نوع مقاله : مقاله پژوهشی
نویسندگان
1 Department of Geography, Faculty of Literature and Humanities, Razi University, Kermanshah, Iran
2 Department of Water Engineering, Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
The freezing level height (FLH) is the height of the location where the air temperature is 0°C (isotherm), and indicates the approximate location of the phase transition of water between solid and liquid and sublimation from solid to vapor. FLH is a critical parameter of hydrological conditions and climate change. The height of the freezing level or the isothermal line of zero degrees in the atmosphere is a parameter that determines the ice cover of mountains and high areas with the change of water to ice. This research has been performed to investigate the temporal and spatial changes of freezing level height in Iran in the statistical period from 1940 to 2023 using the modified Mann-Kendall non-parametric analysis method. The Mann—Kendall (MK) analysis uses non-parametric trend development only for reliable data. It has been generally practical where the data are not identical to a normal distribution (non-parametric). The Mann-Kendall test is used globally to analyze trends in meteorological variables. In this research, the average raster data of the freezing level with a resolution of 0.25 x 0.25 in 12 hours of every month during the years 1940 to 2023 have been used. The mentioned data was downloaded from the Climatic database of the European Centre for Medium-Range Weather Forecasts (ECMWF). The selected range includes from 44 Degrees east longitude to 64 Degrees east longitude and from 23 Degrees north latitude to 44 Degrees north latitude (location of Iran). For statistical analysis, network data were converted into vector data in GIS software, and level maps of freezing level were extracted The results of the study show that the freezing level height shows a significant upward trend from December to April. Except summer, the upward trend of seasonal changes in the freezing level height is quite evident in autumn, winter, and spring. The annual changes in the freezing level height show a significant upward trend during the period. Significant upward trends on a monthly, seasonal, and annual scale can show one of the consequences of climate change in Iran. The results of the survey of spatial changes show that the height of the freezing level has an inverse relationship with the latitude, and as the latitude decreases (towards southern regions of Iran), the height of the freezing level increases. This relationship is more in winter. The correlation coefficient of FLH changes with latitude is significant at the alpha level 0.05. The relationship between the changes in the height of the freezing level and the longitude is direct. As we move towards the east, the height of the freezing level also increases. The highest level of freezing level height is observed in Chabahar (4347.5 meters) in southeastern Iran. Considering the decrease in snow cover and increase in heavy rainfall in Iran, assessing variations in freezing level height can be useful for predicting these variables.
کلیدواژهها [English]
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