GEOGRAPHICAL RESEARCH
Year:2002 | Volume:16-17 | Issue:4-1 (63-64)|Papers Count:25

Scholars have developed different ideas about the division of the Earth. This discrepancy can even be seen among the contemporaries. Furthermore, one's ideas appear differently in various books. There are also different interpretations seen in the translated copies of the works of these scholars. Scales and measures used by different scholars have not been of the same type either. Using various authentic sources, this article makes attempts to present a brief summary of a number of these views and map them on the new drawings. Some tables are also prepared to make the job easier.

In this paper I am concerned with structure of the debate over modernism and postmodernism in geography. Over the last decade human geography has undergone rapid change as geographers have explored new ways of thinking. I use postmodernism to make sense of the past, present and emergent pattern of social being that exist simultaneously in the space and also changes in our society as a whole, in other words in the mode of productions.

In order to determine the types of rain producing weather in Tehran, the rainy days of the station (days with more than or equal to 1 millimeter) were identified during the 1990-95 period. The 12 GMT pressure and height data of the area 200-47.5° and 35°-67.5°E were -extracted from the NCEP Reanalysis file for the grid points 2.50 apart. The synoptic systems and flow directions were determined according to the objective method of computing vorticity. The results first showed 24 pressure patterns for the three groups of light, moderate, and heavy precipitation days. Then these patterns were re-grouped according to their similarities into 10 weather types. These types consist of two cyclonic and anticyclonic, and 8 directional types corresponding to 8 geographical directions. The most frequent type was the Easterly and the most important rain producing type was the cyclonic type. The anticyclonic type was the least rain producing type. Cyclonictypes were more dominant and developed mostly in winter. The anticycloictypes showed lower frequency and concentrated in spring.This study showed that the vorticity computation method is very effective and accurate and capable of quantifying the power of the weather types. The 500 hpa level had more significant effect on the precipitation than the surface pressure changes. The Syrian trough was the most important upper level system which controls the precipitation of Tehran.

There is a complication in the interpretation of Quaternary paleoenvironmental conditions within the Iranian Plateau due to its geographical situation between the area dominated by high-pressure system of Arabia. The monsoon rainfall regions of South Asia, and the winter rainfall area of Eastern Mediterranean region. Furthermore, the paleoenvironmental reconstruction of Iran during Quaternary, the impact of Siberian highpressure system and the effects of topographical characteristics have to bear in mind.The lakes and playas of Iran, which have been developed within structurally -tectonically - controlled basins, have considerable evidence of climatical changes. Such evidence can be seen from the highest to the lowest parts of the basins. For the studying of Quaternary paleoenvironmental conditions of this region, a wide range of data and information have been used by scientists with different disciplinary methods. Without considering the nature and specific conditions of individual basins, their interpretations can lead to misunderstanding of the paleoenvironmental trend in the area. The aim of this paper is to summarize and evaluate the findings from some of the lakes, mostly in the marginal parts of Iran, and to introduce a new scenario on climatical changes within the Iranian plateau.

Temperature is one of the most important climatic factors. Fluctuation in this factor on a global, regional or even on a local scale is more or less influenced by the teleconnection Phenomenon.In this research we tried to recognize and study the role and effect of the fluctuation of North Atlantic Oscillation (NAG) and Southern Oscillation Index (SOI) on the temperature fluctuations in JASK.Primary studies showed that during the last century the general trend or JASK temperature has been influenced by the long term act of the NAG and SOI. This relationship can be more seen in the coefficient of variation of some months of the year. But it is not seen in the general component of the inputs.Therefore, after studying various components of the temperature, different components of NAO and SOI have been studied and compared with each other.In this way it has been shown that the temperature trend has been increasing and NAGS 2nd SOI trends have been decreasing. Thus it seems that in long interval, increasing trend in JASK temperature influenced by the level of NAO and SOI decrease. And comparing the oscillatory components of NAO and SOI influenced JASK temperature and ultimately they justify 40 percent of the temperature oscillatory component change.

One of the basic researches in agriculture is determining the place and the time of occurance of the cold and freezing periods in each region. This will help farmers to protect their crops from such events. Recurance intervals for temperature thresholds of each crop and forecasting the special and temporal changes of air temperature are the main points of such research. Data of the minimum temperature of Tehran station was analysed for a period of 47 years. Occurance of Fail first freezing and spring late freezing with different probability levels were studied. The results show that on average, the date for the occurance of first freezing is November 30 with a variance of 51 days. The study showed that the spring freezing takes place during April 7 to April 13 and fall freezing occurs during December 17 to March 20 for 93 days.

During the 1360 years between the establishments of Media Empire to the fall of the Sassanide, only five dynasties governed Iran. Ruling a vast geographical area during the period of Achaemenids (Hakhamaneshee) dynasty which was six times greater than present Iran, with variations in physical, natural, and human geography the governments required a very systematic administration.In the course of this long period, two types of ruling systems were exerted: The Ashkanid and Satrapid. At the same time these two systems brought about different cultural and civil views that their traces are still evident. Even the divisons of the country, in governments after the rise of Islam have been under the influence of these two ruling systems.

