Rastegar Mohammadi, Mohammad Saligheh, Mohammad Hossein Naserzadeh, Mehri Akbari,
Volume 0, Issue 0 (3-1921)
Abstract
Extratropical cyclones according to the frequency, duration, and intensity, the major cause of mid-and high-latitude precipitation across the Mediterranean during winter and autumn. For this research using network data of ECMWF climatic variables with 6-hour time resolution and 0.25 × 0.25 spatial resolution from1979-2016 and were used of 4 Basin stations precipitation data from the Asfezari database from 1979-2016. The results showed that the first pattern is the Mediterranean trough pattern which has the highest frequency of 42%. In this pattern, the low-level due to the presence of a high-level that acts as a barrier have caused the deepening of the Mediterranean low-level and its axis extends to the Red Sea, and due to the collision of low-level and high-level on the region, instability is intensified and has caused the most rainfall among the patterns. In contrast to the first pattern, The fourth pattern has the lowest frequency of 10% Which is the trough pattern of western winds which is located on the Caspian Sea but due to high-level in the south of the region has prevented the entry of low-level and is located in the northern part of the study area due to this, the isobar in the north of the region have become orbital as a result, fewer cyclones enter the area, resulting in less rainfall between patterns. The results also showed that the frequency of cold-core cyclones was 60% in winter and 40% in autumn, but the frequency of hot core cyclones was 62% in winter and 38% in autumn, which in winter, the frequency of hot core cyclones has increased compared to cold-core cyclones, while in the fall the frequency of hot-core cyclones has decreased compared to cold-core. In the last decade, both the frequency of occurrence of cyclones and their intensity has decreased compared to the last two decades. In terms of cyclogenesis places, the western part of the study area has always been active, And with the onset of the cold season from autumn to winter, cyclogeneses places are gradually becoming more active.
Mohammad Radman, Mohammad Saligheh, Mohammad Hossein Naserzadeh,
Volume 0, Issue 0 (3-1921)
Abstract
In order to comprehend the water flow characteristics and variations of the Karun River, we examined the Zaz, Bazoft, and Beshar sub-basins from its main branches. The reason for choosing these basins was the proximity to the catchment centers of the Middle Zagros and their location upstream of the dams.
Iran Water Resources Management Company provided all the required data (from the water year
1356-57 to 1395-96), and we analyzed them using Kolmogorov-Smirnov tests, data skewness, skewness, and Pearson correlation. Then, we performed the linear regression test to determine the effect of temperature and precipitation on river discharge, and they conducted the Mann-Kendall test to identify the trend and jump points. The results of the data analysis showed that all of them are in normal conditions, although they have some elongation and skewness. The Pearson correlation test revealed a correlation between meteorological and hydrometric data.
The regression model used shows the changes in precipitation and discharge (unlike temperature and discharge) well. The significance number of all stations in the model is less than 0.05, which shows that the changes that occurred between predictor and dependent variables are significant. We see the high performance of the model in explaining the changes in discharge compared to precipitation. According to the regression charts, the decreasing trend of precipitation and discharge and increasing temperature are clear in all three basins.
The Mann-Kendall test reveals a significant trend of increasing temperature in Bazeft and Bashar basins, a decreasing trend of discharge in Bazeft and Bashar basins, and a decreasing trend of precipitation in Zaz and Bazoft basins.except for the temperature of the Zaz basin, all variables show mutations in mutation basins.
Hossein Naserzadeh, Fariba Sayadi, Meysam Toulabi Nejad,
Volume 19, Issue 55 (12-2019)
Abstract
This research was carried out with the aim of understanding the spatial displacement of rainfall nuclei as an effective factor in the future hydrological conditions in Iran. Two types of databases were used to conduct this research. The first type of data is the monthly precipitation of 86 synoptic stations with the statistical period of 1986-1989 and the second type of predicted data from the output of the CCSM4 model under the three scenarios (RCP2.6, RCP4.5, and RCP6) from 2016 to 2036. After collecting and modeling the data, the maps were mapped to the ARCGIS environment. The results of the study showed that the terrestrial nuclei in the whole of Iran's zone in the four seasons will have changes with a negative trend in the future. The coefficient of rainfall variation in the spring, summer, autumn and winter seasons will be 61.4, 101.4, 58.9 and 55.8 percent, respectively. The results of the triple scenario study showed that the displacement of the spring core from all north north of the country to the northwest of the country is limited to the common borders of Iran, Turkey and Armenia (the Maku and Jolfa region), but in summer, the high core The northern shores and parts of the northwest of the country will be transported to the south of the country (around Khash and Saravan). In the autumn, the high-lying zone, which is located throughout the northern part of the country, will move to two distinct nuclei in the central Zagros (Dena and Zadkouh areas) and southwest Khazars (Anzali and Astara areas), and the core of winter from the central Zagros And the Caspian region will be transferred to the northwest of Kurdistan and southwest of West Azarbaijan, which will be seen in all scenarios. Another point is that, in addition to reducing the boulders, in the future, drought areas will cover more of the country.
