Journal of Spatial Analysis Environmental Hazards
تحلیل فضایی مخاطرات محیطی
Journal of Spatial Analysis Environmental Hazards
Literature & Humanities
http://jsaeh.khu.ac.ir
1
admin
2423-7892
2588-5146
10.61186/jsaeh
fa
jalali
1401
9
1
gregorian
2022
12
1
9
3
online
1
fulltext
fa
واکاوی تغییرات سهم سامانه هایی با منشاء کم فشار سودانی در بارندگی دوره سرد کرانه های شمالی خلیج فارس طی سال های 1976-2017
Synoptic analysis of the changes trend of the share of systems due to the Sudan low In the cold period of the Persian Gulf coast during 1976-2017
تخصصي
Special
پژوهشي
Research
<strong>تحقیق حاضر با هدف تحلیل تغییرات طولانی مدت</strong> <strong>بارش هایی با منشاء کم فشار سودان در دوره سرد سواحل شمالی خلیج فارس می باشد. به همین منظور آمار روزانه بارش در 13 ایستگاه سینوپتیک برای چهار سیکل خورشیدی طی سال های 1976-2017 و برای سه ماه پر بارش دسامبر، ژانویه و فوریه از سازمان هواشناسی کشور دریافت شد. براساس معیار بارش بالای 5 میلی</strong><strong>‏</strong><strong>متر در هر ایستگاه، کلیه سامانه های بارشی بدست آمد. برای روزهای دارای بارش و روز قبل تر از آن، از مرکز پیش بینی جوی- اقیانوسی ایالات متحده آمریکا داده های فشار تراز دریا</strong> <strong>و ارتفاع 1000 هکتوپاسکال دریافت شد. با روش تحلیل چشمی موقعیت جغرافیایی، شکل گیری و جابجابی سامانه های فشاری شناسایی و سامانه های سودانی از سایر سامانه های جوی جداسازی شدند. در نهایت بارش‏ها با منشاء سودانی به الگوهای یک الی هفت ‏روز تقسیم‏بندی شدند. تحلیل های همدید و آماری طی چهار دهه اقلیمی صورت گرفت. نتایج نشان داد که 77 درصد بارش دوره سرد سواحل شمالی خلیج فارس از سامانه سودانی مستقل تامین می شود. فراوانی روزهای دارای بارش سودانی در تمام ایستگاه ها طی دهه اول به دهه دوم افزایش دارد. در گذر از دهه دوم به سوم تعداد روزهای دارای بارش سودانی تغییر چشمگیری ندارد اما در دهه پایانی سهم بارش های ناشی از سامانه کم فشار سودانی به نسبت دهه های گذشته افزایش داشت. افزایش فعالیت باران زایی سامانه سودانی بمعنای تغییر اقلیم مثبت درجهت افزایش سهم سامانه سودانی در بارش های جنوب و جنوب غرب ایران می باشد. </strong>
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<span style="font-size:11pt"><span style="line-height:normal"><span calibri="" style="font-family:"><span style="background:white"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span><br>
<span style="line-height:normal"><b><span style="font-size:14.0pt"><span style="background:white"><span new="" roman="" style="font-family:" times="">Synoptic analysis of the changes trend of the share of systems due to the Sudan low </span></span></span></b></span><br>
<span style="line-height:normal"><b><span style="font-size:14.0pt"><span style="background:white"><span new="" roman="" style="font-family:" times="">In the cold period of the Persian Gulf coast during 1976-2017</span></span></span></b></span><br>
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<span style="line-height:normal"><span style="direction:rtl"><span style="unicode-bidi:embed"><b><span dir="LTR" style="background:white"><span new="" roman="" style="font-family:" times=""> Introduction</span></span></b><b><span lang="AR-SA" style="background:white"><span style="font-family:"Times New Roman",serif"></span></span></b></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:normal"><span calibri="" style="font-family:"><span style="background:white"><span new="" roman="" style="font-family:" times="">In the Ethiopian-Sudan range forms the low pressure system without front in the cold and transition seasons that is affecting the climate of the adjacent regions by crossing the Red sea. </span></span><span new="" roman="" style="font-family:" times="">Based on the evidence in the context of Iran, studying Sudan low was first begun by Olfat in 1968. Olfat refers to low pressures which are formed in northeastern Africa and the Red Sea and then pass Saudi Arabia and the Persian Gulf, enter Iran, and finally, cause rainfall.</span> <span new="" roman="" style="font-family:" times="">The most comprehensive research specifically examining Sudan low, was the work carried out by the Lashkari in 1996. While he studying the floods that occurred in southwestern of Iran, he was identified Sudan low by the most important cause of such flooding and he explained how they are formed, and how these low-pressure systems were deployed on the southwest of Iran.</span></span></span></span><br>
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<span style="line-height:normal"><span style="direction:rtl"><span style="unicode-bidi:embed"><b><span dir="LTR" style="background:white"><span new="" roman="" style="font-family:" times=""> Materials and methods</span></span></b><b><span lang="AR-SA" style="background:white"><span style="font-family:"Times New Roman",serif"></span></span></b></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:normal"><span calibri="" style="font-family:"><span new="" roman="" style="font-family:" times="">The study period with long-term variations was considered from 9.5 to 11 years based on solar cycles. Precipitation data for 13 synoptic stations are considered above 5 mm in south and southwestern Iran. With three criteria were determined for the days of rainfall caused by each type of atmospheric system. </span><span style="background:white"><span new="" roman="" style="font-family:" times="">The visual analysis of high and low altitude cores and geopotential height at 1000 hPa pressure level (El-Fandy, 1950a; Lashkari, 1996; 2002) were considered based on the aim of the study. Accordingly, the approximate locations of activity centers, as well as the range of the formation and displacement of the Sudan system were initially identified based on the location of the formation of low and high-pressure cores. Then, the rainy days due to the Sudan system in January were separated from the precipitation of the other atmospheric system.</span></span></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:normal"><span calibri="" style="font-family:"><b><span style="background:white"><span style="font-family:"Times New Roman",serif"></span></span></b></span></span></span><br>
