نوع مقاله : مقاله پژوهشی
نویسندگان
1 دانشگاه علوم کشاورزی و منابع طبیعی گرگان
2 دانشگاه گلستان
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Abstract
Climate change though changing weather patterns can lead to global warming which emerges as change in the climatic extreme indices and disorder in the ecosystems functions resulting in serious environmental consequences. The analysis of extreme values is of vital importance in the planning and policy-making in the agricultural sector and water resources management. In this study, daily timeseries of precipitation and temperatures from a number of synoptic and rain gauge stations within and around the Hablehroud watershed have been analyzed for the statistical period of 1986 – 2017. To this end, the trend of 27 rainfall and temperature indices defined by ETCCDMI expert group was analyzed using the RClimdex software package. The results showed that the majority of the hot temperature indices have experienced a statistically significant upward trend in the study area. Both the monthly maximum value of the daily maximum and minimum temperature, Monthly minimum value of daily maximum temperature, Monthly minimum value of daily minimum temperature, the percentage of summer days (days with a temperature of value more than 25 oC) and tropical nights (nights with a temperature value more than 20 oC) indicate a statistically significant upward trend. Percentage of warm days and nights show a significant upward trend in all the studied stations, while percentage of cool days and nights in all stations present a statistally significant downward trend. Also, the number of stations that show an upward trend for precipitation indices is more than the number of stations showing a downward trend. Annual rainfall in half of the stations shows an upward trend and in the other half a downward trend, although in most cases these trends are not statistically significant. Generally speaking, due to high variation and low amount of rainfall in most of the stations, a specific and uniform pattern in the trends of precipitation indices across the study area is not detectable. However, despite a general perception that climate change has resulted in decrease in precipitation, the recorded long term data at the monitoring stations across study area favours the presence of an upward trend in most precipitation indices.Therefore, it can be concluded that significant climate change such as temperature increase has occurred in the region, but it cannot be said with certainty that statistically significant rainfall changes have occurred in the region.
Introduction
Climate change though changing weather patterns can lead to global warming which emerges as change in the climatic extreme indices and disorder in the ecosystems functions resulting in serious environmental consequences. The analysis of extreme values is of vital importance in the planning and policy-making in the agricultural sector and water resources management.
Materials and methods
In this study, daily timeseries of precipitation and temperatures from a number of synoptic and rain gauge stations within and around the Hablehroud watershed have been analyzed for the statistical period of 1986 – 2017. To this end, the trend of 27 rainfall and temperature indices defined by ETCCDMI expert group was analyzed using the RClimdex software package.
Results and discussion
The results showed that the majority of the hot temperature indices have experienced a statistically significant upward trend in the study area. Percentage of warm days and nights show a significant upward trend in all the studied stations, while percentage of cool days and nights in all stations present a statistally significant downward trend. Also, the number of stations that show an upward trend for precipitation indices is more than the number of stations showing a downward trend. Annual rainfall in half of the stations shows an upward trend and in the other half a downward trend.
Conclusion
Therefore, it can be concluded that significant climate change such as temperature increase has occurred in the region, but it cannot be said with certainty that statistically significant rainfall changes have occurred in the region.Generally speaking, due to high variation and low amount of rainfall in most of the stations, a specific and uniform pattern in the trends of precipitation indices across the study area is not detectable. However, despite a general perception that climate change has resulted in decrease in precipitation, the recorded long term data at the monitoring stations across study area favours the presence of an upward trend in most precipitation indices.
کلیدواژهها [English]
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