GEOGRAPHICAL RESEARCH QUARTERLY
Year:2008 | Volume:39 | Issue:62|Papers Count:17

Long-term historical weather data are needed to conduct crop simulation analysis. Simulated climatic data may be used when long series of historic data are not available or convenient or when future data are needed. The aim of this study was to generate daily weather values for maximum and minimum air temperatures. A number of weather generators are compared here. Data from ten stations in Iran with long-term complete weather records were used to compare actual with generated data sets. The accuracy of the different models was assessed by means of three widely used statistics: coefficient of determination (R2), root mean square error (RMSE), and mean bias error (MBE). The calculated values of temperature are generally in good agreement with the data derived by the observation.

A major part of Iran includes mountain areas. one of the hazards which threaten these areas is the slope instability. Each year the occurrence of this phenomenon causes a lot of damages to the slope lands which are exploited by man. one of the most lot hazardous of these instabilities is landslide. The goal was to investigate the causes of this process and the methods of its stabilization Also. A case study was performed with the aim of zoning the landslide possibility in order to map the present slides in Jolesan Basin (one of the subbasin of Chalkrood). This basin is located in Mazanderan province at the west of Tonekabon city. Due to certain geological, geomorphologic and climatologic condition and also the way of exploiting the land. This area is considered one of the susceptible areas for landslide. Destroying forests, roads, villages and farms are among damages cause by this process and can be seen frequently. For investigating and zoning landslide in this area, at first, the map of main factors in causing this process was designed. Then, using the interpretation technique of satellite images ETM+2002 and field work (GPS). All present slides were identified and registered on the map. Then, by integrating the factor map with landslide map through LNRF model. The numerical amount of each factor was calculated and the percentage for slide occurrence in different units of each map was estimated. At the end. The zoning map of landslide risk with overlaying different information levels was product. the result shows that LNRF model Has excellent efficiency for studying the data and zoning landslide especially in humid areas.

Identification & supervision of fluctuations in physical ecosystems have a special place in optimum using of natural resources. Urmia lake is the largest interior natural lake of Iran which its potentials and ecosystem & environmental characteristics attracted researchers and environmental planners attention. Fluctuations in area and perimeter of the lake attracted many attentions in recent years and some reasons presented for that, but there is not a documentary research in the matter, yet. We used satellite Landsat TM, ETM images and LISS? all together with time resolutions of 1987, 1998, 2001, and 2002 to determine area fluctuations and providing distribution of suspended material map of the lake. Also, we used on screen digitizing for extracting perimeter borders of the lake in time periods after processing and detecting of images and then for providing distribution of suspended material in the lake, we used clustering method. The results of research shows that, maximum area of the lake was in 1998 and minimum attributed to 2002. Also the research shows that suspended material pattern, which indicated the amount of deposited, and concentration of material, in margins of martyr kalantary expressway, is recognable and their distribution pattern has remarkable fluctuations in periods of time. This shows that environmental changes are happening in the region. In this paper someprobable affecting factors in the fluctuations considered and some suggestions for further studies presented, also.

Many researchers have recently considered the use of data obtained from Remote Sensing (R.S) to reveal changes. In the present study, we have attempted to reveal the morphodynamic changes in Taleghan river Basin through image satellite and by analyzing the principal component analysis (PCA) and Fuzzy Logic. The final map indicates the intensity of changes through, 15-years interval observed (1987-2002).The results showed that the most intensive changes were beside flood pasts and slopes, and also in the course of Taleghan River. The least intensity of changes was also found to be in mountainous region and rocky lands of the basin under investigation. Land use is one of the factors that influence the morphodynamic features of the basin. Geomorphologic and morphodynamic forms, therefore, change according to the type of land use. In this research we have compared land use changes during the 1988-2002 intervals.

