Physical Geography Research
Year:2016 | Volume:48 | Issue:1|Papers Count:10

IntroductionSnow is a kind of precipitation that is formed by the condensation of moist air mass and in the condition that temperature is below freezing point. Although small areas of the world are mountainous regions, these small territories play an important role in the hydrological context of river basins. In some areas snow covers and glaciers supply drinking water. Monitoring and forecasting of snow cover areas are essential for the promotion of climatic predictions and water-related decisions, particularly in mountainous regions where a great proportion of needed water is provided. Some works have been conducted about the influence of elevation, slope and aspect on the distribution of snow-covered days. In this part, some of these works have been reviewed here. Endrizzi et al. (2006) have indicated that there is a relation between snow water balance, elevation and aspect. They found that the dependence of snow water balance on elevation is poor in fall and strong in the spring. Gurung et al. (2011) have indicated that in Bhutan the accumulation of snow is varied based on aspect. North-east and north-west facing slopes are favored areas for snow accumulation in the seasons of winter, summer and fall.

IntroductionInteraction between internal and external processes of the earth during time plays an important role in formation and landforms transformation. We can identify course of their process changes with landform survey. In the middle parts of Iran, there are several geomorphologic evidence of arid and rainy climate changes. Playaes and lakes or generally internal holes had an important role in climate balance and ecological changes in the quaternary on its surrounding areas. Therefore, previous studies have always attempted to determine past climate. Morphology and alluvial fan deposits contain traces of past environmental changes. The key issue is that which tectonic factors determined changes in alluvial fan processes and climatic and or geomorphological conditions of alluvial fans.

IntroductionThere are significant differences in the spatial distribution of the Iran annual precipitation. This is resulted from spatial behavior of precipitation in the one hand and variation in the sources of precipitation on the other. The lack of adequate distribution of meteorological stations and the unavailability of long-term statistics of precipitation makes the analysis of precipitation more complicated. Precipitation data are constant inputs of research and the models related to water resources (e.g., climate, agriculture, hydrology, and environment). Most of research institutions are used to record the data and present it to different users. Different ways of interpolation of the data will cause different results. Therefore, it is a critical step to select the appropriate data based on research design. This study evaluates APHRODIATE, GPCC and Delaware University precipitation data (UDel) based on precipitation stations using RMSE, R2 and Taylor diagram techniques.

IntroductionRainfall erosivity, the propulsion or power of causing erosion in separation and transport of soil particles, is in relation to water erosion. Rainfall erosion is causing loss of soil, damage to agriculture and infrastructures which is followed by water pollution. Changes in rainfall patterns exacerbate risk of erosion globally. Rainfall erosivity plays an effective role in soil erosion and represents potential erosion in the study areas. Following the rainfall erosion, all types of water erosion can be occurred. Consequently, it not only makes soil to be eroded but also lead to filling of dam reservoirs, channels, water pollution and ecological changes. Regarding these mentioned problems, it is necessary to investigate various aspects of water erosion. Under the same condition, rate of soil loss is directly proportional to the rainfall erosivity. This can be expressed as erosivity factors which are based on rainfall characteristics. Various researchers have attempted to provide factors that are based on rainfall characteristics using simultaneous measurement of soil splash (or soil loss) and rainfall characteristics to determine relationships between them. Various factors have been proposed throughout the world. These factors are different because of geographical location, scale, local conditions and type of instruments. The concept of rainfall erosivity was proposed by wischmeier and smith (1958) in order to consider the effects of climate on soil erosion. Rainfall erosivity can be determined either using direct measurements or appropriate factors. Direct measurement method is a suitable method to determine rainfall erosivity which is done by measuring the amount of splashed soil. Event-based measurement of erosivity of rainfall for broad area is difficult and time-consuming. Therefore, researchers have attempted to provide factors that are based on rainfall characteristics using simultaneous measurement of soil loss and rainfall characteristics and relationships between them. For different areas, rainfall erosivity can be determined using these characteristics without direct measurement. In general, rainfall erosivity factors can be divided into two groups: 1) factors based on energy and intensity of rainfall; 2) factors based on readily available data. One of the most famous factors is EI30 which is based on kinetic energy and intensity of rainfall. One limitation in using this factor and also other factors which are based on rainfall erosivity is that they need long-term data (>20years) recorded with short intervals. Such data are recorded in the stations equipped with rain gauge. Therefore, due to lack of these long-term data, researchers have proposed factors that use available rainfall data (i.e., daily and monthly data). This recent factors are computed based on regional sediment analysis or its relationship with EI30.The purpose of this study is to prepare rainfall erosivity map for Kerman province with semi-arid climate and to determine the most suitable interpolation method. Although such a map has been produced by Nicknami (2014) for Iran, it's not available for Kerman specifically.

IntroductionThe most notable convective systems are Mesoscale Convective Systems (MCSs). These systems are developed when clouds occurring in response to convective instability organize upscale into a single cloud system with a very large cirriform cloud structure and rainfall covering large contiguous areas (Houz, 2004). Detection and monitoring of MCSs is very important in southwest Iran because they produce hazardous weather, such as lightning, heavy rainfall, hail and strong winds. Several factors influence the development of MCSs such as the flow generated by a weak midlevel trough and the occurrence of low level jets (LLJs). LLJs transport moisture at the jet level, increase the low-level convergence and are responsible for sustaining convection especially at night.

