جستجوی مقالات مرتبط با کلیدواژه « تنش های گرمایی » در نشریات گروه « جغرافیا »

Historical article: Today, one of the most important aspects of climate change is the increase in the frequency of extreme events such as heat waves, cold waves, torrential rains, droughts and other climatic conditions, which is due to increased entropy due to global warming in the climate system. The main purpose of this study is to investigate the temporal and spatial nature of hot waves as a climatic and bioclimatic hazard in the metropolitan area of Ahvaz. In this regard, the daily data of Ahvaz synoptic station during the 60-year period 1961-2019 were used to extract heat waves. Using the normalized daily deviation model from the long-term temperature of the same day, hot waves were identified each year and their time series trends were examined. To investigate the bioclimatic risk of hot waves, a typical hot wave that ruled from 7 to 13 July 2015 in the metropolis of Ahvaz was selected. The ground surface temperature of Ahvaz city was extracted by applying a single channel algorithm on the heat bands of Landsat 8 thermal sensor for July 9, 2015, and using the observation data at 09:00 AM,Ahvaz meteorological station was converted to air temperature for the same day. Using hot spot spatial analysis, critical areas of Ahvaz city were identified during the hot wave and the amount of population exposed to the line was obtained from the population census blocks of the 2016 census using cross-matrix analysis. The results showed that firstly, during the period 1961 to 2019, there was an increasing trend with a slope of 0.08 hot wave per year in hot events in Ahvaz metropolis and secondly, during the hot wave event, the temperature in Ahvaz was different from 44 to 55 degrees.The northern parts of the city and the area around the Karun River, which passes through the center of Ahvaz, as well as the green space around the Karun River, had the lowest surface temperature at this time of day. The temperature in this range varied between 44 and 46 degrees Celsius. A large part of the central areas of Ahvaz, which generally includes the urban area, had a temperature of about 49 to 51 degrees Celsius. The results showed that the total population of Ahvaz is in the critical core of the hot wave and the bioclimatic risk of the hot wave can affect the total population of this metropolis, which was about 1.2 million people. Hot waves and heat stresses caused by heatstroke in urban environments are about to become one of the most important hazards of the urban climate. Awareness of the intensity of hot waves in different urban areas and along with awareness of the vulnerable population at risk of heatstroke ( Both age groups (the elderly and children) can be very useful for organizing the spatial distribution of urban emergency facilities and services and intensive care related to heatstroke. In this study, the spatial distribution of the risk of thermal stresses due to the occurrence of a hot wave in the city of Ahvaz was investigated. In the first step, by examining the spatial distribution of air temperature during the occurrence of a hot wave in the city, satellite images of thermal sensor, TIRS Landsat 8 were used. Demographic analysis in relation to hot wave risk, showed that in general, the population of Ahvaz metropolis, according to the general population and housing census in 2016 was equal to 1184788 people and the population density of the city is 65 people per hectare. Population analysis In 212056 of the population of Ahvaz are in the age category under 10 years, which is equal to 18% of the total population of Ahvaz. These children are very vulnerable to the risk of hot flashes in the city due to low cardiovascular capacity, which has created thermal stresses between 48 and 50 degrees during the peak of the hot wave. The risk of hypothermia or heatstroke in this age group can appear in this age group in the form of dehydration, risk of dehydration or severe dehydration, shortness of breath and increased heart rate and skin burns, suffocation, especially in hot and humid conditions. . In the age group of the elderly or the population over 65, the risk of hot flashes is more acute and destructive. Hot wave is one of the most serious bioclimatic hazards in Ahvaz metropolis that puts the entire population of Ahvaz at risk of acute heatstroke and can cause deaths due to 30% of the vulnerable population of the city (elderly and children). Exacerbate severe heat stress.

