تحليل تغييرات ناهنجاري‌ها و چرخه‌هاي آب قابل‌ بارش جوّ ايران

Analysis of anomalies and perceptible water cycles in Iran atmosphere

هدف از اين مطالعه بررسي ناهنجاري‌ها و چرخه‌هاي آب قابل بارش جوّ ايران زمين است. بدين منظور داده‌هاي فشار و نم ويژه طي دوره 1950-2010 از پايگاه داده‌هاي NCEP/NCAR وابسته به سازمان ملي جوّ و اقيانوس‌شناسي ايالات‌ متحده استخراج و تجزيه‌وتحليل شد. براي انجام محاسبات از امكانات برنامه‌نويسي در محيط نرم‌افزار Grads و Matlab و نيز براي انجام عمليات ترسيمي از نرم‌افزار Surfer بهره گرفته شد. نتايج بررسي ناهنجاري‌هاي آب قابل بارش جوّ ايران نشان داد كه نواحي سواحل به دليل هم‌جواري با منابع عظيم رطوبتي خليج‌فارس، درياي عمان و درياي خزر داراي ناهنجاري‌هاي مثبت و نواحي مركزي، نواحي مرتفع و شمال‌غرب و شمال‌شرق كشور به دليل دور بودن از منابع رطوبتي و متاثر بودن از ارتفاعات داراي ناهنجاري‌هاي منفي است. نتايج حاصل از تحليل چرخه‌ها نشان مي‌دهد كه چرخه‌هاي كوتاه‌مدت دو تا پنج ساله بيشترين حاكميت را در كشور داشتند. با وجود اين، بيشترين چرخه‌هاي كوتاه‌مدت در نواحي جنوب‌شرق رخ داده است. بيشتر دانشمندان چرخه‌هاي دو و سه ساله را با ال‌نينو – نوسانات جنوبي و گردش عمومي جوّ و جريانات مداري مرتبط مي‌دانند. همچنين، چرخه‌هاي دو تا پنج‌ساله را به رخداد ال‌نينو مربوط دانستند.

Introduction Perceptible water is the main part of the water cycle in the atmosphere and important variable for climate studies and important element of the process of atmospheric humidity in particular, atmospheric raining. Perceptible water, therefore have considered as an appropriate index on short and long term changes in climate. Recognizing the changes within a decade of perceptible water for knowing the region and local climate change is essential. Identification of changes within a decade, (decade to decade) of perceptible water can lead to the identification of climate oscillation as a decisive factor in raining and thus plays a significant role in macro planning based on precipitation. Perceptible water has oscillation in different time scales. For example, at the end of afternoon it creases under the influence of sun radiation .such daily variations follow heavy precipitation is very evident .Some anomalies of perceptible water follow the pattern of random behavior and some specific pattern. For example, positive anomalies of mid latitude arise from ocean currents and the effects of beyond phenomenon besides anomalies existing in perceptible water, cycles are also recognizable in this climate element. perceptible water is considered as a guide in numerical weather prediction and climate modeling, thus recognizing the necessity is the basis of climatology) .many scientists studied the cycles of Climatic elements ,first in relation to the Large-and small-scale circulation. One of the most important methods of presenting behavior and oscillating pattern of Climate elements is harmonic analysis. Data and Methods Consider a column of liquid water with cross-sectional area, and certain height. This height is the perceptible water. One way to determining the mass of water vapor (in grams) in a vertical column one square centimeter in cross-sectional area that extends from Earthʹs surface to the upper reaches of the atmosphere. Mathematically, if x(p) is the specific humidity at the pressure level, p, then the perceptible water vapor, PW, contained in a layer bounded by pressures p1 and p2 is given by Where g refers to gravity acceleration. For the purposes of our study, the pressure and specific humidity of NCEP/NCAR which exist for each 6 hours has been used. This data characterized by 2.5 longitude*2.5 latitude degree resolution. In order to estimate perceptible water, anomalies, first the center of perceptible water was calculated during triple period. For extracting of cycle, the harmonic analysis technique was developed. In harmonic analyzing of variance distribution, it use for the whole time series wave length. Each harmonic indicates periodic behavior in a time series. So each sequential wavelength is shown with a harmonic In General, for extraction of cycles by spectrum analyzer the following steps must be taken. (4 (5 In following relation, is the Average perceptible water q is the number of harmonic for even number series (q = n / 2) and for odd time series (q = n-1/2). Finally after extraction of variance, the whole waves were evaluated in terms of statistical significance. Discussion The area per decade over the entire period was faced with positive anomalies determined with dark colors and areas with negative anomalies determined with light-colored. Positive anomalies indicate on increasing of perceptible water and negative anomalies represent a decreasing of perceptible water over the entire period. With increasing of perceptible water in northern and southern coast center of gravity or the center of perceptible water are inclined toward center of the country. In the third period, this center inclined toward south. This indicates the greater weight of perceptible water of south coastal areas relative to the northern coast. The compression of average Center showed that perceptible water in all three periods roughly follows a fairly regular pattern. B) Perceptible water cycle By applying harmonic data analysis technique on Iran atmospheric perceptible water, significant sinus cycles were estimated in Iran area. The results are presented in Figure 1. In the North East of the country , cycle 2 to 5 and 24 years , in South East cycle 2 to 8 years old , in the North West , cycle of 2 to 3 , 6 , 11 and 24 years , and finally in the South West 2 , 3 , 16 and 24 years was dominant . Inter- annual variability (5-2 years old) is shown in a wide range of zones. This indicates that the perceptible water in most parts of the country have been short cycle.