Kamal Omidvar
Abstract
Abstract
In most parts of the country, especially at high altitudes, the predominant form of precipitation is snow, which can be considered as the main source of water for rivers, springs, underground watersheds and Qanats. The heights of Yazd province are also one of the snowy areas of the country ...
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Abstract
In most parts of the country, especially at high altitudes, the predominant form of precipitation is snow, which can be considered as the main source of water for rivers, springs, underground watersheds and Qanats. The heights of Yazd province are also one of the snowy areas of the country because of geographical location and topographic conditions. The purpose of this research is to synoptically-dynamically identify, study and analyze the snowfall in Yazd Province. For this purpose, 12 snowfall periods were identified during the statistical period of 1999 to 2011 after identifying the geographical location of the area and with regard to the required data. To identify the motion of the air mass and to study the synoptic systems of the province, daily snow and rainfall data and synoptic maps of the land surface and upper levels of the atmosphere, jet stream, omega, circulation and humidity advection were extracted from the NCEP/NCA base and the related maps were plotted in the GrADS environment. Three synoptic and pressure patterns were extracted after conducting climatic thermodynamic researches affecting Yazd province and studying dynamic properties in terms of strengthening and weakening of pressure systems and their synoptic analysis. In the first pattern, the low-pressure combinative systems of the Eastern Mediterranean and Sudan along with the deepening of the Eastern Mediterranean troughs and the penetration of cold weather cause snowfall, especially on the highlands of Yazd province. In the second pattern, the emergence of the blocking phenomenon causes snowfall and severe cold in Yazd province. This phenomenon occurs along with deep troughs of the Eastern Mediterranean and the Red sea leading to cold weather and snowfall for several days. In the third and final pattern, with the establishment and high pressure penetration of the Caspian Sea and the Siberia and the creation of a cut-off low-pressure phenomenon in the central and northern parts of Iran, a snowfall occurs in the central regions of Yazd province.
Fatemeh Dargahian; Gholam Hossein Rezaei
Abstract
Since the temperature declared by meteorological stations is the only reading of the temperature inside the screen box regardless of other atmospheric parameters including humidity, it cannot therefore indicate our real sense of the air temperature, because warm air is sensed warmer in case of high humidity, ...
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Since the temperature declared by meteorological stations is the only reading of the temperature inside the screen box regardless of other atmospheric parameters including humidity, it cannot therefore indicate our real sense of the air temperature, because warm air is sensed warmer in case of high humidity, so that when the temperature is 35 ° C, it is felt about 43 ° C if the relative humidity is 55 percent. In this paper, the method of calculating the heat index was used to calculate the real sensed temperature in warm months of June, July, and August for a period of 10 years in 40 synoptic stations in the southern part of the country, and the results were zoned in the ArcGIS software environment as the real sensed isothermal maps and were compared with common isothermal maps. The results show that during the warm season, despite the fact that the southern coastal regions of the country show lower temperature, but have a higherreal sensed temperature, which reducesby getting away from the coast and the reduction of the humidity. In the southern coastal regions of the country, the high real sensed temperature, especially when the heat waves are created, causes problems for the people. Given the real sensed temperature thresholds, the frequency of problems was classified in four categories, each class creating special conditions. The synoptic conditions of a heat wave, which have led to the increase in the real sensed temperature, and the location of coastal stations in extremely dangerous conditions, were investigated. The results show that the prediction and timely warning issuance of heat waves, by the meteorological organization based on this indicator for the warm and humid regions of the country, can lead to the reduction in the casualties caused by this event.
