Analysis of the mechanism underlying Tibetan Plateau vortex frequency difference between strong and weak MJO periods
Tóm tắt
In this paper, the NCEP/DOE reanalysis data, OLR data from NOAA, Australian Meteorological Bureau real-time multivariate MJO index, and Tibetan Plateau vortex (TPV) statistical data from the Chengdu Institute of Plateau Meteorology, are used to discuss the modulation of the TPV by the MJO, through applying the wavelet analysis and composite analysis. The results show that: (1) The MJO plays an important role in modulating the TPV, as the number of TPVs generated in strong MJO periods is three times that in weak periods. (2) During strong (weak) MJO periods, the Tibetan Plateau (TP) is in control of a low-frequency, low-pressure cyclone (high-pressure, anticyclone) system, and thus the atmospheric circulation conditions over the plateau are conducive (inconducive) to the generation of TPVs. (3) During strong (weak) MJO periods, southerly (northerly) winds prevail in the east of the TP, while northerly (southerly) winds in the west. Over the northern part of the TP, easterly (westerly) flow is predominant, while westerly (easterly) flow prevails over the south, thus conducive (inconducive) to the formation of cyclonic circulation (i.e., TPVs) at low altitude over the TP. (4) In strong MJO periods, water vapor is relatively less abundant over most of the TP, inconducive to the generation of TPVs; however, moisture transported by the south branch trough and the low-frequency, high-pressure anticyclone system from the Bay of Bengal, are very important for the development of TPVs. As the strength of the MJO changes continuously during its eastward propagation, the intensity of tropical convection and vertical circulation structures of the tropical atmosphere also change accordingly. Alternation between favorable and unfavorable conditions for the generation of TPVs occurs, thus resulting in significant frequency differences of TPVs between strong and weak MJO periods.
Tài liệu tham khảo
Bond, N. A., and G. A. Vecchi, 2003: The influence of the Madden–Julian oscillation on precipitation in Oregon and Washington. Wea. Forecasting, 18, 600–613, doi: 10.1175/1520-0434(2003)018>0600:TIOTMO<2.0.CO;2.
Chen, B. M., Z. A. Qian, and L. S. Zhang, 1996: Numerical simulation of the formation and development of vortices over the Qinghai–Xizang Plateau in summer. Scientia Atmospherica Sinica, 20, 491–502. (in Chinese)
Ding, Z. Y., J. L. Liu, and J. N. Lü, 1994: The study for the formation mechanism of the Qinghai–Xizang Plateau vortex on 600 hPa. Plateau Meteor., 13, 411–418. (in Chinese)
Donald, A., H. Meinke, B. Power, et al., 2006: Near-global impact of the Madden–Julian oscillation on rainfall. Geophys. Res. Lett., 33, L09704, doi: 10.1029/2005GL025155.
Ji, Z. P., D. J. Gu, and J. G. Xie, 1999: Multiple timescales analysis of climate variation in Guangzhou during the last 100 years. J. Trop. Meteor., 15, 48–55. (in Chinese)
Jones, C., 2000: Occurrence of extreme precipitation events in California and relationships with the Madden–Julian oscillation. J. Climate, 13, 3576–3587, doi: 10.1175/1520-0442(2000)013<3576:OOEPEI>2.0.CO;2.
Kanamitsu, M., W. Ebisuzaki, J. Woollen, et al., 2002: NCEPDEO AMIP-? reanalysis (R-2). Bull. Amer. Meteor. Soc., 83, 1631–1643, doi: 10.1175/BAMS-83-11-1631.
Li, C. Y., J. Pan, T, Hua, et al., 2012: Typhoon activities over the western North Pacific and atmospheric intraseasonal oscillation. Meteor. Mon., 38, 1–16. (in Chinese)
Lyu, J. M, J. H. Ju, J. Z. Ren, et al., 2012: The influence of the Madden–Julian oscillation activity anomalies on Yunnan’s extreme drought of 2009–2010. Science China (Earth Sciences), 55, 98–112, doi: 10.1007/s11430-011-4348-1.
