The Generation of Westerly Waves by Sobaek Mountains

소백산맥에 의한 서풍 파동 발생

  • Kim, Jin wook (Chungbuk Science high school) ;
  • Youn, Daeok (Department of Earth Science Education, Chungbuk National University)
  • 김진욱 (충북과학고등학교) ;
  • 윤대옥 (충북대학교 지구과학교육과)
  • Received : 2016.12.19
  • Accepted : 2017.02.15
  • Published : 2017.02.28


The westerly waves generation is described in the advanced earth science textbook used at high school as follows: as westerly wind approaches and blows over large mountains, the air flow shows wave motions in downwind side, which can be explained by the conservation of potential vorticity. However, there has been no case study showing the phenomena of the mesoscale westerly waves with observational data in the area of small mountains in Korea. And thus the wind speed and time persistency of westerly winds along with the width and length of mountains have never been studied to explain the generation of the westerly waves. As a first step, we assured the westerly waves generated in the downwind side of Sobaek mountains based on surface station wind data nearby. Furthermore, the critical or minimum wind velocity of the westerly wind over Sobaek mountains to generate the downwind wave were derived and calcuated tobe about $0.6m\;s^{-1}$ for Sobaek mountains, which means that the westerly waves could be generated in most cases of westerly blowing over the mountains. Using surface station data and 4-dimensional assimilation data of RDAPS (Regional Data Assimilation and Prediction System) provided by Korea Meteorological Agency, we also analyzed cases of westerly waves occurrence and life cycle in the downwind side of Sobaek mountains for a year of 2014. The westerly waves occurred in meso-${\beta}$ or -${\gamma}$ scales. The westerly waves generated by the mountains disappeared gradually with wind speed decreasing. The occurrence frequency of the vorticity with meso-${\beta}$ scale got to be higher when the stronger westerly wind blew. When we extended the spatial range of the analysis, phenomena of westerly waves were also observed in the downwind side of Yensan mountains in Northeastern China. Our current work will be a study material to help students understand the atmospheric phenomena perturbed by mountains.


westerly waves;potential vorticity conservation;critical velocity;RDAPS


Supported by : 한국연구재단


  1. Bolin, B., 1950, On the Influence of the Earth's Orography on the General Character of the Westerlies. Tellus Series A, 2, 184-195.
  2. Chang, Y.S., 2015, Development and Application of an Experimental Program for Mapping Temperature and Salinity Distribution around the Korean Marginal Seas Using Ocean Data View. Journal of the Korean Earth Science Society, 36(4), 367-389. (in Korean)
  3. Cho, H.O., Son, S.W., and Lee, Y.H., 2016, Spatio-temporal Structure of Diurnal and Semidiurnal Tides in Geopotential Height Field. Journal of the Korean Earth Science Society, 37(6), 465-475. (in Korean)
  4. Chung, Y.S. and Kim, H.S., 2016, The New Classification of Mountains in the Korean Peninsula and the Mountain Associated Influence on Atmospheric Environment. Journal of the Korean Earth Science Society, 37(1), 21-28. (in Korean)
  5. Chung, Y.S., 1977a, On the Orographic Influence and Lee Cyclogenesis in the Andes, the Rockies and the East Asian Mountains. Archiv Für Meteorologie Geophysik und Bioklimatologie, Serie A, 26, 1-12.
  6. Chung, Y.S., 1977b, An Observation Study of the Influence of Large-Scale Mountains on Air Flow and Lee Cyclogenesis. Archiv Fur Meteorologie Geophysik und Bioklimatologie, Serie A, 26, 109-126.
  7. Holton, J.R., 2012, Dynamic Meteorology. 5/E. Academic Press, USA, 576 p.
  8. Jeong, J.W., Kyung, J.B., Wee, S.M., Kim, H.B., Cho, B.G., and Lee, K.H., 2013, Advanced Earth Science. Seoul Metropolitan Office of Education, Seoul, Korea, 365 p. (in Korean)
  9. Kim, J.H. and Chun, H.Y., 2011, Development of the Korean Mid- and Upper-Level Aviation Turbulence Guidance (KTG) System Using the Regional Unified Model. Korean Meteorological Society, 21(4), 497-506. (in Korean)
  10. Névir, P. and Sommer, M., 2009, Energy-Vorticity Theory of Ideal Fluid Mechanics. Journal of Atmospheric Science, 66(7), 2073-2084.
  11. Orlanski, I., 1975, A rational subdivision of scales for atmospheric processes. Bulletin of the American Meteorological Society. 56(5), 527-530.
  12. Thomas, G.B., Weir, M.D., and Hass, J.R., 2010, Thomas' Calculus. 12/E. Pearson, USA, 1047 p.