lack of a sharp edge, which reduces the ripple and improves the accuracy of detect the fluctuations properties. Another and one of the most important reasons for using the Morlet wavelet is that it does not change the temporal resolution of the wave. For these reasons, Morlett 5 was the most sensible and reliable choice for high-temporal and frequency-specific results for this study. Using wavelet analysis, the oscillation characteristics of the intensity are obtained in the network areas and internetwork areas. By Investigation of the intensity profiles in h and k peaks, it was found that the general behavior in them was the same and the only difference was in the intensities of these peaks and therefore their temperatures. In the case of intensity temperature profiles, the general behavior for intensity temperature profiles extracted from h and k peaks, also seems to be the same. By investigation of the wavelet analysis results, it appears that the oscillating behavior at the h and k peaks is almost similar. Using the results of wavelet analysis, in this study, the periods of oscillations in the intensities of bright points in the network and internetwork have been obtained. According to their values, it seems that the bright points of the internetwork have a photospheric origin and the bright points of the network have a chromospheric origin. Another result of the wavelet analysis of this study was the intensity of oscillations with a period of about 64 seconds. This high frequency differs from the solar researchers’ observations of photosphere and chromosphere oscillations, so it cannot be related to those oscillations. It seems that this is the first time that this type of high frequency oscillations has been reported. It seems that these high frequency oscillations can play an important role in heating the TR. For this reason, Accurate study of these high frequency oscillations is necessary to understand the causes and heating mechanisms of TR. These high frequency oscillations have been seen in almost all data and areas under study, so far there is no strong evidence of the origin and cause of these high frequency oscillations, and we hope that with more detailed and extensive studies we can better understand the properties and reason of these oscillations.