重力波一直以來都是研究大氣動力理論值得探討的一環，因觀測技術進步及理論發展，才開始對重力波有了進一步的了解。在觀測技術方面，像過去在極地或海洋地區取得大氣參數並非容易及充足的區域，研究這些資料不易取得地區的重力波活動情形，便往往產生了侷限，福爾摩沙三號於2006年四月發射，由六顆低軌微衛星組成，每天提供在全球約2000~2500個大氣剖面參數，它的主要科學目標是利用掩星觀測信號，推斷大氣參數，包括折射率、溫度、壓力和相對濕度場，為我們在研究重力波時，提供了一個很有利的資料平台。
本論文利用福爾摩沙三號掩星觀測的大氣溫度剖面資料，從2006年九月到2009年十二月，選取高度從20公里至40公里，分析亞洲與澳洲季風區（45°N~45°S, 60°E~160°E）重力波活動之季節變化，計算重力波平均位能能量(AveEp)值，來探討重力波活動在不同季節的變化，以及地域性重力波活動情形，將研究區域以每緯度15度及經度20度為間隔，劃分成三十個不重疊區域，並比較各區間的差異。季節變化中發現在15°N~30°N與15°S~30°S區域，分別在北半球夏季(JJA)與南半球夏季(DJF)有較大的AveEp值，在30°N~45°N與30°S~45°S區域，則分別在北半球冬季(DJF)與南半球冬季(JJA)有較大的AveEp值，地域性的分析觀察到北半球夏季(JJA)與南半球夏季(DJF)時，分別在印度半島與澳洲北部有較大的AveEp值，另外在2007年十二月到2008年二月觀察到AveEp值高出許多，推測很有可能的原因，在於當時反聖嬰現象造成沃克環流增強而產生了影響。

With the improvement of observation techniques and physical theories, scientists became more familiar with the gravity waves, a key factor of the atmospheric dynamics. In the past, atmospheric profiles were not supportive enough for us to conduct research on some hard-to-reach areas, such as the oceans and the Polar regions. Data shortage has caused many difficulties in climate studies until the launch of Formosat-3 in April, 2006. The constellation consists of six Low Earth Orbit (LEO) satellites at the height of 800 km, providing 2000 to 2500 soundings per day. The main scientific goal is to utilize the radio occultation (RO) signals to infer the atmospheric parameters, including refractivity, temperature, pressure, and relative humidity fields. The FORMOSAT-3/COSMIC has provided a very favorable data platform to perform the investigation of the gravity wave activities.
This paper is focused on the studies of the seasonal variations of gravity wave activities using the temperature profiles obtained by the FORMOSAT-3/COSMIC RO technique at height of 20~40 km, from September 2006 to December 2009. The average potential energy (AveEp) of the gravity waves was estimated to quantify the seasonal variations and compare those between Asian and Australian Monsoon regions（45°N~45°S, 60°E~160°E）. The study area was divided into 30 non-overlapped regions, each representing a 15 by 20 degree grid, in latitude and longitude, respectively. We compared those grids in different latitudinal intervals over different geographic locations. The result showed that the larger AveEp values of the 15°N~30°N and 15°S~30°S intervals occurred in summer - JJA for the northern hemisphere and DJF for the southern hemisphere. However, for 30°N~45°N and 30°S~45°S intervals, larger AveEp values appeared in winter - DJF for the northern hemisphere and JJA for the southern hemisphere. Furthermore, the spatial analysis of gravity wave activities indicated that within the higher AveEp value latitudinal intervals, the largest AveEp value located at the Indian Peninsula in the northern hemisphere summer (JJA) and Northern Australia in the southern hemisphere summer (DJF). In this study, we also found that the AveEp values were much higher than those in 07/08DJF and 08MAM. We believed the gravity anomalies were attributed to the strengthening of the Walker Circulation, which was caused by the La Nina phenomenon.

