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Critical roles of convective momentum transfer in sustaining the multi-scale Madden–Julian oscillation |
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| Authors: | Fei Liu Gang Huang Licheng Feng |
| Institution: | 1. Key Laboratory of Regional Climate-Environment Research for Temperate East Asia, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China 2. International Pacific Research Center, University of Hawaii at Manoa, Honolulu, HI, 96822, USA 3. National Marine Environmental Forecasting Center, Beijing, 100081, China |
| Abstract: | To understand the nature and role of multi-scale interaction involved in the Madden–Julian oscillation (MJO), a dynamical model is built based on two essential processes: the convective complex of the MJO modulates the strength and location of synoptic-scale motions, which in turn feed back to the MJO through the convective momentum transfer (CMT). Our results exhibit that: (1) The lower tropospheric easterly CMT coming from the 2-day waves slows down the MJO dramatically; (2) although the lower tropospheric westerly CMT coming from the superclusters can produce the horizontal quadrupole vortex and vertical westerly wind-burst structures of the MJO, it drives the large-scale motions to propagate eastward too fast; (3) the planetary boundary layer provides an instability source for the MJO and pulls the MJO to propagate eastward at a speed of 0～10?ms?1; and (4) the optimal structure of the multi-scale MJO should be: the stronger superclusters/2-day waves prevail in the rear/front part of the MJO and produce lower tropospheric westerly/easterly CMT there. These theoretical results emphasize the role of CMT and encourage further observations in the multi-scale MJO. |
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