ORIGINAL_ARTICLE
Pollen Analysis for Reconstruction the Palaeoclimatic Phases in Lake Neor during the Late-Pleistocene to Holocene
Extended Abstract
Introduction
Numerous palaeoclimatologists have studied the climate of different regions of Iran during Quaternary based on palynology of lake sediments . In this study the paleoclimatic phases of northwest of Iran have been discussed . We used pollen analysis for reconstructing the past vegetation and palaeoclimate of Lake Neor area located in the northwest of Iran . In this research a high resolution pollen study has been done for reconstruction the climate of study region during the late - glacial to early Holocene .
Methodology
In this study we used samples with interval distance equal 5 cm from the 3 meters of lower part of the core in which the samples cover 500 cm to 800 cm hight of the core. The pollen extraction followed the chemical treatment methods based on Moor et al. ( 1991 ) . The chemical treatment carried out in Institut Méditerranéen d’Ecologie et de Paléoécologie ( IMEP, UMR 6116 CNRS ) . Pollen determinations were performed by using the IMEP pollen reference slides collection and pollen atlases of Reille ( 1992 , 1995 , 1998 ) , Beug ( 2004 ) and pollen morphological descriptions by van Zeist and Bottema ( 1977 ) . Then during microscopic analysis we identified and counted the pollen grains by magnification equal 500X by using microscope Laica model . The pollen diagram drawn by the aide of TILIA and TGVIEW ( Grimm , 2004 , 2005 ) . At the first we analyzed the samples by interval distance equal 10 cm . After finding some important events we also analyzed the samples by interval distance equal 5 cm . Therefore in this study the vegetation dynamic studied by relatively high resolution for understanding more about some events which extracted from the pollen diagram .
Results and Discussion
This research showed the vegetation change from ~ 12800 to ~ 7800 years B . P . It represented the transition stage of the late-glacial to early Holocene in Neor Lake . The zonation was based on arboreal vegetation change . We detected the last warm phase of late - glacial ( A1 zone ) , the last cold phase of late-glacial or Younger Dryas ( A2 zone ) and early Holocene ( B1 , B2 , & B3 zones ) by interpretation of pollen diagram of Lake Neor . Chenopodiaceae , Artemisia , and Poaceae were dominant herbal vegetation cover during late-glacial . While Ephedra , Quercus , and Betula was dominant arboreal pollen at the same time . The tree pollen was absent from the area during Younger Dryas . It implied colder and dryer climatic condition during Younger Dryas . After ~ 11800 years B . P . the climate became warmer and early Holocene detected at the same time by increasing tree cover . According to dating result , B1 zone was from ~ 11600 to ~ 9300 years B . P . This period indicated a dominant herbal vegetation cover of Chenopodiaceae, Poaceae, and Artemisia and also tree cover of Quercus, Ephedra, and Betula. The dominant arboreal and non-arboreal pollen during early Holocene (B2& B3 zones) were respectively Quercus, Betula, Ephedra, and Poaceae, Artemisia, and Chenopodiaceae.
Conclusion
As a result, the pollen analysis as well as dating results revealed some minor differences in vegetational and environmental changes in Lake Neor area compared with other sites in the north-west of Iran. The different changes are probably related to high elevation of Neor region about 2500 m a.s.l.
The climatic indicators for detecting the wet and dry phases during the early Holocene consist of Artemisia to Chenopodiaceae ratio (A/C), Poaceae to Artemisia ratio (P/A), and Arboreal Pollen to Non-Arboreal Pollen ratio (AP/NAP). A dry phase detected during B1 zone ~ 9400 years B.P. This dry phase detected by the minimum amount of AP/NAP and A/C indicator.
It also seems that there were two wet phases at B1 zone ~9600 years B.P and at B2 zone~8200 years B.P. respectively. The decrease of Charcoal and increase of Typha latifolia and Myriophyllum is evident during wet phases. The interpretation of pollen diagram of Lake Neor suggested that there were the forest-steppe vegetation cover with Artemisia dominated in the Neor region about 8000-9000 yr B.P during the wet phase.
