Physical Geography Research
Year:2010 | Volume:- | Issue:70|Papers Count:10

introduction: January 2008 was one of the coldest days during the history of registering data in Iran. In this month an unusual cold air mass covered the most part of Iran particularly the north area of the country. As this air mass shifted southward, it produced very cold condition in all of the country and dry snowfall in the north parts and mountain area.Materials and methods: In this paper in order to investigation of unusual cold event on Jan 2008 in Iran, a dataset includes daily minimum temperature of Jan 2008 has been gathered from synoptic stations all over the country. Then, by using cluster analysis extracted 21 stations as selected stations; the final stations almost covered all of the country area. Z score index used for calculated minimum daily temperature anomalies. Then the calculated Z scores applied as an indicator in order to compared January 2008 minimum temperature with the long-term average minimum temperatures of January. Also extracted the four hourly temperature, sea level pressure, geopotential height, and the wind speed components (U & V components) for synoptic analysis of Frost events in the period of study from NCEP/NCAR. Position and movement of the atmospheric systems such as cyclones, anticyclones, fronts and wind fields were identified using synoptic maps. Also the daily temperature data and the wind speed components are used for plotting the composite maps of temperature advection, thickness, temperature gradient’s vectors, and thermal wind.

Introduction: If the human comfort temperature (threshold temperature) is defined as X, the average deviation of daily temperature from the comfort level is termed a degree-day, which represents the need to cool the environment from temperatures above the threshold temperature and the need to warm the environment from temperatures below the threshold temperature (i.e., cooling and heating needs, respectively). Heating degree day and cooling degree day values for a given area indicate the harshness of the climate and bear a direct relation to an area’s population and size of residential areas. HDD and CDD values are also related to climatic change.Materials and Methods: The area considered in this research is northwest Iran (44–50oE and 34-40oN), including the provinces of Gilan, Ardebil, Eastern and Western Azarbaijan, Ghazvin, Hamedan, Kurdestan, Kermanshah, and Markazi. We analyzed daily amounts of HDD and CDD recorded at 28 meteorological stations in northwest Iran for the period 1984-2003, using data provided by the Information and Statistics Center of the Meteorology Organization of Iran.

Introduction: In recent years, characteristics of Canola and its suitable amenity with all climates and weather conditions invarious points of country, had result in expanding implantation of this plant as a good source of meal oil. This is considered in the general perspectives. Continental amenity of this plant and time difference of its growth period and in its capacity for using agronomy frequency, are the positive points of this plant in Iran. Expanded implantation of this kind with other kinds of corps has started since 1997-98 with the surface of 2893 Hectares. According to the last reports, the implantation of this plant in Iran in 2005-06, was about 119321. The average performance of Canola in that period was about 2035 kilograms a hectare.Materials and methods: The study on Okapi and SLM046 Canola has began since 2000 in research farm of Farokhshahr in the research centre of Chaharmahal Va Bakhtiari. For the possibility of expanding these results to farms, we have tried to set real farm situation for the experiment. These steps were done in 7 periods in 2000-2001 to 2006-2007 continuously. The implantation to cropping the products, has longed about 10 months.

Introduction: Emergence of landslide phenomena can be due to the different factors like geology, geomorphology, hydrology, biology and human activities but main role in landslide initiation only is created by triggered factor. Intense rainfall, rapid snowmelt, water-level change, seismic loading and rapid erosion are the most important landslide triggering mechanisms. Rainfall has been known as the most common factor in occurring landslides. In general, infiltration of rainfall in soil causes to increase soil water pressure, reduce matric suction and increase the weight of soil mass and finally, soil strength is decreases and landslide occurs. Moreover, groundwater conditions responsible for slope failures are related to rainfall through infiltration, soil characteristics, antecedent moisture content, and rainfall history. Thus, the most important section of landslide modeling (empirical, statistical or physically-based) is hydrological part. In this study, it has been tried to present the obtained results and the applied idioms in most cited researches about hydrological modeling of landslides. With respect to the human and financial damages due to occurring landslides in our country, designing and applying a landslide warning system is necessary and doing study in this background is huge step for decreasing damages and sustainable managing of natural hazards. Authors hope to witness of creating the advance warning systems for landslides in our country by using obtained experiences around the world and motivations of internal researchers.

