نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
Abstract:
Introduction: Snowfall is a God-given blessing; But, if there is no comprehensive and codified plan to deal with it, this blessing may turn into a crisis. The purpose of this research is to investigate the cause of the Sever cold in Mazandaran in November 2016 and the most important atmospheric phenomena in 6-hour periods from a dynamic point of view. The investigation of the mentioned system was particularly important because of the weakening and strengthening of the Siberian high pressure, the northern Alborz high pressure and the low pressure accompanied by Cut-off low on the earth's surface during different hours of the day and night, the speed, direction and convergence of the wind changed significantly And because the main source of moisture in this system was the Mazandaran Sea, the atmospheric condition of different parts of the province is variable, and investigating the cause of these changes is one of the main goals of this research, so that it can be useful for short-term weather forecasts. In Mazandaran province, due to the changes in the distance from the mountains and the sea and the considerable fluctuations in height, it has led to the special topography of this region. For this reason, the distribution of atmospheric parameters, especially precipitation, is of particular importance. In the meantime, the question arises that with the movement of a wave from west to east, will the rains of this wave regularly affect different parts of the province from west to east?
Methodology: Synoptic maps were obtained from the NOAA website and station data from the National Meteorological Organization. The received data were integrated in Excel software. In this work, while presenting the preliminary topics and prerequisites in the field of atmospheric dynamics, the tables related to the rainfall parameters of the last 6 and 24 hours, temperature, atmospheric condition, direction and wind speed of 15 stations of Mazandaran, including 4 coastal stations, 5 plain stations and 6 It is a mountain station, it was checked in the period of 3 hours from the morning of Tuesday, November 22, to the morning of Friday, November 25, 2016. After drawing the maps, it was observed that according to the average from November 17 to November 30, 2016, in the cold core, the anomaly of the level of 500 millibars is less than -60, the sea level pressure anomaly is more than 9 millibars and the surface temperature anomaly is less than -12 Kelvin and based on these points, this system was analyzed.
Results and discussion: Considering that the formation of any heavy snowfall may not be caused by the occurrence of the blocking phenomenon, but the occurrence of continuous and heavy snowfall (4 days or more) can be related to the occurrence of the blocking phenomenon. At the end of November 2016, with the occurrence of blocking and the advance of a high pressure in the form of a diagonal from Eastern Europe towards the Siberian region in Russia, in the middle level of the atmosphere, a cold trough advanced from Siberia to the region, and on the surface of this cold trough, it was accompanied by the Siberian high pressure and A significant temperature severity occurred in the north of the country; So, since 1951, in some stations of the province there has been no record of seeing snow for the month of November. More precisely, since November 18, 2016, the 3 Teleconnection from the AO (Polar Index), NAO (North Atlantic Oscillation) and PNA (Pacific/North American Oscillation) cycles have gone negative at the same time. After passing the low-height center over the Caspian Sea, a high-height one advanced from Eastern Europe towards Russia, and a long trough was drawn from Siberia to the north of the country. On November 21, this trough turned into a a Cut-off low and on November 23 and 24, we saw the maximum power and influence of this Cut-off low in Mazandaran, so that the core of this Cut-off low with a numerical value of less than 540 decimeters was located in the north of Golestan and North Khorasan provinces. On the surface of the land, the Siberian high pressure was strengthened on November 18, so that the core of this high pressure was located in the north of Siberia on November 18, and on November 23, 2016, it settled in the north of the Caspian Sea and caused polar air flow in Mazandaran. From November 17 and 18, 2016, rains started intermittently in Mazandaran. With the intensification of the cold weather, since November 22, we have seen scattered snowfall in Mazandaran, and since November 23, we have witnessed snowfall in Mazandaran. This system left the east of Mazandaran on the morning of November 25, 2016. In the period from November 22 to 25, 2016, the peak of rainfall was associated with displacement at different times between different parts of the province.
Conclusion: The results of the present study showed that every rainfall does not necessarily progress from west to east in an orderly manner. Many times, a wave is moving from the western half to the eastern half, but its effect will not be the same in the eastern and western regions, and there is not necessarily a linear relationship between the movement path of precipitation systems and the amount of precipitation. Based on the investigations, it can be concluded that in order to make detailed short-term forecasts, before examining any pattern and understanding the concepts of weather, one must first gain sufficient knowledge of the topography and climate of the studied area. Because it was clearly observed that in the northern part of the country, especially in Mazandaran province, there is a significant difference in atmospheric parameters sometimes in short distances and even in short periods of time.
کلیدواژهها English