In this study we have used the monthly data resulted from the calculation of temperature and precipitation for a 52-year period (1951-2003). The doubling effect of carbon dioxide on temperature and precipitation was modeled as the most important climatic parameters. The resulting Hythergraph and Ambrothermic models for Tabriz indicate monthly increases of temperature and precipitation during the doubling periods. A comparison of the present and simulated Ambrothermic models applying Goddard Institute of Space Studies (GISS) shows precipitation and temperature changes in Tabriz. A decrease in the duration and intensity of cold period and freezing days, a reduction in spring and winter precipitation, a shift in precipitation from snow to rain, the extension of growth season, the increase in temperature and the resulting dryness are the signs of such changes.

In this study we have used the monthly data resulted from the calculation of temperature and precipitation for a 52-year period (1951-2003).The doubling effect of carbon dioxide (CO2) on temperature and precipitation was modeled as the most important climatic parameters. The resulting Hythergraph and Ambrothermic models for Tabriz indicate monthly increases of temperature and precipitation during the CO2 doubling periods. A comparison of the present and simulated Ambrothermic models applying Goddard Institute of Space Studies (GISS) shows precipitationand temperaturechanges in Tabriz. A decrease in the duration and intensity of cold period and freezing days, a reduction in spring and winter precipitation, a shift in precipitation from snow to rain, the extension of growth season, the increase in temperature and the resulting dryness are the signs of such changes.

Many people know the important effects of Caspian Sea winds and storms on the economy of three provinces of Iran including Gilan, Mazandaran, and Golestan that they form one exclusive and extent area which have moderate and humid climate. This paper used a synoptic climatologically approach, which combine a number of atmospheric factors. Using daily and monthly winds data including their speed and direction for determining of 61 wind waves (1983 to 1985), and then 20 representative ones and analyzing daily air maps, 13 synoptic patterns of troughs, and polar front jet stream (PFJ) at 500 hPa level, and Siberian High is produced during the peak days of wind waves and middle days of calm periods. Results indicate that much of troughs grouped in the west of Caspian Sea during the peak days of wind waves but they were completely scattered during the middle days of calm periods. Also, the northwest-southeast direction of trough axes and FPJ location between 40 to 50°E confirmed that troughs have dominant effect for the appearing of sever winds. Finally, the schematic and tridimentional pattern of southern Caspian Sea winds as another result showed during autumn, dominant wind speed is lower than winter. This can be the principal factor of maximum rainfall during autumn in study area.

Recognition of effective factors on landslide occurrence and so high and low hazard region is one of the most important and necessary works for mitigation of landslide damages. In this study, from all of the effective factors on landslide occurrence, land use changes and road construction, into a parts of Tadjan watershed with area about 708.08 square kilometers in south of sari, was studied. In study area was detected 68 landslides with using aerial photos and comprehensive field works, then landslides was located by GPS and was mapped in GIS environment. Also, some information of landslide gathered by questionnaire and field works. For evaluating the effect of land use change in landslide occurrence, after preparing land use map and its correction with using interpretation of aerial photos dated 1373, questionnaire analyses, field works and using GIS software integration, it is indicated that 35.28 percent of landslides with area of 34.81 hectares was occurred in regions that land use transformed from forest land to dry land farming and garden. Also, after preparing of roads map with using topographic map and its correction with aerial photo, analysis of questionnaire information and GIS techniques, it is concluded that most landslide occurrence density was take placed into maximum distance of 75 meters from road with 21 landslides and density of 0.219 ( per square kilometer).

The averages of monthly minimum temperature and wind speed in 32 synoptic stations in northwest and west of Iran used for calculate windchill temperature from November to April. Then maps of spatial differences were drawn for every month and windchill regions classified by cluster analysis.

