PDF Parameterizations for Clouds, Forcing, and Scale ... · Forcing, and Scale: Inferences from the...
Transcript of PDF Parameterizations for Clouds, Forcing, and Scale ... · Forcing, and Scale: Inferences from the...
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PDF Parameterizations for Clouds, Forcing, and Scale: Inferences from
the ARM SGP Observations
Leo Donner, Yanluan Lin, Chris Golaz, Huan GuoGFDL/NOAA, Princeton University
Shaocheng XieLawrence Livermore National Laboratory
Spring 2012 ASR Science Team Meeting
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Motivation
• Use multi-variate probability density functions with dynamics (MVD PDFs) to parameterize boundary layers and clouds
• ARM GCSS shallow cumulus SCM test behaves differently from SCM tests with ARM analysis
• Moisture profile in ARM analysis differs appreciably from GCSS analysis, which is closer to single sounding
• Does horizontal scale of the analysis driving the SCM influence the success of the MVD PDFs? How well does LES perform? Limits to parameterization?
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3 - Close2 - Select
1 - Prognose
Building a PDF-based parameterizationAdvance prognostic moment equations
Select PDF from functional form to matchmoments
Use PDF to close higher-order moments, buoyancy terms
Diagnose cloud fraction,liquid water, dropletnumber from PDF
Adapted from Golaz et al. (J. Atmos. Sci.,2002), following concepts introduced by Randall et al. (1992, J. Atmos. Sci.)
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AM3 Single Column
Model using Multi-Variate Probability
Density Function with
Dynamics, Aerosol
Activation, and Double-
Moment Microphysics from Guo et al.
(2010, Geosci. Model Dev.)
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GCSS ARM case
AM3
MVD PDFs
Cloud fraction
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Vertical motion PDF comparison
ARM GCSS 21 June 97Brown et al.
(QJRMS, 2002)
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ARMLH: solid line
SH: dashed lines
Surface latent and sensible heat flux from ARM variational analysis and GCSS forcing
Symbols are fluxes at the
central facility.
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Initial T and Qv
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qv adv (g/kg/
hr)
T adv (K/hr)ARM
Variational
GCSS
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• MVD PDFs fail to produce cloud using ARM (300 km) variational analysis
• GCSS and ARM analysis differ in initial T and q soundings, surface fluxes, and advection of T and q
• Analyze dependence of MVD PDFs on initial conditions and scale of analysis
• Compare with LES
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Scale of ARM analysis has little effect on MVD PDF simulations. Simulated cloud fractions well below
observed.
MVD PDFs have been “tuned” by restricting characteristics of bi-normals, slightly increasing
cloud fraction when ARM analysis is used.
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MVD PDF simulations depend strongly on initial conditions. GCSS sounding moister and less stable
(below 2km) than ARM sounding.
GCSS forcing in all simulations
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LES (Golaz et al., 2005, Boundary-Layer Meteorol.) also strongly dependent on initial sounding and exhibit
many common characteristics with MVD PDFs.
GCSS forcing in all simulations
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Summary• MVD PDFs successfully simulate cloud fraction,
water path, and droplet numbers for Sc and shallow Cu GCSS cases
• MVD PDF simulations are not as successful using ARM-scale analysis, with strong dependence on initial conditions
• LES also depends on initial conditions, with cloud amounts compared to MVD PDFs sounding-dependent
• Results suggest limits on parameterization at coarser resolutions
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GCSS ARM case
AM3
MVD PDFOBS
MVD PDFs with reduced LH
Cloud fraction