Document Type : Applied Article
PhD Student, Climatology, Faculty of Humanities, Islamic Azad University of Najafabad
Associate Professor, Department of Meteorology, Faculty of Humanities, Islamic Azad University of Najafabad
Associate Professor, Rangeland Research Department, Forests and Rangelands Research Institute, Agricultural Research, Education and Extension Organization, Tehran, Iran
Changes in climate systems are one of the most challenging environmental phenomena. This phenomenon affects environmental characteristics such as rainfall, drought, high-quality waste movement, etc., and may cause their order to be disrupted . Drought is a recurring climatic phenomenon in the climate system whose effects are not limited to arid and semi-arid regions . There are several factors that contribute to the occurrence of drought. Changing and intervening in these factors in order to prevent drought occurrence is beyond human power and is impossible. On this principle, it is possible for these conditions to occur in any region of the globe in rich and poor, wet and dry, developed and under developing countries, and so on . Due to the fact that drought indicators are valid only for one place and do not have the necessary spatial resolution to assess drought, and also due to the complexity and mechanism of climate, especially in the changes from year to year and decades, it is necessary to study the detection of processes affecting these changes and fluctuations. One of the most important factors affecting climate fluctuations on an annual basis is the role of climate patterns and indicators far from the region .
Materials and methods
In this study, the average monthly temperature data of Borujen, Lordegan, Shahrekord, and Koohrang stations were used. Remote link pattern data was also obtained from NASA. In this study, 26 remote linking models were used. In the present study, the results were evaluated seasonally for the years between 1397 to 1399 using Mann Kendall test. Afterward, relationship between temperature and drought of SPEI index has been used. In order to evaluate the trend of change in mean temperature, first, the statistical quality and homogeneity of data of Borujen, Lordegan, Shahrekord, and Koohrang stations were evaluated using test run test. Then, the relationship between drought using SPEI drought index and following a series of data from the homogeneous pattern was confirmed. The anomaly and normality of the mean temperature data were then investigated using the Kolmogorov-Smirnov test. According to the results and analyzes of the Kolmogorov-Smirnov test, if it was significant, ie p was less than 0.05, it means that the distribution is not normal. Mann-Kendall test was used to evaluate the significance of the change trend, and 95% and 99% confidence intervals were examined.
Discussion and Results
The results of descriptive statistics show that the highest average temperature in Borujen, Shahrekord, Koohrang and Lordegan stations in July is 22.74, 23.38, 22.21 and 27.80 ° C, respectively, and the lowest average temperature in Borujen, Shahrekord, Koohrang, and Lordegan stations in January are -0.99, -1.20, -3.85 and 3.76 degrees Celsius, respectively. The annual averages in Borujen, Shahrekord, and Koohrang and Lordegan stations are 11.29, 11.48, 9.90, and 15.79 degrees Celsius, respectively. The results showed that Chaharmahal and Bakhtiari province seems that the implantation of drought areas based on teleconnection patterns and its relationship with drought index is a kind of association of the passage of precipitation systems for this. Although there are areas in this province that are not the same in terms of rainfall, but the lack of patterns and systems from a distance will be the absence of rainfall and drought in the whole province. Not only there will be a drought in the rainy areas of the province, but it will also cause a lack of rainfall for the low rainfall areas as well as a drought. In the spring observations, it was found that based on climatic scenarios, there are no changes in the number of events and even drought classes compared to the base aura. However, in the Middle Ages, drought events and drought classes have changed to moderate to severe drought segments relative to the North Atlantic and Arctic linkage patterns for all stations. The fluctuations of drought and wetlands in Chaharmahal and Bakhtiari province are different from other areas. The relationship between droughts in this area and the negative phase pattern has led to drought in this area.
The aim of this study was to identify and zoning the drought of Chaharmahal and Bakhtiari province with the help of SPEI drought index. Then, the relationship between each zone and atmospheric-oceanic connection patterns was analyzed. The results showed that Chaharmahal and Bakhtiari province was divided into four different and distinct zones in terms of the severity of the drought index: southeastern, northwestern, northern, and southern half, which shows the location of the zones. The effect of precipitation systems and their passage on Chaharmahal and Bakhtiari province. Drought and wet season in each of the areas (Shahr-e Kurd, Borujen, Lordegan, and Koohrang) where drought and wet season are seen consecutively in these areas. The most severe droughts are related to area four (Koohrang). Among the remote connection patterns, the western hemisphere hot pool pattern has the greatest impact on the occurrence of drought in the southwestern regions of the province. The relationship between this index and drought is positive in this area. Due to the drought in the Borujen area, most of the long-distance link patterns, including the Atlantic Index and the Pacific and North Atlantic Decades fluctuation pattern in autumn are significant. Drought in the southern hemisphere (Lordegan) in the warm season (spring and summer) shows a significant relationship with the tropical pattern of the South Atlantic, the tropical index of the North Atlantic and the East Atlantic. Droughts in the northwest (Shahrekord) R show a significant relationship with the multivariate index of Enso and North Atlantic and East.