<span style="line-height:normal"><span style="direction:rtl"><span style="unicode-bidi:embed"><b><span dir="LTR" style="background:white"><span new="" roman="" style="font-family:" times=""> Results and discussion</span></span></b></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:normal"><span calibri="" style="font-family:"><span style="background:white"><span new="" roman="" style="font-family:" times="">According to the selected criteria in the forty-year statistical period, 507 precipitation systems were identified with different continuities that led to precipitation in the northern coast of the Persian Gulf.</span></span> <span style="background:white"><span new="" roman="" style="font-family:" times="">The pattern of independent Sudan low rainfall was responsible for 77% of the precipitation in the Persian Gulf. Decade frequency share of Sudan low was lower in the first decade (16%) compared to the next three decades.</span></span> <span style="background:white"><span new="" roman="" style="font-family:" times="">This system of rainfall was more activated during the second and third decades compared to the first decade. However, rainfall changes were not evident in the mid-decade. Independent Sudan low precipitation provide 25% and 27% of the cold season precipitation of the Persian Gulf during the second and third decades respectively. In accordance with the 24th solar cycle, at the end of the study period, the Sudan low was more effective on the Gulf coast than ever before. During this decade, 125 cases of Sudan low rainfall was recorded for the Persian Gulf. Thus, the frequency of Sudan low during the fourth decade was about 31%, which was higher than in the rest of the decade.</span></span> <span style="background:white"><span new="" roman="" style="font-family:" times="">Overall, the Sudan low rainfall was repeated 151 times for 2 days rainfall, during the statistical period studied. This Precipitation has increased over the last decades compared to other periods.</span></span></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:normal"><span calibri="" style="font-family:"><span style="background:white"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span><br>
<span style="line-height:normal"><span style="direction:rtl"><span style="unicode-bidi:embed"><b><span dir="LTR" style="background:white"><span new="" roman="" style="font-family:" times=""> Conclusion</span></span></b></span></span></span><br>
<span style="font-size:11pt"><span style="line-height:normal"><span calibri="" style="font-family:"><span style="background:white"><span new="" roman="" style="font-family:" times="">The severe variability of rainfall along the timing and location of the permanent Persian Gulf coasts can have a significant impact on the economic and agricultural behavior of the Gulf population in the three provinces of Ahwaz, Bushehr and Hormozgan.The purpose of this study was to evaluate the precipitation changes due to Sudan low in the Persian Gulf coastal region during the cold period.</span></span> <span style="background:white"><span new="" roman="" style="font-family:" times="">The results of this study showed that the role of integration patterns in influencing the precipitation of the Persian Gulf coast has decreased with the strengthening and further activation of the Sudan low system during the last two decades. That way, about 77percent of the region's rainfall is provided by independent Sudan low. At the end of the course (in accordance with 24th solar cycle activity) the Sudan low system was more active than before. Although the Sudan low activity was different at each station during the period studied, but in the historical passage incremental and decade's positive behavior of Sudan low was common to all stations.</span></span> <span style="background:white"><span new="" roman="" style="font-family:" times="">Evaluation of changes in rainfall duration shows that the pattern of precipitation with 2days duration is more frequent than the patterns of one to several days.</span></span></span></span></span><br>
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<span style="font-size:11pt"><span style="line-height:115%"><span calibri="" style="font-family:"><b><i><span style="background:white"><span new="" roman="" style="font-family:" times="">Keywords</span></span></i></b><span style="background:white"><span new="" roman="" style="font-family:" times="">: </span></span><span new="" roman="" style="font-family:" times="">Sudan low- Solar cycle- Persian Gulf.</span></span></span></span><br>
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چرخه خورشیدی, دوره سرد, خلیج فارس , کم فشار سودان
Solar cycle, cold period, Persian Gulf, Sudan low
1
18
http://jsaeh.khu.ac.ir/browse.php?a_code=A-10-1099-1&slc_lang=fa&sid=1
Hassan
Lashkari
حسن
لشکری
dr_lashkari61@yahoo.com
100319475328460010401
100319475328460010401
Yes
دانشگاه شهید بهشتی
Fahimeh
Mohammadi
فهیمه
محمدی
f_mohammadi@sbu.ac.ir
100319475328460010402
100319475328460010402
No
دانشگاه شهید بهشتی