水汽层析技术在研究气候变化、极端天气预警、辅助数值天气预报等方面发挥着重要作用。常规的水汽层析技术在计算层析方程系数时，需要进行大量的求交运算。对此，本文提出了一种投影面算法，提高了运算速度和反演的精度。本文采用的试验数据是香港卫星定位参考站网（SatRef）提供的GPS信号数据，与传统算法相比，投影面算法的计算速度更快、计算量更小，不受层析区域大小影响，水汽层析的结果与探空数据具有良好的一致性。
Water vapor tomography is of crucial theoretical importance to and widely applied in meteorology and climatology, for instance, extreme weather forecasting and now casting, numerical weather prediction and climate change study. Conventional water vapor tomography strategy for calculating equation coefficient needs extensive calculation. To solve this problem, projection plane algorithm is developed for improving the speed of calculation and the accuracy of inversion. The GPS signal data used in this article comes from Hong Kong SatRef. The result, which is compared to the traditional algorithm, indicated that new algorithm reduces the computing time greatly and is not affected by size of tomography area and there is consistency in the results of tomographic inversion and radiosonde.
[1] JIANG P,YE S R,LIU Y Y,et al.Near Real-time Water Vapor Tomography Using Ground-based GPS and Meteorological Data:Long-term Experiment in Hong Kong[J].Annales Geophysicae,2014,32(8):911-923.
[2] FLORES A,RUFFINI G,RIUS A.4D Tropospheric Tomography Using GPS Estimated Delays[C]//Proceedings of the IEEE 1999 International Geoscience and Remote Sensing Symposium,1999.Hamburg:IEEE,1999,1:675-677.
[3] SHRESTHA S M.Investigations into the Estimation of Tropospheric Delay and Wet Refractivity Using GPS Measurements[R].Calgary,Alberta:University of Calgary,2003.
[4] HOYLE V A.Data Assimilation for 4-D Wet Refractivity Modelling in a Regional GPS Network[R].Calgary,Alberta:University of Calgary,2005.
[5] PANY T,PESEC P,STANGL G.Atmospheric GPS Slant Path Delays and Ray Tracing through Numerical Weather Models:A Comparison[J].Physics and Chemistry of the Earth,Part A:Solid Earth and Geodesy,2001,26(3):183-188.
[6] BI Yanmeng,MAO Jietai,LI Chengcai.Preliminary Results of 4-D Water Vapor Tomography in the Troposphere Using GPS[J].Advances in Atmospheric Sciences,2006,23(4):551-560.
[7] TROLLER M,LEUENBERGER D,BROCKMANN E,et al.GPS-tomography:Results and Analyses of the Operational Determination of Humidity Profiles over Switzerland[J].Geophysical Research Abstracts,2007,9:11-18.
[8] BENDER M,RAABE A.Preconditions to Ground Based GPS Water Vapour Tomography[J].Annales Geophysicae,2007,25(8):1727-1734.
[9] BOCK O,DOERFLINGER E,MASSON F,et al.GPS Water Vapor Project Associated to the ESCOMPTE Programme:Description and First Results of the Field Experiment[J].Physics and Chemistry of the Earth,2004,29(2-3):149-157.
[10] PERLER D,GEIGER A,HURTER F.4D GPS Water Vapor Tomography:New Parameterized Approaches[J].Journal of Geodesy,2011,85(8):539-550.
[11] CHAMPOLLION C,MASSON F,BOUIN M N,et al.GPS Water Vapour Tomography:Preliminary Results from the ESCOMPTE Field Experiment[J].Atmospheric Research,2005,74(1-4):253-274
[12] XIA P,CAI C,LIU Z.GNSS Troposphere Tomography Based on Two-step Reconstructions Using GPS Observations and COSMIC Profiles[J].Annales Geophysicae,2013,31(10):1805-1815.
[13] ROHM W,BOSY J.The Quality of Meteorological Observations and Tropospheric Delay from EPN/IGS Permanent Stations Located in the Sudety Mountains and in the Adjacent Areas[J].Acta Geodynamica et Geomaterialia,2007,4(4):145-152.
[14] VEDEL H,HUANG Xiangyu.Impact of Ground Based GPS Data on Numerical Weather Prediction[J].Journal of the Meteorological Society of Japan,2004,82(1B):459-472.
[15] 丁金才.GPS气象学及其应用[M].北京:气象出版社,2009.DING Jincai.GPS Meteorology and Its Applications[M].Beijing:China Meteorological Press,2009.
[16] BEVIS M,BUSINGER S,HERRING T A,et al.GPS Meteorology:Remote Sensing of Atmospheric Water Vapor Using the Global Positioning System[J].Journal of Geophysical Research:Atmospheres,1992,97(D14):15787-15801.
[17] 刘春华.三维投影矩阵的刻画及迭代重建的加速研究[D].太原:中北大学,2008.LIU Chunhua.The Study of Building Three-dimensional Projection Matrix and Accelerate Iterative Image Reconstruction[D].Taiyuan:North University of China,2008.
[18] BRESENHAM J E.Algorithm for Computer Control of a Digital Plotter[J].IBM Systems Journal,1965,4(1):25-30.
[19] AMANATIDES J,WOO A.A Fast Voxel Traversal Algorithm for Ray Tracing[J].Eurographics,1987,87(3):10.