IntroductionIran forms a relatively compact zone of active continental deformation resulted from the northward collision of Arabia with Eurasia during late Cenozoic times, which is continuing to the present-day at a rate of 25 mm/yrs (from GPS data). Evidences of active tectonic in different parts of Iran, has been studied and identified. The arid climate, low rates of erosion, and minimal vegetation cover across the majority of the country result in excellent preservation and exposure of surface deformation produced by active faults. Geomorphic indices are useful tools for evaluation of active tectonics because they can provide rapid insight concerning specific areas within a region which is undergoing adjustment to relatively rapid and even slow rates of active tectonics. Alluvial fans, river terraces, runoff anomaly and horizontal and vertical displacement of faults are the most important landforms that indicate active tectonics and active faults. Active tectonics play a very important role in deformations of the alluvial fans. Without continued tectonics, fans may become minor or short-lived features. Morphological evidence of different types of faults such as thrust faults and strike-slip faults can be determined in surface of quaternary landforms. For example, Late Quaternary activity on strike-slip faults can be determined from the lateral displacement of young landforms such as river terraces and alluvial fans, or from scarps introduced by slight dip-slip components of motion. In this study, the evidence and impacts of the active faults have been investigated in quaternary landforms such as river terraces, stream displacements and spatially alluvial fans morphometry and morphology located at the south part of the MishoDagh Mountain in northwest Iran.

IntroductionNumerous studies have demonstrated the relationship between the amount of CO2 in the atmosphere and climate change. In this respect, developed countries have an undeniable role and cause serious damage to earth environment throughout the world. IPCC’ forth evaluation report implies that adding greenhouse gases to the atmosphere during recent decades prevents the heat rays to emit which, in turn, cause atmospheric temperature to increase. During the past centuries, the temperature has increased by 3 to 6 Degrees Centigrade, with a rapid speed in the recent decades. It is believed that if greenhouse gases continue to increase at the present rate, an average increase in temperature, from 1c to 3.5c, is expected by the year 2100. Therefore, it is necessary to study and evaluate climate changes in the future decades so as to plan a proper environmental program corresponding to future climate conditions, consequently reduce its unfavorable effects. With the uncertainty in Atmospheric Circulation Models being taken into account, the present study investigates the temperature and precipitation changes in Southeastern Iran during the following periods: 2011-30, 2044-65, and 2080-99.

IntroductionIran Kaluts (Yardang) which are considered as special models in terms of magnitude and extension have been shaped in the west part of the central Lut desert. Although these Kaluts now are influenced by the selective windy erosion, they can be shaped through the process of wind and water erosion. The suitable environment for formation of these Kaluts are the arid region together with little raining and the intensive and continuous wind. The Lut desert Kaluts are shaped in the grounds with finer structure and wind and water erosion. This erosion can be produced when the water is accumulated in the small pit and holes in the humid season after temporary precipitation in the desert. Then, a doughy substance is made and wakened. After drying and as a result of the predominant wind on the district, these pit and holes gradually become enlarged and the long silts produce the Kaluts. In this research, we want to study the sedimentary characteristics of the Kaluts and Iran pluvial lakes by sampling of one of the high Kaluts in Lut desert through sedimentary and granulometery experiences on these samples.

IntroductionFlood is a natural hazard that its occurrences can be observed more frequently in recent years. For better flood mitigation and control, it is needed to identify flood production factors and determine the high potential flood areas. Hydrological model is a simplified representation of natural system and the rainfall-runoff model is one of the most frequently used events for flood simulation. HEC-HMS is one computer model that becomes very popular for its ability in simulation of short time events. The aim of this research is to investigate spatial prioritization of flooding in Beheshtabad sub-catchments using HEC-HMS software.

IntroductionShamal winds recognized as a climate regime with a common occurrence in the Persian Gulf makes periodically adverse weather conditions in this region. Among the phenomena occurring under the influence of Shamal wind, we can mention dust storms, low-level winds and turbulent marine conditions (Rao, 2003). Shamal winds are categorized into two types, winter Shamal and summer Shamal. Sea-land breezes are also classified as a frequent mesoscale and heat driven flow associated with coastal areas. Temperature gradient between sea and land is the main reason for the formation of a sea breeze circulation blowing from sea to land in low level coastal atmospheric boundary layer. The suitable condition for sea-land breezes is when the synoptic winds are weak (low synoptic forcing) and temperature level is high in the coastal city of Bushehr (Bidokhti and Moradi, 2004).The purpose of this research is to investigate seasonal Shamal wind event and its associated synoptic conditions by observations analysis and numerical experiments on Persian Gulf. The impacts of these conditions on wind pattern are studied in the northwestern Persian Gulf coastal area and in optional case in the coastal area of Bushehr. It is intruded interaction between meteorological mesoscale (sea-land breeze) and large-scale (synoptic pattern Shamal wind) forcing effects in this area.