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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  31 Oct 2020

31 Oct 2020

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This preprint is currently under review for the journal ACP.

Microphysical Processes Producing High Ice Water Contents (HIWCs) in Tropical Convective Clouds during the HAIC-HIWC Field Campaign: Evaluation of Simulations Using Bulk Microphysical Schemes

Yongjie Huang1, Wei Wu2, Greg M. McFarquhar1,2, Xuguang Wang1, Hugh Morrison3, Alexander Ryzhkov2,5, Yachao Hu2,4, Mengistu Wolde6, Cuong Nguyen6, Alfons Schwarzenboeck7, Jason Milbrandt8, Alexei V. Korolev8, and Ivan Heckman8 Yongjie Huang et al.
  • 1School of Meteorology, University of Oklahoma, Norman, OK, USA
  • 2Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, OK, USA
  • 3Mesoscale and Microscale Meteorology, National Center for Atmospheric Research, Boulder, CO, USA
  • 4Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing, China
  • 5NOAA/OAR National Severe Storms Laboratory, Norman, OK 73072, USA
  • 6National Research Council Canada, Ottawa, Canada
  • 7Université Clermont Auvergne, CNRS, UMR 6016, Laboratoire de Météor Physique, Clermont-Ferrand, France
  • 8Environment and Climate Change Canada, Dorval, Quebec, Canada

Abstract. Regions with high ice water content (HIWC), composed of mainly small ice crystals, frequently occur over convective clouds in the tropics. Such regions can have median mass diameters (MMDs) < 300 μm and equivalent radar reflectivities < 20 dBZ. To explore formation mechanisms for these HIWCs, high resolution simulations of tropical convective clouds observed on 26 May 2015 during the High Altitude Ice Crystals – High Ice Water Content (HAIC-HIWC) international field campaign based out of Cayenne, French Guiana, are conducted using the Weather Research and Forecasting (WRF) model with four different bulk microphysics schemes: the WRF single‐moment 6‐class microphysics scheme (WSM6), the Morrison scheme and the Predicted Particle Properties (P3) scheme with one- and two-ice options. The simulations are evaluated against data from airborne radar and multiple cloud microphysics probes installed on the French Falcon 20 and Canadian National Research Council (NRC) Convair 580 sampling clouds at different heights. WRF simulations with different microphysics schemes generally reproduce the vertical profiles of temperature, dew-point temperature and winds during this event compared with radiosonde data, and the coverage and evolution of this tropical convective system compared to satellite retrievals. All of the simulations overestimate the intensity and spatial extent of radar reflectivity by over 30 % above the melting layer compared to the airborne X-band radar reflectivity data. They also miss the peak of the observed ice number distribution function for 0.1 < Dmax < 1 mm. Even though the P3 scheme has a very different approach representing ice, it does not produce greatly different total condensed water content or better comparison to other observations in this tropical convective system. Mixed-phase microphysical processes at −10 °C are associated with the overprediction of liquid water content in the simulations with the Morrison and P3 schemes. The ice water content at −10 °C increases mainly due to the collection of liquid water by ice particles, which does not increase ice particle number but increases the mass/size of ice particles and contributes to greater simulated radar reflectivity.

Yongjie Huang et al.

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Yongjie Huang et al.

Yongjie Huang et al.


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Latest update: 24 Nov 2020
Publications Copernicus
Short summary
Numerous small ice crystals in the tropical convective storms are difficult to detect and could be potentially hazardous for commercial aircraft. This study evaluated the numerical models against the airborne observations and investigated the potential cloud processes that could lead to the production of these large numbers of small ice crystals. It is found that key microphysical processes are still lacking or misrepresented in current numerical models to realistically simulate the phenomenon.
Numerous small ice crystals in the tropical convective storms are difficult to detect and could...