https://jphgr.ut.ac.ir/article_30432_43afa0546379fded031fdca532769222.pdf
2013-05-22
1
20
10.22059/jphgr.2013.30432
Lake Neor
Late-Glacial
northwest of Iran
palaeoclimate
Palynology
Younger Dryas
Ghasem
Azizi
ghazizi@ut.ac.ir
1
دانشیار گروه جغرافیای طبیعی، دانشکدهی جغرافیا، دانشگاه تهران
AUTHOR
Tayebeh
Akbari Azirani
t_akbari@sbu.ac.ir
2
دانشجوی دکترای اقلیمشناسی، دانشکدهی جغرافیا، دانشگاه تهران
AUTHOR
H
Hashemi
tayebakbari3@gmail.com
3
دانشیار گروه زمینشناسی، دانشکدهی علوم، دانشگاه خوارزمی
AUTHOR
mojtaba
yamani
myamani@ut.ac.ir
4
دانشیار گروه جغرافیای طبیعی، دانشکدهی جغرافیا، دانشگاه تهران
AUTHOR
mehran
maghsoudi
maghsoud@ut.ac.ir
5
دانشیار گروه جغرافیای طبیعی، دانشکدهی جغرافیا، دانشگاه تهران
AUTHOR
A
Abasi
tayebakbari2@gmail.com
6
کارشناس ارشد جغرافیا، گرایش ژئومورفولوژی، دانشگاه تهران
AUTHOR
ORIGINAL_ARTICLE
Alteration Mapping Based on Mixture Tuned Matched Filtering Method and with Use of Spectral Images
Extended Abstract
Introduction
Hyperspectral satellite imagery like Hyperion impliescollecting data from large number of spectral bands . Therefore, they can be used for some applications that cannotbe executed by multispectral satellite images . The advantage of higher spectral resolution is accompanied by the weakness of lower spatial resolution for some applications . Consequently , we are always facing with mixed pixels , i .e . mixed , or a mixture of spectral responses of background and several objects ( Fauvel et al ., 2006 ) . Sub - pixel target detection methods are able to identify the percentage and location of objects in a mixed pixel. Accordingly , more attention has been paid to them compared tothe classification procedures. In recent years, due to some shortages in pixel-based classification methods, the number of methods and publications in sub-pixel target detection have been increased, especially for mineral mapping and alteration in geological units (Kruse et al., 2003; Ellis and Scott, 2004; Qiu et al., 2006; Zhang et al, 2007; Mezned et al., 2009; Gabr et al., 2010; Hosseinjani and Tangestani , 2011 ; Kruse , 2012 ) . Some studies show the superiority of sub-pixel over pixel-base methods for these fields of applications . Kruse , et al., (2013) compared mineral maps obtained from airborne hyperspectral with space borne EO-1/Hyperion using Mixture Tuned Matched Filtering ( MTMF ) , Minimum Noise Fraction ( MNF ) and N - dimensional visualization , in Nevada and Wissy valley . Hosseinjani and Tangestani ( 2011 ) used ASTER data by LSU and MTMF methods . Theyclassified three different groups of alterations , including Perilofiet- Aloniet, Serisit- Caleouniet, Clorit-Calsit- Ipidot. In this work, after prerequisite stages of image pre-processing for Hyperion images, MTMF method was utilized for determining mineral alteration in Mozahem-Babak city ( volcanic area ) .
Methodology
Mozahem volcano area isone of the greatest Caldera in Iran whichis located between 55?16?0?E to 55?22?0?longitude and 30? 15? 0?N to 30? 21? 0?N latitude. Lithological studies were conducted by field measurements and laboratory analysis. The mineralogical studies , X - Ray Diffraction ( XRD ) test and spectroscopy on various samples from the study areawere also carried out . The obtained results in combination with geochemical studies indicate that there are three types of alterations rocksin the central parts of the Caldera ; weak altered , semi altered and intense altered. After pre - processing the satellite data using MRNF transformation the optimal bands were selected . The Matched Filtering ( MF ) values computed training data that were obtained from field studies . Using the earlier results,the MT values were evaluated . The data cloud of MF Score and Infeasibility value were adopted asthreshold . Consequently , the classification of these units was produced by images. The final results were compared with Liner Spectral Unmixing method to assess the accuracyof the classification performed.
Results and Discussion
The results of MTMF showed that the main part of intense alteration has been located in the central part of the MozahemCaldera. The surrounding area also belongs to the alterations with lower intensity. After calculating the confusion matrix from classification of three alteration areas, the accuracy of 77.7 % and Kappa coefficient of 0.6757 was obtained for MTMF method while the accuracy of LSU was 57.6% and it’s Kappa coefficient was 0.4456. Also the ROC curve evaluation showed that the better performance of MTMF method compered to LSU method.
Conclusion
The results of this study show that for discriminating the alteration units , sub - pixel target detection procedure is more powerful than pixel-based techniques of classification . On the basis of the mechanism of MTMF , MT part could offer classification results with higher accuracy for decreasing the false positive . The MT part is considerablystronger than conventional methods for detection in sub-pixel level as LSU . Also, due to the MT part and reduction of false positive alarms in the structure of MTMF method , theperformance was better than the MF method used by Khaleghi and Ranjbar ( 2010 ) . Therefore, the presented method in this paper can do better in detecting alterations.
Keywords : Hyperspectral Remote Sensing , Alteration Mapping , MTMF , Hyperion .
