فصلنامه جغرافیای طبیعی
پیاپی 18 (زمستان 1391)

In order to study of dust storm of Bushehr Province¡ all dust storms events collected and recognized as different patterns. The 24 February 2010 event selected as study sample and using graphical and calculational method¡ speed and direction in sea level and 500 hPa¡ vertical lifting speed of air mass from ground to 500 HPa maps prepared and analyzed. The result of this study indicated that in the study period¡ occurrence of blocking and vorticities in 500¡ 600 and 700 hPa¡ intensity instability and convection in all atmospheric levels from 1000 to 500 hPa and positive vorticities in 500¡ 600¡ 700 and 850 hPa observed. Also creating an anticyclone system in north of Caspian Sea obstacles of movement of this blocked system to east. At this time in Sudan and south of Saudi Arabia prevalent an intensity thermal convection system.

Today¡ air pollution is one of the most problems that devoted many studies due to destructive and harmful effect on the human health¡ animals and ecosystem through the world and also Iran. Accordingly¡ various measures has taken place to air pollutants detect¡ published source detection¡ published rate determination and its control and management methods. In this research¡ Kurdestan province was selected as the study area for proximity with Iraq country and as much existed dust phenomena. Also¡ 11¡ 14¡ 16 days of May¡ 1388¡ 1389¡ 1390 years were studied because this area has dust phenomena in spring month especially May month. To estimate dust rate in this area and study time zone¡ TOMS sensor images of Nimbus7 satellite were prepared due to its ability to detect types of particles in air on absorption properties and their sizes¡ and per processing operation was done on them. Then dust types rate was calculated in this area by applying dust index (Aerosol Index) that is sensor product. Comparing results derived from this index can conclude that without dust type rate and middle dust have reducing trend overall and weak and Severe dust have increasing trend. As the severe dust has to be an increasing trend.

To identify various effective factors in the earthquake occurrence and seismic hazard zoning maps preparation with different parameters¡ are the initial actions and proper effective solutions in order to reduce loss of slope movement. In writing this investigation¡ at first the research framework was determined. Thus¡ a descriptive and analytical method based on library studies¡ using existing documents¡ previous research articles¡ natural and human factors¡ with field visit¡ photography¡ using GPS devices and finally using hierarchical analysis method and ARCGIS were analyzed. This research has been done in Masal whose total area is 190. 782 square meters with the purpose of seismic hazard zoning and identifying the areas prone and with the high potential to landslides. In this investigation effective natural and human factors and variants have been used. At first initial maps such as¡ topographical map scaled 1.25000 and geological map scaled 1.100000 have been prepared¡ classified and pressed. Initial layers have been entered in Geography information system (GIS) environments which have been including natural and human factors such as¡ roads¡ preserve land¡ raining¡ channel¡ geological units¡ faults¡ heights¡ and slope sides of Masal. Then redundancy of every aforementioned variants when encounter with earthquake occurred¡ have been evaluated. After comparison between named factors by the use of Analytical Hierarchy Process (AHP) analysis in matrix tables in order to determine the relative weight have been done. The process continued by the sum of products of scale''s significance and in factor''s weights¡ final weight is attained. At the end¡ after compounding the location layers and data bank prepared from these factors in Geography information system (GIS) environments¡ seismic hazard zoning map in 3 levels including; safe¡ less dangerous¡ most dangerous also is attained.

The main feature of the Earth system is climate changes altering climatic elements such as precipitation and temperature¡ in short and long-term periods. Drought is one of the climate changes affecting on several arid¡ semi-arid and even wet regions of the world with different intensities. The main goal of this study is investigation on the synoptic effective mechanisms in order to identify the monthly dry periods in the southern coasts of Caspian Sea as well as presenting its patterns. First of all¡ in order to recognize the patterns affecting on the drought of this area¡ 30-year statistical data (1977-2006) extracted and then¡ the wet and dry months were identified using the standard score index (Z). Afterwards¡ the synoptic maps were provided using the Grads software based on geopotential data and the pressures of the sea levels¡ 850¡ 700¡ 500 hpa. Moreover¡ these maps were used to extract the relative pattern. Statistical processing of precipitation and temperature data illustrates that in most of the wet months¡ standard precipitation index (z) and temperature Z are positive and negative¡ respectively. Due to high rainfall¡ temperature is lower than normal and its reverse is observed in dry months. It means that the low rainfall coincides with the negative precipitation and positive temperature indexes. Synoptic maps show that Siberian high pressure and blocking system over Eastern Europe (located on the Ural Mountains) have the most influence on the southern coasts of Caspian Sea¡ Therefore¡ by means of creation of the blocking systems and their spatial displacement are originated the wet and dry periods in the area.

