پديد آورندگان :
گلكار، فريد دانشگاه آزاد اسلامي واحد علوم و تحقيقات تهران , حجام، سهراب دانشگاه آزاد اسلامي واحد علوم و تحقيقات تهران , وظيفه دوست، مجيد دانشگاه گيلان
كليدواژه :
مُد 06 , محصولات فيزيك ابر , سنجنده مديس , باروري ابرها
چكيده فارسي :
بررسي مشخصه‌هاي فيزيكي ابر با هدف سنجش وقوع بارش به مطالعه امكان اجراي باروري ابر در زمان و مكان مناسب و كاهش خطاهاي تصميم‌گيري در اجراي عمليات افزايش بارش و در نتيجه كاهش هزينه‌هاي اجراي پروژه‌ها كمك مي‌كند. يكي از بهترين گزينه‌ها براي دستيابي به خصوصيات فيزيكي و ميكروفيزيكي ابرها بويژه در شرايط نبود داده‌هاي رادار هواشناسي، استفاده از محصولات و داده‌هاي ماهواره‌هاي هواشناسي از جمله سنجنده مديس است. قدرت تفكيك طيفي بالاي سنجنده مديس با 36 باند طيفي و همچنين حساسه‌هاي نصب شده مختص مطالعات ابر محقق را در شناسايي انواع ابرها توانمند مي‌نمايد كه از اين ميان 26 باند براي اهداف مطالعات مشخصات اتمسفر از قبيل پوشش ابري، نيمرخ جو، مشخصه‌هاي هواويزها، آب قابل بارش مجموع و ويژگيهاي ابر اختصاص دارد. از اساسي‌ترين مراحل كسب موفقيت در بارورسازي ابرها، تشخيص به موقع و دقيق شرايط و ابر مناسب براي باروري است. در كشورهاي توسعه يافته جهان با استفاده از ابزار سنجش از دور مانند ماهواره و بخصوص رادار هواشناسي، همچنين هواپيماهاي مجهز به آزمايشگاه فيزيك ابر اين كار انجام مي‌گردد (خطيبي، 1390 و شيواجي، 2005). در ايران به دليل نبود چنين امكاناتي مانند پوشش گسترده رادار هواشناسي و آزمايشگاه هوابرد، ناگزير بايد با انجام برخي روشهاي ابتكاري، با استفاده از داده‌هاي ماهواره‌اي موجود به اين اهداف دست يافت. بنابراين جنبه مجهول و مبهم قضيه، تشخيص موقعيت ابرهاي بارانزا از غير بارانزا در گستره وسيع و متنوع جغرافيايي و در كوتاه‌ترين زمان مي‌باشد. در سنجش غير مستقيم يا دور ابر، از مشخصه‌هاي فيزيكي ابر براي تشخيص بارش و پيش‌بيني آن استفاده مي‌شود.پژوهش حاضر در طول ماه فوريه سال 2009 ميلادي در استان فارس انجام گرديده است. در اين ماه بيشترين پروازهاي ماهيانه باروري سال 2009 (13 پرواز در 8 روز عمليات باروري ابر) انجام شده و منطقه فاقد اطلاعات رادار هواشناسي است. براي انجام تحقيق بر روي صحت انجام پروازهاي باروري در اين بازه زماني علاوه بر استفاده از داده‌هاي سنجنده مديس شامل محصولات فيزيك و ميكروفيزيك ابر اخذ شده از طريق تارنماي سازمان ناسا، از نقشه‌هاي هواشناسي مورد نياز تهيه شده از تارنماي نوا (نقشه‌هاي بازتحليل شده NCEP-NCAR) نيز استفاده گرديد. نتيجه كاربردي بدست آمده از اين تحقيق نشان مي‌دهد در صورتي كه در زمان اجراي پروژه باروري ابرها از محصولات مد 06 استفاده مي‌گرديد، مي‌توانست تعداد روزهاي اجراي باروري ابر از 8 روز ابري با وضعيت نامشخص از ديد وجود شرايط مناسب براي باروري ابرها به 3 روز مفيد و باراني كاهش يافته و از اجراي 6 پرواز باروري ابر بي‌اثر يا اثر، اجتناب نمود. بنابراين علاوه بر كاهش هزينه‌ها، امكان افزايش دقت اجراي پروژه و استفاده از فرصتهاي باروري در ديگر مناطق كشور فراهم مي‌شد.