https://jphgr.ut.ac.ir/article_30433_30e18ef6d7bbbe544cbee5ceae06294b.pdf
2013-05-22
21
38
10.22059/jphgr.2013.30433
Alteration Mapping
hyperion
hyperspectral remote sensing
MTMF
S.,
Goodarzimehr
goodarzi.saeed@ut.ac.ir
1
کارشناس ارشد سنجش از دور و سیستم اطلاعات جغرافیایی، گروه کارتوگرافی، دانشکدهی جغرافیا
AUTHOR
S. K.
Alavipanah
myamani7@ut.ac.ir
2
استاد سنجش از دور و سیستم اطلاعات جغرافیایی، گروه کارتوگرافی، دانشکدهی جغرافیا
AUTHOR
A.,
Darvishi Bloorani
ali.darvishi@ut.ac.ir
3
استادیار سنجش از دور و سیستم اطلاعات جغرافیایی، گروه کارتوگرافی، دانشکدهی جغرافیا
AUTHOR
ORIGINAL_ARTICLE
Relationship between Teleconnection Patterns and Total Ozone in Isfahan Station
Extended Abstract
Introduction
The ozone layer, as a life protective shield on the Earth, has attracted the man’s attention from various aspects. For the same reason, different dimensions of the ozone layer have been studied by researchers. The changeable amount of total ozone is affected by the sun, atmospheric elements, and climatological photochemical activities. Hence, the major amount of ozone is affected by atmospheric instability in the upper troposphere, and the atmospheric instability is united through the teleconnection patterns with climatic indices. Therefore, the total amount of ozone is connected to the climatic indices. The aim of this research is to study of climatic indices on the total ozone (TO) oscillations in Isfahan station.
Methodology
According to this research, a 15-year daily statistics of total ozone (TO) in synoptic station and ozone evaluating in Isfahan from 1996 until the end of 2010 were used. The available defects in the ozone date using the satellite date from NASA/GSFC were obtained. Also, the data relating to NINO 1-4, SOI, NAO, AO and the wind blowing in the atmospheric various balances from NCEP/NCAR database were extracted and used. In this research the climatic indices were classified into the three categories. The first category is related to the remote teleconnection indices on the north hemisphere, of which the most important one include the North Atlas Oscillation (NAO) and the North Pole Oscillation (AO). The second category includes the south hemisphere teleconnection patterns. For this purpose, the SOI and NINO1-4 in the South Pacific Ocean were used. The third category includes the study of winds effect on the (TO) changes. Assuming that the effect of the wind waves natural (orbital or meridian) can affect the rich/poor ozone weather transfer. Therefore the effects of the wind blowing index in the level of 200mb on the (TO) changes in Isfahan were also studied. The levels height temperature of 10, 100 and 500mb were extracted and their relations with climatic indices and (TO) were studied. The correlative regressive analytical statistics were used for studying the relationship between the (TO) changes and climatic indices.
Results and Discussion
The relationship between the (TO) amount and reversed NAO and AO indices and during the cold months of December, January, & February comparing to other months is stronger. The AO correlative coefficients with the (TO) follow a logic process (reversed and regular in the cold months; Positive and irregular in the warm months), but this process is not seen in the NAO index. The relationship between the SOI index with the (TO) reversed and follow a specified monthly process. This relationship is significant at the 95% confident level. The NINO1-4 indices have a positive relationship with the (TO) changes, and its correlation follow a specified monthly process. The relationship of the (TO) amount with the NINO1-4 indices is significant in the cold months. Consequently, when the SOI index include the negative/positive amounts, the (TO) amount is increased/decreased. When the water level temperature indices is increased in the South Pacific Ocean, the (TO) amount is increased in Isfahan especially in the cold season. Various regressive models were tested in order to study the relationship of the (TO) with climatic indices in different months, from which the higher correlative coefficient was in February. The results show that the NINO1-4 and the SOI indices in the South Pacific Ocean explain more than 70% of (TO) changes in February, while the NAO and AO indices explain only 30% of the (TO) changes in the same month. The highest amount of (TO) monthly average have been 433DU occurring during a 15-year statistic course, when the SOI index bearing the lowest amount, and during the same time, the NINO1-4 showing the highest amount. The reversed, strong, and significant relationships of orbital wind blowing index in the level of 200mb with (TO) changes show that through the wind leading to meridian, the (TO) amount is increased strongly.
Conclusion
Studying the correlative relationships between the climatic indices and (TO) changes show a stronger correlation of the (TO) changes with climatic indices in the south hemisphere on the Pacific Ocean. These relationships are stronger and more significant in the cold seasons with the (TO) indices in Isfahan station. In such a manner among the entire studying indices, the SOI bear the best correlation with the (TO) amount. The most important effect of AO on the (TO) changes primarily is due to (TO) change affected by the polar (TO) changes. Transferring the polar ozone by the polar vertex to Isfahan is related to change in tropopause height. In this manner, when the AO index is being negated, the tropopause is increased, and the polar zone weather enriched with ozone is permitted to enter to Isfahan, and the ozone is increased. The relationship between the amount of AO and SOI indices with wind blowing index are negative and strong in the level of 200mb, and these relationships in the levels of 0.01 and 0.05 respectively are significant. Consequently, upon the AO and SOI are being negated, the wind blowing index is inclined towards the meridian.
