Correlation between the average temperature of the Abargu-Sirjan Basin and the teleconnection patterns from the Atlantic Ocean

Introduction
Climate is variable in time and space, so detecting a significant trend is a major challenge for researchers. Calculating the trends of climatic elements such as average temperature, maximum, and minimum temperature has been the subject of many studies in recent years. It has been carried out in different regions around the world. Most studies in this field have focused on large-scale temperature trends. However, more research is needed to focus on the change that occurs at the regional level. In this way, the research conducted on the decadal trends of the average temperature in different regions provides impressive results. In order to study how global warming affects life at the regional level, climate change models and assessments often assume that the impact will be uniform. However, temperature does not increase uniformly in space or time.
 
Materials and Methods
In this research, the analyzed monthly data of ERA-Interim with a resolution of 0.25*0.25 degrees during the time period of 1979-2019 from the ECMWF website (European Center for Weather Forecasting) has been used. According to the area of the Abraqo-Sirjan catchment area and the resolution of the studied data, 338 points of the entire basin were covered and studied. Also, the data of the link indices from the North Atlas and South Atlas regions, which were extracted from the NOA site at the same time as the mentioned period, were used. Pearson's correlation and linear regression tests were used to investigate the relationship between the average temperature of the watershed and the remoteness indices.
 
Results and Discussion
Examining the average temperature trend of the Abrago-Sirjan basin area showed that except for the months of April, May, August, and December, the other months only have an increasing trend. In April, the northern areas and parts of the west and east of the basin have an increasing trend. Other parts of the basin have no trend. In this month, 37.05% of the area of the basin is covered by the increasing trend zone and 62.94% by the non-trending zone. In May, the northern half of the basin has an increasing trend and covers 48.95% of the area of the basin. The southern half with an area of 29252.85 square kilometers is without trend and covers 51.04% of the area of the basin. In August, only a very small part of the north of the basin showed an increasing trend. This area with an area of 5728.55 square kilometers includes 9.99% of the area of the basin. Other parts of the basin, which includes about 90% of the area of the basin, do not have any trend. In the month of December, the area has been expanding and has covered more parts of the area of the basin. In this month, an increasing trend has been observed in the northern half of the basin, parts of the center, and south of the basin. The area of increasing trend in this month with an area of 43,886.6 km² has covered 76.57 km² of the area of the basin. The no-trend area with an area of 13422.44 km²  includes 23.42% of the area of the basin. Correlation between the average temperature of the basin and teleconnection patterns also showed that only the NAO pattern in February showed an inverse correlation at a 95% significance level with the temperature of the basin and other patterns had a direct correlation with the temperature of the basin. In January, TSA and AMO patterns, in February, NAO, TNA, AMO, AMM and NTA patterns; in March TNA, TSA, AMM and NTA patterns; In April, TNA, TSA, AMO patterns; In May, TSA and AMO patterns; In June, the AMO pattern; In July, NTA and TNA patterns; In August, AMO and NTA patterns; In September, AMM and NAO patterns; In November, AMM, AMO and TNA patterns and in December, AMM and TNA patterns have shown correlation with average temperature. In the months of February, March, May, July and September, in addition to the correlation at the significance level of 95%, correlations were also observed at the 99% level, and a major part of the basin has correlations with distant teleconnection patterns.
 
Conclusion
The results of investigating the average temperature trend of the Abarqo-Sirjan basin showed that the temperature in this basin has only an increasing trend, and during the period of 1979-2019, there was no decreasing trend in the average temperature of this basin. In the months of January, February, March, June, July, September, October, and November, and on an annual scale, all basins have an increasing trend. In the months of April, May, August, and December, apart from the increasing trend zone, the no-trend zone is also observed at the basin level. Among the studied patterns, the AMO pattern has shown more correlation with the average temperature of the basin than other patterns. After that, TNA, AMM, NTA, and TSA patterns have the highest correlation. In the cold months of the year, the lowest correlation between the distance and average temperature of the basin was observed, and in the warm months of the year, a larger area of the basin showed a correlation.