Document Type : Research Paper

Authors

• Parsa Haghighi ¹
• Seyed Masoud Soleimanpour ²
• Sohrab Sadeghi ³

¹ Master, Soil Conservation and Watershed Management Research Department, Fars Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Shiraz, Iran

² Associate Professor, Soil Conservation and Watershed Management Research Department, Fars Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Shiraz, Iran

³ Scientific Member (Training Instructor) of Fars Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Shiraz, Iran

Abstract

Introduction
Studies conducted in the field of climate change in the world indicate that even a small change in temperature causes a change in the occurrence of extreme phenomena such as drought, heavy rainfall, and storms. Severe changes in the behavior of atmospheric indicators, especially during the 21st century, indicate signs of climate change occurrence. Therefore, climate change and climate warming can directly affect the extreme values ​​of climate and the temporal and spatial changes of these events; thus, this study analyzes the trend of occurrence of extreme climate events shortly in Fars Province.
 
Materials and methods
In this study, in order to analyze the trend of extreme climate events shortly in Fars Province, the ACCESS-ESM1-5 model related to the IPCC Sixth Assessment Report and the latest series of climate scenario releases (SSP) was used after exponential downscaling using the LARS-WG statistical model at the station level. Daily precipitation, maximum and minimum temperature data from three synoptic stations of Abadeh, Shiraz, and Lar in Fars Province were used. After exponential downscaling of the ACCESS-ESM1-5 model, precipitation, and minimum and maximum temperatures were predicted for the near future period (2026-2055). Then, using the RClimdex package in R software, fourteen extreme climate indices (7 temperature indices and 7 precipitation indices) were extracted for the base period and the near future. After calculating 14 climate extreme indices for the 30 years] of the near future period (2026-2055) and the base period (1991-2020) on an annual basis, the trend for each index was determined using the Mann-Kendall test and the slope of the age line. Then, the climate extreme indices were placed in two groups of the near future period and the base period, and the type of data distribution was determined. In order to reveal the existence of a difference in the means of the two groups (the first group: values ​​of the extreme indices of the base period, the second group: values ​​of the extreme indices of the near future period), an independent t-test was used.
 
Results and discussion
The results of the exponential downscaling of the ACCESS-ESM1-5 model indicate an increase in the minimum and maximum temperatures of the near future period (2026-2055) compared to the base period (1991-2020) in all three stations and all three scenarios. The average precipitation values ​​are also predicted to decrease at the Shiraz station and to increase at the Abadeh and Lar stations. The results of determining the trend in climate indices showed that the trend in temperature extreme indices is more noticeable than precipitation extreme indices. The number of frost days (FD) has a significant downward trend and the number of summer days (SU25), the monthly maximum daily maximum temperature (TXx) and the monthly maximum daily minimum temperature (TNx) have an upward trend in all three stations and three scenarios compared to the base period and a significant difference at the 95% confidence level. The maximum one-day precipitation index (RX1day) is also significant and has an upward trend in all three stations and three scenarios, with an average increase of 16.59 mm in the maximum one-day precipitation in the province compared to the base period. The daily precipitation intensity index (SDII) is also a significant upward trend in all three stations and three scenarios, with an average increase of 3.83 mm/day for the province in the near future compared to the base period.
 
Conclusions
Severe climate changes and global warming in recent years have led to changes in weather patterns and the emergence of climate anomalies in most parts of the world. The present study shows a significant increase in extreme climate events in Fars Province. The trend in extreme temperature indices is more noticeable than extreme precipitation indices. An increasing trend in extreme hot indices and a decreasing trend in extreme cold indices will occur in the near future (2026-2055) in Fars Province; therefore, it is necessary to adopt and implement preventive decisions and plans at different management levels to deal with the possible consequences of increasing temperatures and extreme hot events. Based on the results obtained from examining the frequency of extreme precipitation events, it also shows an increase in the daily precipitation intensity index, an increase in the maximum one-day precipitation in three stations of Abadeh, Shiraz, and Lar, and an increase in the number of days with heavy and very heavy precipitation in two stations of Abadeh and Lar. These conditions could indicate an increase in intense and short-term rainfall, as well as a shortening of the region's rainy season. Consequently, given the damaging consequences of extreme rainfall events such as drought and flood, more attention should be paid to monitoring and observing these weather disasters in order to minimize the damage caused by them, so that active and intelligent management can be applied to move more quickly towards risk management and risk reduction.
 

Keywords

• Climate change
• SSP scenarios
• Climate extreme index
• ACCESS-ESM1-5 model