صنم کوهی

Torrential rains because of the suddenness of damage in different parts of the infrastructure, construction and agriculturalareas of high rainfall regions of our country, especially in Regions with abundant rainfall. In the presentstudy, we have identified sea level pressure patterns and analyzed the synoptic and thermodynamic conditions of superheavy rainfall days in Golestan province.For this purpose, first, using ground station data and taking into account twothreshold conditions above 98% percentile and over 50% incidence, 15 days of super heavy rainfall were extracted duringthe spring of the 1970–2019 statistical period.Sea level pressure data are extracted on 0.25 /0 0.25 degree arc cells at 10 to70 degrees north latitude and 10 to 90 degrees east longitude from the European Mid-Term Forecast Center (ECMWF)Were. Cluster analysis by Ward integration method was performed on the sea level compressibility matrix data for15 days of super heavy rainfall and 3 synoptic pressure patterns observed during spring super heavy rainfalls eventsof Golestan province. The results of the synoptic analysis of the maps showed that during the heavy rainfall events,tabs of cold pressures based on Europe, Russia and Siberia and multi-core warm pressures located in the Arctic, mideasternregions of Iran, Pakistan and Aral and Balkhash Lake are spread northeast of Iran and Golestan province.Theseconditions have created active frontal zones and consequently severe pressure gradient in northeast and atmosphere ofGolestan province and have led to super heavy rainfall days in the study area. The results of moisture flux convergencefunction analysis also showed that the highest moisture flux convergence was at lower atmospheric levels (1000 and850 hPa) and by Caspian, the Persian Gulf and Oman water resources, respectively. But in the middle levels of theatmosphere (700 and 500 hPa) with the zonal atmospheric currents, In addition to the Caspian Sea, Mediterranean andBlack seas sources have also been responsible for the moisture supply of these rainfalls.

Synoptic analysis of Iran’s northwest dust storms This study was conducted to identify the effective synoptic patterns in creating dust storms using hourly visibility data and considering the meteorological codes related to the dust phenomenon in 8 meteorological stations located in East and West Azerbaijan for a period of 14 years (1996-2010). Then, using the network data of the US Center for Atmospheric and Oceanic Forecasting, the scan-synoptic characteristics of each dust storm were analyzed. The determination of the main sources of dust for each of the selected storms was performed using the Lagrangian model of dust particle tracking and using the regression tracking method. The results show that most dust storms in the northwest of the country occur in spring and May. Also, 2008 and 2009 had the highest frequency of dusty days. The synoptic view found that the pervasiveness, durability, and intensity of dust storms were consistent with the location of low-pressure surface systems located in western and southwestern Asia. In the synoptic study of the association of dust storms, 3 sea level pressure patterns with different arrangements were identified as the main patterns at the time of the storms. The results show a strong pressure gradient due to the expansion of warm low pressures from southern latitudes and cold high pressures from high latitudes to the west and southwest of Asia and the rise of dust particles from the ground and dust currents blowing towards the research area with The southwest-northeast direction is by low depth trough based on dust sources in Syria, Iraq and Saudi Arabia in the middle levels of the troposphere. Key words: Dust storm, Low pressure, LAGRANGIAN particle tracing model, low depth trough, North West of Iran Key words: Dust storm, Low pressure, LAGRANGIAN particle tracing model, low depth trough, North West of Iran.

In this study, first pollutants concentration data was obtained. After that for atmospheric right scrolling with using RAOB software and high level atmospheric data of Mehrabad station draw the thermodynamic chart (SKEW-T).In order to analyzing the atmospheric circulations with using European among scale center data base (ECMWF), the related maps draw in GRADS software. In this research, first seasonal trend and number of Pervasive polluted days in a time period of 1390-1396 extracted and analyzed. The founded expresses decreasing trend in pollutants concentration like PM2.5, O3, CO,SO2 and increasing trend in NO2, PM10 concentration in a understudy time period. After that with determining most intensive and inclusive polluted days, paid to analyze the synoptic selected samples. In winter and spring season with penetrating migrant cold high pressure on north half of Iran in sea level and stretching a high pressure on Arabia and Iraq countries in mid troposphere level and confirm to sea level high pressure, was the dominant condition in a time of inclusive and severe pollutant occurrence. Also in the summer and fall season similar to them with settling the high pressure on Caspian and north bar of country and spreading the Pakistan low pressure to south Alborz regions and in troposphere mid level with penetrating shallow trough belong to Russia north low pressure on the research area with creating quite wind and decreasing the boundary depth layer provided suitable condition for increasing Tehran’s pollution potential.