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GEWEX Cloud Systems Studies (GCSS)
GCSS Boundary Layer Cloud WG (BLCWG) Home Page
Objectives of the Working Group
The GCSS ( GEWEX Cloud System Study) Boundary
Layer Cloud Working Group aims to improve physical parameterizations
of clouds and cloud related processes, and their interactions. We
conduct careful intercomparisons between observational or laboratory
case studies, 3D large-eddy-simulation models, single-column-model (SCM) versions of climate and numerical weather prediction (NWP) models of cloud-topped boundary layers. Most of the leading groups modelling boundary layer clouds have participated in our annual workshops, held every 12-18 months.
The BLCWG is currently chaired by
A. Pier Siebesma of KNMI, de Bilt, Netherlands.
If you would like to keep in touch with our activities, you can join our email
list. Please send an email to
A. Pier Siebesma an you will be added to the list and you will be kept updated to the activities of the workshop.
Current GCSS BLCWG activities
Precipitating trade cumulus off Antigua during
RICO.
Controlled Microphysics Case
- As an outcome of the
DYCOMS RF02 nocturnal drizzling stratocumulus
intercomparison case there is a strong need for a simple case that can evaluate microphysics schemes used in GCM's in isolation as to disentangle errors due to dynamics and errors due to microphysics. The actual construction for such a case is still under debate.
- Contact Persons: Andy Ackerman of NASA/GISS
(LES) and Chris Bretherton of the University of Washington.
Related links to current GEWEX activities
- GABLS (the GEWEX Atmospheric
Boundary Layer Study), whose mission is to coordinate research on boundary
layer physics to improve the representation of the atmospheric boundary layer
in numerical models.
-
GPCI (the GCSS Pacific Cross-Section Intercomparison), which is comparing
the observed thermodynamic structure and clouds along a vertical cross-section
from the California coast to the central Pacific ITCZ during July 1998 and
2003 with simulations from regional and global simulations.
- An Ad Hoc activitity called DIME has the goal to provide "test
kits" for model evaluation based on the GCSS Model Intercomparison Projects, including detailed results from the participating Cloud Resolving Models. William Rossow, NASA, GISS, is the chairperson.
Past GCSS BLCWG cases
Preliminary results from this case were discussed in
May 2005 at the Athens pan-GCSS meeting (see talks). Final results for a
revised case specification were submitted in late 2005, and are
being drafted for publication by case coordinators Andy Ackerman of NASA/GISS
(LES) and Matt Wyant
of U. Washington (SCM), with two papers to be submitted to JGR
or MWR in Oct. 2006.
- LES and
SCM case specifications/results.
- Talks
from pan-GCSS BLCWG session.
- Update presentation
of the DYCOMS precipitation case at the GCSS-BLCWG meeting Sept 2006 in New York.
-
LES case description/instructions/results. Case coordinator: Bjorn
Stevens (bstevens@atmos.ucla.edu)
-
SCM case description/instructions/results. Case coordinators: Martin Koehler, ECMWF
(Martin.Koehler@ecmwf.int) and Ping Zhu, U. Washington
(zhup@fiu.edu).
-
Stevens,
B., and coauthors, 2005: Observations of nocturnal marine
stratocumulus as represented by large eddy simulation.
Mon. Wea. Rev., 133, 1443-1462.
Full text
copy.
-
Zhu,
P., and coauthors, 2005: Intercomparison and interpretation of
single column model simulations of a nocturnal stratocumulus topped
marine boundary layer. Mon. Wea. Rev., 133, 2741-2758.
Full text
copy.
- Case coordinator: Peter Duynkerke, KNMI (deceased)
- Case coordinator: Bjorn Stevens, NCAR, USA (bstevens@mmm.ucar.edu)
-
B. Stevens et al., 2000: Simulations of trade-wind cumuli
under a strong inversion, J. Atmos. Sci, 58,1870-1891.
Full text copy.
- Case
summary, goals, specifications and results
-
Animation of simulated cloud field, from 7-8 hours into an ATEX
simulation, and one with a
smaller subgridscale turbulent
mixing length which generates a much larger cloud fraction
near the inversion (courtesy Andy Ackerman of NASA/Ames).
- Case Coordinator: Pier Siebesma, KNMI, Netherlands (siebesma@knmi.nl)
-
Siebesma, A. P., and coauthors, 2003: A
large-eddy simulation intercomparison study of shallow cumulus
convection. J. Atmos. Sci., 60, 1201-1219.
Full text copy.
- Case summary and goals, detailed case specifications, and preliminary results.
- Animation of cloud top heights
from a BOMEX trade cumulus simulation on an approximately 25
by 25 km domain using 256x256x72 gridpoints and a 100 m
horizontal and 50 m vertical grid spacing, made by Dave
Stevens of Lawrence Berkeley Labs. Blue cloudtops are at 600
m, just above the subcloud lifted condensation level, and red
corresponds to about 2 km cloud tops. Note range of cloud top
heights.
- Case Coordinator: Peter Duynkerke (deceased)
- Case summary, goals, specifications and results are not available.
- Related observations from
Stephan de Roode of IMAU, including references.
- Case coordinators: Steve Krueger, Univ. of Utah, USA
(skrueger@met.utah.edu),
and Chris
Bretherton, Univ. of Washington, USA (breth@atmos.washington.edu).
- Bretherton, C. S., S. K. Krueger, M. C. Wyant, P. Bechtold, E. van
Meijgaard, B. Stevens, and J. Teixeira, 1999: A GCSS boundary layer model
intercomparison study of the first ASTEX Lagrangian experiment.
Bound.-Layer Meteor., 93, 341-380.
Full text copy.
-
ASTEX Lagrangians modellers data set
- Case summary,
goals, and specifications
- Case coordinators: Malcolm MacVean,
UKMO, England (mkmacvean@meto.gov.uk) and Chris
Bretherton, Univ. of Washington, USA (breth@atmos.washington.edu).
-
Bretherton,
C. S., M. K. MacVean, and 14 coauthors, 1999: An intercomparison of
radiatively-driven entrainment and turbulence in a smoke cloud, as simulated
by different numerical models. Quart. J. R. Meteor. Soc., 125,
391-423.
Full text copy.
- Case summary, goals, and
specifications
- Case coordinator: Chin-Hoh Moeng, NCAR, USA (moeng@ucar.edu)
- Moeng,
C.-H., and coauthors, 1996: Simulation of a stratocumulus-topped PBL:
Intercomparison among different numerical codes.
Bull. Amer. Meteor. Soc., 77, 261-278.
Full text copy.
-
Bechtold,
P., and coauthors, 1996: Modeling a
stratocumulus-topped PBL: Intercomparisons among different 1D codes
and with LES. Bull. Amer. Meteor. Soc., 77, 2033-2042.
Full text copy.
Presentations from Lake Arrowhead
Workshop on the Planetary Boundary Layer, 14-16 June
2005. Many GCSS BLCWG participants attended this excellent
workshop, though it was not formally a GCSS event.
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