Comparison of Observed and Simulated Drop Size Distributions from Large-Eddy Simulations with Bin Microphysics

Witte, Mikael K.1; Chuang, Patrick Y.2; Ayala, Orlando3; Wang, Lian-Ping4,5; Feingold, Graham6

2019-02

10.1175/MWR-D-18-0242.1

MONTHLY WEATHER REVIEW   影响因子和分区

0027-0644

1520-0493

Two case studies of marine stratocumulus (one nocturnal and drizzling, the other daytime and nonprecipitating) are simulated by the UCLA large-eddy simulation model with bin microphysics for comparison with aircraft in situ observations. A high-bin-resolution variant of the microphysics is implemented for closer comparison with cloud drop size distribution (DSD) observations and a turbulent collision-coalescence kernel to evaluate the role of turbulence on drizzle formation. Simulations agree well with observational constraints, reproducing observed thermodynamic profiles (i.e., liquid water potential temperature and total moisture mixing ratio) as well as liquid water path. Cloud drop number concentration and liquid water content profiles also agree well insofar as the thermodynamic profiles match observations, but there are significant differences in DSD shape among simulations that cause discrepancies in higher-order moments such as sedimentation flux, especially as a function of bin resolution. Counterintuitively, high-bin-resolution simulations produce broader DSDs than standard resolution for both cases. Examination of several metrics of DSD width and percentile drop sizes shows that various discrepancies of model output with respect to the observations can be attributed to specific microphysical processes: condensation spuriously creates DSDs that are too wide as measured by standard deviation, which leads to collisional production of too many large drops. The turbulent kernel has the greatest impact on the low-bin-resolution simulation of the drizzling case, which exhibits greater surface precipitation accumulation and broader DSDs than the control (quiescent kernel) simulations. Turbulence effects on precipitation formation cannot be definitively evaluated using bin microphysics until the artificial condensation broadening issue has been addressed.

SCI ; EI

英语

其他

National Center for Atmospheric Research[] ; National Science Foundation[AGS-1139746]

Meteorology & Atmospheric Sciences

Meteorology & Atmospheric Sciences

WOS:000460766000002

AMER METEOROLOGICAL SOC

20190706504937

Aircraft ; Aircraft accidents ; Computational fluid dynamics ; Condensation ; Drops ; Liquids ; Size distribution ; Turbulence

Fluid Flow:631 ; Aircraft, General:652.1 ; Computer Applications:723.5 ; Chemical Operations:802.3 ; Mathematics:921 ; Mathematical Statistics:922.2

GEOSCIENCES

Web of Science

1.Natl Ctr Atmospher Res, POB 3000, Boulder, CO 80307 USA
2.Univ Calif Santa Cruz, Earth & Planetary Sci, Santa Cruz, CA 95064 USA
3.Old Dominion Univ, Engn Technol Dept, Norfolk, VA USA
4.Univ Delaware, Dept Mech Engn, Newark, DE 19716 USA
5.Southern Univ Sci & Technol, Dept Mech & Aerosp Engn, Shenzhen, Peoples R China
6.NOAA, Div Chem Sci, Earth Syst Res Lab, Boulder, CO USA

Witte, Mikael K.,Chuang, Patrick Y.,Ayala, Orlando,et al. Comparison of Observed and Simulated Drop Size Distributions from Large-Eddy Simulations with Bin Microphysics[J]. MONTHLY WEATHER REVIEW,2019,147(2):477-493.

Witte, Mikael K.,Chuang, Patrick Y.,Ayala, Orlando,Wang, Lian-Ping,&Feingold, Graham.(2019).Comparison of Observed and Simulated Drop Size Distributions from Large-Eddy Simulations with Bin Microphysics.MONTHLY WEATHER REVIEW,147(2),477-493.

Witte, Mikael K.,et al."Comparison of Observed and Simulated Drop Size Distributions from Large-Eddy Simulations with Bin Microphysics".MONTHLY WEATHER REVIEW 147.2(2019):477-493.