[1] Tsuda, T., Nishida, M., Rocken, C., and Ware, R. H., 2000：A Global Morphology of Gravity Wave Activity in the Stratosphere Revealed by the GPS Occultation Data, J. Geophys. Res., 105, pp.7257-7273
[2] Pavelyev, A.G., Y.-A. Liou*, J. Wickert, K. Zhang, C.-S. Wang, and Y. Kuleshov, 2010: Analytical model of electromagnetic waves propagation and location of inclined plasma layers using occultation data. Progress in Electromagnetics Research (PIER), pp. 177-202, July 2010. (SCI, IF= 3.763)
[3] Hu, X., Y.-A. Liou, X.-Y. Gong, T.-C. Chiu, Yeh, W.-H. Yeh, X. Wang, X.-C. Wu, C.-Y. Xiao, L. Xu, 2009: Inversion of COSMIC atmospheric open-loop radio occultation data. Chinese Journal of Geophysics-Chinese Edition, 52 (9): 2195-2200, 10.3969/j.issn.0001-5733.2009.09.002. (SCI, IF=0.844, RF=51/64)
[4] Chiu, T.-C., Y.A. Liou*, W.-H. Yeh, and C.-Y. Huang, 2008: NCURO data retrieval algorithm in FORMOSAT-3 GPS radio constellation mission, IEEE Trans. Geosci. Remote Sensing, Vol. 46, No. 11, doi:10.1109/TGRS.2008.2005038. (96-NSPO(B)-SP-FA07-02(N)) (SCI, IF=2.234) (2/2/2)
[5] *Liou, Y.-A., M. Hernandez-Pajares, V. Chandrasekar, and E. R. Westwater, 2008: Guest Editorial – Special Session on Meteorology, Climate, Ionosphere, Geodesy, and Reflections from the Ocean Surfaces: Studies by Radio Occultation Methods, IEEE Trans. Geosci. Remote Sensing, Vol. 46, No. 11, doi:10.1109/TGRS.2008.2005049. (SCI, IF=2.234, RF=2/15, REMOTE SENSING) (0/0/0)
[6] *Liou, Y.-A., A.G. Pavelyev, S. F. Liu, A.A. Pavelyev, N. Yen, C.Y. Huang, C. J. Fong, 2007: FORMOSAT-3 GPS radio occultation mission: preliminary results, IEEE Trans. Geosci. Remote Sensing, Vol. 45, No. 10, doi:10.1109/TGRS.2007.903365. (SCI, IF=2.234, RF=2/15)(21/9/21)
[7] *Liou, Y.-A., and A. G. Pavelyev, 2006a： Simultaneous observations of radio wave phase and intensity variations for locating the plasma layers in the ionosphere, Geophys. Res. Lett., 33, L23102, doi:10.1029/2006GL027112. (NSC 94-2811-M-008-055) (SCI, IF=3.204,) (5/3/5)
[8] *Liou, Y.-A., A.G. Pavelyev, J. Wicker, S.F. Liu, A.A. Pavelyev, T. Schmidt, and K. Igarashi, 2006: Application of GPS radio occultation method for observations of the internal waves in the atmosphere, J. Geophys. Res., 111, D06104, doi: 10.1029/2005JD005823. (SCI, IF=3.082, RF=11/144) (15/3/15)
[9] *Liou, Y.-A., 2005: Letter from the guest editor. GPS Solutions, 9, 85-87, DOI: 10.1007/s10291-005-0136-8. (SCI, IF= 2.04, RF=8/15, REMOTE SENSING) (1/1/1)
[10] Pavelyev, A.G., J. Wickert, T. Schmidt, Ch. Reigber, S. S. Matyugov, A.A. Pavelyev, Y.-A. Liou, and K. Igarashi, 2005a: Effect of solar activity in late October 2003 on radio occultation signals from the CHAMP German satellite. Geomagnetism and Aeronomy, Vol. 45, No. 1, 2005, Pp. 134-139. (SCI, IF= 0.947, RF=42/63) (2/0/2)
[11] *Liou, Y.A., A.G. Pavelyev, and J. Wickert, 2005a: Observation of the gravity waves from GPS/MET radio occultation data. J. Atmos. Solar-Terr. Phys., 67(3), 219-228, February 2005, doi:10.1016/j.jastp.2004.08.001. (SCI, IF= 1.643, RF=30/64) (5/2/5)
[12] Pavelyev A.G., Y.-A. Liou*, and J. Wickert, 2004: Diffractive vector and scalar integrals for bistatic radio-holographic remote sensing, Radio Science, Vol. 39, 39(4), RS4011, 1-16, doi:10.1029/2003RS002935. (SCI, IF = 1.012, RF=25/67, TELECOMMUNICATIONS) (5/4/5)
