نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه جغرافیای طبیعی، دانشکده علوم زمین، دانشگاه شهید بهشتی، تهران، ایران
2 پژوهشکده هواشناسی، پژوهشگاه هواشناسی و علوم جو، تهران، ایران
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Introduction
Nowadays, many specialists testify the reality of global warming. This warming affects many thermal anomalies. Some of these anomalies show themselves in the form of warmth records especially over cold and moderate realms. At a national level, the Iranian city with the highest temperature makes new headlines. For instance, in 2015 the temperature of more than 49 degrees Celsius was recorded for Gonbad-Kavoos City in the province of Golestan as the warmest city of Iran.
Materials and methods
In this investigation, we obtained the data of daily temperatures of 33 cities over Iran for warm half of year (1971 to 2010) based on the method of environment to circulation. The extracting of daily records of weather stations and their frequencies were finalized in MATLAB platform. When daily temperature tables were set, the Hottest City (HC), their Frequencies (FC) and their temperatures (TC) were determined. In these tables, cities were sorted based on their descending latitudes. In this stage, the highest records during every year were defined on based on access to daily weather charts and designed synoptic patterns. For instance, the annual highest record of warmth was 19.5 degrees Celsius. It was related to Lengeh port in Southern Iran at 1971. These daily charts were obtained from ENCEP/ENCAR. Based on them, the centers of all high-pressure effective systems including Azores, Sahara and Hijaz were determined on base maps in order to design synoptic patterns and their analysis across Atlantic Ocean to Pacific.
Results and discussion
Results showed RC frequency has reduced from 11 cities to 6 ones during the three last decades. It means, we will have less HC but more FC in future over Iran. This reduction is not gratifying because results show that records have grown for Abadan, Ahwaz and Bandar-abbas Cities over Sothern Iran. Designed synoptic patterns of high-pressures included Azores and Sahara and Indus Low during high TCs over based maps showed that:
1) The centers of Azores Highs appear like a group in the middle of the Atlantic Ocean but they appeared straggly during low ones. 2) We found similar results for Sahara Highs over Africa. 3) Also, the location of Indus Low centers over Southern Asia appeared more zonal in comparison with low records. Altogether, the high TCs in Iran accompanied with baro-tropic atmosphere from the center of Atlantic Ocean to India Peninsula.
Conclusion
Overall, the highest records of warmth are accompanied by baro-tropic atmosphere over Atlantic Ocean to the Indian Peninsula. Alongside weakening of thermo-dynamic Siberian Highs, it seems that concentration of Azores Highs over Eastern Atlantic Ocean and Saharan Highs over Africa and Hijaz ones over Southern Iran cause an increase in the frequency of high warmth-records over Iran.
کلیدواژهها [English]
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