Arabian Journal of Geosciences

, Volume 5, Issue 4, pp 781–787 | Cite as

Abel inversion for deriving refractivity profile from down-looking GPS radio occultation: simulation analysis

Original Paper

Abstract

Down-looking (DL) Global Positioning System (GPS) radio occultation can produce an estimate of the atmospheric refractivity profile. The main observations are the bending angle as a function of the impact parameter. DL provides both negative as well as positive elevation angle measurements. Abel inversion can be operated on a profile of partial bending angle found by subtracting the positive elevation measurement from the negative one with the same impact parameter. Abel inversion requires the spherical symmetrical assumption. Basically, partial bending calculation removes the ionospheric bending and hence it is possible to use a single frequency GPS receiver. The current paper introduces a simulation data for the case of a receiver on mountain top. The simulation uses model refractivity from MSISE-90 model as well as radiosonde data. Random noises are added to the bending angle profile before inversion. The result shows that it is possible to produce accurate vertical refractivity profile below the receiver altitude. The calculation of the water vapor profile is also made using temperature profile information from the MSISE-90 model as well as radiosonde. The errors in the retrieved vapor profile are always less than 0.1 mbar.

Keywords

GPS occultation Abel inversion Down looking Refractivity 

Arabic Summary

الملخص العربي

تستخدم موجات GPS القادمة من أسفل و المستترة في الغلاف الجوي في حساب التوزيع الرأسي لمعامل الانكسار في الغلاف الجوي. و تعتبر زاوية انحناء الأمواج كدالة في معامل التأثر هي الأرصاد الرئيسية لهذا الاستخدام. توفر موجات GPS القادمة من أسفل كل من الأرصاد ذات زوايا الارتفاع الموجبة و السالبة. ولحساب التوزيع الرأسي لمعامل الانكسار في الغلاف الجوي يمكن استخدام طريقة اّبل العكسية. و تتطلب طريقة أبل شرط التماثل الكرى. و لذلك يتم حساب فرق زاويا انحناء الأمواج ذات زوايا الارتفاع الموجبة و السالبة مما يعنى التخلص من تأثير طبقة الأينوسفير و ذلك يتيح استخدام مستقبل GPS أحادي التردد.

البحث الحالي يقدم تقييم لطريقةاّّبل لحساب التوزيع الرأسي لمعامل الانكسار في الغلاف الجوي باستخدام نماذج المحاكاة التي تستعين ببيانات النماذج الرياضية للغلاف الجوي و كذلك أرصاد البالونات. و قد تم إضافة الأخطاء العشوائية للتوزيع الرأسي لزاوية انحناء الأمواج قبل حساب معامل الانكسار. و تم تحليل البيانات باعتبار الغلاف الجوي في حالتيه الجافة و الرطبة. و قد أظهرت النتائج أنه يمكن استخدام طريقة اّبل لحساب التوزيع الرأسي لمعامل الانكسار للمنطقة أسفل مستقبل GPS و كذلك لحساب التوزيع الرأسي لضغط بخار الماء بدقة عاليه. و كانت قيمة الخطأ النسبي المئوية في حساب بخار الماء في حدود0,1% .

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Copyright information

© Saudi Society for Geosciences 2010

Authors and Affiliations

  1. 1.National Research Institute of Astronomy and GeophysicsCairoEgypt
  2. 2.Research Institute of Sustainable HumanosphereKyoto UniversityUjiJapan
  3. 3.Maritime Studies Department, Faculty of Marine ScienceKing Abdul Aziz UniversityJeddahSaudi Arabia

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