Having regard to the fact that the (TO) amount bearing a strong and negative correlation in the level of 200mb with orbital wind blowing index, and by inclining to west winds leading to the meridian, the (TO) amount is increased over Isfahan. The Polar wind blowing index was affected by AO and SIO indices. The (TO) amount can be also affected by the negative relationship of the Polar wind blowing index with AO and SOI indices. Therefore the (TO) changes through wind blowing index is linked with AO and SOI indices.
https://jphgr.ut.ac.ir/article_30434_0aac0f86878fa178d073d5012d37d539.pdf
2013-05-22
39
52
10.22059/jphgr.2013.30434
AO
indices
Isfahan Station
NAO
SOI
Total Ozone (TO)
Abbas
Arvin
1
استادیار و عضو هیأت علمی دانشگاه پیام نور
AUTHOR
ORIGINAL_ARTICLE
Studying and Determining of Synoptic Patterns of Climatic Seasons in the West of Iran
Extended Abstract
Introduction
Classifying the seasons is mainly carried out based on the daily movement of the sun. Around the world and especially within the middle latitudes as in Iran, there is not a full coordination between the seasons of a year and planetary seasons. Accordingly, in addition to planetary definitions,numerous definitions have been offered for seasons based on meteorology and climatology criteria. Therefore,season is part of a year which is distinct from other parts, because of a regular frequency of the planetary or climatologic phenomena. In other word, natural season is a time period of calendar year distinguished by homogenous and congruent weather. The natural seasons i.e. spring, summer, fall and winter are calendar time intervals which are naturally determined through different types of the congruent climatic regimes like temperature and wind speed changes. In fact, in such a classifying the seasons are defined based upon climatic elements e.g. temperature and wind representing the climatic facts of that place, with or without connection to the calendar seasons. Based on the above statement, this paper aims to find out a real definition for each season in the west of Iran, in which the seasons will be defined based on the climatic facts of the region, not on the basis of a planetary definition.
Methodology
The studiedregion consisted of Kermanshah, Kurdistan, Hamedan, Ilam and Lorestan provinces (Fig. 1). The area of the region is about 121000 Km2 and situated between 31o and 51' to 36o and 28' north latitudes, and 45 o and 27' to 50 o and 4' east longitudes. In this research, we have employed the average weekly maps of pressure, relative humidity and wind direction for surface and geopotential height, temperature, relative humidity and wind direction at the level of 500 hPa. The main structure of 7-days average data have been arranged based on the Jalaali calendar as well. For example, periods of 21st -27th March, have been selected as the first week in accordance with 1st-7thFarvardin in Jalali calendar. In this division, the last week for each year has been considered from 12th - 20th March, regardless of the calculation of Leap years, equals with 22nd – 29thEsfand.
Cluster analysis has been used for statistical analyses. For cluster analysis, the mean surface pressure and 500 hpageopotential height maps were employed as the most important climatic variables.Finally, were obtained weeks and climatic season’s duration by computing the prevailing weekly pattern in each of these clusters. At first, the prevailing pattern of air-mass for each season was computed by calculating the air-mass frequency in every climatic season, and presented in terms of percentage. Then, the prevailing air-mass frequency and flow patterns of the surface and 500 hPa maps were determined and one pattern was discussed as a representative for each season.
Results and Discussion
The obtained results of charts show that the climatic 4-seasons control the western parts of Iran. Winter with 18-weeks duration, was recognized as the longest and the main season, while spring with 7-weeks duration identified as the shortest season in the west of Iran. The summer is considered as the second important and long season in the region, as it takes around 16-weeks long, and fall with 11-weeks, is the third season in the view of duration in the study area. The climatic summer lasts from 11-weeks to the end of 26-weeks in the west of Iran, and generally it takes 16-weeks long.In fact,this season starts around 3-weeks earlier than the planetary summer time in the northern hemisphere which is the first of Tir.Furthermore, the end ofsummer usually takes place about 4-days sooner than 31st of Shahrivar, which is the end of planetary summer season. The most percentage of the summer season’s air-masses is dedicated to the continental-tropical air-mass (CT) around 72.7%.
Conclusion
The winter is the most important and the longest climatic season in the region and the continental polar air-mass was identified as the most air-mass of this season. This air-mass represents the arrival of air-masses from higher latitudes towards the west of Iran. In winter,topography and high-pressure centers in the west of Iran intensifythe cooling of air-masses and their impacts. The results show that winter is the longest season in the west of Iran, and their prevailing patterns include CP and CT air-masses respectively. The reason for CP air-mass frequency during the winter season is the Siberia high reinforcement and extension of its troughs towards the west of Iran where the movement is much more during the winter rather than fall. In addition, the reason for CT air-mass frequency during the summer season is the Azores dynamic high-pressure predominant in the middle levels of the atmosphere. The prevailing air-masses of the spring are similar to those of the summers’ and the fall season also looks highly alike to the climatic winter’s air-masses in the region.
