فهرست مطالب mehrdad hoseini

One of the basic and most fundamental factors in the structure of the planet is the climate. There is no doubt that humans, living things and manifestations of life on the Earth are affected by climatic conditions and atmospheric phenomena. Inappropriate distribution of dry land and water, different latitudes, passage of atmospheric systems, heights and elevations covered by snow and ice, dry desert without water and grass, forests covered by trees,... In different regions of the planet, has created different climatic conditions, in such a way that in the broad geography of the world, atmospheric and hydrological hazards such as floods, storms, thunder and lightning, fatal cold, overwhelming heat, etc., annihilate thousands of humans and living organisms annually, or bring about many financial and environmental losses. In this regard, today's civilized human is releasing into the atmosphere millions of tons of carbon dioxide and toxic pollutants annually in order to gain industrial agriculture, so that greenhouse gases have formed a dark blanket on the ozone layer, and this harsh and fatal contamination has seriously threatened the lives of humans and living beings. Therefore, today's violent climate and humans have caused climatic changes in micro and macro climatic levels. Therefore, it is desirable and imperative to identify and investigate climatic changes and to prepare research plans in order to overcome the hydrological atmospheric hazards and to reduce and control pollution and human industrial toxicants.

Precipitation is a climatic element that changes year by year, and in fact precipitation is a random variable over time. If long-term precipitation data are available, the probability of occurrence of precipitation can be determined by statistical methods. In this study, the city of Semnan has been selected in order to determine the probability of annual, seasonal and monthly precipitation. Precipitation data in this city have been analyzed using computer software and statistical methods. Wet and dry periods, seasonal and monthly variations in precipitation and the probability of occurrence of seasonal and monthly precipitation have been determined.

Climate change in Iran and the world is considered by most scientists to be due to the emergence of “greenhouse” state that will have adverse effects on the Planet from different viewpoints. Due to human interference in climate change, undeniable climate change has been asserted in various world reports and the latest statements by the International Community, but scientific doubts also exist on reasoning behind climate change reported by “CHANGEINTERGOVERNMENTALPANELONCLIMATE”. As BRYSON (1977) states, surge from one pattern to another might change the climate of some of the mid-range-latitude areas drastically, and it is very likely to create a “drought-or-flood” pattern. The increase in temperature in some of Iran's meteorological stations indicates a tendency towards arid climate, and probably the period of climate change has begun in the country of Iran. The country, according to the research, has a pattern of a number of years of droughts alternated by a number of rainy years. Environmental problems such as global warming, frequent occurrence of droughts, expansion of deserts and the increasing trend of desertification, increasing number of forbidden areas for the extraction of water and occurrence of destructive floods have caused ecological instability in the country and have increased the vulnerability of the country's natural resources.

Rainfall is a climatic element that changes year by year, and in fact rainfall is a random variable over time. If the long-term rainfall data are available, the probability of occurrence of precipitation can be determined by statistical methods. In this study, the city of Semnan has been selected in order to determine the probability of annual, seasonal and monthly precipitation. Precipitation data in this city have been analyzed using computer software and statistical methods. Wet and dry periods, seasonal and monthly variations in precipitation and the probability of occurrence of seasonal and monthly precipitation have been determined.