EUCLIPSE First Period Report

Figure 13. Time series of the inversion height, mean cloud base height, and lowest cloud base
height (upper panel), and the cloud cover (lower panel) from five large-eddy simulations of
ASTEX. MPI and TUD operates the UCLA LES and DALES model, respectively, and the NASA
and the University of Washington have contributed to the EUCLIPSE Lagrangian transitions
with DHARMA and SAM, respectively. Line styles are according to the legend.
The SCM cloud cover results shown in Figure 12 exhibit a larger spread than the LES
results. A preliminary analysis indicates that the most advanced parameterization
schemes like the Eddy-Diffusivity Massflux approach (Neggers et al. 2009) or the
University of Wisconsin model CLUBB appear to have the best agreement with the
observations and LES results.
As a next step a detailed comparison of turbulent fluxes and variances from LES
results with the ASTEX aircraft observations will be made. In addition, the LES results
of the transitions will be exploited to diagnose the degree of the decoupling as
measured by mean differences of thermodynamic quantities between the subcloud
and cloud layer and the vertical turbulent transport across their interface. In addition,
quantities that constitute the main ingredients of boundary-layer cloud
parameterization schemes like the eddy-diffusivity and mass-flux profiles which are
otherwise difficult to obtain from field measurements will be determined. Although
their vertical profiles have been reported for either stratocumulus or shallow cumulus
topped boundary layers, it is not yet well understood how they should be treated
when the cloud layer is decoupled and contains both cloud types simultaneously.
b) CGILS
Figure 14 shows SCM results of the diagnosed cloud radiative feedback (ΔCRF) for the
three selected CGILS grid points (courtesy Minghua Zhang). Models which apply
parameterizations that yield rather vertically well mixed boundary layers (non-local
diffusion, counter-gradient transport, some TKE and higher order closure) tend to
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