ارزیابی بکارگیری نهفتگی رادیویی زمین پایه جهت رصد تغییرات رطوبت نسبی و فشار لایه های جو پایین در کشور

امروزه کاربردهای نوینی از سیستم ماهواره‌های ناوبری مانند gpsدر زمینه های هواشناسی مطرح شده است. استخراج پارامترهای جوی با استفاده از روش نهفتگی رادیویی با توجه به قرارگیری ماهواره‌های ناوبری gpsدر مدار زمین، در سال های اخیر به یک روش کاربردی تبدیل شده است. نهفتگی رادیویی زمین‌پایه یک تکنیک نو برای کاوش جو پایین می‌باشد. در این پژوهش شبیه‌سازی ای از نهفتگی رادیویی زمین‌پایه بر روی کوه دماوند، کوه سبلان در منطقه شمال غربی و کوه بزمان در جنوب غربی ایران انجام شده و برنامه استخراج داده های جوی با استفاده از این روش پیاده سازی شده است. اعتبار داده های بدست آمده از پدیده نهفتگی رادیویی زمین‌پایه بر روی قله دماوند در دو روز متفاوت مورد بررسی قرارگرفته است. پارامترهای جوی بدست آمده از این روش با داده‌های رادیوسوند واقع در منطقه مهرآباد مورد ارزیابی قرارگرفته و نتیجه نشان می‌دهدکه نمودارهای بدست آمده از روش نهفتگی رادیویی زمین‌پایه مطابقت خوبی با نمودارهای رادیوسوند در منطقه دارد. همانطور که در کشورهای دیگر نیز آزمایش شده، روش نهفتگی رادیویی زمین‌پایه به عنوان یک تکنیک نو و اقتصادی برای کاوش تغییرات جو پایین و روش مکمل رادیوسوند برای جمع‌آوری داده‌های مربوط به جو پایین است که از اهمیت به سزایی برخوردار می باشد و موجب بالا بردن دقت پیش‌بینی های هواشناسی در کشور می شود.

Assessment of utilizing the ground-based radio occultation for monitoring the relative humidity and lower atmosphere layers pressure by using the GPS signals in Iran

Introduction The typical method in meteorology organizations for derivate the profiles of atmospheric parameters variations, is the meteorology balloon equipped with radiosondes. In each its ascent and in 2 hours period of flight, it can derivate the different heights data from the earth surface to 30 km from the sea level. Considering the high costs of radiosonde transmitters, meteorology stations are able to just one or maximum two launches per day, generally. Therefore, this limitation causes to reduction of the time accuracy of the atmospheric variations forecasts in heights, specifically the relative humidity. Consequently, it decreases the prediction of atmospheric conditions in seasons like spring that the conditions even vary hourly. Materials and Methods   Utilizing the complementary methods, covering these disadvantages and making it possible to assess the atmospheric conditions more times throughout the day, is too considered by the world meteorology research centers.Nowadays, new applications of navigation satellites systems like GPS and GLONASS are considered in the field of meteorology. According to preliminary tests conducted in China, it was found that by inserting a GPS receiver with a 360 degree field of view on a 5kmhigh mountain, 80 to 100 latency events are detectable.The same coefficient of refraction can be calculated on a daily basis. This information, which can be converted to atmospheric parameters, is located around the receiver’s location. The results obtained from this method and its comparison with the data extracted from the radiosonde indicate that it is reliable. This is the method. In order to provide the necessary conditions for conducting such tests in Iran, high points were selected for placing MBRO receivers. Recent years, derivation of the atmospheric parameters by using the radio occultation, has become a practical method. Groundbased radio occultation is a novel technique for exploring the lower atmosphere parameters. In this research, a simulation of groundbased radio occultation has been carried out, on Damavand Mountain, Sabalan Mountain in the northwest region, and Bazman Mountain in the southwest of Iran and the atmospheric parameters derivation program based on this method has been implemented. Also for verification, Atmospheric parameters derived by MBRO such as relative humidity and water vapor pressure, on Damavand mountain in two different days are compared to radiosondes data of Mehrabad region and the result shows that curves of groundbased radio occultation has fine confirmation with radiosondes curves. As experiments in other countries, MBRO is an affordable method for exploring the variation of lower atmosphere and a complementary method of radiosondes for gathering the lower atmosphere data. Resutls In this paper, the concept and function of the Mountain based radio occultation (MBRO) method are presented and the results are evaluated by simulation and comparison method. The simulation results show that with the placement of MBRO receivers in different mountains of Iran, a suitable coverage of tangent points can be obtained. The amount of this coverage and the number of occultation phenomena and the length depend on the geographic location of the receiver’s placement and its height. The maximum duration of the satellite’s exposure to the occultation in Iran is about 20 minutes. By obtaining these tangential points in the desired areas and determining the bending strength of each received signal, and using partial bending which is obtained due to reception of a positive and negative upward angle signal in the receiver, we can obtain the refractive index of the barley At high altitudes below the receiver’s location and therefore atmospheric parameters reached low altitudes, and due to the large amount of latency information in the range of several hundred kilometers of high points in Iran at a low cost, measurements performed by radiosonde in shorter time intervals were completed. Improve weather forecasts and shortterm forecasts. We simulate the simulation on the mountains (Damavand, Sabalan, Bazman). At the end of the comparison between the results of the application of Layer Radio latency on Mount Damavand in two different seasons with Radiosonde information located at Mehrabad Airport and its results are presented. When receiver combined with receivers that can receive other signals from satellite navigation satellites such as Glonass and Galileo, the available data volume and accuracy of results will increase significantly. The evaluation shows that the use of groundbased radio occultation method due to increased extraction of atmospheric data, especially at low altitudes, has a significant effect on raising the accuracy and speed of meteorological forecasts and increasing its efficiency in warning at the time and reducing the damage caused by phenomena such as flood.