Nowadays, extreme events, as one of the signs of climate change, have become major climatic hazards. The main objective of this study is to investigate the population exposed hyperthermia in Kermanshah at the time of the heat waves. In this regard, the heat waves of Kermanshah synoptic station were extracted during 2000-2015, and the heat wave in July from 7 to 13 was selected as the case study. The land surface temperature of Kermanshah city was extracted by applying a single channel algorithm on the thermal bands of ،TIRS sensor of the Landsat 8 platform for July 9, 2015. The obtained LST turned into air temperature using 09 UTC air temperature of Kermanshah meteorological Synoptic station. Using spatial statistics analysis of hot spots, critical regions of Kermanshah were identified during heat wave and the population of high risk was obtained from demographic block of 2016 census using tabular matrix analysis. The results showed that 6 districts of Kermanshah with an area of 3072 hectares form a critical heat core. The daily temperature mean of this heat core for 6 heat wave days was not less than 36 degrees Celsius, while the mean of maximum temperature of this part of the city was 47 degrees Celsius. The analysis of the tabular matrix indicates that according to the census of 2016, 0.52 of the total population of the city of Kermanshah, 492285 people, were located in the critical core area, and the population density in this core was 160 people per hectare, which is twice the density of Kermanshah city. 0.44 of the population of two demographic class (99893 people) that have high vulnerability to heat waves, heat stress and hyperthermia, namely, young children (under the age of 10) and the elderly (over the age of 60) are located in the heat core area. Nowadays, the climate change or, more precisely, global warming has had the greatest impact on different aspects of human life as the most serious environmental challenge facing human societies. Urban areas occupy less than 0.1 percent of the earth's surface (Lee and Baik, 2011), but most of the world's population (6.6 billion) is currently living in urban areas (Miller et al, 2013). High population density in urban areas, potentially increase the vulnerability of cities and cause environmental hazards to be more damaging, especially climate hazards. Over the past decades, population growth, rapid growth of industrialization, increased air pollution at low levels of the atmosphere, and the effects of island heat, cause dramatic changes in the  local weather and climate of the big cities. Increasing of climatic hazard frequency, severity and emerging climatic hazards are the most important aspects of climate change. Increasing frequency of extreme event, such as heat waves as one of the critical climatic hazards, has been listed in the World Health Organization since 2005 (Arbuthnott, 2016). The city of Kermanshah with a population of 946,651 people in 2017 is the largest city of Kermanshah province and the second most populous western city of the country after Tabriz and the ninth most populous city of Iran after Tehran, Mashhad, Isfahan, Tabriz, Karaj, Shiraz, Ahvaz and Qom. 0.48 percent of the total populations of the Kermanshah province live in the Kermanshah city (census of 2017). The main objective of this research is to investigate the vulnerability of Kermanshah city in the face of heat waves as one of the emerging climatic hazards. Two types of data were used in this study. The first batch was observed daily air temperature data, and the second batch was Landsat 8 imagery. We calculated daily mean air temperatures obtained from synoptic station of Kermanshah. To distinguish days with extreme air temperature, we used the method of (Fumiaki et al., 2007) that is called normalized temperature deviation or Fumiaki index. Considering the fact that there is only one synoptic station located on the northeastern part of the city, it is not possible to assess the degree of damage caused by heat wave hazard in different parts of Kermanshah city. For this reason, we used data from thermal bands of Landsat 8 (10 and 11 bands) to calculate the land surface temperature of Kermanshah city for the heat wave days. First, land surface temperature was obtained by calculating the brightness temperature, and in the next step, LST was transformed to two-meter air temperature using the development of a function. The hot spots analysis model was used to identify and detect blocks or critical areas of Kermanshah city during the occurrence of heat waves. This analysis, based on Getis-Ord Gi* is used to identify areas or neighborhoods of Kermanshah where during the heat wave event their air temperature was significantly (at a confidence level of 0.95 (P_value = 0.05) higher than the surrounding area. Using tabulate matrix analysis, the relationship between detected critical temperature regions during the heat wave and the population at risk of critical temperatures were identified in different regions of Kermanshah. To assess the potential risk of hyperthermia and the population at risk of it, the heat wave of 7-12 July 2015 was selected as the case study. This heat wave began on 7 July 2015. The warmest day of this heat wave, in terms of daily maximum air temperature, was on the fourth day of the heat wave namely, 11 July. In this day, the mean air temperature of Kermanshah reached 39.3°C, while the maximum air temperature reached 43.2° C. The results of the Getis-Ord Gi hot spot analysis, show that a large part of Kermanshah's area has an instantaneous air temperature that is significantly higher than its surrounding areas. These parts of the city, which have temperatures between 42 to 45°C have a significantly higher temperature than the surrounding areas at a confidence level of 0.95 (P_value = 0.05), forming a significant hot spot. The area of this critical category was 3072 hectares, equal to 0.32 of the total area of the Kermanshah. The daily mean air temperature of this hot core was not lower than 36°C during the 6-day heat wave in 2015, while the mean maximum air temperature of this part of the city was 47°C. The results of the cross tabulate analysis reveals that, 0.522 of the total population of the city of Kermanshah, 492285 people are located in the parts of the city, which its air temperature during the heat wave is in the significant critical area based on the hot spots index. As it can be seen, out of the 40% of the Kermanshah children, 54,436 people were located in this thermal core in which mean air temperature was over 38°C. 0.38 of the elderly population of the total population (33,376 people) was also located in this hot core with a maximum air temperature of 44°C during the heat wave. It was revealed that during the heat wave, a significant part of the area of Kermanshah is exposed to the risk of critical temperatures above 40°C. The area of the city which forms the critical hot core during the heat wave includes a significant part of the population of Kermanshah that is equal to 52% of the total population of the city. Out of 40% of the Kermanshah children, 54,436 people were located in this thermal core in which mean air temperature was over 38°C. 0.38 of the elderly population of the total population (33,376 people) was also located in this hot core with a maximum air temperature of 44°C during the heat wave.