In addition to a power peak at the period of about 6 days, spectrum analyses of daily rainfall during the mainrainfall season (March-June) show two other major power peaks on the subseasonal time scales within the period ranges of 10-18 and 30-70 days, respectively. Various lag-correlations for these three oscillation modes are estimated corresponding to the phases with maximum rainfall. It is of interest to note that the synoptic-scale (2-10 days) signals have certain properties of the Kelvin-type modes, and the 30-70-day ones have coherent associations among various components similar to the global tropical intraseasonal mode, i.e., the Madden-Julian Oscillation (MJO). The climatological features of the 30-70-day signals are further examined by a harmonic analysis of the 9-year-mean daily TRMM rainfall. The 4-15 harmonics, roughly corresponding to these signals, seem to be an important component of seasonal rainfall variations, which provide much more detailed subseasonal features than the first 3 harmonics usually applied to represent the seasonal cycle. This is further confirmed by the results from a relatively long-time-record satellite product: the 28-year (1979-2006) daily Outgoing Longwave Radiation (OLR) measurements.
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