Showing 4 results for Anticyclone
Kamal Omidvar, Mehdi Mahmodabadi, Parisa Shams, Mahbobeh Amiri Esfandegheh,
Volume 7, Issue 3 (11-2020)
Abstract
Due to the fact that the mechanism of anticyclone Movements is the desire to descend and suppress the air, so the effect of these movements and their location in the occurrence of flood falls is significant. For this purpose, in this paper, flood precipitation in the last two decades of Kerman province was studied and two of the most severe ones were selected. Due to the emphasis of this paper on the province of Kerman, the heavy rainfall was calculated for each station in the province using the Gumble Type 1 Distribution Statistical Index. Then, the thermodynamic properties of the precipitation were analyzed using radial data and Kerman station's sketch diagram. For analysis of these floods, daily rainfall data of the synoptic station 10 of the province and sea surface pressure maps and850,500,300 hectopascal levels were used. Then, the arrangement of the simulated pattern and its trend in the air maps, were studied during a selective period daily3. The results of the study indicate that the main cause of flood precipitation in the study area is to strengthen the eastern Mediterranean landfall in the middle troposphere, so when moved downward to the bottom of the polar system, it is transmitted to lower latitudes As a result, Western systems, with their movements on the southern warm waters, have a high moisture content and cause heavy rainfall in the region. Also noteworthy in the occurrence of precipitation is the presence of intense swinging movements on the southern waters, especially the Oman Sea, which causes more humidity to be injected into the interior areas of the country and provides the conditions necessary for the occurrence of such rainfall.
Ghasem Keikhosravi, Shahriar Khaledy, Ameneh Yahyavi,
Volume 7, Issue 3 (11-2020)
Abstract
This study was conducted to investigate the foehn mechanism in the Alborz Mountains.For this purpose, daily temperature, mean and maximum daily temperature, minimum, mean and maximum daily relative humidity, hourly wind direction and velocity data were collected and prepared at 8 selected stations over a 10-year statistical period (2006-2010). To derive the sum of frequency of occurrence of foehn, hot days are extracted using Baldy index and taking into account wind direction relative to station position and temperature rise compared to previous days were identified as days associated with foehn. Then, using NCEP / NCAR database data, different atmospheric alignment maps were obtained for the selected samples and plotted in Grads software environment. Then the position of high pressure cores and adjacent low pressures on the maps were determined. Results showed that Masouleh station with 41 days frequency and Astara and Bandar Anzali station with 18 days had the highest and lowest occurrence of foehn. Investigations on the synoptic maps of 35 foehn events showed that a total of three groups of Anti-cyclone or high-pressure centers were affected by the synoptic pattern of the region in the days involved. The first group is the Siberian High Pressure Tabs, whose cores are located in the confines of Lake Baikal, Balchash and northern Pakistan, depending on the season and synoptic conditions. The low pressure cores are located on the Caspian Sea and the pressure difference between the high pressure tab of the Alborz Outer Slopes and the Caspian Sea causes a compressive stress. In this model, Cyclone currents with increasing moisture of the Caspian Sea on the western slopes of Alborz Heights cause precipitation and warm flow due to warming under windward slopes. The second group is the anticyclone of Saudi Arabia, in which specimens with spin cores are deployed on southwestern Iran. As the north side of the Arabian High Pressure extends northwest of Iran and the presence of low polar pressure in the Caspian region with intensified compressive flow causes currents southwest along the perpendicular heights. Western anticyclone currents in the Arabian Sea circulate the moisture of the southern warm seas to northwestern Iran. The third group is a combination of African anticyclones, immigrants, Siberian highs and its tabs that create a thermal and compressive style over the study area and west of the Alborz Mountains. And provide the basis for the formation of the foehn phenomenon.
Halimeh Kargar, , Mohammad Saligheh, Mehry Akbary,
Volume 8, Issue 4 (1-2021)
Abstract
Conclusion
The results showed that the length of the precipitation period in the study area is 8 months (out of 213 systems, 60 systems were recorded in January and 50 systems were recorded in December). June, July, August and December did not have a comprehensive rainfall system. The difference in height between the Mediterranean Cyclone and the Arabian Anticyclone, i.e. the MAI index, was identified in 5 categories. The results showed that the higher the value of MAI index, the less rainfall systems and the higher the rainfall intensity. Most rainfall systems occur when the MAI index reaches 100 to 150 geopotential meters. In addition, the concentration of precipitation occurred in February when the MAI index reached 200 geopotential meters and above. In the continuation of the research, the difference between the Sudan Cyclone and Arabian Anticyclone, i.e. the SAI index, was also identified in 5 categories. The results showed that most of the systems occurred in the third category with a value of SAI index between 100 and 150 geopotential meters. Moreover, the results showed that the higher the value of the SAI index (, the lower the number of rainfall systems and the higher the average of rainfall systems.
Dr. Mostafa Karimi, Norouzi Fahimeh, Dr. Mahnaz Jafari, Dr. Khoshakhlagh Faramarz, Dr. Shamsipour Aliakbar,
Volume 9, Issue 1 (5-2022)
Abstract
Vulnerability assessment of Miangaran wetland ecosystem
To support the proper management of ecosystems, vulnerability analysis of ecosystems is very important. Vulnerability analysis of ecosystems provides information about weaknesses and capacity of the studied ecosystem for recovery after damage. Considering the degradation status of Miangaran wetland, vulnerability evaluation of this wetland is one of the most important management methods in the region. For this purpose, in this study, after identifying and evaluating the threatening factors of Miangaran wetland, these factors were scored using evaluation matrices. Then, the interaction between these values and threatening factors was examined and the vulnerability of wetland values was obtained by multiplying the scores of all studied factors. Finally, management solutions were presented to deal with the most important threatening factors. According to the results, the most vulnerability is to the hydrological and ecological values of the wetland. The highest effects of threats on the ecological value are also on the birds of Miangaran wetland. The results of the evaluation of Miangaran Wetland show that this wetland has a high potential for ecosystem functions of the wetland. These functions have been neglected in the planning and managing of wetlands at the local, regional and national levels. As a result, ecosystem-based management is suggested as the best management approach. The management in these areas should take action to prevent the vulnerability of Miangaran wetland. Also, the vulnerability evaluation method used in this study can provide a good understanding of the relationship between wetland functions and the resulting services for the management of the ecosystem of Miangaran Wetland.
Key words: Miangaran wetland, ecosystem management, vulnerability assessment
