عنوان مقاله [English]
Although climate seems to be a constant phenomenon, past geological study shows that climate conditions have constantly changed with other internal and external developments of the Earth, with frequent cold, hot, or dry and humid periods often overlapping. Considering the importance of the issue of climate change in the present century, the study of the trend of climate parameters is particular importance. Changes in climate parameters such as temperature and precipitation as the most important climatic parameters can be affect the hydrological processes, agriculture, environment, health, Affecting industry and the economy, and assessing these changes in a region will be of great help to the challenges of water resource managers and planners. Therefore, in this study, the trend of climate change through the trend of temperature and precipitation changes on an annual basis of a 30 year period (1986-2018) at synoptic stations located in Iran and the countries of the region that have been affected by drought crisis in recent decades and was encountered with Dust, done by The trend analysis using statistical methods.
Materials and methods:
The studied meteorological stations consisted of 66 synoptic stations located in 18 countries of the region, and the methods used to study the trend include non-parametric Mann-Kendall test, Sen Slope estimator and slope of regression line. The Mann-Kendall nonparametric test, completed by me in 1945 and then completed by Kendall in1975, is based on the order of the data in a time series. This test is used to check the randomness of data (no trend) versus trend in hydrological and meteorological time series. The advantage of this test over other trend-setting tests is the use of time series data regardless of the value of the variables. Because of this property, this test can also be used for skewed data, and the data need not be distributed. There will be something special. of Sen slope estimator was presented to identify trends in a time series of data. This method is a nonparametric method that calculates the median slope for the time series of data by analyzing the difference between observations of a time series. The Trend Line helps us to predict the state of the data, in addition to detecting the data change process. The main reason for using nonparametric methods compared to parametric statistical methods is that nonparametric methods work best for data without normal distribution.
The mean annual temperature distribution of the study area indicates that the southern and southwestern regions of the study area have a higher average temperature than the other regions, and by moving to higher latitudes the average temperature will generally decrease at the regional level. The case study fluctuates between 10 and 28 degrees Celsius. The annual precipitation distribution of the study area also shows that in general the precipitation in the study area is between 38 and 404 mm. As can be seen, the stations located in the north and west and northwest of the region have good rainfall. The lowest rainfall in the study area is also in the east, south and southwest of the region and around the Persian Gulf and most of the countries of Saudi Arabia, Oman, United Arab Emirates, Bahrain, southeastern Iran, and Pakistan and Afghanistan. These areas are among the least rainfall areas in the study area. The results showed that change is significant in some time series and in some stations in the form of short-term fluctuations and in others it is significant. The trend and type of trend in the precipitation series are decreasing and negative, with the highest decrease being in Sanandaj and Van stations with a slope of -5.3. The highest increase in precipitation is also in the station. Slope closet is 34.8. Except for Hyderabad and Lahore stations and to some extent in Shahrekord and Shiraz stations in general, temperature has been increasing in general. Overall, based on the results of the study of annual changes in temperature and precipitation at the regional level, it was found that precipitation in the study area has a decreasing trend and temperature has an increasing trend, with decreasing and increasing trend in some stations and in some series. Has become meaningful. In general, according to the method of Sen slope and the regression slope, the annual precipitation changes are more severe and more pronounced than the regional temperature changes. Therefore, considering the changing climatic parameters in the study area and being aware of the negative effects of climate change, relevant planners especially in the sectors of water resources management, agriculture, environment, health and economic and natural resources sectors. Adopt strategies to mitigate the consequences and adapt to the new climate and, given the current status and trends of climate change, fundamental revisions to environmental planning and the allocation and utilization of resources, especially water resources and it seems necessary.