At present, there isn't a clear and generally accepted definition for the term "Monsoon". Parameters used for studying monsoon are also quite different. S1fmmer monsoon affects east part of Afghanistan. In spite of climatic variety and wide mountainous area, network of meteorological stations of Afghanistan often lacks sufficient and long-term data. Monsoon circulation is originated by formation of thermal lows after June until September. The lows of L1 and L2 in Pakistan and Afghanistan are representatives of Intertropical Front (ITF). Within the low of L1 exists shallow maritime airmass, but there is warm continental airmass in L2. In most parts of Pakistan monsoon rainfall includes nearly 50% of total precipitation, whereas in Afghanistan monsoon rainfall is short and limited to eastern part of the country. Afghanistan monsoon rainfall falls into isolated storms with great time intervals. The monsoon circulation should be set before its first low reaches the country. The first stage of monsoon starts the second half of May until the beginning of June and its peak period is established when the first low reaches in early June and the last storms in August and September. It is expected that westward penetration of maritime airmass over Afghanistan in advancing periods of monsoon occurs in upper levels. Conditions of monsoon in Afghanistan are nearly similar to West Africa regions and furthermore it is complicated by Hindu Kush Range. Last limit of monsoon penetration reaches around north and northwest vallyes of Kabul, and Hindu Kush blocks its further penetration to west. One of the monsoon's features is periodic and non-periodic displacement of ITF. Its reason sets in consecutive displacing of continental airmass with maritime one and vice Versa. Another interesting feature of monsoon is its breaks. This phenomenon is established by temporal retreat or chang of monsoon airmass stratification due to penetration of midlatitude troughs to south and subtropical regions.

In this article, the temporal and spatial patterns of daily rainfall have been analysed, and for so doing, the data of 22 synoptic and climatological stations in west of Iran have been adopted for a 20 year period from 1971 to 1990. At first, advanced statistical approaches including factor analysis have been carried out and the matrices of daily rainfall obtained from 5 regions, and then the synoptic analysis has been done for two levels of 500 Hpa and earth surface. The study of synoptic patterns of daily precipitation in 5 regions in central, southwestern, eastern, northeastern, and northwestern parts indicate that there is a considerable difference between the synoptic patterns of precipitation between the surface level regions and 500 Hpa heights.

During the 20th century, Iran unwillingly and unreasonably, has been subjected to invasions by foreigners for three times during which all or parts of the country were occupied. However the governments and people dealt with these in completely different ways. Although these differences in part stem from political-security policies of the states, at the same time have their roots in the different ideological positions of Iranians. Throughout these periods one can see the extent to which Iranians converge on or diverge from the government ideals. One way to know about the extent of people's convergence on these ideals would be the degree of their participation and particularly their devotion to and self-sacrificing for the objectives of the government. This investigation, for the first time, has tried, through a statistical analysis on the martyrs of war and sacred eight year defense, to illustrate the extent of people's devotion in this; period and present an outlook on the geography of martyrs.

In order to evaluate the effect of irrigation regimes on yield and growth parameters of cumim [Cuminum cyminum L.] an experiment was implemented in Mashhad during the years 1998-2000. Six irrigation treatments were used as; T1: No irrigation during growing period (rainfed). T2: One irrigation during the flowering stage, T3: One irrigation during the seed formation T4: Tow irrigation during the growing season: one at the flowering stage and one at the seed formation, T5: Three irrigation during the growing season: one after germination, one at flowering and one at seed formation stage, and T6: full irrigation during the growing season. During The growing season, treatments of rainfed and full irrigation received 190 mm and 350 mm of water respectively. The resuets showed that by reducing numbers of irrigation in various treatments, plant water potential also decreased. It reached to-30 bars without showing any sign of witting in T1 as compared to-15 bars at T6-Seed yield the number of umbells per plant and the number of seeds per umbeI1swere not significantly different at 5 percent level of significance. However, treatment T6, showed to have the least weight or 1000 seeds and harvest index and highest total biomass. Differences between Height of 1000 seeds of 11 and harvest index in T3. T4, T5 and total biomass of T1, T2, T3, T4 with T6 were significantly different at 5 percent level. The overall results of one year experiment showed hat in Mashhad climatic condition, cumin doesn't need to be irrigated in normal years.

Historically, designing and utilizing different binds of models has always been regarded as a main principle by geographers. In the past decades, physical geographers have tried to solve the main problems and to answer the questions in the realms of physicalgeography. Therefore, they have experimented different modeling types for achieving the main predetermined objectives.Addressing these tasks, they have properly utilized the technology of their own age to reflect and to display the realities of the earth's surface by different models and styles. However, in recent decades, the surprisingly advanced technology in computer science, invention of the new observation tools, development of communication systems and the need for applied aspects have all brought about some essential changes in modeling strategies.The main purpose of the present paper is to address the role of different models to show the realities in the field of modern physical geography. Thus, first an introduction will be offered to emphasize the importance of some goals in physical geography. Then, the subject and characteristics of different models and methods of new modeling systems will be discussed.