https://jphgr.ut.ac.ir/article_30435_d77d4077aaf48777cff39a7a8ca3a998.pdf
2013-05-22
53
70
10.22059/jphgr.2013.30435
Air-Masses
Climatic Seasons
Cluster Analysis
synoptic pattern
West of Iran
Hasan
Zolfaghari
h.zolfaghari2002@yahoo.com
1
دانشیار گروه جغرافیا، دانشگاه رازی کرمانشاه
AUTHOR
jafar
masoompour samakosh
j.mclimate27@gmail.com
2
استادیار گروه جغرافیا، دانشگاه رازی کرمانشاه
AUTHOR
A
Jalilian
jalilian.azar@ymail.com
3
کارشناس ارشد اقلیمشناسی، دانشگاه رازی کرمانشاه
AUTHOR
A.,
Fathnia
h_zolfaghari2002@yahoo.com
4
استادیار گروه جغرافیا، دانشگاه رازی کرمانشاه
AUTHOR
ORIGINAL_ARTICLE
Assessing the Accuracy of DEMs Derived from Contour Line Maps and Comparing with ASTER DEMs
Introduction
DEM accuracy properties including grid size could however vary from source to source for an area of interest.The sensitivity of principal topographic derivatives used in hydrologic modeling to DEM resolution, however has been systematically explored in few studies.A medium and large scale topographic map is one source of digital elevation models in many countries. In Iran GIS users digitize the1:50000scale maps to constructing of DEMs with10×10meters resolution.However these data are used for scientific analysis but the accuracy and quality of them is not completely known.Therefore in this paper we first examined the accuracy of a DEM derived from topographic maps and then investigated its quality by comparison the results with results derived from an ASTER DEM.
Methodology
The materials of this paper included the contour line map with1:50000 scale, IRSpan satellite image with5.8×5.8 m resolution and an ASTER DEM from Terra satellite in2003. We first transformed the scanned map to UTM coordinate system and then digitized the contour lines by ArcGIS Editor Tools.A TIN map was constructed from digitized contours,then transformed to a DEM with 10m meters cell size as we called it TOPO DEM. The river network of the study area was firstdrawn from IRS pan satellite Image by ArcGIS sketch tools after geometric transformation of image in UTM coordinate system. The criterion used to define first-order stream channels was based on channel morphology and a length of over50m.The extraction of the drainage network of the study area carried out from both DEMs,in raster format with a 10m*10m grid cell size for theTOPO DEM and30x30m for ASTER DEM.Hydrology toolsets in ArcGIS software, version9.3 (ESRI2008)was used for extraction of drainage system.
For determination of TOPODEM accuracy we took the extracted networks from satellite images as a real stream channels. This is partly because more detailed scale of the satellite images guarantees a good reference map to compare the network obtained from the DEM. The comparison process has been done in both raster and vector formats. These comparisons included morphometric characteristics as river frequency, stream length, stream density and drainage ratio as well as the spatial pattern of the drainage lines, which was evaluated by visual analysis and calculating the differences rate between two networks. We used the drainage network characteristics extracted from ASTER DEM as a criterion to assessing the quality of the TOPO DEM.
Study Area
The study area with 443 Km2 is located in the east part of Iran(Figure2)which consists of4geomorphologic units including mountain, pediment, alluvial fans and flood plain. Highest elevation in the area is about2200 m in the northeast corner and the lowest elevation at the southwest part is about 1000m. Mountainous area with199 km2 is the main geomorphologic unit which is characterized with dendretic drainage pattern.The Elevation is ranging between1000m in the flood plain area to 2200 m in the mountainous sections.
Results and Discussion
A)DEM accuracy in comparison with real ground
Visual study and numerical results showed only a network Map which is derived in 50 threshold value is near to the network extracted from satellite image. River order and cell frequencies are being decreasing in higher threshold values. The comparison of the cell and vector data presented good agreement for all stream orders but there are large differences for 4, 5 and sixth-order streams.
The results showed better agreement in the mountainous and hilly parts only for the first and second-order streams. The river length measurements show satisfied agreement degree for pediment and mountain units especially for second-order rivers. We found the lower agreement degrees for alluvial fans and plain sectors.
Drainage density calculated for whole basin area shows a good agreement between rivers, which extracted by different methods. Obviously, differences appear in separate Geomorphologic units as we can see completely incorrect results for alluvial fan and plain sectors for rivers which are delineated from DEM. The best agreement of drainage density is recognized for the pediment where the surface slop is moderate. In the mountain area drainage density for the layer extracted from satellite image is higher than the layer extracted from TOPODEM while the results are inversely for alluvial fans and plain areas. The best agreement of drainage density is recognized for pediment where the surface slop is moderate.
B)DEM quality in comparison with an ASTER DEM
In this case we used an ASTER DEM for assessing criteria;both DEMs must to be in a same cell size, therefore the TOPODEM resampled to30×30 meters dimensions. Based on stream frequency calculations we found out only small differences between two DEMs.Stream frequency for all stream orders in threshold 50 is completely equal for two DEMs.In other thresholds also the amount of the stream frequency explained high quality of the DEM. The differences between two DEMs were arising when we derived the river length in different thresholds. The lowest differences are associated to threshold of50while it increases for higher or lower thresholds. There are recognizable differences at the some river orders, for instances we can refer to the rivers with 1 order.
