Multiphase Chemistry Department Max Planck Institute for Chemistry Mainz Germany, Centro de Previsão de Tempo e Estudos Climáticos Instituto Nacional de Pesquisas Espaciais Cachoeira Paulista Brazil
Mesoscale and Microscale Meteorology Laboratory National Center for Atmospheric Research Boulder CO USA
Institute of Physics University of Sao Paulo São Paulo Brazil
Multiphase Chemistry Department Max Planck Institute for Chemistry Mainz Germany, Scripps Institution of Oceanography University of California San Diego La Jolla CA USA, Department of Geology and Geophysics King Saud University Riyadh Saudi Arabia
Multiphase Chemistry Department Max Planck Institute for Chemistry Mainz Germany
Institute of Earth Sciences The Hebrew University of Jerusalem Jerusalem Israel
Centro de Previsão de Tempo e Estudos Climáticos Instituto Nacional de Pesquisas Espaciais Cachoeira Paulista Brazil
Institut für Physik der Atmosphäre Deutsches Zentrum für Luft und Raumfahrt Wessling Germany, Institut für Physik der Atmosphäre Johannes Gutenberg‐Universität Mainz Mainz Germany
Leipziger Institut für Meteorologie Universität Leipzig Leipzig Germany
In this study, the variability of the spectral dispersion of droplet size distributions (DSDs) in convective clouds is investigated. Analyses are based on aircraft measurements of growing cumuli near the Amazon basin, and on numerical simulations of an idealized ice‐free cumulus. In cleaner clouds, the relative dispersion , defined as the ratio of the standard deviation to the mean value of the droplet diameter, is negatively correlated with the ratio of the cloud water content ( ) to the adiabatic liquid water content ( ), while no strong correlation between and is seen in polluted clouds. Bin microphysics numerical simulations suggest that these contrasting behaviors are associated with the effect of collision‐coalescence in cleaner clouds, and secondary droplet activation in polluted clouds, in addition to the turbulent mixing of parcels that experienced different paths within the cloud. Collision‐coalescence simultaneously broadens the DSDs and decreases , explaining the inverse relationship between and in cleaner clouds. Secondary droplet activation broadens the DSDs but has little direct impact on . The combination of a rather modest DSD broadening due to weak collision‐coalescence with enhanced droplet activation in both diluted and highly undiluted cloud regions may contribute to maintain a relatively uniform within polluted clouds. These findings can be useful for parameterizing the shape parameter ( ) of gamma DSDs in bulk microphysics cloud‐resolving models. It is shown that emulating the observed relationship improves the estimation of the collision‐coalescence rate in bulk microphysics simulations compared to the bin simulations.
Hernández Pardo, Lianet, et al. "Observed and Simulated Variability of Droplet Spectral Dispersion in Convective Clouds Over the Amazon." Journal of Geophysical Research: Atmospheres, vol. 126, no. 20, Oct. 2021. https://doi.org/10.1029/2021JD035076
Hernández Pardo, Lianet, Machado, Luiz A. T., Morrison, Hugh, Cecchini, Micael A., Andreae, Meinrat O., Pöhlker, Christopher, Pöschl, Ulrich, Rosenfeld, Daniel, Vendrasco, Eder P., Voigt, Christiane, Wendisch, Manfred, & Pöhlker, Mira L. (2021). Observed and Simulated Variability of Droplet Spectral Dispersion in Convective Clouds Over the Amazon. Journal of Geophysical Research: Atmospheres, 126(20). https://doi.org/10.1029/2021JD035076
Hernández Pardo, Lianet, Machado, Luiz A. T., Morrison, Hugh, et al., "Observed and Simulated Variability of Droplet Spectral Dispersion in Convective Clouds Over the Amazon," Journal of Geophysical Research: Atmospheres 126, no. 20 (2021), https://doi.org/10.1029/2021JD035076
@article{osti_1827478,
author = {Hernández Pardo, Lianet and Machado, Luiz A. T. and Morrison, Hugh and Cecchini, Micael A. and Andreae, Meinrat O. and Pöhlker, Christopher and Pöschl, Ulrich and Rosenfeld, Daniel and Vendrasco, Eder P. and Voigt, Christiane and others},
title = {Observed and Simulated Variability of Droplet Spectral Dispersion in Convective Clouds Over the Amazon},
annote = {Abstract In this study, the variability of the spectral dispersion of droplet size distributions (DSDs) in convective clouds is investigated. Analyses are based on aircraft measurements of growing cumuli near the Amazon basin, and on numerical simulations of an idealized ice‐free cumulus. In cleaner clouds, the relative dispersion , defined as the ratio of the standard deviation to the mean value of the droplet diameter, is negatively correlated with the ratio of the cloud water content ( ) to the adiabatic liquid water content ( ), while no strong correlation between and is seen in polluted clouds. Bin microphysics numerical simulations suggest that these contrasting behaviors are associated with the effect of collision‐coalescence in cleaner clouds, and secondary droplet activation in polluted clouds, in addition to the turbulent mixing of parcels that experienced different paths within the cloud. Collision‐coalescence simultaneously broadens the DSDs and decreases , explaining the inverse relationship between and in cleaner clouds. Secondary droplet activation broadens the DSDs but has little direct impact on . The combination of a rather modest DSD broadening due to weak collision‐coalescence with enhanced droplet activation in both diluted and highly undiluted cloud regions may contribute to maintain a relatively uniform within polluted clouds. These findings can be useful for parameterizing the shape parameter ( ) of gamma DSDs in bulk microphysics cloud‐resolving models. It is shown that emulating the observed relationship improves the estimation of the collision‐coalescence rate in bulk microphysics simulations compared to the bin simulations. },
doi = {10.1029/2021JD035076},
url = {https://www.osti.gov/biblio/1827478},
journal = {Journal of Geophysical Research: Atmospheres},
issn = {ISSN 2169-897X},
number = {20},
volume = {126},
place = {United States},
publisher = {American Geophysical Union (AGU)},
year = {2021},
month = {10}}