Vertical Shift of Stable Layers under the Different MJO Phases

During a two-month special observing period (October - November 2011) of the CINDY/DYNAMO/AMIE/LASP field campaign, two MJO events developed over the central Indian Ocean. Radiosonde sounding data were examined to study the vertical moistening process related to these events. Frequency distribution of temperature lapse rate as a function of temperature clearly shows the upward shift of stable layer from 0C level to upper level, as the MJO phase which is defined based on Wheeler and Hendon Index shifts from 1-2 to 3-4 over the central equatorial Indian Ocean. In addition, so-called trade wind inversion became dominant in phases 3-4, and corresponding humidity distribution was confirmed. Namely, relatively dry condition appeared above these two layers in phases 3-4 clearly. This result indicates that stepwise vertical moistening seems to be a self-regulating feature, and cloud systems restrain further development.