واكاوي شار همگرايي رطوبت و آب قابل بارش جو بارش هاي بهارۀ ايران

Analysis of atmospheric precipitation water and moisture flux convergence spring rains Iran

بررسي سازوكار انتقال و شناسايي منابع تامين رطوبت بارش هاي يك منطقه و شناخت مؤلفه هاي چرخه آب بر روي آن از موضوعات موردتوجه در علوم جوي است. پژوهش حاضر باهدف مطالعه شار همگرايي رطوبت و آب قابل بارش جو و شناسايي منابع تامين رطوبت بارش هاي بهاره ايران صورت گرفته است. براي اين منظور از داده هاي بارش روزانه 483 ايستگاه سينوپتيكي، كليماتولوژي و باران سنجي در يك دوره آماري 50 ساله (1961- 2010) استفاده شده است. پس از استخراج روزهاي بارشي فراگير به كمك تحليل خوشه اي الگوهاي شار همگرايي رطوبت و آب قابل بارش جو بارش بهاره شناسايي شده اند و سپس اقدام به استخراج نقشه هاي فشار تراز دريا، 850 و 700 هكتوپاسكال به همراه شار همگرايي رطوبتي و آب قابل بارش جو در منطقه موردمطالعه شده است. نتايج نشان داد كه مكانيسم بارش هاي فراگير بهارۀ ايران و شار همگرايي رطوبت در ارتباط با همگرايي شار رطوبتي ناشي پرفشار سيبري- كم فشار عربستان ، شار همگرايي رطوبت ناشي از پرفشار قزاقستان – كم فشار خليج فارس، شار همگرايي رطوبت ناشي از پرفشار شمال درياي خزر - كم فشار شرق تركيه، كم فشار عربستان، شار همگرايي رطوبت ناشي از پرفشار سيبري- كم فشار عربستان، سودان و شار همگرايي رطوبت ناشي از پرفشار سيبري – كم فشار تركمنستان، كم فشار سودان بوده است. بيشترين مقدار رطوبت و شار همگرايي رطوبت از سمت درياي عرب، خليج فارس، درياي خزر و درياي سرخ در ترازهاي پايين جو و درياي مديترانه و سياه درترازهاي بالايي جو است.

Introduction A large amount of water in the seas and oceans on the earth is concentrated and a large body of water, water, gases, aerosol particles and momentum exchanges with the atmosphere (big et al 2003:275). So, how patterns of atmospheric circulation, especially with the increasingly moisture flux patterns are consistent with pressure (ghaemi 1994:272). Various forms of water transfer in addition to the dependence on atmospheric general circulation in different time periods. In general, two types of moisture flux vertical and horizontal in the atmosphere are always combined with each other and only possible and under certain conditions the amount of them may increase flux horizontally by advection of air to carry moisture from the Evaporative to other parts of flux and vertical evaporative to transfer moisture from the surface into the atmosphere takes place in the vertical direction (Lindesay and. Dabreton 1993: 13). Transfer of water vapor in the atmosphere conditions are directly related to atmospheric circulation and changes in atmospheric circulation over time, the amount and the flow of moisture as well as altered. It pays to check the moisture flux convergence fact that wind is causing how much water vapor at different levels of the atmosphere(Masoudian and Mohammadi 2010: 47-70). Materials and Methods In this study in order to investigate explores the convergence of moisture flux and atmospheric water precipitation in the spring rainfall, the researchers used two types of databases:Environmental data: environmental data is collected in two parts. Data is obtained in two parts, in the first part of 1460 seeking observations from daily rainfall synoptic and climatic stations and humidity and climate station 483 from 1340 to 1383 Esfezari database is used. The division of the distance is 15.15 km spatial resolution data is in the Lambert cone-shaped image are written. It has the cell density is 7187 cells throughout Iran. In order to increase the temporal resolution of the database daily precipitation observations from 1383 to the end of 1390 using the same method and the same spatial resolution, interpolation is added to the data base. Then the database is used to determine the rainy day of three conditions:1 day which has at least 3 types of coverage in distance is a 2 mm and above have experienced at least two days to continue. 3 cover at least 50 percent of place. 2. The weather data: in this section to determine the flux convergence humidity and water precipitation rain sweeping spring of data, sea level pressure, water temperature, wind component zonal and meridional moisture, especially in heights of the database (NCEP / NCAR) dependent on the United States of America at the National Oceanic and atmospheric levels of 850, 700 and 1000 hPa is extracted. Results and Discussion In search of moisture flux and the participation levels of water to provide humidity, precipitation in the spring of Iran or in other words in the convergence of moisture flux toward Iran fluctuations and changes observed is such that these variations in the levels of the sea, 850 700 hp with an intensity that has faced. In between the Arabian Sea, Persian Gulf, Red Sea, at 850 and 700 hPa as pronounced in flux, humidity, precipitation in the spring of and the Caspian Sea, in addition to providing moisture coastal areas in sea level of moisture sources Home rains of spring Northwest. In this regard, the Mediterranean when the low pressure Sudan is activated by South Stream and East Mediterranean to the northern Red Sea moves and in accordance with flowing toward the south and southwest of Iran is shifted while the humidity of the Black Sea, because of systems and the presence of northern and northeastern Iran East side to side pass. Minimal role in flux rainfall events in the spring of Iran, especially in the south-eastern region studied the Indian subcontinent, and any time that the transfer of moisture from the Indian subcontinent and the Arabian Sea synchronized as can moisture precipitation in the southeast of the country meet. Thus it can be seen that between the Red Sea and Gulf of changes lower levels in the atmosphere, there is no coordination with the Arabian Sea and Oman. At the same time, the autocorrelation Space moisture in the country has shown that moisture values prized high autocorrelation high ledges in the spring in the coastal strip of the Caspian Sea, Persian Gulf and parts of the North West there; so that the least amount of change autocorrelation Space Conclusions This study aimed to study the convergence of moisture flux and atmospheric water precipitation and identify sources of moisture in the spring precipitation has been Iran. For this purpose, the daily precipitation data of 483 synoptic, climatological and rain in a 50-year period (1961- 2010) is used. After extraction rainy days sweeping through cluster analysis patterns flux convergence humidity and water precipitation atmosphere of spring precipitation has been identified and then proceed to derive maps of sea level pressure, 850 and 700 hp with flux convergence humidity and water precipitation barley the study area is. pressure East, Turkey, Saudi pressure, moisture flux convergence of high pressure low pressure Siberian- Saudi Arabia, Sudan and moisture flux convergence of Siberian high pressure - Turkmenistan low pressure, low pressure Sudan. Most of the moisture content and moisture flux convergence of the Arabian Sea, Persian Gulf, Caspian Sea and the Red Sea and the Mediterranean and Black upper atmosphere at levels lower atmosphere.