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Showing 3 results for Heat Waves

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Volume 19, Issue 52 (3-2019)
Abstract

The heat waves today are one of the most important climatic hazards in the world. According to many scientists, the Severe and frequent occurrence of heat waves in recent years has been due to the emission of greenhouse gases and consequent increased global warming. The purpose of this study is to investigate changes in the frequency and intensity of heat waves As well as their relationship with Global land-ocean temperature anomalies and greenhouse gases in the north-west of Iran. At First, maximum temperature of two meters of the surface during the period from 1851 to 2014 for 164 years was obtained from NASA’s website, then the maps of heat waves was drawn and extracted. Then, we analyzed and evaluated the frequency and severity of the heat waves, as well as changes in the annual, decade, fifty years old fluctuations and their centenary were analyzed. To achieve the research objectives, Pearson and Spearman correlation methods, linear and polynomial regression and non-parametric Mann-Kendall test were used. The results showed that the frequency of occurrence of heat waves in the considered period interval is incremental and relevant, and the most frequency of occurrence was in decades. Also the intensity of the heat waves is associated with a relatively significant increase, and the most intense heat waves occurred in the decades of the late 20th and early 21st century until the present period. The results of the correlation coefficients indicated that the intensity and frequency of the heat wave incidence have a positive and significant correlation with the Global land-ocean temperature anomalies. The results of investigating the relationship between frequency and intensity of heat waves with 4 important greenhouse gases, including: (CO2, CH4, N2O, SF6), showed that, except for the positive and significant correlation of carbon dioxide gas with the most severe  heat waves in June, There was no meaningful relationship between them. The results of the Mann-Kendall test indicate an incremental and significant increase in the frequency and intensity of heat wave events in the North-West region of Iran.

Dr Mahmoud Hooshyar, Dr Behrouz Sobhani, Nader Parvin,
Volume 19, Issue 54 (9-2019)
Abstract

Early heat waves are extreme events that cause heavy losses in plant and animal life and cause many social and economic problems for communities. The purpose of this study was to identify synoptic patterns and statistical analysis of preterm heat waves in northwestern Iran. To do this, the maximum daily temperature data of March 14th was used for fourteen synoptic stations in the northwest of the country during the statistical period (1333-1393) Hijri Shamsi. Then, on the basis of the threshold, the Baldy index was selected for 61 days of heat wave. All statistical characteristics of the data were processed in SPSS software. They were The elevation data of the middle atmosphere of the atmosphere was extracted from a NCEP / NCAR database on a network with an arc 2/5 × 2/5 degree on the 0 to 70 degree eastern longitude and 0 to 60 degrees north latitude. The matrix was made up of 864 columns in 40 rows, with rows of days with thermal waves and elevation data on the columns on the middle of the atmosphere. The analysis of the basic components was performed on the algebraic data matrix matrix And 12 components that account for about 93 of the variations in pressure levels above 500 hp, were identified. To identify the coherent patterns, cluster analysis was performed on the scores of the components by the WARD integration method. Five types of pre-heat generation waveform patterns were identified. The results of this study showed that the premature heat waves in the northwest of Iran are due to high altitude formation in southern Arabia, the Aden valley and the center of Sudan at a level of 500 hpa and the formation of Sudan's low pressure in the sea level and the discharge of its tabs to the north and northeast of the region The case study (Northwest of Iran) also includes events occurring.
Mrs. Nasibeh Baharvandi, Dr. Firouz Mojarrad, Dr. Jafar Masompour,
Volume 20, Issue 59 (12-2020)
Abstract

The heat wave is a long period of warm climate, compared to the expected conditions in a region over a certain period of the year. Heat waves cause mortality, disease and various problems in different fields of transportation, agriculture, production and energy. It is very important to study the changes in spatial and temporal patterns of these waves to understand the causes of the incident and confront them. In the present study, using the "Heat Wave Magnitude Index daily" (HWMId), which takes into account both the intensity and the wavelength of heat, the heat waves of Iran between 1985 and 2015 have been analyzed in terms of spatial and temporal distribution. For this purpose, using the maximum daily temperature data of 44 synoptic stations of the country and on the basis of the threshold of the 90th percentile, the heat waves greater than or equal to three days were identified at each station. After applying the HWMId on the days of each heat wave, the magnitude of each wave was calculated. Then, the average number and magnitude of all waves, as well as the most severe ones, were calculated in annual and seasonal scales and the corresponding maps and charts were drawn up. The results of the study showed that the highest number of heat waves occurs in the western part of the Zagros Mountains and then the Kavir Plain; while the maximum magnitude of heat waves belong to the south-east and central parts of the country. Autumn and then winter season have a high share of the most severe heat waves during the study period; while the spring and summer heat waves are relatively weaker, and are more limited in terms of expansion. The most severe heat waves during the study period have occurred in the winters of 2008 and 2010. The number and magnitude of heat waves in the country is increasing significantly. The largest increase in the number belongs to the summer and the magnitude belongs to the winter.


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