Showing 2 results for Mediterranean Cyclone
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 Nabi Mirzaei, Dr Bouhlul Alijani, Dr Mohamad Darand,
Volume 8, Issue 4 (1-2021)
Abstract
subtropical high pressure (STHP) and Mediterranean cyclone are among the most important synoptic systems affecting Iran's climate. In this study, the effect of the high altitude location of the sthp on the Mediterranean gyres during the droughts and wetness of Iran during 1979 to 2020 was analyzed. In this regard, two datasets were used. Station data were used to identify drought and wetness periods, and ECMWF-ERA5 grid data was used to identify the location of high pressure in the subtropical region. The results showed that STHP with 3 anticyclone cells (ridge) affects the position of atmospheric waves affecting Iran's rainfall. The STHP system, especially the Arabian Subtropical anticyclone (ASA) and North Africa, play a more important role in the location of the cyclone affecting Iran's rainfall, so that widespread droughts with the expansion of the ASA to the west and its integration with the African anticyclone, the lack of expansion of the Mediterranean trough to the sea Redness and reduction of Sudan low and Mediterranean integration systems occur. With the eastward movement of the ASA over the Arabian Sea and the northern Indian Ocean, the Mediterranean trough deepens and the amount of waves and consequently the rainfall of the country increases. Therefore, the eastward expansion of the Arabian Peninsula and the strengthening of the North African Ridge provide the conditions for the expansion of the Mediterranean Sea. Whenever the ASA is located in its easternmost position on the Oman Sea and the Arabian Sea, it will lead to the advection of moisture for Iran through the access to the large areas of southern water and eventually rainfall. The main cause of the occurrence of drought and wetness in Iran is the spatial variations of atmospheric waves due to the spatial variations in the ASA.