Introduction: Rice is one of the most important crops in tropical areas, specifically in Southeast Asia. The specific climatology with always cloudy conditions; temporal variability in sowing, growing, and harvesting of rice crops and also different cultivation timetables, make the necessity of using multi-temporal RADAR and Synthetic Aperture Radar (SAR) images for obtaining quantitative and qualitative information from rice fields in tropical areas. The objective of this research is the evaluation of the ability of multi-temporal ENVISAT-ASAR datasets for temporal and spatial discrimination of rice fields, therefore, Palolo Valley, Central Sulawesi, Indonesia as the area of study was selected. The evaluated images were acquired in multi-polarimetric mode (HH, HV or VV, VH) from 4th February to 28th July 2004. These datasets includes two raw or primary datasets: Co-Polarized (HH, VV) and Cross-Polarized (HV, VH) and five derivative or secondary datasets: Mean Texture Co-Polarized, Mean Texture Cross-Polarized, Monthly Subtraction, Polarized Subtraction and Normalized Polarized Subtractions. Here the advantages of the relationship between rice growth process and the changes in the SAR backscatter coefficients using the multi-temporal ENVISAT-ASAR datasets are taken. After doing the preprocessing and the processing stages, the obtained results were evaluated using high resolution Quickbird/MS satellite imagery and available field works information. The obtained results for spatial discrimination of rice fields show the highest accuracy for Co-Polarized dataset with an overall accuracy (88.05%) and Kappa coefficient (0.867), while Normalized Polarization Subtraction dataset offered the lowest amount of accuracy with an overall accuracy (80.23%) and Kappa coefficient (0.781). The results of temporal discrimination of rice fields show a good correspondence between the rice growth and SAR backscatter coefficients.

Introduction: Tectonic of Binaloud mountain ranges is controled by thrust faults system and folds related to these faults. Parts of this mountain ranges and Neyshabour plain is as study area in north eastern Iran and between latitudes 36o 11’ 00 to 36o 30´ 00 and longitudes 58o 35´ 00 to 59o 00´ 00. In this paper we first study morphometric indices in this area then analyze drainages and allovial fans to identify activity of Binaloud mountain.materials and Methods: In order to identify activities in Binaloud mountain, studing morphometric indices and analysis of drainage network together be done. The first step for calculating morphometric analysis in the region is to digitize topographical maps with the scale 1:50000 by ArcGIS software to extract required data and then morphometrical data is formulized and calculated exactly and the results is interpreted.

Introduction: Hoor-al-azim wetland is one of the most important wildlife refuges and marine ecosystems in the south-west of Iran where structure and function has been significantly affected by different changes during the 2 recent decades. Changes in water regime of Hoor-al-azim wetland and human activities are some of the most important factors. Changes in water regime and anthropogenic activities in the region are the most important factors that affected the wetland. nevertheless the foundation of our concerns must be put on the assessment of ecosystem’s ability and determining the system’s self-organizing level for reaching the balance which helps the system to diminish impacts of disturbances. Reviewing and determining self-organizing potential of the system not only can recognize existing mechanisms and indicate a true image of them, but also can show convenient amendatory strategies for reduction or elimination of their impacts. In fact, reviewing self-organizing mechanism in a specific period can give a rather precise image of the progressive and developing or declining process of the system.

Introduction: New meteorological numerical methods are developed into general circulation climate models since 1970, therefore. And different climatic models have been developed. Regional Climate Model (RegCM3) is used for climate studies and dynamic downscaling of atmosphere general circulation models output. Until now, many studies have been done using this model. Sensitivity of RegCM Model to different cumulus scheme for winter precipitation 1997 and 2000 are demonstrated by Babaeian and et al (2007). Result showed That Grell scheme with approximately 20% errors have good ability for winter precipitation simulation of Iran. Onol and et al (2009) have been investigated RegCM skill over Mediterranean region countries by using Kuo scheme. They found that annual mean simulated temperature is greater than CRU data. In this paper according to the role of autumn precipitation in water resource providing of the Khorasan area and for calibration and validation of RegCM3 as a research and seasonal prediction tool, a ten years Climate of Khorasan has been modeled for autumns 19991-2000.