Radar observations of MJO and Kelvin wave interactions during DYNAMO/CINDY2011/AMIE
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© 2014. American Geophysical Union. All Rights Reserved. Radar and sounding data collected during the Dynamics of the Madden-Julian Oscillation (DYNAMO), the Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 (CINDY2011), and the Atmospheric Radiation Measurement (ARM) Madden-Julian Oscillation Investigation Experiment (AMIE) field campaigns in the equatorial Indian Ocean to study the initiation of the Madden-Julian Oscillation (MJO) are used to examine the precipitation, cloud, and moisture characteristics during the MJO and convectively coupled Kelvin waves (KWs). Three MJO events and 10 KWs were identified from satellite data using different wave number frequency filters, although event identification varied based on the chosen range of latitude, frequency, and outgoing longwave radiation threshold. Radar and sounding data were composited for the three MJO events, four KWs during the active MJO, five KWs during the suppressed MJO, and one KW during the developing MJO. The MJO composite was generally consistent with past studies, although an increase in convective rain appeared to precede relative humidity increases at low- to middle-levels. The active and developing MJO KWs produced more rain and cloud than suppressed MJO KWs and had a secondary peak in stratiform rain potentially associated with subsynoptic-scale cloud clusters. The suppressed MJO KW composite displayed previously documented structure of vertical moisture buildup prior to the KW passage, whereas the developing MJO KW did not. The KW moisture signature during the active MJO was somewhat overwhelmed by the moist environment associated with the active MJO. Upper level moisture was enhanced after KW passage, regardless of MJO phase. However, upper level moisture was most enhanced after the developing MJO KW passage, providing deep tropospheric moisture that may have assisted MJO onset. Nonprecipitating upper level cloud and midlevel altocumulus/altostratus also persisted after most KW passages.
author list (cited authors)
DePasquale, A., Schumacher, C., & Rapp, A.