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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2018-190
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
01 Mar 2018
Review status
This discussion paper is a preprint. It has been under review for the journal Atmospheric Chemistry and Physics (ACP). The revised manuscript was not accepted.
Cloud-top microphysics evolution in the Gamma phase space from a modeling perspective
Lianet Hernández Pardo1, Luiz Augusto Toledo Machado1, and Micael Amore Cecchini2 1Centro de Previsão de Tempo e Estudos Climáticos, Instituto Nacional de Pesquisas Espaciais, Cachoeira Paulista, Brazil
2Departamento de Ciências Atmosféricas, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Brazil
Abstract. This research employs the recently introduced Gamma phase space to study the evolution of warm cloud microphysics, to evaluate different microphysics parameterizations and to propose an adjustment to bulk schemes for an improved description of cloud droplet size distributions (DSDs). A bin parameterization is employed to describe the main features of observed cloud-top DSD paths in the Gamma phase space. The modeled DSD evolution during the warm cloud life cycle is compared to the results obtained from HALO airplane measurements during the ACRIDICON-CHUVA campaign in the Amazon dry-to-wet season transition. The comparison shows an agreement between the observed and simulated trajectories in the Gamma phase space, providing a suitable qualitative representation of the DSD evolution. The degree of similarity between the trajectories is defined by the conditions of the environment, such as the aerosol number concentration, which modify the DSD evolution through modulation of its driving forces. The modeled DSD properties were also projected in the Nd − Deff space to obtain further insights into their life cycle. Two different bulk microphysics parameterizations were evaluated regarding the evolution of the DSD and using the bin scheme as a reference. The results show the weakness of bulk schemes in representing trajectories in the Gamma phase space; thus, a new closure is proposed for better comparisons to the reference. The new closure resulted in an improvement in the representation of the DSD evolution, cloud droplet effective diameter and rain mixing ratio.
Citation: Hernández Pardo, L., Toledo Machado, L. A., and Amore Cecchini, M.: Cloud-top microphysics evolution in the Gamma phase space from a modeling perspective, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2018-190, 2018.
Lianet Hernández Pardo et al.
Lianet Hernández Pardo et al.

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