| Preliminary Results of 4-D Water Vapor Tomography in the Troposphere Using GPS |
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| 作者姓名： | 毕研盟 毛节泰 李成才 |
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| 作者单位： | Department of Atmospheric Sciences, School of Physics, Peking University, Beijing 100871 |
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| 基金项目： | Acknowledgments. The authors would like to ac- knowledge Massachusetts Institute of Technology （MIT） for their GAMIT package. We thank the SuomiNet program for providing the GPS data at station SA34. We also wish to thank Dr. Fu Yang for providing partial GPS data. We thank Dr. Song Shuli and Dr. Cao Yunchang for their useful discussions and suggestions about the tomographic problem. |
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| 摘 要： | Slant-path water vapor amounts (SWV) from a station to all the GPS (Global Positioning System) satellites in view can be estimated by using a ground-based GPS receiver. In this paper, a tomographic method was utilized to retrieve the local horizontal and vertical structure of water vapor over a local GPS receiver network using SWV amounts as observables in the tomography. The method of obtaining SWV using ground-based GPS is described first, and then the theory of tomography using GPS is presented. A water vapor tomography experiment was made using a small GPS network in the Beijing region. The tomographic results were analyzed in two ways: (1) a pure GPS method, i.e., only using GPS observables as input to the tomography; (2) combining GPS observables with vertical constraints or a priori information, which come from average radiosonde measurements over three days. It is shown that the vertical structure of water vapor is well resolved with a priori information. Comparisons of profiles between radiosondes and GPS show that the RMS error of the tomography is about 1–2mm. It is demonstrated that the tomography can monitor the evolution of tropospheric water vapor in space and time. The vertical resolution of the tomography is tested with layer thicknesses of 600 m, 800 m and 1000 m. Comparisons with radiosondes show that the result from a resolution of 800m is slightly better than results from the other two resolutions in the experiment. Water vapor amounts recreated from the tomography field agree well with precipitable water vapor (PWV) calculated using GPS delays. Hourly tomographic results are also shown using the resolution of 800 m. Water vapor characteristics under the background of heavy rainfall development are analyzed using these tomographic results. The water vapor spatio-temporal structures derived from the GPS network show a great potential in the investigation of weather disasters.
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| 关 键 词： | 层析术 水蒸气 GPS 全球定位系统 倾斜路径 |
| 收稿时间： | 2005-07-05 |
| 修稿时间： | 2005-12-02 |
Preliminary results of 4-D water vapor tomography in the troposphere using GPS |
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| Yanmeng Bi,Jietai Mao,Chengcai Li.Preliminary Results of 4-D Water Vapor Tomography in the Troposphere Using GPS[J].Advances in Atmospheric Sciences,2006,23(4):551-560. |
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| Authors: | Yanmeng Bi Jietai Mao Chengcai Li |
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| Institution: | Department of Atmospheric Sciences, School of Physics, Peking University, Beijing 100871,Department of Atmospheric Sciences, School of Physics, Peking University, Beijing 100871,Department of Atmospheric Sciences, School of Physics, Peking University, Beijing 100871 |
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| Abstract: | Slant-path water vapor amounts (SWV) from a station to all the GPS (Global Positioning System)satellites in view can be estimated by using a ground-based GPS receiver. In this paper, a tomographic method was utilized to retrieve the local horizontal and vertical structure of water vapor over a local GPS receiver network using SWV amounts as observables in the tomography. The method of obtaining SWV using ground-based GPS is described first, and then the theory of tomography using GPS is presented.A water vapor tomography experiment was made using a small GPS network in the Beijing region. The tomographic results were analyzed in two ways: (1) a pure GPS method, i.e., only using GPS observables as input to the tomography; (2) combining GPS observables with vertical constraints or a priori information,which come from average radiosonde measurements over three days. It is shown that the vertical structure of water vapor is well resolved with a priori information. Comparisons of profiles between radiosondes and GPS show that the RMS error of the tomography is about 1-2 mm. It is demonstrated that the tomography can monitor the evolution of tropospheric water vapor in space and time. The vertical resolution of the tomography is tested with layer thicknesses of 600 m, 800 m and 1000 m. Comparisons with radiosondes show that the result from a resolution of 800 m is slightly better than results from the other two resolutions in the experiment. Water vapor amounts recreated from the tomography field agree well with precipitable water vapor (PWV) calculated using GPS delays. Hourly tomographic results are also shown using the resolution of 800 m. Water vapor characteristics under the background of heavy rainfall development are analyzed using these tomographic results. The water vapor spatio-temporal structures derived from the GPS network show a great potential in the investigation of weather disasters. |
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| Keywords: | GPS slant path water vapor tomography |
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