Validation of the COSMIC Radio Occultation Data over Gadanki (13.48°N, 79.2°E): A Tropical Region
Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC), consisting of six Low Earth Orbit (LEO) Global Position System (GPS) receivers, on board the Formosat Satellite 3 (FORMOSAT-3) is providing dense observations of density, refractivity, temperature and water vapor profile...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Springer
2009-01-01
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| Series: | Terrestrial, Atmospheric and Oceanic Sciences |
| Subjects: | |
| Online Access: |
http://tao.cgu.org.tw/images/attachments/v201p059.pdf
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| _version_ | 1818139476526891008 |
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| author | D. Narayana Rao M. Venkat Ratnam Sanjay Mehta Debashis Nath S. Ghouse Basha V. V. M. Jagannadha Rao B. V. Krishna Murthy T. Tsuda Kenji Nakamura |
| author_facet | D. Narayana Rao M. Venkat Ratnam Sanjay Mehta Debashis Nath S. Ghouse Basha V. V. M. Jagannadha Rao B. V. Krishna Murthy T. Tsuda Kenji Nakamura |
| author_sort | D. Narayana Rao |
| collection | DOAJ |
| description | Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC), consisting of six Low Earth Orbit (LEO) Global Position System (GPS) receivers, on board the Formosat Satellite 3 (FORMOSAT-3) is providing dense observations of density, refractivity, temperature and water vapor profiles of the neutral atmosphere since middle of July 2006. Special radiosonde (Väisälä) campaign was conducted at Gadanki (13.48°N, 79.18°E), a tropical site in India, during July 2006 to March 2007 to validate these meteorological parameters. Co-located Nd: YAG Rayleigh lidar was also operated during the overpass of COSMIC and is utilized to validate the temperatures in the height range of 30 to 40 km. Atotal of 142 overpasses occurred during the above mentioned period within 300 km distance from Gadanki out of which 41 overpasses occurred within a time difference of ±4 hours of radiosonde launch. In addition, 18 overpasses occurred within the time difference of ±4 hours of lidar operation. A detailed comparison has been made with all these overpasses for the refractivity, temperature and water vapor obtained from COSMIC. The water vapor comparison has shown generally a good agreement with a mean difference of 5 - 10% below 6 - 7 km. Although there is a colder bias between COSMIC and radiosonde, a very good comparison in temperature is also found between 10 and 27 km with a mean difference of less than 1 K (RMS difference is only 0.64 K). There exists a large difference in temperature of about 8 K between 30 and 40 km (between COSMIC and lidar). Possible reasons for these large differences are given. There was one event that occurred just over Gadanki for which a detailed comparison has been made with special emphasis on water vapor retrievals. Sensitivity test is also done on the fractional difference in N for the event that occurred on 24 July 2006 between COSMIC (1D-var) and radiosonde and found that pressure plays a key role than temperature in determining the refractivity. |
| first_indexed | 2024-12-11T10:28:42Z |
| format | Article |
| id | doaj.art-92c48ff31c574be7a3b661486e6f18a3 |
| institution | Directory Open Access Journal |
| issn | 1017-0839 2311-7680 |
| language | English |
| last_indexed | 2024-12-11T10:28:42Z |
| publishDate | 2009-01-01 |
| publisher | Springer |
| record_format | Article |
| series | Terrestrial, Atmospheric and Oceanic Sciences |
| spelling | doaj.art-92c48ff31c574be7a3b661486e6f18a32022-12-22T01:11:03ZengSpringerTerrestrial, Atmospheric and Oceanic Sciences1017-08392311-76802009-01-0120105910.3319/TAO.2008.01.23.01(F3C)814Validation of the COSMIC Radio Occultation Data over Gadanki (13.48°N, 79.2°E): A Tropical RegionD. Narayana RaoM. Venkat RatnamSanjay MehtaDebashis NathS. Ghouse BashaV. V. M. Jagannadha RaoB. V. Krishna MurthyT. TsudaKenji NakamuraConstellation Observing System for Meteorology Ionosphere and Climate (COSMIC), consisting of six Low Earth Orbit (LEO) Global Position System (GPS) receivers, on board the Formosat Satellite 3 (FORMOSAT-3) is providing dense observations of density, refractivity, temperature and water vapor profiles of the neutral atmosphere since middle of July 2006. Special radiosonde (Väisälä) campaign was conducted at Gadanki (13.48°N, 79.18°E), a tropical site in India, during July 2006 to March 2007 to validate these meteorological parameters. Co-located Nd: YAG Rayleigh lidar was also operated during the overpass of COSMIC and is utilized to validate the temperatures in the height range of 30 to 40 km. Atotal of 142 overpasses occurred during the above mentioned period within 300 km distance from Gadanki out of which 41 overpasses occurred within a time difference of ±4 hours of radiosonde launch. In addition, 18 overpasses occurred within the time difference of ±4 hours of lidar operation. A detailed comparison has been made with all these overpasses for the refractivity, temperature and water vapor obtained from COSMIC. The water vapor comparison has shown generally a good agreement with a mean difference of 5 - 10% below 6 - 7 km. Although there is a colder bias between COSMIC and radiosonde, a very good comparison in temperature is also found between 10 and 27 km with a mean difference of less than 1 K (RMS difference is only 0.64 K). There exists a large difference in temperature of about 8 K between 30 and 40 km (between COSMIC and lidar). Possible reasons for these large differences are given. There was one event that occurred just over Gadanki for which a detailed comparison has been made with special emphasis on water vapor retrievals. Sensitivity test is also done on the fractional difference in N for the event that occurred on 24 July 2006 between COSMIC (1D-var) and radiosonde and found that pressure plays a key role than temperature in determining the refractivity. http://tao.cgu.org.tw/images/attachments/v201p059.pdf GPS ROWater vaporTemperatureValidation |
| spellingShingle | D. Narayana Rao M. Venkat Ratnam Sanjay Mehta Debashis Nath S. Ghouse Basha V. V. M. Jagannadha Rao B. V. Krishna Murthy T. Tsuda Kenji Nakamura Validation of the COSMIC Radio Occultation Data over Gadanki (13.48°N, 79.2°E): A Tropical Region Terrestrial, Atmospheric and Oceanic Sciences GPS RO Water vapor Temperature Validation |
| title | Validation of the COSMIC Radio Occultation Data over Gadanki (13.48°N, 79.2°E): A Tropical Region |
| title_full | Validation of the COSMIC Radio Occultation Data over Gadanki (13.48°N, 79.2°E): A Tropical Region |
| title_fullStr | Validation of the COSMIC Radio Occultation Data over Gadanki (13.48°N, 79.2°E): A Tropical Region |
| title_full_unstemmed | Validation of the COSMIC Radio Occultation Data over Gadanki (13.48°N, 79.2°E): A Tropical Region |
| title_short | Validation of the COSMIC Radio Occultation Data over Gadanki (13.48°N, 79.2°E): A Tropical Region |
| title_sort | validation of the cosmic radio occultation data over gadanki 13 48°n 79 2°e a tropical region |
| topic | GPS RO Water vapor Temperature Validation |
| url |
http://tao.cgu.org.tw/images/attachments/v201p059.pdf
|
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