Thomas Ackerman Roger Marchand University of Washington.
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Transcript of Thomas Ackerman Roger Marchand University of Washington.
Evaluating the MMF Using High Resolution Data
Thomas AckermanRoger Marchand
University of Washington
As we move towards higher resolution models with more realistic simulations of cloud processes and cloud properties, how do we evaluate model cloud properties? What are the metrics? How do know we are improving those
metrics?
The Question
Occurrence in space and time – cloud fraction
Cloud top height Optical depth – an optical (radiation)
measure of the total condensed water and ice in a cloud
Statistical distributions of these quantities
The Metrics
The tools
CloudSat – 3 mm radarNASA A-Train, launched
2006Profiles of cloud reflectivity
MISR – multi-angle radiometer
NASA Terra, launched 1999
Cloud height and optical depthARM sites – multiple instruments
Established 1996 – 1998Cloud profiles and integrated properties
Cyclone Nargis in the Bay of Bengal before landfall in Myanmar
MODIS image
CloudSat curtain along red line
CloudSat data – an example
B
Simulator Simulator
Synthetic Signals
In situ Observations Model Cloud
Properties
Remote Sensing Signals
Retrieved Model Cloud Properties
Retrieved Cloud Properties
Cloud M odel
D
A
C
Retrieval Algorithms
CloudSat Instrument Simulator
MMF August Composite
MAM (Diff = MMF – CS)
JJA (Diff = MMF – CS)
SON (Diff = MMF – CS)
DJF (Diff = MMF – CS)
What have we learned
MMF captures general cloud structure and seasonal movement
MMF generally overproduces convective cloud Too much high cloud and too optically thick
MMF underpredicts BL cloud (Stratus, Trade Cu)
Produces too much precipitation Simulated Radar reflectivity values are too high Too much drizzle
CloudSat has limited temporal coverage ARM radar has limited spatial coverage Combine them to provide detailed
regional data Work in progress
Detailed comparison ofradar signals
Apply to simulations inTWP
CloudSat and ARM
MISR measures stereo cloud-top height and cloud optical depth
Plot as 2D joint histogram
MISR simulatorincorporated into MMF
Using MISR Joint Histograms
64 or 128 Columns
2°
2.5°
Multi-scale Modeling Framework (MMF)Testing the effect of increasing resolution
3-month MMF runs Increasing resolution
•Control run• 4 km horizontal• 64 columns• 26 vertical layers
• Test A• 1 km horizontal• 64 & 128 columns• 26 vertical layers
• Test B• 1 km horizontal• 64 columns• 52 vertical layers
Run on SDSC Datastar with support from CMMAP
Sensitivity of low cloud amount to CRM resolution
Hawaiian Trade Cumulus
Summary of Low Cloud Response
Going from 4 km to 1 km reduced low cloud amount. Much (but not all) due to dissipation of “stratofogulus” Generally, little change in amount of low cloud with optical
depths less than 10.
Going from 4 km to 1 km and vertical resolution to 52 levels (50 in CRM) resulted in …
Small increase in the amount of low-level cloud relative to the simulations with 4 km horizontal resolution.
Increase in cloud with optical depths less than 10 (better agreement with MISR observational data)
Stratocumulus zones show a significant improvement in cloud top height.
BUT Total amount of model low cloud remains too low Too much low cloud with optical depths larger than 23 (the
largest two optical-depth bins).
New instruments well suited to evaluating MMF Model spatial resolution matches
sensors Simulator approach easy to implement
in MMF Provide new metrics
Profiles of cloud occurrence Optical depth – cloud top height joint
histograms Test model improvements against
these same metrics
Concluding thoughts
Thank you for your attention!
Mace, G. G., Q. Zhang, M. Vaughan, R. Marchand, G. Stephens, C. Trepte, and D. Winker (2009), A description of hydrometeor layer occurrence statistics derived from the first year of merged Cloudsat and CALIPSO data, J. Geophys. Res., 114, D00A26, doi:10.1029/2007JD009755.
McFarlane, S. A., J. H. Mather, and T. P. Ackerman, 2007: Analysis of tropical radiative heating profiles: A comparison of models and observations, J. Geophys. Res., 112, D14218, doi:10.1029/2006JD008290
Marchand, R. T., J. Haynes, G. G. Mace, T. P. Ackerman, and G. Stephens, 2009: A comparison of CloudSat cloud radar observations with simulated cloud radar output from the Multiscale Modeling Framework global climate model, J. Geophys. Res., 114, D00A20, doi:10.1029/2008JD009790
Marchand, R. T., and T. P. Ackerman, 2009: Analysis of the MMF global climate model using ISCCP and MISR histograms of cloud top height and optical depth, manuscript in preparation
Marchand, R. T., T. P. Ackerman, M. Smyth, P. Hubanks, S. Platnick, and W. Rossow, 2009: A comparison of cloud top height and optical depth histograms from MISR, ISCCP, and MODIS, manuscript in preparation
References
Research supported by DOE ARM, NASA, and CMMAP