Physical Geography Research
Year:2017 | Volume:49 | Issue:1 |Papers Count:13

Introduction: Climate change caused some changes in the global environmental conditions in the recent decades. One of the climate change impacts is the disturbance of the hydro-climatic cycle in the world. The effects of climate change on the hydrological cycle are including changes in groundwater levels, lakes, as well as changes in the distribution of rainfall timing and intensity and river flows. Intensity and frequency of extreme precipitation events and the risk of floods and droughts are increasing due to the climate change in the large parts of the world....

Introduction: Freeze is one of the serious climatic phenomena that influence different aspects of human life including agriculture, transportation and energy. The effects of freeze in agriculture are more than other activities. The effects in agriculture section appear more than its earliness or lateness aspects. In Ardabil Province, in most years, early and late freezes have caused serious damages to agricultural products. For example, in April 2014, the gardens in Ardabil Province experienced a loss of more than 4 billion Rials due to late spring cold. Due to this cold, 21000 Hectares of the gardens were damaged.....

Introduction: The Caspian Sea (CS) can be subdivided into three parts: North, Middle and south parts. The sea experienced many cycles of Sea-level changes with vast emerged and submerged areas. In the terraces in Dagestan, two major phases have been distinguished. The Early Khvalyn transgression is represented by five successive marine terraces between +50 and 0 m atabsolute height. Furthermore, at the boundary of Late Pleistocene and Holocene a-50 and by other researcher a-113 sea level record has been identified. This is why many researchers call it as a capricious level due to great sea level changes. Recent sea-level changes also got attention, experienced around 3 m sea-level changes between 1929 and 1977 and rose back in 1995. Five late Holocene records have been identified at least up to-22 absolute elevation. Present work aims at showing two phases of transgression and its impact on Iranian coast by Arial photograph and radiocarbon dating, a 2600 BP and Littlie Ice age....

Introduction: One of the most important issues in development of any scientific discipline including geomorphology is introduction of new viewpoints and special conceptualization. Introduction of relativism in philosophy, language and sociology has brought about deep evolutions in the epistemology of the research methodology in these sciences. Although this viewpoint was already introduced in geomorphology by the American scientist G. K. Gilbert one hundred and thirty years ago, temporal conditions did not let the development and understanding of the conceptions for others. Recognition of Gilbert’ s views and its comparison with relativism concepts in this age can familiarize us with Gilbert’ s thought and the evolutions it made in relativism concept. Besides, it can prevent us from considering Gilbert’ s relativism to be in parallel with many concepts introduced by others.....

Introduction: Rangelands are natural ecosystems with native plant species. Water, soil and vegetation have fundamental role in management of natural ecosystems such as rangelands. Thus, it is essential to perform researches for preservation of the natural and human environment. Proper and allowable utilization of the rangelands in range management projects is the important scientific and technical measure of the range management in Iran. Range management projects as improvement-restoration and reclamation guidelines have particular importance in the Natural Resources Organization of Iran. On the other hand, erosion and soil loss and sediment production has become today one of the main problems in the human environment. Restoration of vegetation and its effects on reduction of erosion have been studied by Li, 2006, Zhou, et al. 2008, Zhanga et al. 2004, Abdelkrima, et al. 2013. The Goal of the improvement-restoration operations in natural ecosystems is recovery plant composition for more protection of water and soil and decrease in soil erosion. Therefore, soil management for optimal utilization is essential to reduce its degradation. Mapping the rate of erosion and sediment yield and regional prioritization are effective steps for management, protection and utilization of the soil. The purpose of this study is to estimate the amount of soil erosion and to simulate the effects of improvement and restoration of soil loss in the Lar area, Mazandaran....

Introduction: With the onset of fall season, the air temperature on the Caspian Sea is diminished, but due to the difference in the specific heat capacity of air and water, the reduction rate of temperature is far greater than that of the sea. Therefore, the surface of Caspian Sea remains warmer than air. Establishment of dynamic high-pressure centers or diffusion of Siberian high pressure system over Caspian Sea especially during fall results in development of southward air stream over the sea. Caspian Sea as the first supplier of moisture resources for heavy precipitation and especially ultra-heavy precipitation of its southern coasts plays a principal role in explanation of the occurrence of precipitations in these coasts....

Introduction: There are wind belts or bands extending long distances over a region. According to the definition of World Meteorological Organization, if the speed of wind bands exceeds 30 m/s, jet streams emerge. However, based on the definition of Climate and Air Dictionary, jet streams are the highly intense horizontal winds with a speed more than 50 nodes or about 25 m/s blowing above planetary winds. In fact, jet streams are speed cores moving below short and high waves and, like them, have convergence and divergence areas. Windward core speed is also reduced from core center to the arounds; this reduction toward the pole is cyclicity or positive and toward the equator is anti-cyclicity or negative....

Introduction: Tropopause is the transitional layer between the troposphere and stratosphere. This layer determines the upper limit of the troposphere and somehow expresses the spatial and temporal variations in the thickness of the layers and the layer indicated his thermodynamic variability. This is the layer that short-term and long-term atmospheric phenomena occur in. In other words, this layer determines the thickness and upper limit of the troposphere layer. Iran in terms of geographical location is on the northern side of the Hadley cells in the general circulation. That’ s why when handling the extremely cells, we observe changes in the climate of this country. That's why the country is in the range of atmospheric systems of important effects such as (Arabian subtropical high pressure, Siberian high pressure, Azores high pressure, Mediterranean cyclones and Sudan low).....

Introduction: In the recent decades, the prediction of suspended sediment load was highly regarded by water resources management and engineering researches, particularly in flood prone areas. Nowadays, the methods and artificial intelligence techniques to predict hydrologic properties have become very popular. In recent studies, we have used various parameters such as the spectral reflection bands of satellite images, land use and geology maps and climatic data. Landsat satellite images have good spatial resolution. Da Silvia (2015) also used spectral calibration of multispectral satellite images to assess suspended sediment concentration. Their results showed that the concentration of suspended sediment has been strongly influenced by seasonal rainfall. The yellow river sediment using Landsat satellite images were evaluated by Zhang et al (2014)....

Introduction Evaporation is a fundamental component of the hydrology cycle and has an important role in water resources management. Daily evaporation is an important variable in reservoir capacity, rainfall-runoff modeling, crop management and water balance. Measurementof actual evaporation is almost impossible, but evaporation can be estimated using several methods. There are two general viewpoints for estimation of evaporation: direct and indirect methods. It is inoperative to measurement of the evaporation by direct methods in all locations. The direct methods are usually used for proximate reservoirs or irrigation projects. The indirect methods of evaporation estimation need various input data that are not easily available. Moreover, the evaporation have very complex and nonlinear process that simulation of its complex process using simple methods is impractical. In recent years, the artificial intelligent methods such as Artificial Neural Network (ANN) and Support Vector Machine (SVM) have been successfully utilized for modeling the hydrological nonlinear process such as rainfall, precipitation, rainfall-runoff, evaporation, temperature, water quality, stream flow, water level and suspended sediment, etc. Therefore, this research evaluates the performance of ANN and SVM models in daily evaporation estimation.