Aircraft Radar Observations of Convective Characteristics during a Madden-Julian Oscillation during the DYNAMO field project

The DYNAMO (Dynamics of the Madden-Julian Oscillation) field experiment employed a large number of measurement platforms with which to study environmental and convective cloud system characteristics of the Madden-Julian Oscillation (MJO) initiation region in the Indian Ocean. One such platform, the NOAA P-3 instrumented aircraft, provided mobility to sample intense convective cloud systems along with the surrounding environment. In this presentation, characteristics of mesoscale convective systems (MCSs) are explored throughout an MJO occurring in late November 2011. The radar convective element (RCE) flight module (flight pattern) used during DYNAMO was employed to provide a detailed sampling of the MCS 3-D reflectivity and kinematic structure. Horizontal and vertical distributions of reflectivity were used to characterize system structure and intensity and infer a rudimentary picture of microphysics. The fore-aft scan strategy utilized on the P-3 resulted in coincident Doppler radar data measurements approximately every 1.2-1.5 km. A pseudo-dual-Doppler analysis technique was applied to radial velocity data obtained by the to derive horizontal winds and estimate vertical wind motions. Also, GPS dropwindsondes provided a thermodynamic characterization of the convective environment, particularly cold pool extent and depth. Though many of the MCSs existed as part of the eastward propagating deep convective signal associated with the MJO, weak environmental flow meant they were largely quasi-stationary during a typical aircraft investigation. All convective lines investigated by the aircraft were roughly oriented parallel to the low-level shear. Similar thermodynamic convective environments were observed, though distinct differences in convective morphology were observed. Convective characteristics were compared to the traditional view of suppressed and active MJO phase precipitation systems; and changes in both horizontal and vertical structure were consistent with the transition from isolated to more widespread convection (greater stratiform signal) in the region of interest. Echo top height and radar reflectivity vertical distributions indicated the presence of deep updrafts lofting hydrometeors to high levels, supporting the importance of ice microphysics in the maintenance of MJO convection, especially during the peak MJO period. The results were also compared to aircraft observations taken during the TOGA COARE experiment, showing distinct differences in the organization with DYNAMO MCSs less linearly organized, having weaker associated cold pools, and no distinct strong rear-inflow jets present.