The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY (한국해양학회지:바다)

The Korean Society of Oceanography (한국해양학회)
권호 표지

A Study of Global Ocean Data Assimilation using VAF

VAF 변분법을 이용한 전구 해양자료 동화 연구

  • Ahn, Joong-Bae (Department of Atmospheric Sciences, Pusan National University,) ;
  • Yoon, Yong-Hoon (Meteorological Research Institute) ;
  • Cho, Eek-Hyun (Korea Meteorological Administration) ;
  • Oh, He-Ram (Department of Atmospheric Sciences, Pusan National University,)
  • 안중배 (부산대학교 대기과학과) ;
  • 윤용훈 (기상연구소 해양기상지진연구실) ;
  • 조익현 (기상청 수치예보과) ;
  • 오혜람 (부산대학교 대기과학과)
  • Published : 2005.02.28
Download PDF
⟨ Previous Next ⟩

Abstract

ARCO and TAO data which supply three dimensional global ocean information are assimilated to the background field from a general circulation model, MOM3. Using a variational Analysis using Filter (VAF), which is a spatial variational filter designed to reduce computational time and space efficiently and economically, observed ARGO and TAO data are assimilated to the OGCM-generated background sea temperature for the generation of initial condition of the model. For the assessment of the assimilation impact, a comparative experiment has been done by integrating the model from different intial conditions: one from ARGO-, TAO-data assimilated initial condition and the other from background state without assimilation. The assimilated analysis field not only depicts major oceanic features more realistically but also reduces several systematic model bias that appear in every current OGCMs experiments. From the 10-month of model integrations with and without assimilated initial conditions, it is found that the major assimilated characteristics in sea temperature appeared in the initial field remain persistently throughout the integration. Such implies that the assimilated characteristics of the reduced sea temperature bias is to last in the integration without rapid restoration to the non-assimilated OGCM integration state by dispersing mass field in the form of internal gravity waves. From our analysis, it is concluded that the data assimilation method adapted in this study to MOM3 is reasonable and applicable with dynamical consistency. The success in generating initial condition with ARGO and TAO data assimilation has significant implication upon the prediction of the long-term climate and weather using ocean-atmosphere coupled model.

본 연구에서는 전구 해양에서 관측되는 ARGO및 TAO해양 자료를 이용하여 해양의 3차원적인 구조를 분석.동화하고 궁극적으로 해양대순환모형을 위한 초기장을 생산하였다. 초기장의 생산을 위하여 전구 해양대순환 모형인 MOM3.1을 이용하였으며 생산한 배경장에, 계산시간과 계산공간을 절약할 수 있는 공간필터를 사용한 변분법(VAF, variational analysis using filter)을 이용하여 ARGO와 TAO 수온 자료를 동화하였다. 또한 본 연구에서는 자료 동화가 미치는 지속적인 영향을 살펴보고자 실험적분을 수행하였는데, 모형의 초기입력 자료를 자료동화 기법을 적용한 경우와 적용하지 않은 두 가지로 나누어 비교 실험을 수행하였다. 본 연구에서 자료 동화된 분석장은 OISST와의 비교를 통해 적절히 생산되었음을 보여주었다. 관측자료를 동화한 분석장을 초기자료로 한 10개월간의 적분결과를 살펴보면, 자료 동화를 통해 제거된 모형의 계통적 bias가 적분이 진행되는 과정에서 관성 중력파 등의 형태로 소멸되지 않고 지속적으로 관측과 유사하게 유지되었다. 이는 본 연구에서 실행한 자료동화가 모형의 역학적인 균형을 유지하면서 적절히 이루어졌음을 의미하며, 전구 대순환 모형을 이용한 중.장기 대기.해양 예측에 이러한 해양 자료동화가 대단히 유용하다는 것을 의미한다.