چكيده لاتين :
Introduction
Study of the physical characteristics of cloud with the aim of estimate of precipitation occurence helps to study the possibility of performing cloud seeding project in the appropriate time and place and reduce errors in making decisions in execution of increased precipitation operations and thus reduce the costs of projects. One of the best options to achieve physical and microphysical properties of clouds, especially in the absence of weather radar data, is the use of meteorological satellites products and data, such as MODIS.
MODIS high spectral resolution with 36 spectral bands and also installed sensors for cloud studies will enable researchers to identify different types of clouds among which 26 bands are allocated for purposes of investigation of atmospheric characteristics such as cloud cover, atmospheric profiles, characteristics of aerosols and total precipitable water and cloud properties.
Also, the findings of Seemann and his colleagues in MODIS high spatial resolution imagery (1 km and less) makes it very suitable for meteorological applications.
The purpose of this research is the use of cloud physics level-2 products (mode 06) of MODIS to identify and separate raining from non-raining cloud regions in order to increase accuracy and reduce operation costs of precipitation enhancement project and to investigate the precipitation conditions and forecast using cloud physical and microphysical characteristics. Due to lack of extensive coverage in weather radar and airborne laboratory in Iran, inevitably must do some innovative methods using available satellite data to detect the position of the rain clouds in the broad and diverse geographic extent in the shortest time.
Materials and methods
Rosenfeld et al., (1994) investigated Relationship between precipitation and effective particle diameter in the top of cloud and showed that in clouds that the average of effective droplets radius is over 14 microns, the probability of precipitation is very high so that the results mentioned above are also used in this study.
On the other hand the results of the study conducted by Nauss and Kokhanovsky (2006) about a description of precipitation using cloud properties derived from optical satellite data for mid latitude front clouds were used.
Therefore, this article attempts to separate the raining and non-raining clouds using the results of research conducted, also the optical depth of clouds over a maximum of 40 units from 60 units with a high probability of precipitation were analyzed. On indirect or remote sensing is used physical characteristics of clouds for detection and prediction of precipitation. Present study was conducted in February 2009 in the Fars province. In this month the most cloud seeding flights of the year 2009 was performed (13 flights in 8 days cloud seeding operations) and local weather radar information is lacking.
To do a research on accuracy of flights during this time, in addition to MODIS satellite data including Physics and cloud microphysics products obtained through the NASA Web site, required weather maps produced by NOAA website (reanalysis maps from NCEP-NCAR) were used. Timely implementation of cloud seeding operations requires instantaneous information of weather conditions and cloud physics in the area. So that the country has access to MODIS sensor data through satellite receivers, it is possible to use these products for operational purposes and cloud seeding. For research purposes of available data of MODIS products on the NASA Website can also be used. MOD06 products which contains information on the characteristics of the cloud such as cloud phase, cloud top temperature, cloud top pressure, effective droplets diameter in the top of cloud and cloud optical depth or optical thickness have been used in the MOD06 algorithms and the results of it.
Results and conclusion
Due to the large number of days and performed cloud seeding flights on February 2009 and also pictures and maps of flights, was decided to discuss as an example, two different and chosen days regarding to appropriate cloud systems or inappropriate for seeding is discussed. Therefore, the general conditions for cloud seeding operation is available if these conditions are occurred simultaneously, optical depth is greater than 35 units, cloud top temperature more than - 30 ° C, height of top of middle clouds is higher than 500 mb, diameter of inside middle cloud droplets is more than 19 mm and cloud fraction is as a unit in designed area.
Otherwise if don't establish two or more of the criteria listed, the cloud seeding operation should be avoided .This study determined if cloud seeding project in Fars province on February 2009 was used products from MOD06, the number of cloud seeding operation days can be reduced from 8 of cloudy day (in uncertain conditions of existence of appropriate measures for cloud seeding) to 3 useful and rainy days and consequently can be avoided of 6 completely ineffective cloud seeding flights.
So, in addition to reduce costs the possibility of increasing project accuracy and using of other seeding opportunities in other talented areas of the country was provided.
