Comparison of observed and simulated spatial patterns of ice microphysical processes in tropical oceanic mesoscale convective systems

• Published in: Journal of geophysical research. Atmospheres 2016-07, Vol.121 (14), p.8269-8296
• Main Authors: Barnes, Hannah C., Houze, Robert A.
• Format: Article
• Language: English
• Subjects: Agglomeration; Aggregation; Brackish; cloud microphysics; Computer simulation; Doppler radar; Doppler sonar; dual‐polarimetric radar; Geophysics; GEOSCIENCES; Ice; Inflow; Marine; Mathematical models; Mesoscale convective complexes; Mesoscale convective systems; Mesoscale phenomena; Microphysics; Oceans; Parameterization; Parametrization; particle identification algorithm; Radar; Radar data; Radial velocity; Reflectance; Reflectivity; Simulation; Spatial data; Spatial variability; Spatial variations; stratiform precipitation; Tropical climate; Velocity; Vertical velocities; Water inflow; Weather forecasting
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1002/2016JD025074

To equitably compare the spatial pattern of ice microphysical processes produced by three microphysical parameterizations with each other, observations, and theory, simulations of tropical oceanic mesoscale convective systems (MCSs) in the Weather Research and Forecasting (WRF) model were forced to develop the same mesoscale circulations as observations by assimilating radial velocity data from a Doppler radar. The same general layering of microphysical processes was found in observations and simulations with deposition anywhere above the 0°C level, aggregation at and above the 0°C level, melting at and below the 0°C level, and riming near the 0°C level. Thus, this study is consistent with the layered ice microphysical pattern portrayed in previous conceptual models and indicated by dual‐polarization radar data. Spatial variability of riming in the simulations suggests that riming in the midlevel inflow is related to convective‐scale vertical velocity perturbations. Finally, this study sheds light on limitations of current generally available bulk microphysical parameterizations. In each parameterization, the layers in which aggregation and riming took place were generally too thick and the frequency of riming was generally too high compared to the observations and theory. Additionally, none of the parameterizations produced similar details in every microphysical spatial pattern. Discrepancies in the patterns of microphysical processes between parameterizations likely factor into creating substantial differences in model reflectivity patterns. It is concluded that improved parameterizations of ice‐phase microphysics will be essential to obtain reliable, consistent model simulations of tropical oceanic MCSs. Key Points Simulated ice processes in the midlevel inflow are consistent with radar observations and theory Of the processes considered, simulated riming and aggregation differ the most from observations Disparate simulated ice microphysical patterns factor into reflectivity differences