Keywords

References

  1. 박혜선, 2003. 대기-해양-해빙 접합 모형 개발과 ENSO 예측성 연구. 부산대학교, 이학박사 학위논문, pp. 42-45
  2. 안중배, 이진아, 2001. 해양대순환모형을 이용한 해빙의 역할에 관한 수치실험 연구. 한국해양학회지, 6: 225-233
  3. Arfken, G., 1985. Mathematical Methods for Physicists, 3rd ed. Orlando, FL. Academic Press: pp. 428-436
  4. ARGO, cited 2004. Part of the integrated global observation strategy. Available online from http://www-argo.ucsd.edul
  5. Bouttier, E, and P. Coutier, 1999. Data assimilation concepts and methods: Meteorological training course lecture series. ECMWF, pp.3-33
  6. Busalacchi, A.J., 1997. Oceanic Observations. J. Meteor. Soc. Japan, 75: 131-154
  7. Carval, T., 2002. Argo data management: User's manual. Ifremer, pp.6-7
  8. Coriolis, cited 2004. Global ocean profiles. Available online from http:// www.coriolis.eu.org/cdc/DataSelection/cdcDataSelections.asp
  9. Courtier, P., 1997. Variational methods. J. Meteor. Soc. Japan, 75: 211-218
  10. Derber, J. and A. Rosati, 1989. A global oceanic data assimilation system. J. Phys. Oceanogr., 19: 1333-1347 https://doi.org/10.1175/1520-0485(1989)019<1333:AGODAS>2.0.CO;2
  11. Han, Y.-J., 1984. A Numerical World Ocean General Circulation Model. Part II. Baroclinic Experiment. Dyn. Atmos. Oceans, 8: 141-172 https://doi.org/10.1016/0377-0265(84)90020-4
  12. Huang, X.Y., 2000. Variational analysis using spatial filters. Mon. Wea. Rev., 128: 2588-2600 https://doi.org/10.1175/1520-0493(2000)128<2588:VAUSF>2.0.CO;2
  13. Kalnay E., 2003. Atmospheric modelling, data assimilation and predictability. Cambridge University Press, pp. 136-204
  14. Levitus, S., 1982. Climatological Atlas of the World Ocean. NOAA Prof. Paper 13, U.S. Government Printing Office, Washington D.C., 173 pp
  15. Lorenc, A.C., 1986. Analysis methods for numerical weather prediction. Quart. J. Roy. Meteor. Soc., 112: 1177-1194 https://doi.org/10.1002/qj.49711247414
  16. Lorenc, A.C., 1988. Optimal nonlinear objective analysis. Quart. J. Roy. Meteor. Soc., 114: 205-240 https://doi.org/10.1002/qj.49711447911
  17. Lorenc, AC., 1992. Interactive analysis using covariance functions and filters. Quart. J. Roy. Meteor. Soc., 118: 569-591
  18. NOAA, cited 2004. Tropical Atmosphere Ocean Project: Data delivery. Available online from http://www.pmel.noaa.gov/tao/data_deliv/
  19. Pacanowski, R.C. and S.M. Griffies, 1998. The GFDL modular ocean model user guide. The GFDL Ocean Group Technical Report NO. 2, Geophysical Fluid Dynamics Laboratory, Princeton, USA
  20. Semtner, A.J., 1976. A model for the Thermodynamic Growth of Sea Ice in Numerical Investigations of Climate. J. Phys. Oceanogr., 6: 379-389 https://doi.org/10.1175/1520-0485(1976)006<0379:AMFTTG>2.0.CO;2
  21. Service Argos, 2001. Basic description of the Argos system. Available online from http://www.argosinc.com/
  22. Storch, J.S., V.V. Kharin, U. Cubasch, G.C. Hegerl, D. Schriever, H. Storch, and E. Zorita, 1997. A Description of a 1260-Year Control Integration with the Coupled ECHAM1/LSG General Circulation Model. J. Climate, 10: 1525-1543 https://doi.org/10.1175/1520-0442(1997)010<1525:ADOAYC>2.0.CO;2