جستجوی مقالات مرتبط با کلیدواژه « synoptic analysis » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

Floods are among inevitable hazards but its frequencies and volumes can be varied due to climate change. A comprehensive analysis of synoptic status can be useful for predicting similar events in the future. It is therefore very important for a good environmental management. Flash flood of July 2015 in Saghez was a catastrophe and did severe damage. In order to analyze the catastrophic precipitation, sea level pressure, 300 hPa, 500 hPa, 700 hPa, 850 hPa maps along with Omega, perceptible water map and humidity maps were investigated and analyzed, starting two days before the rainfall until the end of rainfall and even a day after. Results show that immigrant European high-pressure system along with Arabian low-pressure tongue have caused intense rainfall during the day. Mediterranean Sea, black sea and red sea have been effective in enhancing the system too. A day before the rainfall, at surface level, a high-pressure European system from the North West and the low-pressure tongue from the south west were approaching the country and the combination of these two systems have caused intense rainfall on the region. Ag the higher level, trough axis was over Turkey, Iraq and Persian Gulf. Short waves displacements along with change in axis positioning eastward caused pressure centers in the surface level to get closer. At this time, all the western part was located under the eastern axis short wave trough, causing intensifying instabilities along with uplifting humid weather and finally a catastrophic intense rainfall on Saghez and its surroundings on July 18 2015. It is important to pay attention to comprehensive watershed management as one of the major strategies for adaptation and resilience in flood-prone areas.

increasing dusty storms has been one of the most important consequences of climate change in recent years that directly or indirectly affected human society. Countries located in the arid and semiarid regions of the world, including Iran, have been affected more than other parts of the globe by this natural disaster and its harmful consequences, especially the atmospheric dust, which could bring about a wide variety of detrimental effects such as the reduction in growth and yield of crops, the occurrence of plant plagues and diseases, an increase in road accidents due to the decrease in the vision field, cancellation of flights, and rising health costs. These facts, along with repeated droughts in recent years and the potential consequences of climate change as a result of desertification, have brought the issue of dust storms and their relevant side effects, including increasing respiratory and pulmonary diseases, a disorder in the ground and air transportation, environmental destruction, and pollution of agricultural products to the attention of many researchers. Therefore, numerous researches have been carried out on the increase of global and regional dust and the identification and analysis of dust-generating regionschr('39') circulation patterns. These include Romanof (1951), Goudie and Midelton (2001), Kutiel (2003), Barkan et al. (2005), Dayan et al. (2008), Barkan (2008), Calastrini et al. (2012), Awad and Mashat (2014), Kang et al. (2016), Beegum et al. (2018), Hemmati( 1995), Dehghanpour (2005), Zoualfaghari and Abedzadeh (2006), Heidari (2007), Raeispour (2008), Karami (2009), Tavousi et al. (2011), Movahedi et al. (2012) Tavousi and Zahraei (2013), Zangeneh (2014), Khorshiddoust, et al. (2014), Omidvar and Sepandar (2018) to mention a few.

as located near deserts, Ahwaz city is directly exposed to dusty storms. This study, therefore, set out to investigate the relationship between circulation patterns that cause severe specks of dust in Ahwaz and the environment-circulation approach. To this end, the required data were collected from the environmental database of 390 sever dusty days of the region during 14 years (2001-2014), and the severity of dusty days was determined according to the allowance limit index AQI (150 μg/m3) for two cold (161 days) and hot (229 days) periods. The data were then evaluated based on the frequency of severe dusty days throughout the hot period. For this reason, daily network data regarding the geopotential height in 500 hPa, sea level pressure, and the zonal and meridional wind were obtained from the database (NCEP/NCAR). Conducting an accumulation hierarchical cluster analysis for sea level pressure and geopotential height map with matrix in 229×1617 dimension and linkage days using Ward method, three circulation patterns were identified for level 500 hPa, and three circulation patterns were found for sea level pressure. Moreover, for every pattern, one day has been determined as an indicator based on the correlation coefficient of 95% threshold, and the composite maps of sea level pressure and height patterns of geopotential in level 500 hPa, the speed vectors, and streamlines in these days have been drawn and analyzed.

The results of the study indicated that according to patterns 1 and 2 in level 500 hPa and at sea level pressure, severe dusty storms in Ahwaz were influenced by the eastern Mediterranean currents and low thermal pressures of the earth surface, especially the Persian Gulf low pressure. In pattern 3, the two levels mentioned above, cyclonic system zonal convergence of the Persian Gulf, Azores high pressure, and enhancement of gradient pressure on the region, resulted in the distribution and transfer of the dust phenomenon in Khuzestan province and Ahwaz city.

According to the findings of this study, the most important sources of dust distribution in the study area are the deserts of Iraq, Saudi Arabia, and Syria. This studychr('39')s results could be useful for preventing and controlling dust storms via the identification of dust-generating regions. To reduce the damages caused by the study regionchr('39')s dust phenomenon, an international agreement with the adjacent countries needs to be made. Moreover, the issue requires inter-organizational cooperation of relevant entities at the domestic scale.

The main of the factors limiter the happen the sultry comfort conditions in the coastal zone, which is under the control of the temperature and humidity. The research designed as the country's southern coast within the province of Bandar Abbas, (Because of little distance to the coast) is selected. The climate data used in this study included based on The air temperature, relative humidity percentages, and the wind speed in knots whose hourly Statistics hourly data parameters of the are three synoptic stations in the Persian Gulf coasts the range, of Meteorological Organization in the 30-year period (1985 -2014) of Bandar Abbas stations. This index is of the formula often used to calculate heat index. After calculation of the thermal index chart every month the average both daily and hourly resolution from the index values were provided in the station.  Then, the final tables were obtained which, incidentally, were not specified for the sincere period for every hour of the day, different levels of probability (the number of occurrences with the probability of 50 to 70, 70 to 90, and above 90) was determined. Synoptic analysis method was used for synoptic analysis. In this study, using data related to components, sea level pressure, Geopotential heights, temperature, wind direction, wind speed and relative humidity, sea level pressure maps, Geopotential elevation, thickness map, Relative Humidity Distribution Map and vorticity Map (vorticity) were mapped and analyzed. The results showed that the establishment of a very strong heat Low pressure on the Persian Gulf and the high pressure of the deserts of Saudi Arabia and Central Iran caused an Extend the pressure and the transfer of hot and burning air to the Persian Gulf and, eventually, the occurrence of severe evaporation of the sea, has provided.

This study is designed، aiming to detect changes in the composition and configuration of landscape in Rasht township between 1989 and 2011. It has been conducted applying synoptic analysis. Hence، landscape maps have been generated from three TM satellite images at 1987، 1999 and 2011 applying hybrid classification method. Some composition and configuration-based metrics including NP، PD، LSI، LPI، SHDI، CONTAG، ED and PLAND were then calculated at two class and landscape levels and their changes is detected. The results indicated that، in general، the landscape has been more fragmented، more complex and irregular in shape، more disconnected in continuity of patches and more diversified in the term of land use/ land cover types. It was in spite of the differences between trend and gradient of changes in Rasht county landscape at two period of time (1987- 1999 and 1999- 2011). Moreover، the results revealed that sprawl of the manmade areas have caused increase in fragmentation، irregularity and complexity of agriculture patches and decrease in total area of agriculture class. Hence، an intense degradation of ecosystems might be resulted if the current trend continues in future in the study area.