چکیده:
Among the most important atmospheric hazards that create unfavorable conditions for drivers, one can mention snowfall and rain, icing, fog occurrence, and storms. Usually, snowfall and icing create more dangers for drivers compared to fog occurrence, with the difference being that snowfall and icing can be predicted with probability and even controlled with equipment such as snowplows and salt spreaders if necessary; wind prediction is also usually accurate, and the resulting dangers can be locally reduced by precise design of parts of roads, bridge structures, and also the deployment of windbreaks; however, fog is an atmospheric disaster that is very difficult to predict, and the reason for this is the temporal and spatial changes of this atmospheric phenomenon (18, 1972, MooreCooper, ). Fog is one of the atmospheric phenomena that directly and immediately affects transport safety. The presence of fog, especially thick fog, is accompanied by a reduction in traffic volume on roads and an increase in the risk of road accidents. In this research, in order to investigate the climatic conditions affecting transport safety and determine critical thresholds, meteorological data (visibility less than 1000 meters) across the country has been analyzed. In this study, to facilitate the application of results in research centers, data extraction has been performed based on solar materials. By examining (1). This article is from the results of the project for zoning and feasibility of weather forecasting for the country's roads, which is being implemented with the accreditation of the Transport Research Institute, by the Amirkabir Research Institute, and with the support of the National Meteorological Organization. The above data were determined at 120 synoptic meteorological stations over a ten-year statistical period for the temporal and spatial distribution of vulnerable points based on critical thresholds. Accordingly, the provinces of Khuzestan, Ardabil, and Sistan and Baluchestan have been identified as the most important critical regions. Finally, given the increasing trend of vehicle production and increased traffic, the need for expansion and development of new roads arises; therefore, the role of climatic studies in this stage, much like the maintenance stage of existing roads, will be very important.
خلاصه ماشینی:
Usually, snowfall and icing create more dangers for drivers compared to the occurrence of fog, with the difference that the occurrence of snow and icing can be predicted with probability and even, if necessary, can be controlled with equipment such as snowplows and salt spreaders; wind prediction is also usually accurate, and the resulting dangers can be reduced by precise design of parts of roads, bridge structures, and also by local deployment of windbreaks, but fog is an atmospheric disaster that is very difficult to predict, and the reason for this is the temporal and spatial changes of this atmospheric phenomenon (Moore, 1972, 18, Cooper, ).
In the southeast of the country, besides the monsoon winds, the 120-day Sistan winds also play an effective role along with dust in creating conditions of visibility less than 1000 meters, and in this month, the stations of Khuzestan province and the islands of the Persian Gulf are most involved with this phenomenon (Figure 4-A).
One of the most important reasons for the frequency in the Persian Gulf islands is the phenomenon of humidification resulting from the establishment of a subtropical high-pressure system and the entry of seasonal moist air from the southeast and the Sudanese system from the southwest of the country (Figure 3-C) (Refer to the page image) Data and Research Method In this research, in order to examine the climatic conditions affecting transport safety and to determine critical thresholds, meteorological data (visibility less than 1000 meters) across the country were analyzed (Habibi Noukhandan, 1383).
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