Introduction

T. Periods of climatic comfort, periods with hot and cold thermal stress, can be shifted in the climate change conditions and their length can also change during the year. Knowledge of these bioclimatic changes of climate comfort can provide a good basis for climate change adaptation planning. The city of Ahvaz is one of the main and major metropolises of the country, which faces significant challenges in terms of bioclimatic conditions. Thermal stresses in the hot period of the year and the frequency of heat waves along with dust events, especially in the last two decades, have severely affected the climatic comfort and bioclimatic conditions of the city.



Materials and methods

Ahvaz city is the center and largest city of Khuzestan province. Ahvaz city is located between 48 degrees to 49 degrees and 29 minute’s east longitude from the Greenwich meridian and 30 degrees and 45 minutes to 32 degrees north latitude from the equator. In this research, daily temperature and relative humidity data were used during the statistical period of 1970-2020, for the synoptic station of Ahvaz city. The monthly average of minimum and maximum temperature as well as the monthly average of minimum and maximum relative humidity for the mentioned statistical period were obtained from the National Meteorological Organization. The data related to the near future climate, i.e. the statistical period of 2021-2040, was obtained from the output of the HADGM3 general circulation model based on the 6th CMIP6 climate change report under the SSP245 release trajectory, for the Ahvaz station location. The bioclimatic calendar of Ahvaz city was produced during three periods using the EVANZ model, which included the base period (1970-1990), the current period (2000-2020) and the near future period (2021-2040).



Findings

The average minimum and maximum temperature in the current period is generally 1.2 degrees Celsius and in the future climate period is 1.5 to 2 degrees Celsius more than the base period, and based on this, the bioclimatic calendar of Ahvaz city has undergone changes. In the metropolis of Ahuz, in the basic and present period in 6 months of the year, i.e. from May to October, during the day there is heat stress and a feeling of heat discomfort in the city, while the number of these months is associated with heat stress in the climate. The simulated future is extended to nearly 8 months of the year, considering that the use of electricity-based cooling energy during daytime hours to adjust the indoor temperature is one of the active strategies recommended in the EVANZ model in these months. Therefore, in the future climate period, due to the lengthening of the heat stress period from 6 months to 8 months, the amount of electricity consumption in Ahvaz city will increase by about 30%. On the other hand, in this research, it was seen that in the basic period during the 4 months of December to March, the conditions of bioclimatic comfort are available during the day, while in the current climate and the future climate, the length of the climatic comfort period is close to 3 months (November until February) has decreased. Climatic comfort at night in Ahvaz metropolis also saw significant changes in the future climate compared to the climate of the base period. The results of this research showed that in the climate of the current and base period, in 6 months of the year, from November to April, there is limited cold stress during the night during the hours of the night, while the simulated future climate of these cold stress conditions It exists only in 5 months of the year, from November to March, and the month of April has changed the bioclimatic situation in the future climate and entered the climatic comfort class without cold stress. Another significant change that has been made in the bioclimatic calendar of Ahvaz city is that in the climate of the basic period only in July and August there are nights with heat stress causing discomfort, which requires artificial cooling of the environment, while In the climate of the present period and the near future period, this period has been extended to 4 months of the year, i.e. June to September, and there is a need for artificial cooling of the home environment during the night hours, which is the problem of the electricity consumption of Ahvaz city in the field of cooling the home environment. It increases by about 50%.



Conclusion

In Ahuz metropolis, during the base period from May to Mehr, during the day there is heat stress and a feeling of heat discomfort in the city, while the number of these months with heat stress in the simulated future climate has reached 8 months. It means that the two months of April and November have also been transferred to this floor along with the daily heat stress. Therefore, in the future climate period, due to the lengthening of the heat stress period from 6 months to 8 months, the amount of electricity consumption in Ahvaz city will increase by about 30%. Also, the results showed that in the climate of the current and base period, there is limited cold stress during the night for 6 months of the year, that is, from November to April, while the simulated climate of the future has this cold stress condition for 5 months. Also, in the climate of the basic period, there is a need for artificial cooling of the environment only in two months, while in the climate of the current period and the near future period, this period has increased to 4 months, and there is a need for artificial cooling of the home environment during the night hours, which The problem of electricity consumption in Ahvaz city increases in the field of environmental cooling.