Precipitation hydrometeor type relative to the mesoscale airflow in mature oceanic deep convection of the Madden‐Julian Oscillation

Abstract

AbstractComposite analysis of mature near‐equatorial oceanic mesoscale convective systems (MCSs) during the active stage of the Madden‐Julian Oscillation (MJO) shows where different hydrometeor types occur relative to convective updraft and stratiform midlevel inflow layers. The National Center for Atmospheric Research (NCAR) S‐PolKa radar observed these MCSs during the Dynamics of the Madden‐Julian Oscillation/Atmospheric Radiation Measurement‐MJO Investigation Experiment (DYNAMO/AMIE). NCAR's particle identification algorithm (PID) is applied to S‐PolKa's polarimetric data to identify the dominant hydrometeor type in each radar sample volume. Combining S‐PolKa's Doppler velocity data with the PID demonstrates that hydrometeors have a systematic relationship to the airflow within mature MCSs. In the convective region, moderate rain occurs within the updraft core; the heaviest rain occurs just downwind of the core; wet aggregates occur immediately below the melting layer; narrow zones containing graupel/rimed aggregates occur just downstream of the updraft core at midlevels; dry aggregates dominate above the melting level; and smaller ice particles occur along the edges of the convective zone. In the stratiform region, rain intensity decreases toward the anvil; melting aggregates occur in horizontally extensive but vertically thin regions at the melting layer; intermittent pockets of graupel/rimed aggregates occur atop the melting layer; dry aggregates and small ice particles occur sequentially above the melting level; and horizontally oriented ice crystals occur between −10°C and −20°C in turbulent air above the descending midlevel inflow, suggesting enhanced depositional growth of dendrites. The organization of hydrometeors within the midlevel inflow layer is insensitive to the presence or absence of a leading convective line.