Environmental Science Division (EVS)a Division of Argonne National Laboratory

Aircraft Observations of Convective Systems in the Indian Ocean

August 23, 2013

Bradley Nicholas Guy
National Research Council Postdoctoral Fellow
NOAA National Severe Storms Laboratory
Friday, August 23, 2013
11:00 a.m.
Argonne National Laboratory
TCS Building 240
Room 4301

In the DYNAMO (Dynamics of the Madden-Julian Oscillation) field experiment, a large number of measurement platforms were deployed to study environmental and convective cloud system characteristics of the Madden-Julian Oscillation (MJO) initiation region in the Indian Ocean. A mobile platform, the NOAA P-3 instrumented aircraft, sampled intense convective cloud systems, along with the surrounding environment.

This presentation will explore the characteristics of mesoscale convective systems (MCSs) during an active and inactive MJO in late November and December 2011. A tail-mounted Doppler radar was used during DYNAMO for detailed sampling of the MCS three-dimensional reflectivity and kinematic structure. Horizontal and vertical distributions of reflectivity characterize the system’s structure and intensity and, by inference, yield a rudimentary picture of microphysics.

Convective systems investigated by the P-3 aircraft were oriented roughly parallel to the low-level shear, with weak linear organization and weak associated cold pools. 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 maintaining the MJO convection, especially during the peak MJO period. Comparison of the results with aircraft observations during the TOGA COARE experiment shows distinct differences. The DYNAMO MCSs are less linearly organized, having weaker associated cold pools and no distinct strong rear-inflow jets.

Drop size distributions (DSDs) were also analyzed by using data acquired from the Particle Measuring System two-dimensional precipitation (2D-P) probe aboard the P-3. Both Z-R relationships and DSD model characteristics will be compared to the TOGA COARE observations and placed in the larger context of previously published results. Comparison and corroboration of results for time periods during the active MJO and suppressed (dry) phases suggest microphysical differences between the two.

Photo of B. Nicholas Guy
Photo of B. Nicholas Guy
portrait of Scott Collis