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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 9 | Copyright
Atmos. Chem. Phys., 18, 6493-6510, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 08 May 2018

Research article | 08 May 2018

Microphysical variability of Amazonian deep convective cores observed by CloudSat and simulated by a multi-scale modeling framework

J. Brant Dodson1, Patrick C. Taylor2, and Mark Branson3 J. Brant Dodson et al.
  • 1Science Systems and Applications, Inc., Hampton, VA, USA
  • 2Climate Science Branch, NASA Langley Research Center, Hampton, VA, USA
  • 3Department of Atmospheric Science, Colorado State University, Ft. Collins, CO, USA

Abstract. Recently launched cloud observing satellites provide information about the vertical structure of deep convection and its microphysical characteristics. In this study, CloudSat reflectivity data is stratified by cloud type, and the contoured frequency by altitude diagrams reveal a double-arc structure in deep convective cores (DCCs) above 8km. This suggests two distinct hydrometeor modes (snow versus hail/graupel) controlling variability in reflectivity profiles. The day–night contrast in the double arcs is about four times larger than the wet–dry season contrast. Using QuickBeam, the vertical reflectivity structure of DCCs is analyzed in two versions of the Superparameterized Community Atmospheric Model (SP-CAM) with single-moment (no graupel) and double-moment (with graupel) microphysics. Double-moment microphysics shows better agreement with observed reflectivity profiles; however, neither model variant captures the double-arc structure. Ultimately, the results show that simulating realistic DCC vertical structure and its variability requires accurate representation of ice microphysics, in particular the hail/graupel modes, though this alone is insufficient.

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Short summary
The vertical profiles of convection in the Amazon are sampled using CloudSat, with particular emphasis on day–night contrast. Focusing on vigorous deep convective cores reveals a distinct, previously unreported double-arc reflectivity feature in the contoured frequency by altitude diagram, likely corresponding with two modes of ice hydrometeor phase: snow versus graupel/hail. Replicating this feature in cloud-resolving models requires further improvements in the microphysical parameterization.
The vertical profiles of convection in the Amazon are sampled using CloudSat, with particular...