Evaluating the effects of climate change on the climatic classification in Iran

Abstract

Introduction

The average weather condition in a certain region is described as climate. The diversity of climatic elements is effective in determining the climate of a region and causes the formation of diverse and different climates. One of the effects of climate change is that it causes an increase or decrease in a climatic zone and as a result leads to displacement in climatic zones. Climatic classification is an attempt to identify and recognize the differences and similarities of climate in different geographical regions and discover the relationships between different components of the climate system. Climate classification systems are used to visualize the current climate and quantify future changes in climate types, as predicted by climate models. The studies conducted on these methods show that climatic factors affecting experimental methods such as temperature and rainfall should be considered as effective factors in determining climatic boundaries in a new way. The De Martonne aridity index is an empirical index for climate classification based on two components of precipitation and temperature. Due to its high accuracy, the use of data that is more accessible and can be measured at all synoptic stations, De Martonne’s method has been given more attention by researchers and has been used in many researches to conduct climate studies. Therefore, the purpose of this research is to evaluate the effects of climate change on the climatic classification of Iran.

Materials and Methods

In this research, for the purpose of investigating the effects of climate change on the climatic classification of Iran, the De Martonne aridity index has been used. In order to show the impact of climate change in the past and the future on Iran's climate, meteorological data related to 120 synoptic stations of Iran, which are distributed in different places with different climates, were collected and analyzed in the statistical period of 1933-2022, and the climatic condition of Iran in the basic period, it was determined according to the De Martonne aridity index. Also, in order to investigate the effects of climate change in the coming periods on the climatic classification of Iran, the data related to the output of the CanESM2 model, which is one of the CMIP5 models that hybrid by the Canadian Center for Climate Modeling and Analysis (CCCMA) by combining CanCM4 and CTEM models, was used. In order to examine the changes of climatic classes of Iran under different scenarios and conditions, the output of two release scenarios, RCP2/6 and RCP8/5, were used. Due to the large-scale output of General Circulation Models (GCM), the output of the above model was scaled down using the LARS-WG model which is considered one of the most famous and widely used models for generating random weather data, which is used to generate precipitation values, minimum and maximum temperature, as well as daily radiation, under basic and future climate conditions.

Results and Discussion

According to the results, most of the area of Iran (90.49%) has a Arid and Semi-arid climate, so that the percentage of Arid climate is 68.82% and Semi-arid climate is 21.97%. Therefore, Iran should be called a Arid and semi-arid country in terms of climate. By examining the effects of climate change, it can be seen that in the coming periods, the precipitation and average annual temperature will increase, and this increase will be greater under the RCP8/5 scenario than the RCP2/6 scenario. The study of the climatic classification of Iran in the coming periods shows that most of the area of Iran will remain in Arid and Semi-arid climate. The sum of Arid and Semi-arid climates will reach its lowest level in the period of 2020-2041 and under the RCP2/6 scenario, and after that, these climates will expand again. According to the RCP8/5 scenario, in the periods of 2021-2040, 2041-2060 and 2061-2080, the total area of Arid and Semi-arid climates will decrease, but after that, in the period of 2081-2100, this trend will be reversed and we will see an increase in these climates. According to the results of this research and according to the forecast, although according to different release scenarios, the difference in the area of different classes can be seen, but in the future, Arid and Semi-arid climatic classes will still form the majority of Iran.

Conclusion

In this research, by using the latest available data, Iran's climate is classified by the De Martonne aridity index, and then the changes in Iran's climate classes under the influence of climate change in the coming periods, according to the output of the CanESM2 model from the CMIP5 modes, which is downscaled with the LARS-WG model, and it has been investigated according to two emission scenarios, RCP2/6 and RCP8/5. The results showed that Arid climate with 68.82% and Semi-arid climate with 21.97% constitute the largest area of Iran, and the amount of the rest of the classes is less than 10% of Iran's area. Therefore, Iran should be called an Arid and semi-arid country in terms of climate. Investigating the effects of climate change on precipitation and temperature showed that both precipitation and annual average temperature will increase in the coming periods, although the increase in both parameters will be more intense according to the RCP8/5 scenario. The study of the climatic classification of Iran in the coming periods indicates that most of the area of Iran will have an Arid and Semi-arid climate. The results of this research show the need to pay attention to the climate change and the need for experts and macro planners to pay attention to the effects of climate change. It is suggested to use the output of other GCM models in future research due to the uncertainty of climate scenarios. Also, the use of different climate classification methods that consider other parameters besides precipitation and temperature is suggested for better identification of climate characteristics.