فصلنامه پژوهش های جغرافیای طبیعی
پیاپی 83 (بهار 1392)

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.

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).

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.

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.

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.

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.

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

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.