Physical Geography Research
Year:2013 | Volume:45 | Issue:1 (83)|Papers Count:11

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.

Hyper spectral satellite imagery like Hyperion implies collecting data from large number of spectral bands. Therefore, they can be used for some applications that cannot be 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.

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.

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 the 1: 50000 scale maps to constructing of DEMs with 10×10 meters 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 huge structures 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.

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.

During the past years, as a result of various factors, the water level of Urmia (Oroumieh) Lake has dropped and complete 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. Although several 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.