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The BSISO indices used in this activity have been newly developed by Lee at al. (2013). The philosophy behind these newly developed indices is similar to the Real-time Multivariate MJO (RMM) indices of Wheeler and Hendon (2004), except that the focus is on the intraseasonal variability that is specific to the Asian monsoon region. In particular, the new indices capture the observed northward propagation that occurs in the Asian monsoon, as well as higher frequency (periods of 10-30 days) components exhibiting a Rossby wave like character. Two propagating modes, each comprising a pair of multivariate empirical orthogonal functions, are used to capture this variability, and are respectively called BSISO1 and BSISO2. BSISO1 captures the canonical northward-propagating BSISO component and BSISO2 captures the higher-frequency pre-monsoon and onset component.

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Shown below are the composite anomalies of various variables with respect to each BSISO mode and phase selected when the strong BSISO occurs. Reference periods are 1991-2020 except for precipitation (1997-2020).



Lee, J.-Y., B. Wang, M. C. Wheeler, X. Fu, D.E. Waliser, and I.-S. Kang, 2013: Real-time multivariate indices for the boreal summer intraseasonal oscillation over the Asian summer monsoon region. Clim. Dyn., 40, 493-509. 

Wheeler M. and H. Hendon, 2004: An All-Season Real-Time Multivariate MJO Index: Development of an Index for Monitoring and Prediction. Monthly Weather Review, 132, 1917-1932.