TY - JOUR
T1 - Drop size distribution broadening mechanisms in a bin microphysics Eulerian model
AU - Pardo, Lianet Hernández
AU - Morrison, Hugh
AU - Machado, Luiz A.T.
AU - Harrington, Jerry Y.
AU - Lebo, Zachary J.
N1 - Funding Information:
This research was supported by the São Paulo Research Foundation, Project 2014/14497-0. Lianet Hernández Pardo was supported under São Paulo Research Foundation Grants 2016/24562-6 and 2019/06988-4. Jerry Y. Harrington was supported under National Science Foundation Grant AGS-1824243. Zachary J. Lebo was supported under National Science Foundation Grant AGS-1822268. We acknowledge support from U.S. Department of Energy Atmospheric System Research DE-SC0020118. Data were obtained from the Atmospheric Radiation Measurement (ARM) user facility, a U.S. Department of Energy (DOE) Office of Science user facility managed by the Biological and Environmental Research Program. We thank the GoAmazon and ACRIDICON-CHUVA teams for their effort to produce the observational data. This material is also based on work supported by the National Center of Meteorology, Abu Dhabi, UAE, under the UAE Research Program for Rain Enhancement Science. We thank G. Feingold for hosting and maintaining the TAU microphysics code. Comments by W. W. Grabowski on an earlier version of the manuscript are appreciated. We would also like to acknowledge high-performance computing support from Cheyenne (doi:10.5065/D6RX99HX) provided by NCAR's Computational and Information Systems Laboratory. We thank the CPTEC Satellite Division and Environmental Systems team, especially Renato Galante Negri and Mario Figueiredo, for the support in providing access to the data repository. This publication includes data analysis and visualizations created with NCL (NCAR 2018). The National Center for Atmospheric Research is sponsored by the National Science Foundation.
Funding Information:
Acknowledgments. This research was supported by the São Paulo Research Foundation, Project 2014/14497-0. Lianet Hernández Pardo was supported under São Paulo Research Foundation Grants 2016/24562-6 and 2019/06988-4. Jerry Y. Harrington was supported under National Science Foundation Grant AGS-1824243. Zachary J. Lebo was supported under National Science Foundation Grant AGS-1822268. We acknowledge support from U.S. Department of Energy Atmospheric System Research DE-SC0020118. Data were obtained from the Atmospheric Radiation Measurement (ARM) user facility, a U.S. Department of Energy (DOE) Office of Science user facility managed by the Biological and Environmental Research Program. We thank the GoAmazon and ACRIDICON– CHUVA teams for their effort to produce the observational data. This material is also based on work supported by the National Center of Meteorology, Abu Dhabi, UAE, under the UAE Research Program for Rain Enhancement Science. We thank G. Feingold for hosting and maintaining the TAU microphysics code. Comments by W. W. Grabowski on an earlier version of the manuscript are appreciated. We would also like to acknowledge high-performance computing support from Cheyenne (doi:10.5065/D6RX99HX) provided by NCAR’s Computational and Information Systems Laboratory. We thank the CPTEC Satellite Division and Environmental Systems team, especially Renato Galante Negri and Mario Figueiredo, for the support in providing access to the data repository. This publication includes data analysis and visualizations created with NCL (NCAR 2018). The National Center for Atmospheric Research is sponsored by the National Science Foundation.
Publisher Copyright:
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PY - 2020
Y1 - 2020
N2 - In this study, processes that broaden drop size distributions (DSDs) in Eulerian models with two-moment bin microphysics are analyzed. Numerous tests are performed to isolate the effects of different physical mechanisms that broaden DSDs in two- and three-dimensional Weather Research and Forecasting Model simulations of an idealized ice-free cumulus cloud. Sensitivity of these effects to modifying horizontal and vertical model grid spacings is also examined. As expected, collision-coalescence is a key process broadening the modeled DSDs. In-cloud droplet activation also contributes substantially to DSD broadening, whereas evaporation has only a minor effect and sedimentation has little effect. Cloud dilution (mixing of cloud-free and cloudy air) also broadens the DSDs considerably, whether or not it is accompanied by evaporation. This mechanism involves the reduction of droplet concentration from dilution along the cloud's lateral edges, leading to locally high supersaturation and enhanced drop growth when this air is subsequently lifted in the updraft. DSD broadening ensues when the DSDs are mixed with those from the cloud core. Decreasing the horizontal and vertical model grid spacings from 100 to 30 m has limited impact on the DSDs. However, when these physical broadening mechanisms (in-cloud activation, collision-coalescence, dilution, etc.) are turned off, there is a reduction of DSD width by up to;20%-50% when the vertical grid spacing is decreased from 100 to 30 m, consistent with effects of artificial broadening from vertical numerical diffusion. Nonetheless, this artificial numerical broadening appears to be relatively unimportant overall for DSD broadening when physically based broadening mechanisms in the model are included for this cumulus case.
AB - In this study, processes that broaden drop size distributions (DSDs) in Eulerian models with two-moment bin microphysics are analyzed. Numerous tests are performed to isolate the effects of different physical mechanisms that broaden DSDs in two- and three-dimensional Weather Research and Forecasting Model simulations of an idealized ice-free cumulus cloud. Sensitivity of these effects to modifying horizontal and vertical model grid spacings is also examined. As expected, collision-coalescence is a key process broadening the modeled DSDs. In-cloud droplet activation also contributes substantially to DSD broadening, whereas evaporation has only a minor effect and sedimentation has little effect. Cloud dilution (mixing of cloud-free and cloudy air) also broadens the DSDs considerably, whether or not it is accompanied by evaporation. This mechanism involves the reduction of droplet concentration from dilution along the cloud's lateral edges, leading to locally high supersaturation and enhanced drop growth when this air is subsequently lifted in the updraft. DSD broadening ensues when the DSDs are mixed with those from the cloud core. Decreasing the horizontal and vertical model grid spacings from 100 to 30 m has limited impact on the DSDs. However, when these physical broadening mechanisms (in-cloud activation, collision-coalescence, dilution, etc.) are turned off, there is a reduction of DSD width by up to;20%-50% when the vertical grid spacing is decreased from 100 to 30 m, consistent with effects of artificial broadening from vertical numerical diffusion. Nonetheless, this artificial numerical broadening appears to be relatively unimportant overall for DSD broadening when physically based broadening mechanisms in the model are included for this cumulus case.
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U2 - 10.1175/JAS-D-20-0099.1
DO - 10.1175/JAS-D-20-0099.1
M3 - Article
AN - SCOPUS:85094326118
VL - 77
SP - 3249
EP - 3273
JO - Journals of the Atmospheric Sciences
JF - Journals of the Atmospheric Sciences
SN - 0022-4928
IS - 9
ER -