Conclusion
The DEM based on1:50000 topographic maps have enough accuracy for extracting of the first and second-order rivers in mountain areas with50 threshold values. The morphmetric analysis based on extracted networks from these DEMs give weak accuracy through alluvial fan and plain areas but there is a good agreement for river length in the mountain,hill and pediment landforms.10*10 in resolution of TOPO DEMs is not enough to derive river networks in the alluvial fan and plain sectors. It is possible to increase the threshold values for network extraction on the alluvial fan and plain sectors. However the comparison of TOPODEM data with real ground illustrates a weakly coincidences but in comparing with a DEM from satellite sources resulted good quality in the data group. We found out large similarities between TOPODEM and ASTER DEM in drainage network analysis. The differences rate in all morphometric parameters and at different geomorphologic units were very low. It means the TOPODEM data has a high quality and GIS users can use these data with high confidence.
https://jphgr.ut.ac.ir/article_30436_94bc7e829e397b39cac3e681133cee19.pdf
2013-05-22
71
86
10.22059/jphgr.2013.30436
DEM Analysis
geomorphology
Raster and Vector Data
River Network Extraction
S. R.,
Hosseinzadeh
srhosszadeh2@um.ac.ir
1
دانشیار گروه جغرافیا، دانشگاه فردوسی مشهد
AUTHOR
M.,
Naddaf Sangani
srhosszadeh@um.ac.ir
2
کارشناس ارشد جغرافیای طبیعی، دانشگاه فردوسی مشهد
AUTHOR
ORIGINAL_ARTICLE
Morphologic Change Assessment of Riverbed Before and after Dam Construction Using HEC RAS Modeland GIS (Case Study: Downstream of SatarkhanDam)
Morphologic Change Assessment of Riverbed Before and after Dam Construction Using HEC RAS Modeland GIS
(Case Study: Downstream of SatarkhanDam)
Extended Abstract
Introduction
Rivers are important sources of water supply in the world . So reduction of their water canimpact on human life . This water supply is facilitated by dams as hugestructures that save water and make big reservoirsbehind. Dams are well known for influencing channel and vegetation dynamics downstream, but little work has focused on distinguishing effects of land use and channel responses to the impoundment. The impact of construction of dams and reservoirs on alluvial rivers extends both upstream and downstream of the dam . Downstream of dams, both the waterand sediment supplies can be altered leading to adjustmentsin the river channel geometry and ensuing changes in riparian and aquatic habitats.Construction oflarge water structuressuch as dams across rivers may lead to considerable decrease in the flood discharge proportionate to structure size which will in turn result in lower flood probability . Assessmentofthe vulnerability of river boundary is of great importance due to their rich soil and easy access to irrigationwater which makes such riverbank farms economically valuable especially in dry areas. The results of suchassessment can be used in land use planning.In this paper, we examinedthe interacting effects of Satarkhan dam on downstream changes in channel morphology of Aharchai River . Satarkhan dam was constructed on the main stem of the Aharchai in 1998 for water supply , flood control and sediment retention . This dam is located between Ahar and Varzaghan city , eastern Azarbaijan , northwest of Iran .
Methodology
Base line data including mean annual sediment, mean daily discharge and cross sections data located downstreamwere collected from several sources.Dams influence the two primary factors—waterand sediment—that settle the shape, size, and overallmorphology of a river and represent fundamental interventionsin the fluvial system.These datawere calculated and estimated for two period asbefore (1989-1997) and after (2003-2009) dam construction.To measure the cross sections changes, HEC RAS model and two hydrometric station’s data (Oshdologh and Tazekand) were used to estimate mean discharge of the river and annual sediment transportation. Also satellite images SPOT 2006), aerialphotos 1995 (scale, 1:40000) and 1:25000 map were used to study the changes in river path. These datawere calculated in Arc map and the results represented as maps.
Results and Discussion
Prior to the construction of the Satarkhan, the total mean flow discharge measured at Tazekandand Oshdologh stations varied along the whole year, and ranged between 2.3 m3/s to 9.3 m3/s and 1.8 m3/s to 7.3 m3/s.The total annual sediment for this stations varied between 287000 to 100000 t/y and 275000 to 51000 t/y. As Satarkhan was completed, a complete control of the Aharchai River discharges was achieved and the channel has no longerbeen subjected to high floods.The flow rate of water also became under full control. Accordingly, the average annual discharge has been reduced by 63% and 61% at Tazekand and Oshdologh stations. Moreover, a substantial change in the sediment regime of the river downstream of the damoccurred, which in turn disturbed the stability of the hydraulic geometry of the river.
Conclusion
Changes in the release schedule for Satarkhan dam have led to a decline in the frequencyand greatness of peak flows that trigger channel changes. The river is morestable some distance downstream from the sedimentsources because of the decline in channel avulsion.But far from the dam, this influence is weak. On the other hand, agreat change in the flow regime of the Aharchai River occurs downstream of the Dam, with is captured all upstream flows early in the rainy season,most low flows, many larger flows and the reduction in magnitude of some floods that arereleased downstream.The change in flow regime is also likely to have caused a change insediment load. Changes in the water and sediment regimes of the river resulted channel adjustments inboth the vertical and lateral dimensions. The channel pattern has shifted from a wide, braided shape with mid channel bars, to a single-thread straight and meandering planform. The channel pattern change was studied by comparing the SPOT satellite image and the aerial pictures for prior and after dam construction.