This research attempts to investigate the role of the blocking systems in surface cyclogenesis over eastern Mediterranean sea; but particular attention is focused on the flood of Iran during march 2000 over western states of Iran as: Hamadan, Ilam, Lorestan, Kermanshah, Kurdestan, Zanjan, Ghazvin.The data used for this research includes upper level and mean sea level pressure charts every 12 hours during 15 to 27 March 2000 from NCEP center, also The data of temperature, pressure, humidity studied every 3 hours and data of daily precipitation totals studied from 19 important Iran synoptic stations during 1 to 30 march 2000.Results shows that: the trough in eastern flank of Atlantic Ocean blocking system was the main reason of March 2000 flood over Iran; During blocking system activity in east of Mediterranean sea, the splitting of jet stream has occurred near the second ridge over Iran and it has intensified low pressure systems the near west of Iran; The development of Sudan low pressure system has caused enhance the intensity the eastern trough of blocking system and lead to flood over west of Iran.

Many indices designed by researches for study of human-biometeorology and bioclimatology that today broadly using for assessing the relationships between the climate and tourism .Among the proposed indices, thermo- physiological indices as PET and PMV that derived from human energy balance models, important from others. To define of proper calendar for tourism in Tabriz we have used of thermal-physiology indexes. Conclusion of this study that was done with Ray Man Model show there are a lot of time limitation for tourism in Tabriz because of limited days of thermal comfort. With regard to concluded results of mentioned indexes, thermal comfort in Tabriz is not more than 45 days, While Period of Cold stress is more than 240 days and heat stress is about 80 days. Thus cold weather is the principal problem in regard to tourism climatology in Tabriz. It is necessary and vital for related organizations, trip tourism executors and voyager that have more notice to this critical subject.

This research has been carried out with the aim of the determination of the land-use changes of the forests in the protected area of Arasbaran. The determination of the changing points and the factors influencing these changes by the use of GIS and remote sensing are the main aims of this research. Accordingly, the satellite pictures pertaining to the years 1987 and 2005 along with other necessary data were gathered. Thereafter, the required data such as topography, the land-use, the roads, settlement centers and so on were entered into the GIS environment. The radiometric correction activities, the geometric correction, the image classification, and finally, the uncovering of the land-use changes were carried out. Then with the combination of the parameters affecting the land-use changes of Arasbaran forests such as the settling areas, the height surface, the gradient, and so on the factors affecting the changes in Arasbaran forests were discovered. Accordingly, at first the 6 km. domain was selected as the space affected by the villages. The height surfaces were also calculated based on the Digital Elevation Model (DEM). Based on this finding, the area surface gradient was also estimated. By the use of overlaying method, the relationship between the changed areas with the existing parameters and also the amount of area were calculated. The results indicated that among the affective elements in the land-use changes of the Arasbaran forests, the settlement center have been the main factors in the changing trends which should be seriously taken into the consideration for the future planning.

In this article the relationship between the amount of seasonal rainfall (autumn, winter and spring) and climate indices in Iran have been studied. The Climate indices (the Southern Oscillation(SOI),the North Atlantic Oscillation(NAO), Arctic Oscillation(AO),NINO 3/4,The Multivariate ENSO Index(MEI),Trans_ NINO Index(TNI) and the Pacific Decadal Oscillation(PDO) are used as independent variables. The monthly data of 25 synoptic stations have been used from 1951 to 2003. These stations have the long term data and can cover the most rainfall regions in Iran. The results of this regression analysis show that the relationship between the amount of spring rainfall and climate indices is week. Also the study shows that among of ENSO indices, the NINO 3/4 has more strong relationship with the amount of autumn and winter rainfall. SOI and MEI are in second rank. It seems there isn't significant relationship between PDO and TNI with seasonal rainfall (autumn, winter) has been shown. The relationship between autumn and winter rainfall with MEI and TNI is positive while about SOI is negative. This study also identified that the effects of AO and NAO over the amount of winter rainfall is more than the amount of autumn rainfall. The relationship coefficient between autumn and winter rainfall with NAO and AO is negative therefore there is an inverse relationship between autumn and winter rainfall and AO and NAO indices.