One of the most important environmental factors affecting agricultural production¡ climate and small-scale man Spending it can control costs is costly. So the only way to tackle climatic limits the cognitive constraints in terms of coping with them and the crop is managed. The present study for corn cultivation Zoning in Lorestan province¡ the climatic elements of temperature¡ relative humidity¡ and degree days of the ten synoptic stations in the Lorestan province additional environmental parameters were used for slope and soil PH. Among the important factors in temperature due to its more importance in degree of phonological form was investigated¡ then the zoning maps for the production of these crops GIS techniques were used. After the initial production of maps for definition matched layers and influential areas of fuzzy standard method were used. Finally¡ in order to integrate data based on the weight of the evaluation hierarchy (AHP) was used to map land prone Zoning corn planted in Lorestan province¡ respectively. Zoning results using these methods showed that 2.34 percent province¡ an area prone to these crops¡ 8.55 percent semi-prone¡ poor and 13.08 percent in 76.03 percent in province with poor conditions where results indicate is most desirable places in the West region¡ central and northern parts of the province are scattered.

Asemanabad river basin is located in northwest zagros mountain and in south of Kermanshah province and in west of Iran. Being young zagros geomorphologic landforms and studied district is result of continuing neotectonic movements in quaternary era. The goal of this research is tectonic evaluating of district active by using Asemanabad river drainage network analysis and comparing achieved results of geomorphic indices¡ geomorphologic documents and GPS data. Asemanabad River has mixed load and kind of (3B) and me Andric design as sinus shape in which width of river becomes wider in meanders. In this research several landforms field visits¡ geomorphologic indices (SL¡ AF¡ P¡ S)¡ topographic plans 1:50000 geological plans 1:100000 and aerial photos 1:55000 ¡ IRS satellite image 2002 in district¡ GPS data and ARC GIS 9.3 software¡ Envi 4.3¡ Corel drew x4 as research tool for analyzing district active tectonic has been used. The achieved results certify active tectonic movements as high appearance and shortage in quaternary and in northwest zagros and studied field. Layer traces¡ vertical wall influenced on river bed¡ cut meander¡ widening and interrupting river and High compression ratio are geomorphologic documents of tectonic effect on Asemanabad River.

Management of natural resources¡ accurate and timely data are necessary for operation and conservation of them. 3D visualization of vegetation as implemented in web platform in Way to display and navigate in the virtual environment is dynamic¡ will facilitate accessing to relevant experts in a simulated forest environment. The study area is the vegetative part of tropical in Oman Sea coast of Sistan and Baluchistan province. Due to the high dispersion of vegetation and the precision required¡ Using aerial photos provide a useful tool in preparing the database in GIS environment. In this study¡ spatial data and descriptive information about the degree of congestion¡ vegetation type and area¡ in order to visualization in Google Earth (GE) were used. The final results show that visualization of the three-dimensional data extracted from aerial photos with high precision is implemented in GE and adaptation of forest boundaries in aerial photos with their boundaries on GE has a significant accuracy. In addition¡ sharing of natural resources data in the context of Web will enhance the process of Management and decision-making.

In order to analysis short-term wet and dry periods and predict the occurrence probability of wet periods in 1 to days in the several climatic areas of Iran¡ the rainy days with 0.1 mm and more for 30 years (1976-2005) at 9 selective station were investigated by applying the tow-state¡ First-order Marcov chain. The important features in relation to short wet and dry periods as well as conditional and climatic probabilities¡ day¡ s abundant¡ the length of wet and dry periods and eventually the occurrence probability of 1 to 6 day periods were recognized. In all of these stations under study¡ the most abundant percentage of wet days occurs in winter and decrease in spring and autumn and the amount of reduction intensifies in the stations in the south¡ south eastern and central area of Iran. The maximum transition probability of two successive wet day (P11) occurred in Rasht¡ Khorramabad and Tabriz and the minimum P11occures in Zabol¡ Yazd and Bandarabbas. The more we move from the north and west to the south eastern of Iran¡ the more the climatic probability of wet periods (π1)¡ the length of wet period (E1) and the frequency of rainfall 1 to 6 days decreases and in the other hand duration of the weather cycle (Ec) increases. In all of station¡ the occurrence probability of one-wet-day is more than others and the more duration of wet period’s increases¡ the occurrence probability of them decreases.