[13] *Liou, Y.-A., A.G. Pavelyev, J. Wickert, C.-Y. Huang, S.-K. Yan, S.-F. Liu, 2004: Response of GPS occultation signals to atmospheric gravity waves and retrieval of gravity wave parameters. GPS Solutions, 8, 103-111. (DOI: 10.1007/s10291-004-0090-x) (SCI, IF= 2.04, RF=8/15) (2/2/2)
[14] *Liou, Y.-A., A.G. Pavelyev, C.-Y. Huang, K. Igarashi, K. Hocke, and S.-K. Yan, 2003: An analytic method for observing the gravity waves using radio occultation data. Geophysical Research Letters, Vol. 30, no. 20, 2021, doi: 10.1029/2003GL017818. (SCI, IF=3.204, RF=17/144) (6/1/4)
[15] Pavelyev A.G., T. Tsuda, K. Igarashi, Y.-A. Liou, and K. Hocke, 2003: Wave structures in the electron density profile in the ionospheric D and E-layers observed by radio holography analysis of the GPS/MET radio occultation data. J. Atmos. Solar-Terr. Phys., 65(1), 59-70. (SCI) (11/3/11)
[16] *Liou, Y.-A., A.G. Pavelyev, C.-Y. Huang, K. Igarashi, and K. Hocke, 2002: Simultaneous observation of the vertical gradients of refractivity in the atmosphere and electron density in the lower ionosphere by radio occultation amplitude method. Geophysical Research Letters, Vol. 29, No. 19, 43-1-43-4, doi:10.1029/2002GL015155. (SCI, IF=3.204 (5/4/4)[26]
[17] Pavelyev A.G., Y.-A. Liou*, C. Reigber, J. Wickert, K. Igarashi, K. Hocke, C.Y. Huang, 2002: GPS radio holography as a tool for remote sensing of the atmosphere and mesosphere from space. GPS Solutions, 100-108, Vol. 6, No. 1-2, 2002. (SCI, IF= 2.04, RF=8/15)
[18] Liou, Y.A., A.G. Pavelyev, S.S. Matugov, O.I. Yakovlev, and J. Wickert, 2010 (February)：Radio occultation method for remote sensing of the atmosphere and ionosphere. ISBN 978-953-7619-60-2, pp. 176, I-Tech Education and Publishing KG, Croatia.
[19] Liou, Y.A., J. Wickert, A.G. Pavelyev, C. Reigber, T. Schmidt, C.Y. Huang, and S. Yan, 2005b： Gravity wave "portrait" reconstructed by radio holographic analysis of the amplitude of GPS radio occultation signals 549-554. In Earth Observation with CHAMP Results from Three Years in Orbit Reigber, C.; L?hr, H.; Schwintzer, P.; Wickert, J. (Eds.) 2005, XVI, 628 p. 445 illus., 96 in colour., Hardcover ISBN: 3-540-22804-7. (NSC91-2811-M008-001, NSC91-2111-M008-029,)
[20] Pavelyev, A.G., J. Wickert, Y.-A. Liou*, Ch. Reigber, T.Schmidt, A.A. Pavelyev, and S.S. Matyugov, 2005b: Different mechanisms of the ionospheric influence on GPS occultation signals. GPS Solutions, 9(2), 96-104, DOI: 10.1007/s10291-005-0138-6
[21] Pavelyev, A.G., Liou, Y.A., Wickert, J., Schmidt, T., Pavelyev, A.A., and Matyugov, S.S., 2009：Phase acceleration: a new important parameter in GPS occultation technology.”, GPS Solutions, doi:10.1007/s10291-009-0128-1
[22] Pavelyev, A.G., Y.-A. Liou, J. Wickert, A.A. Pavelyev, and K. Igarashi,2009：New applications and advances of the GPS radio occultation technology as recovered by analysis of the FORMOSAT-3/COSMIC and CHAMP database., In New Horizons in Occultation Research - Studies in Atmosphere and Climate, Steiner, A.; Pirscher, B.; Foelsche, U.; Kirchengast, G. (Eds.), pp. 163-176, Springer Berlin Heidelberg
