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Early Radar Echoes from Ultragiant Aerosol in a Cumulus Congestus: Modeling and Observations

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  • 1 University of Oklahoma, Norman, Oklahoma
  • | 2 National Center for Atmospheric Research,* Boulder, Colorado
  • | 3 University of Oklahoma, Norman, Oklahoma
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Abstract

The growth of ultragiant aerosol (UGA) in a Lagrangian framework within a simulated three-dimensional cloud is analyzed and compared with radar and aircraft observations of a cumulus congestus collected during the Small Cumulus Microphysics Study (SCMS). UGA are ingested into the simulated cloud and grow by continuous collection; the resulting radar reflectivity factor and raindrop concentrations are evaluated at 1-min intervals. The calculations produce a substantial echo (>30 dBZ) within a short time (18 min), containing few raindrops (0.3 L−1). The calculated radar echo is very sensitive to the amount of UGA ingested into the modeled cloud and its liquid water content. The modeled radar echo and raindrop concentrations are consistent with the observations in that the differences fall within the modeling and measurement limitations and uncertainties.

Corresponding author address: Dr. Sonia G. Lasher-Trapp, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000. Email: slasher@ncar.ucar.edu

Abstract

The growth of ultragiant aerosol (UGA) in a Lagrangian framework within a simulated three-dimensional cloud is analyzed and compared with radar and aircraft observations of a cumulus congestus collected during the Small Cumulus Microphysics Study (SCMS). UGA are ingested into the simulated cloud and grow by continuous collection; the resulting radar reflectivity factor and raindrop concentrations are evaluated at 1-min intervals. The calculations produce a substantial echo (>30 dBZ) within a short time (18 min), containing few raindrops (0.3 L−1). The calculated radar echo is very sensitive to the amount of UGA ingested into the modeled cloud and its liquid water content. The modeled radar echo and raindrop concentrations are consistent with the observations in that the differences fall within the modeling and measurement limitations and uncertainties.

Corresponding author address: Dr. Sonia G. Lasher-Trapp, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000. Email: slasher@ncar.ucar.edu

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