پیش‌بینی بارش برخی ایستگاه های استان لرستان در دو دهه آینده با استفاده از مدل LARS-WG

Abstract
Using R2, MAE, and RMSE statistical parameters, the feasibility of the LARW-WG model for producing and simulating daily rainfall data in the study areas was examined in this study. As a result, after confirming the model's capability, the HadGEM2 atmospheric general circulation model was used to forecast the changes in rainfall in the study area for the future period of 2021 to 2040. The results showed that at the confidence level of 99% there is no significant difference between the real data and the data obtained from the model, and the model has the necessary efficiency to generate daily data. According to Elshtar stations forecasted climatic parameters, annual rainfall would rise by 3.6 to 9 mm on average, and in Aliguderz station, rainfall will rise by 0.31 to 2.33 mm on average. indicated an improvement. Additionally, it is expected that the precipitation parameter in Kohdasht station would drop from -0.70 to -3.80 mm. Elshtar station showed an increase in all seasons except for spring, and Aligudarz station showed an increase in all other seasons except for summer, with the exception of Kohdasht station, which decreased in all seasons. These findings indicate that the climate in the province of Lorestan will change drastically from the current climate during the next 20 years. Kohdasht station's findings indicate that rainfall will be less than at the other two locations.
Introduction
The most significant issues of the twenty-first century are known to be climate change and its effects, particularly global warming. The world's industrialized nations have been focused on the topic of climate change as one of their top concerns in recent years. One of the most significant and fundamental environmental problems in recent years is the changing climate brought on by the release of greenhouse gases and the rise in energy use. Many scientists think that the rise in greenhouse gas emissions is what drives climate change and global warming. The increase in greenhouse gases, which affects air temperature, precipitation patterns, wind speed, and temperature globally, is to blame for climate change. Water resources, the frequency and severity of floods, droughts, and hydrological processes are all significantly impacted by climate change; hence, several studies have been carried out to examine climate changes at various scales. Scientists now concur that the primary causes of climate change are believed to be rising greenhouse gas emissions and global warming. The primary resource for recreating past, present, and future global climates as well as various climate change scenarios is integrated climate models. The difference in climate change today is that it is occurring more quickly than ever before, and that humans have contributed significantly to this warming. Threatened by climate change. War and conflict are not directly brought on by climate change, but it can result in global instability, starvation, poverty, and violence. According to research, climate change has implications on things like rainfall patterns, historical instability, global warming, water resources and water levels, oceans and seas, groundwater levels, agricultural productivity, and economic and social issues.
Methodology
The Lorestan Province (study region) is situated in western Iran between 32°37' and 34°12' north latitude and 46°51' to 50°3' east longitude from the Greenwich meridian. With a land area of 28064 square kilometers in the mountainous region of the Zagros Mountains, this province makes up roughly 1.8% of Iran's total land area. It is situated in the west of the country. Khomein, Arak, Malayer, and Nahavand city are its northern neighbors. Feridon, Golpayegan, and Feridonshahr are its eastern neighbors; Andimshek and Dezful are its southern and southernmost cities; and Islamabad, Dareh Shahr, and Haris are its westernmost cities. In order to microscale the data of the HadGEM2 atmospheric general circulation model from the LARS-WG6 model, one of the most well-known and significant models, and because it achieved good and favorable results regarding the study of the effects of climate change scenarios on the climate variables of Lorestan province, random weather data generators were used. In accordance with current and projected climate conditions, this model is used to generate precipitation values at a station. Due to this, a study on numerous stations in the research region was done. Scaling and rainfall forecasting were done in recent years using the daily rainfall data from the base stations, such as Aliguderz, Elshtar, and Kohdasht stations. The necessary rainfall data was then gathered from the Meteorological Organization for use in the subsequent research's model implementation by first using the 21-year period between 1376 and 1397 (1997-2018) as the basis period.
Conclusion
According to the HadGEM2 atmospheric general circulation model's prediction results for the RCP 2.6, RCP 4.5, and RCP 8.5 emission scenarios, Elshtar station's average annual precipitation data showed an upward trend compared to base period data. Elshtar station's average annual precipitation for the base period was 238.2 mm, which shows an upward trend in comparison to the predictions made by HadGEM2 atmospheric general circulation models. With the exception of spring and mid-summer, it is 3.9 and 6 mm, while the rest of the seasons and months saw an increase in rainfall. According to the predictions made by the HadGEM2 atmospheric general circulation model under the RCP 2.6, RCP 4.5, and RCP 8.5 emission scenarios, the average annual precipitation data at the Aliguderz station are trending higher than the data from the base period. The average annual rainfall in Oligoderes during the base period was 32.12 mm. In comparison to the predictions of the HadGEM2 atmospheric general circulation models, there is an increasing trend in the coming years; the rainfall will rise overall, with the exception of the summer, by 2.19, 2.33, and 0.31 mm, respectively. Additionally, the end of the autumn season revealed an upward trend for the remaining months and seasons. The HadGEM2 atmospheric general circulation model's predictions of the average annual precipitation data at Kohdasht station under the RCP 2.6, RCP 4.5, and RCP 8.5 emission scenarios indicate a decreasing trend compared to the data from the base period. In the base period, Kohdasht experiences an average annual precipitation of 31.55 mm. According to the three scenarios RCP 2.6, RCP 4.5, and RCP 8.5, there is a decreasing trend in comparison to the output of HadGEM2 atmospheric general circulation models in the future, which is roughly -2.20, -0.70, and -3.80 mm, respectively. With the exception of the spring season, which had a minor rise, the precipitation parameter exhibited a decreasing tendency throughout the other seasons.