[23] Wang, C., Liou, Y.-A., and Yeh, T.,2008：Impact of surface meteorological measurements on GPS height determination, Geophys. Res. Lett., 35, L23809
[24] Pavelyev, A. G., Y. A. Liou, J. Wickert, A.A. Pavelyev, T. Schmidt, K. Igarashi, and S.S. Matyugov,2008：Location of layered structures in the ionosphere and atmosphere by use of GPS occultation data, Advances in Space Research, Vol. 42
[25] Hei, H., Tsuda, T., Hirooka, T.,2008：Characteristics of Atmospheric Gravity Wave Activity in Polar Regions Revealed by GPS Radio Occultation Data with CHAMP, J. Geophys, pp.113, D04107
[26] Kafando, P., Chane-Ming, F., and Petitdidier,M.,2008：Climatology of Gravity Wave Activity During the West African Monsoon, Ann. Geophys., 26, pp.4081–4089
[27] de la Torre and P. Alexander, 2005：Gravity waves above Andes detected from GPS radio occultation temperature profiles: mountain forcing?, Geophys. Res. Lett. 32, p. L17815
[28] Ratnam, M. Venkat, G. Tetzlaff, Christoph Jacobi, 2004: Global and Seasonal Variations of Stratospheric Gravity Wave Activity Deduced from the CHAMP/GPS Satellite. Journal of the Atmospheric Sciences, 61, 1610-1620
[29] Baumgaertner, A. J. G., and McDonald, A. J.,2007：A gravity wave climatology for Antarctica compiled from Challenging Mini satellite Payload/Global Positioning System (CHAMP/GPS) radio occultations, JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, D05103, doi:10.1029/2006JD007504
[30] Eckermann, S. D., Hirota, I., and Hocking, W. K., 1994：Gravity Wave and Equatorial Wave Morphology of the Stratosphere Derived from Long-term Rocket Soundings, Q. J. R. Meteorol. SOC., 121, pp. 149-186
[31] Nappo, C. J.,2002：An Introduction of Atmospheric Gravity Waves, Elsevier Academic Press, USA. pp.26~149, pp. 210~233
[32] Holton, J. R.,2004：An Introduction To Dynamic Meteorology, Elsevier Academic Press, USA, P269~P311
[33] Tsuda, T., Ratnam, M. V., Alexander, S. P., Kozu, T. and Takayabu, Y.,2009：Temporal And Spatial Distributions of Atmospheric Wave Energy In the Equatorial Stratosphere Revealed by GPS Radio Occultation Temperature Data Obtained With the CHAMP During 2001-2006, Earth Planets Space, 61, pp.525-533
[34] Kafando, P., Chane-Ming, F. and Petitdidier, M.,2008：Climatology of Gravity Wave Activity During the West African Monsoon, Ann. Geophys., 26, pp.4081-4089, 2008
[35] Chane-Ming, F., Faduilhe, D., Leveau, J.,2007：Latitudinal and Seasonal Variability of Gravity-Wave Energy in the South-West Indian Ocean, Ann. Geophys., 25, pp.2479-2485
[36] Kuo, Y. H., Wee, T. K., Sokolovskiy, S., Rocken, C., Schreiner, W., Hunt D. and Anthes, R. A.,2004：Inversion and Error Estimation of GPS Radio Occultation Data, J. of the Meteorological Society of Japan, Vol. 82, No. 1B, pp.507-531
[37] Hayashi, H., Furumoto, J.I., Lin, X., Tsuda, Y.S., Shoji, Y., Aoyama, Y. and Murayama, Y.,2007：Statistical Comparisons of FORMOSAT-3/COSMIC Radio Occultation Soundings with Balloon-borne Observations, Second FORMOSAT/COSMIC Data User Workshop, United State
[38] 羅正麟，「重力波非線性交互作用之模擬研究及觀測資料分析」，國立中央大學太空科學研究所博士論文，2000年。
[39] 陳崗熒，「重力波暫態現象之基波分析」，國立中央大學太空科學研究所碩士論文，1994年。
[40] 白劍鴻，「利用中壢特高頻雷達研究降水激發大氣重力波」，國立中央大學太空科學研究所碩士論文，2007年。
[41] 劉智中，「福衛三號低層大氣溫度資料分析」，國立中央大學太空科學研究所碩士論文，2008年。
[42] 黃成勇，「GPS掩星觀測反演與反演誤差探討」，國立中央大學太空科學研究所博士論文，2005年。
[43] 國家太空中心 http://www.nspo.gov.tw