Keywords: Catchment Area, River Morphology, HEC RAS, Cross Section, Satarkhan Dam.
https://jphgr.ut.ac.ir/article_30437_fdea46f164dd0d2c57fed2d3c82700c7.pdf
2013-05-22
87
100
10.22059/jphgr.2013.30437
Catchment area
Cross section
HEC RAS
river morphology
Satarkhan Dam
mohammad
ashouri
ashourim99@yahoo.com
1
کارشناس ارشد ژئومورفولوژی، دانشگاه تبریز
AUTHOR
Mohammad Hossein
Rezaei Moghaddam
rezmogh@yahoo.com
2
استاد گروه جغرافیای طبیعی، دانشگاه تبریز
AUTHOR
Z.,
Piry
zahrapiry07@yahoo.com
3
کارشناس ارشد ژئومورفولوژی، دانشگاه تبریز
AUTHOR
ORIGINAL_ARTICLE
Assessing the Relationship between Ground and Soil Temperature at Different Depths: A Case Study of Kermanshah Province
Extended Abstract
Introduction
The study of soil temperatures at different depths is significant from various perspectives, including meteorology, climatology, agriculture, industry, and other related bio - activities. Vertical distribution of temperature in soil depends upon three factors, namely:
1) the structure and physical characteristics of soil and its thermal properties;
2) land cover (bare, grass, snow, etc.);
3) the effect of climatologic factors including temperature, precipitation, wind, solar radiation, and humidity.
This paper reports the results of a statistical study on the relationship between ground and soil temperature at different depths (10, 50, and 100 cm) in five synoptic stations in Kermanshah province.
Methodology
Exact measurement of ground heat flux is a formidable task. Most techniques measure the ground heat flux by measuring the soil temperature at different depths. Given the difficulty of such measurements, it seems that developing the statistical modeling's could be useful. Data were collected for daily minimum air temperatures (meteorological screen) and daily minimum ground temperatures, in addition to soil temperatures at 10, 50, and 100 cm depths at 6:30 am and 6:30 pm local time within a 14-years period (1993 to 2006), adopted from the Kermanshah Regional Meteorological Office. The data were then used to study the relationship between the ground and soil temperature at different depths. The paired-samples t-test was employed to analyze the data. In addition, a multivariate regression model was employed to estimate temperatures at various soil depths (10, 50, 100 cm) based upon variables including ground temperature, Julian day, and depth.
Results and Discussion
As we go down the soil profile in the stations, the mean annual minimum temperature increases and reaches its peak at a depth of 100 cm, mainly due to regular thermal conduction. However, during the warm periods of the year, temperaturesare higher at depths of 10 and 50 cm compared to the other depths, due to extra heating of layers close to the surface. The mean minimum temperatures are very similar at 50 and 100 cm depths. The paired-samples t-test indicated no statistically significant difference between the mean minimum annual temperatures at these two depths. Increase in the depth of the soil leads to a lesser annual temperature range, specifically the diurnal temperature range. The diurnal range almost disappears at the depth of 50 cm. It was also found that the diurnal temperature range at each depth was at its maximum during the summer. The annual temperature difference between ground and various depths increases up to 50 cm, but it levels at lower depths. The paired-samples t-test showed no significant difference between diurnal temperature ranges at 50 and 100 cm.
The similar behavior of temperature curves at different depths indicates that soil type does not have a significant role in distribution of temperature at various soil depths, regardless of climatic differences. In winter, the lowest minimum temperatures at 10, 50, and 100 cm depths, were delayed for 3, 13, and 33 days respectively compared with the lowest temperatures of the ground. This delay for the highest minimum temperatures was a few days longer in the summer
Conclusion
Soil temperature is an important feature that affects various activities. The results of the present study indicate that temperature irregularities are more frequent at ground, with such irregularities decreasing at lower depths. The similarity of results of the present study with previous researches regarding the one month delay of ground and soil depth temperatures indicates that soil type play a secondary role in thermal delay.
Given the difficulty of including various influencing factors in the models due to lack of sufficient data on the one hand, and relative inefficiency of numerical models in simulation of thermal distribution in soil on the other hand, it seems that employing empirical, semi –empirical and statistical models are useful measures to estimate temperatures at various soil depths. The multivariate regression model used in the present study efficiently estimated soil depth temperatures, specifically during spring and autumn. It should be noted that in all studies on the estimation of temperatures at various soil depths, it would be necessary to have a good understanding of soil layers properties, including physical characteristics, structure, thermal conductivity, etc. It should further be understood that no mathematical, statistical or empirical model can be used in different locations unless calibrated according to local conditions. We suggest that empirical, semi-empirical, deterministic and analytic models be employed to estimate soil depth temperatures, and the results be then compared with regression forecasting.
