Physical Geography Research
Year:2012 | Volume:44 | Issue:2 (80)|Papers Count:11

Introduction:The Caspian Sea as the largest land-locked water body is susceptible to environmental changes. The Caspian Sea has experienced different sea-level fluctuations with an impact on the rivers mouth and displacement of the mouth, changes in depositional regime, deformation of delta or renewed excavations of channel in mouth location. The south-eastern Caspian sea, as the study area is one of the most appropriate regions for studying and reconstructing the changes in coastal line, changes in river courses, delta displacement, lagoons and coastal barriers. Each of them is important as a result of geomorphologic evidence of the Caspian Sea level changes.

Introduction:The rapid reduction of fossil fuels, global warming, green house effects, environmental pollution and falling of acid rains have increased the need of attention to renewable energies especially wind energy as a clear interminable and free energy source (Rahman at el, 2003). Therefore, in order to exploit the potential energy of wind, assessment in different areas should be considered. This study assessed the potential of wind energy at Kermanshah province. Wind energy potential based on statistics of three hours wind direction and speed of synoptic stations of province including Kermanshah, Eslamabade Gharb, Ravansar, Kangavar and Sarpolzahab, Was assessed from 1997 to 2006. For showing wind speed and direction of province stations, the Wrplot software was used as well us the Weibull mathematical model for befitting of data possibilities distribution.

Introduction:When a river reaches from high gradient mountains to a low gradient plain, aggradations phenomenon is occurred and alluvial fans are built. At least five factors influence fan processes, including catchment bedrock lithology, catchment shape, neighboring environments, climate, and tectonics. Rocks of differing lithology yield contrasting sediment suites and volumes due to their variable response to weathering. Bedrock in desert settings is optimal for fan development, especially tectonically maintained mountain fronts, yields sediment in varying size.

Introduction:Synoptic systems control precipitation patterns. One of the synoptic systems aspect that could determines the rainfall amount and spatial distribution, is geographical distribution of synoptic patterns. Moreover, changes in synoptic patterns in each region could explain daily weather conditions. Identifying synoptic systems in each region could provide a clear picture of that region climate. Climate as one of the basic structure of the environment has direct interaction with human life and activity.

Introduction:Studies have shown that Earth's climate is not stable and any changes in climate can be result of climatic system variability and external factors that can be assessed at various scales monthly, quarterly and annually. Teleconnection such as ENSO, including measures are able to assess the quantity, quality and power of a broad synoptic pattern, in the form of numerical criteria are. ENSO is one of the atmospheric phenomena with warm phase (El Nino) and cold phase (La Nina) that occurs in East of Darwin and Tahiti and West of Pacific.

Introduction:Ilam, Kermanshah and Kordestan are three provinces in Western Iran regarded as the second agriculture realm with 65 rainy days per year. It is proved that the dynamic high pressure is prevailing system over study area during warm season. It is known by the name of Azores high but we find a different situation during cold season. The tongues of Siberian high and slow-migrant ones are alternately dominant and vanished. This alternation happened in the context of westerly winds with their ridges and troughs as western waves.

Introduction Dust storm is one of the most important natural phenomena and a kind of severe natural disaster that begins and diffuses under the influence of atmospheric systems. It occurs frequently in deserts and their surrounding areas in arid and semi arid regions. So, the major and most persistent sources for dust scattering in the Northern Hemisphere are located in the ‘‘dust belt’’ which extends from 20oN to 30oN and are developed under the subtropical high-pressure subsidence (Kalderon et al., 2009).

Introduction:Generally, yearly variability of precipitation make rangelands unsuitable for crop production, and livestock grazing presents a sustainable means of food and fiber production. Droughts which often occur within a long period, may drastically affect plant community composition and may make rangelands more susceptible to diseases, insect pests, weed invasions, and overgrazing. Therefore, continuous monitoring of rangeland status would help decision makers to do necessary interventions and proper reactions against drought spells. In this regard, current ground-based methods seem to be not suitable for rangeland monitoring and regional assessment of drought impacts on its vegetation cover and seasonality.