Multiscale Convective Interactions During DYNAMO/CINDY2011/AMIE

Abstract:

Radar and sounding observations are used to examine precipitation, cloud, and environmental characteristics over Addu Atoll from the Dynamics of the Madden-Julian (MJO) 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. Particular focus is placed on how the existence of and interactions between three MJO events, 10 Kelvin waves (KWs), and the diurnal cycle impact convective system properties. For example, the average MJO characteristics were generally consistent with past studies, although an increase in deep convective rain and echo tops appeared to precede relative humidity increases at low- to middle-levels. MJO convective organization was also impacted by deep tropospheric wind shear. 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 diurnal cycle of rain was also more pronounced during the active MJO. The suppressed MJO KW composite displayed previously documented structure of vertical moisture buildup prior to the KW passage, whereas the developing and active MJO KWs did not. Upper level moisture was enhanced after KW passages, 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. Non-precipitating upper level cloud and midlevel altocumulus/altostratus also persisted after most KW passages with potential radiative impacts.