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Report of the CSM Polar Climate Working Group
By Dick Moritz, John Weatherly, and Bill Large, Co-Chairs
19-20 January, 1999
NCAR, Boulder, Colorado
PRESENTATIONS AND DISCUSSION
John Weatherly opened the meeting and noted administratively the CSM Polar Climate Working Group (PCWG) has three co-chairs: Weatherly and Moritz (outside NCAR) and Large (NCAR).
Weatherly noted that VP and EVP ice models have been tested on rotated polar grids in ice/ocean simulations forced by fields of atmospheric quantities and can be tested in the fully coupled CSM, if needed. However, it was also noted that it is undesirable to have to interpolate between a sea ice grid and a (different) ocean grid, so in the long run, we should aim for a CSM with sea ice on the same grid as the ocean. This has been problematic for the ice model with the present CSM ocean grid with the active tracer at the North Pole.
A series of presentations was given as follows:
Moritz - Column Radiation Modeling with SHEBA Data and Polar Single Column Model Developments
Briegleb - Effects of Boundary Layer Turning Angle on Simulated Meridional Ice Transport
Hunke - LANL EVP Model - Linear Analysis of Stress States On/Off the Yield Curve and
Brief Overview of the LANL CICE Model
Zhang - Global ADI Ice-Ocean Simulation and Treatment of the North Pole Problem
Curry - A New Sea Ice Thermodynamic Model
Peters - Message Passing in Parallel Processing with a Sea Ice Model
Lipscomb - Ice Thickness Distribution: Conservation of Volume and Energy
Hibler - Energetics of Plastic Rheology
Discussions during/after the presentation:
The group discussed modifications that should be made to the "next" version of the CSM sea ice model and agreed it should have:
(1) An elliptical yield curve.
(2) Multiple category representation of the ice thickness distribution.
STATUS OF CSM SEA ICE MODEL
The status of the CSM sea ice model and CSM PCWG activities may be summarized as follows:
(1) Earlier CSM runs were carried out with a sea ice model affected by three bugs:
Code that is free of these bugs is ready for the "next" version.
(2) Ice models with elliptical yield curves are being tested on the present CSM spherical grid, but still present stability problems with the high resolution near the pole. The participants (Briegleb and Zhang) will be trying to work out solutions in the next three months.
(3) Ice models with multiple ice thickness categories exist and will be implemented in the CSM framework within the next 12 months.
(4) Models with enhanced sea ice thermodynamics are under development but are not likely to be ready to implement in CSM in the same timeframe as the elliptical yield curve and multiple ice thickness categories.
(5) The ice transport algorithm in the current CSM sea ice model may be too diffusive for some applications (e.g., accurately simulating ice edge position).
PLANS FOR CSM PCWG
A. Sea Ice Model Development
(1) Implement elliptical yield curve in the next major CSM run, eliminating the bugs of previous CSM ice runs (TIMEFRAME < 1 year).
NB: The outcome of activities under item (1) above will be the CSM PCWG response to the CSM management "challenge" to have an improved CSM sea ice model for a major integration of CSM beginning circa January, 2000. The challenge includes limiting the sea ice computational burden per gridpoint to a factor of two increases over the current version of CSM. Participants: Zhang (VP), Bitz (multiple thickness), Hunke (EVP), Lipscomb (multiple thickness), Weatherly and Briegleb (CSM Implementation), Large (Flux Coupler), and Moritz (Evaluation design and data sets).
(2) Develop/implement enhanced sea ice thermodynamics, including test integrations in CSM versions of the Polar Single Column Climate Model (PSCCM) and forced ice/ocean experiments (TIMEFRAME < 2 years). Participants: Bitz, Lipscomb, Curry, Moritz, and SHEBA Science Team.
(3) Develop the general framework for multiple thickness categories and enhanced thermodynamics in the context of the CSM flux coupler, defining the inputs/outputs and the best module (ocean, coupler, ice, atmosphere) within which the different computations should be carried out. Participants: Bitz, Lipscomb, Curry, Schramm, and Large.
B. Use of the CSM
(1) Simulate and diagnose polar climate interannual-decadal variability. Participants: Moritz, Bitz, Bromwich, and colleagues from Ohio State.
(2) Paleoclimate simulations (e.g., Last Glacial Maximum). Participants: Vavrus.
(3) Diagnose the CSM simulated polar climate of the 21st century. Participants: Moritz.
(4) Diagnose the CSM arctic hydrologic cycle and freshwater budget. Participants: Bitz and Moritz.
C. Polar Topics for CCM Model Development and Evaluation
(1) Atmospheric longwave radiation code. Participants: Moritz and Briegleb.
(2) Arctic SLP and wind fields. Participants: Weatherly, Briegleb, Bitz, and Zhang.
(3) Arctic cloud simulation. Participants: Curry, Moritz, and Briegleb.
(4) Collaboration on PSCCM development. Participants: Moritz and Briegleb.
D. Produce Standard Polar Forcing and Evaluation Data Sets (in collaboration w/SHEBA, NASA EOS' Polar Exchange at the Sea Surface (POLES), NSF's Arctic Transitions in the Land Atmosphere System (ATLAS), and other projects)
(1) Ice dynamics and ice/ocean.
(2) Ice thermodynamics and ice/ocean.
(3) Column models.
Participant List: Dick Moritz John Weatherly Bill Large Bill Lipscomb Bruce Briegleb Bill Hibler Keith Hines Jinlun Zhang Uma Bhatt Judith Curry Elizabeth Hunke Amanda Lynch Cecilia Bitz Maurice Blackmon