New Method Tracks Diverse Cloud Characteristics and Evolution

Ovchinnikov, M., Pacific Northwest National Laboratory

Cloud Distributions/Characterizations

Convective Processes

Heiblum RH, O Alaratz, I Koren, G Feingold, AB Kostinski, AP Khain, M Ovchinnikov, E Fredj, G Dagan, L Pinto, R Yaish, and Q Chen. 2016. "Characterization of cumulus cloud fields using trajectories in the center of gravity versus water mass phase space: 1. Cloud tracking and phase space description." Journal of Geophysical Research: Atmospheres, 121(11), 10.1002/2015jd024186.

Heiblum RH, O Altaratz, I Koren, G Feingold, AB Kostinski, AP Khain, M Ovchinnikov, E Fredj, G Dagan, L Pinto, R Yaish, and Q Chen. 2016. "Characterization of cumulus cloud fields using trajectories in the center of gravity versus water mass phase space: 2. Aerosol effects on warm convective clouds." Journal of Geophysical Research: Atmospheres, 121(11), 10.1002/2015jd024193.

Science

Cloud fields composed of clouds in a wide range of sizes and at different stages of their lifetimes are difficult to compare. A new method that combines tracking individual clouds and projecting cloud populations onto the space of the cloud center of gravity altitude versus cloud mass (CvM) offers a new way to characterize the evolution of modeled cloud fields, their response to a changing environment, and the dependency on model physics.

Impact

Complex simulated cloud fields presented in the CvM phase space provide new insights into the role of precipitation processes, aerosol effects, and microphysical representations used in the model.

Summary

In a new approach, researchers, including Department of Energy scientists at Pacific Northwest National Laboratory, developed a way to characterize cumulus cloud fields composed of clouds of different shapes, sizes, and evolution histories. The method is based on tracking individual clouds in a simulated cloud field from formation to dissipation. The researchers followed clouds in the CvM phase space of center of gravity (CoG) altitude versus liquid water mass. They analyzed clustering in the CvM space for simulations with different environments and microphysics treatments. The approach is applied to investigate aerosol effects on cloud fields of warm cumuli. The method demonstrates a clear effect of the aerosol loading on the shape and size of CvM clusters. The research also shows fundamental differences in the clustering in the CvM space between simulations depending on whether the shape of the droplet size distributions is prescribed or predicted, with the latter scheme exhibiting a much higher sensitivity to changes in aerosol concentrations.