Quad-Doppler and microphysical observations of the BAMEX 29 June 2003 MCS

On 29 June 2003, two Doppler radar-equipped aircraft sampled a mesoscale convective system (MCS) over north-central Kansas and far south-central Nebraska. For most of the sampling period, the MCS was characterized by loosely-organized lines of convection with 10 – 15 m s-1 ground-relative rear-to-front flow at mid-levels. However, between 0445 and 0545 UTC, a 20 m s-1 rear inflow jet (RIJ) formed, descended to near the surface, and was coincident with the rapid formation of a bow echo. This bow echo persisted for approximately one hour before rapidly losing its linear coherence shortly after the weakening of the RIJ.

Quad-Doppler radar analyses of the wind and reflectivity fields will be presented in order to study the physical processes associated with the evolution of the bow echo. Dynamically-retrieved perturbation pressure fields will be presented to investigate the forcing of the rear-to-front flow.

A Lagrangian spiral descent was executed between the –10 and +8 °C levels by the NOAA P-3 aircraft approximately 25 km behind the convective cells at the apex of the bow echo during the period when the bow echo was rapidly developing. Cloud and precipitation optical array probes aboard the NOAA P-3 aircraft revealed that ice particles were present down to +7 °C within the descending RIJ. Estimations of mass and reflectivity from the probe data will be presented and compared with aircraft radar reflectivity measurements. These are used to calculate latent cooling from evaporation, sublimation and melting using a 1-D parcel model.