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پژوهش های جغرافیای طبیعی، جلد ۴۶، شماره ۱، صفحات ۱۲۳-۱۳۶
عنوان فارسی بررسی نوسان اقلیم در استان فارس با استفاده از جابه‎جایی نصف النهاری نوار پرارتفاع جنب گرمسیری
چکیده فارسی مقاله نوار همگرایی درون­گرمسیری­ (ITCZ) درگذر فصل دارای جابه‎جایی نصف­النهاری است. تغییر موقعیت ITCZ روی موقعیت نوار پرارتفاع جنب­ گرمسیری (STH) اثر ­می­گذارد. هدف پژوهش، بررسی نوسان اقلیمی در فارس با مطالعۀ موقعیت پرارتفاع جنب گرمسیری است. داده­های ماهانۀ ارتفاع ژئوپتانسیل سطح 500 میلی­بار، از تحلیل مجدد NCEP به‎دست آمد و نصف­النهار E°5/52 در نظر گرفته شد. با مشاهدۀ سری نقشه­های 500 میلی­باری و توجه به امواج غربی و STH، تراز ارتفاعی 5840 متر، به‎منزلۀ مرز شمالی نوار پرارتفاع جنب­ گرمسیری (NBSTH) مد نظر قرار گرفت و سری زمانی ماهانۀ موقعیت NBSTH به‎کمک برنامه‎نویسی در GrADS ساخته شد. نتایج نشان داد موقعیت NBSTH به اندازۀ 7/2 به‎سمت عرض­های جغرافیایی شمالی­تر جابه‎جا شده است، بنابراین سیگنال نوسان اقلیمی در منطقه مشخص شد. این مسئله موجب افزایش دورۀ حاکمیت STH و کاهش دورۀ فصل بارش می‎شود. موقعیت و جابه‎جایی NBSTH بیش از اینکه بر میزان بارش مؤثر باشد، روی طول فصل بارش اثر دارد. زمانی­که موقعیت NBSTH از عرض جغرافیایی ایستگاه پایین­تر رود، فصل بارش آن ایستگاه آغاز خواهد شد و زمانی پایان می­پذیرد که تحت تأثیر پرارتفاع جنب گرمسیری (NBSTH) باشد. نتایج نشان داد طول فصل بارش در آباده شش ماه و نیم، شیراز شش ماه و در لار پنج ماه در سال است.
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عنوان انگلیسی Climate Oscillation Assessment by Meridional Displacement of Sub Tropical High Passing over Fars Province
چکیده انگلیسی مقاله IntroductionAccording to General Circulation Model (GCM), zonal thermal belts are: 1. Inter- TropicalConvergence Zones (ITCZ) around equator; 2. Sub Tropical High (STH) belt around 30 degreelatitude; 3. Sub Polar Low (SPL) belt around high latitudes. Inter- Tropical Convergence Zonesbelt has meridional migration on the different seasons and its position affects directly thesituation of STH. The STH situation is the most important synoptic climatological pattern inMiddle East and Iran due to changing season. The belt of Inter Tropical Convergence Zone(ITCZ) displaces in meridional path, about 5° over oceans and up to 40° in continents, duringseasons of a year. The position of Sub Tropical High (STH) belt has been also affected by ITCZmovements. STH displacement may change the area covered by westerly Baroclinic Waves(BW) in temperate regions. The Northern Boundary Sub Tropical High (NBSTH) movescoincidently as the northern border of the STH belt. The position of the NBSTH is an importantissue for changing precipitation regime and onset of precipitation events in Fars Province. Thegoal of this research is to determine the position of NBSTH over Fars in monthly scale duringthe period 1948 - 2010, undertaking its meridional displacement.MethodologyDataset of geopotential height in multi levels (monthly scale) was extracted from NCEP/ DOEReanalysis published by NOAA using by GrADS (Grid Analysis and Display System) softwarefor 52.5°E meridian over Fars Province. By consecutive observation of 756 numbers of 500 hPamonthly maps in GrADS scope, 5840 gpm contour was indicated as the NBSTH indicator. It is􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯∗E-mail: golmohammadianhadis@yahoo.com Tel: +98 939657396222 Physical Geography Research Quarterly, 46 (1), Spring 2014because southern area of 5840 gpm contour is almost covered by STH system while thenorthern area occupied by westerlies during monthly round maps. This result agrees withprevious studies. The strip of NBSTH is considered with 20 m width ranging from 5830 gpm to5850 gpm. Monthly time series of NBSTH position (unit: degree of northern latitude) was thendetected using GrADS programming. The non-parametric Mann-Kendall trend test was appliedon time series of NBSTH position in monthly and annual scale.Results and DiscussionResults show that the position of NBSTH is between 10°N and 47.5°N as the most extremes inwinter and summer, respectively. For long term means, the minimum latitude of NBSTH was inaverage observed in January, placed on 18°N zone while maximum is happened in August,crossing 41°N zone during the investigated period. Its meridional displacement then reaches to23° over Iran in average. Moreover, climatic means of Northern Boundary Sub Tropical Highpositions during 1981- 2010 period with respect to 1951 - 1980 period were migratedapproximately 2.7 ° northward. The non-parametric Mann-Kendall trend test was then applied. Itshowed generally raising trends under 0.01 significance level, with 0.07 slope approximationsduring 1948-2010. It demonstrated the signal of climatic variability of atmospheric circulationover Fars. This significant trend may also shorten the period of the rainy season in Fars. Rainyseason of the most stations in Fars may be defined as the period when the NBSTH position goesto the southern zones of the station and consequently subjected to the atmospheric baroclinicstate of westerlies.ConclusionThe more precise results need primitive data in daily scale that suggested for the next step.Nevertheless, it is generally deduced that the lower latitudes of Fars have thus shorter durationof the precipitation seasons. The belt of STH dominates over a zone when the NorthernBoundary Sub Tropical High (NBSTH) position is above latitude the station. Changes inprecipitation regimes are also related to the NBSTH position. The onset of precipitation eventsfor the stations located in the Fars starts climatically later than those located in the north becauseof NBSTH situations. It is also suggested to use time series of NBSTH position as the input ofclimatic prediction models yielding temperature and precipitation. It is suggested that the timeseries of NBSTH position is as the input of climate prediction models yielding temperature andprecipitation as well as drought study. In drought study, agricultural management as well asmassive economical and social programming in Iran seems to be essential due to NBSTHposition.
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نویسندگان مقاله حدیث گل محمدیان |
کارشناس ارشد هواشناسی کشاورزی، دانشکدۀ کشاورزی، دانشگاه شیراز
سازمان اصلی تایید شده: دانشگاه شیراز (Shiraz university)

نشانی اینترنتی http://jphgr.ut.ac.ir/article_50623_6caa75b40ac43a6584ccf9af34017d17.pdf
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