It could then be concluded that lowest temperatures reach more quickly than highest temperatures to a certain depth. The temperatures of various soil depths were estimated by employing a multivariate regression model with good accuracy at the stations for spring, autumn, and winter.
https://jphgr.ut.ac.ir/article_30438_86d1092493898e2bc6a6006b2e69271c.pdf
2013-05-22
101
118
10.22059/jphgr.2013.30438
Diurnal Range
Kermanshah province
soil depth
temperature
Firouz
Mojarrad
f_mojarrad@yahoo.com
1
استادیار گروه جغرافیا، دانشکدهی ادبیات و علوم انسانی، دانشگاه رازی کرمانشاه
AUTHOR
H.,
Sadeghi
hadis.sadeghi12@yahoo.com
2
کارشناس ارشد اقلیمشناسی، گروه جغرافیا، دانشگاه رازی کرمانشاه
AUTHOR
ORIGINAL_ARTICLE
The Numerical Modeling and Simulating of Winds Over Urmia Lake Basin
Extended Abstract
Introduction
During the past years, as a result of various factors, the water level of Urmia (Oroumieh) Lake has dropped andcomplete dryness of the lake may be possible in the coming years. Dryness of the lake with a bed of salt deposits exposures in wind and air can create significant changes in thermal conditions, energy balance and dispersion suspended particles around the lake. Increased frequency of dust events around the lake is complications of climate, which transfers suspended particles and salts to the surrounding area. Using regional-scale climatic modeling, it has been possible to use different scenarios such as dried or filled lake, to be simulated its impact on climate of region. Althoughseveral studies have been done related to Urmia Lake, there are few studies on dried lake and its environmental impact on the surrounding area with climate model. The main aim of this study is to model the local wind behavior over the lake basin and simulates the dominant particulate pollutants dispersion directions.
Methodology
Lake Urmia is a salt lake in northwestern Iran, near Iran's border with Turkey. The lake is between the provinces of East Azerbaijan and West Azerbaijan. It is the largest lake in the Middle East, and the third largest salt water lake on Earth, with a surface area of approximately 5000 to 6000 km², 140 km length, 55 km width, and 5 to 16 m depth.
To develop the research design and explanation theoretical principles library method were used. This study utilizes three-hourly data of wind direction and velocity from five synoptic stations of Urmia Lake basin and using mesoscale of the air pollution model (TAPM) to estimate the density of suspended particles and its spatial dispersion pattern in the region. The Air Pollution Model (TAPM) is a software package developed by CSIRO to estimate the spread and impact of air pollution. TAPM is a meteorological, prognostic air pollution model, which is dynamic and the limited area model that predicts three-dimensional meteorology and air pollution concentrations. TAPM uses surface dataset such topography, soil texture, surface covering and the surface and upper atmospheric layers
Results and Discussion
Affected by the lake dryness,circadian oscillations of air temperature and relative humidity will increase as altitude of the mixed layer increases.Comparing of temperature between two scenarios of non-dried water and dried lake bed in July, it was observed that dried salt bed has a higher temperature on day, and is cooler in night time. So regarding water presence, heatcapacity is high, whereas in the dryness by lowering heat capacity fluctuations of circadian temperature were increased.The amount of humidity is higher in non-dried lake especially in day time, and during the night corresponding to temperature drop humidity is approximately equal. In late summer, with relatively cool air, temperature drop is considered in both condition, however, the same condition of July is observed.In dried Lake, relative humidity dropped during the day, andis higherduring the night. Rising and falling temperatures canlead to a change in the height of the mixed layer. The prevailing winds directions are west and north, so four days were selected from arid months with frequency of a few hours north and west winds. Lake and its margins emissions were obtained about as 10,624 grams per second, based on Environment organization that was calculated equal to 6 kg per hectare at hour.
According the model outputs, prevailing wind direction is generally north, and just in midnight hours redirect to the East. And among the four days of modeling, 20 July had the lowest velocity, which in midnight is becoming to storm condition. Finally the wind direction in every four days at midnight hours was from the East.
Conclusion
Circadian oscillations of the air temperature and relative humidity and mixed layer height increasing, would be some results of dried Urmia Lake. Air pollution dispersion modeling results indicate that the particle dispersion most likelyoccurs in the North in August and in the South in October. Due to the prevailing wind conditions in summer, salt particles dispersion mostly occurs in the northwest at noon and in the evening. In May, August and September pattern of dispersion particles is changed and predominantly have been observed in the West and Southwest of the Lake.The area includes fertile agricultural lands and orchards, and is more likely be threatened by salt dispersions remained from dried lake.
https://jphgr.ut.ac.ir/article_30439_a05d5db619b0fa446e4b45938fb6e9ff.pdf
2013-05-22
119
134
10.22059/jphgr.2013.30439
Modeling and Numerical Simulation
Salt Particles
TAPM
Urmia Lake
Ali
Shamsipour
shamsipr@ut.ac.ir
1
استادیار اقلیمشناسی، دانشکدهی جغرافیا، دانشگاه تهران
AUTHOR
F.,
Najibzadeh
shamsipr3@ut.ac.ir
2
کارشناس ارشد اقلیمشناسی، دانشکدهی جغرافیا، دانشگاه تهران
AUTHOR
Z.,
Zarei Chaghabalki
shamsipr2@ut.ac.ir
3
کارشناس ارشد اقلیمشناسی، دانشکدهی جغرافیا، دانشگاه تهران
AUTHOR