Ma, N, Y. F. Li, and J. H. Ju, 2011: Intraseasonal oscillation characteristics of extreme cold, snowy and freezing rainy weather in southern China in early 2008. Plateau Meteor., 30, 318–327. (in Chinese)
Madden, R. A., and P. R. Julian, 1971: Detection of a 40–50-day oscillation in the zonal wind in the tropical Pacific. J. Atmos. Sci., 28, 702–708, doi: 10.1175/1520-0469(1971)028<0702:DOADOI>2.0.CO;2.
Madden, R. A., and P. R. Julian, 1972: Description of global-scale circulation cells in the tropics with a 40–50-day period. J. Atmos. Sci., 29, 1109–1123, doi: 10.1175/1520-0469(1972)029<1109:DOGSCC>2.0.CO;2.
Pan, J, C. Y. Li, and J. Song, 2010: The modulation of Madden–Julian oscillation on typhoon in the northwestern Pacific Ocean. Chinese J. Atmos. Sci., 34, 1059–1070. (in Chinese)
Qian, Z. A., F. M. Shan, and J. N. Lyu, 1984: The statistical analysis of the Qinghai–Xizang plateau vortex and the climatic factors for its generation in the summer of 1979. Tibetan Plateau Meteorological Science Test Anthology (2), Group of “The Qinghai–Xizang Plateau Meteorological Science Experiment Anthology”, Ed., Chinese Science Press, Beijing, 182–194. (in Chinese)
Sun, G. W., and B. D. Chen, 1988: Oscillation characteristics and meridional propagation of atmospheric low frequency waves over the Qinghai–Xizang Plateau. Scientia Atmospherica Sinica, 12, 250–256. (in Chinese)
Sun, G. W., and B. D. Chen, 1994: Characteristics of the lows flocking with Tibet atmospheric low-frequency oscillation over the Qinghai–Xizang (Tibet) plateau. Scientia Atmospherica Sinica, 18, 113–121. (in Chinese)
Torrence, C., and G. P. Compo, 1998: A practical guide to wavelet analysis. Bull. Amer. Meteor. Soc., 79, 61–78, doi: 10.1175/1520-0477(1998)079<0061:APGTWA>2.0.CO;2.
Wang, C. H., Y. Cui, and S. L. Jin, 2011: Oscillation propagation features of the atmosphere around the Qinghai–Xizang Plateau during the spring season of typical strong and weak monsoon years. Science China (Earth Sciences), 54, 305–314, doi: 10.1007/s11430-010-4113-x.
Wheeler, M. C., and H. H. Hendon, 2004: An all-season real-time multivariate MJO index: Development of an index for monitoring and prediction. Mon. Wea. Rev., 132, 1917–1932, doi: 10.1175/1520-0493(2004)132<1917:AARMMI7gt;2.0.CO;2.
Wheeler, M. C., H. H. Hendon, S. Cleland, et al., 2009: Impacts of the Madden–Julian oscillation on Australian rainfall and circulation. J. Climate, 22, 1482–1498, doi: 10.1175/2008JCLI2595.1.
Xu, G. Q., and Q. G. Zhu, 2000: Analysis of features of atmospheric LFO structures over the Tibetan Plateau in 1998. J. Nanjing Inst. Meteor., 23, 505–513. (in Chinese)
Xu, G. Q., and Q. G. Zhu, 2002: Source or sink features of atmospheric low frequency oscillation over the Tibetan Plateau. J. Nanjing Inst. Meteor., 25, 358–365. (in Chinese)
Yu, S. H., and G. B. He, 2001: Numerical experiment of influence of water vapor in the middle and upper troposphere on the formation of vortex over the Tibetan Plateau. J. Nanjing Inst. Meteor., 24, 553–559. (in Chinese)
Zhang, P. F., G. P. Li, M. Y. Wang, et al., 2010: Preliminary study on relationship between clustering activity of Tibetan Plateau vortex and 10–30-day low-frequency oscillations. Plateau Meteor., 29, 1102–1110. (in Chinese)
Zhao, F. H., G. P. Li, C. H. Huang, et al., 2016: The modulation of Madden–Julian oscillation on Tibetan Plateau vortex. J. Trop. Meteor., 22, 30–41.