Kirshbaum D. and K. Lamer (under review). Climatology of cloud entrainment in marine and continental shallow cumulus and its sensitivity to environmental factors. Journal of Climate Marine clouds: Naud D. and coauthors (2020). On the Relationship Between The Marine Cold Air Outbreak M Parameter And Low-Level Cloud Heights In The Midlatitudes. Journal of Geophysical Research: Atmospheres, e2020JD032465
Lamer K., and coauthors (2020). Relationships between precipitation properties and large-scale conditions during subsidence at the eastern north Atlantic observatory. JGR: Atmospheres, 124
Zhu, Z., K. Lamer and coauthors (2019). The Vertical Structure of Liquid Water Content in Shallow Clouds as Retrieved from Dual-wavelength Radar Observations. JGR-Atmospheres
Lamer K., P. Kollias, and L. Nuijens (2015). Observations of the variability of shallow trade wind cumulus cloudiness and mass flux. JGR: Atmospheres, 120(12), 6161-6178.
Continental clouds: Lamer K. and P. Kollias (2015). Observations of fair‐weather cumuli over land: Dynamical factors controlling cloud size and cover. GRL, 42(20), 8693-8701.
Endo, S. and coauthors (2019). Reconciling differences between large-eddy simulations and Doppler-lidar observations of continental shallow cumulus cloud-base vertical velocity, GRL
Because of their ubiquitous nature and of the way they interact with solar and longwave radiation, warm boundary layer clouds play a crucial role in the global energy budget [Klein and Hartmann, 1993]. Unfortunately, numerical models still struggle to properly represent their coverage, vertical distribution, and brightness (e.g., [Nam et al., 2012]). This uncertainty ultimately affects our confidence in future climate projections [Bony et al., 2015; Sherwood et al., 2014]. Climate simulations could be improved from comparisons with additional observations of the macrophysical and microphysical properties of warm boundary layer clouds, as well as from improvements in our understanding of the relationships between low-level clouds and their environment.
In collaboration with scientists from around the world I have assembled climatologies of: cloud fraction, cloud base updraft and downdraft properties, mass flux, cloud base rain rate, rain-to-cloud fraction and bulk entrainment; For boundary layer clouds forming under a range of conditions including marine and continental regions and following cold front passages. Amongst other things, these climatologies can be used to benchmark models, which currently lack information about the properties of these clouds.
I was also part of efforts to improve our understanding of the factors controlling low-level cloud cloudiness and rain properties. For example, my work has revealed that elevated cloudiness in the Trade wind region coincides with the presence of precipitating cumulus clouds and is associated with elevated environmental relative humidity. The presence of shallow cumulus with stratiform "outflows" has also been documented for the sub-tropical region of the Azores and the mechanisms controlling their occurrence remains an active area of research. Entrainment/detrainment processes undeniably play a role in controlling cloud fraction. Recent work I have supervised has shown evidence suggesting that cloud top entrainment leads to a reduction of liquid water content near cloud top. Other processes including rain formation were also shown to affect the vertical distribution of liquid water in clouds. In convective regimes, our work has shown that continental cloud fraction is related to the formation of coherent updrafts in the subcloud layer. It was shown that the width and intensity of these coherent updraft is strongly tied to the properties of active shallow cumulus clouds near cloud base. More recently, work I have led has showed that rain rate at the base of shallow clouds forming in subsidence regimes is influenced by cloud top phase as well as large-scale stability and surface forcing parameter. This work also showed that ice-topped shallow clouds tend to be found under unstable conditions best characterized by the Marine Cold Air Outbreak M-parameters.
The identification of such relationships between clouds and their environment reveals important information about cloud processes and could lead to improvements in cloud parameterizations.