”This revision took quite some time as problems with the sea ice model surfaced
resulting in 2 major updates to the rheology, and in addition we needed to provide two
releases of the forecast to CMEMS. However, we have now been able to finish it — T Williams et al 7 Nov 2020”
So will the original paper be withdrawn? The (unavailable) revised manuscript would have to be peer-reviewed from scratch, despite many initial review suggestions adopted (to be reviewed, next post). This leaves CMEMS hosting imagery documented by an unreleased preprint. Without the daily dramatic imagery provided by CMEMS/Lobelia, this model would just be another tree falling silently in a forest of forgotten sea ice models. Why now, Maxwell Elastic Brittle after all these decades of viscous plastic?
https://link.springer.com/article/10.1007/s40641-020-00162-y/tables/2 long table of model acronyms with links
From the perspective of our forums, there has to be quality assurance at the source. If unreliable data is hosted for one variable, is it a one-off situation or pervasive site-wide? We’ve seen too much ice thickness and snowpack eye candy over the years with no (or no demonstrated) underlying reality. It is just not realistic to expect 1800 members to individually evaluate dozens of technical continuum mechanics and adaptive mesh numerical analysis papers. More likely, they will be taken in by fancy graphics and animation, assume here CMEMS has done its job, and possibly misinform themselves and others from there.
https://psl.noaa.gov/forecasts/seaice/ CAFS RASM POP2 CICE5.1 CLM4.5 CESM GEFS AMSR2
https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arcticictn_nowcast_anim30d.gif Hycom
https://tinyurl.com/y3zcaqpq CMEMS hosting stack of 5 neXtSim products: snow, thickness, x, y velocities
Should Sea-Ice Modeling Tools Designed for Climate Research Be Used for Short-Term Forecasting?
E Hunke et al 26 September 2020
https://link.springer.com/article/10.1007/s40641-020-00162-y very readable review
In regards to the five neXtsim products (
https://tinyurl.com/yxm847ye), Lobelia has not yet added vector display as requested @lavergneth; separate display of x and y components of modelled sea ice velocity by color is utterly ineffectual. OsiSaf has long offered two-day arrows and is currently looking into swath-to-swath orbitals which provide many more AI matches and a hope for shorter term ice motion display as well as auto arrow-artifact removal. (However it is mostly pitched at a 2028 satellite launch; the long lead time is incompatible with rapidity of Arctic sea ice change.) Neither CMEMS nor OsiSaf provide Panoply-compliant netCDFs (in which x,y arrows can be drawn).
Towards a swath-to-swath sea-ice drift product for the Copernicus IMR mission
T Lavergne et al
https://tc.copernicus.org/preprints/tc-2020-332/tc-2020-332.pdfThe snow product is fascinating but where does it come from, how well does it agree with ice buoys especially designed to measure it? Here it is necessary to text-search the full succession of neXtSim papers to see if snow depth is observation-based altimetry or just some funky pre-reanalysis weather precip forecast. The attached graphic shows its Dec 6th thickness semi-transparently over the puzzling sea ice thickness leads. [Note Lobelia does not dim the palette nor show % transparency.]
Snow is not a well-defined term: on sea ice, it evolves through many states according to its initial properties and subsequent history. Mosaic could only document five snowfalls over 12 months -- and that snow blew around, mostly piling up on the lee side of pressure ridges.
Like all CMEMS products, the neXtSIM daily releases are shown in EPSG 3408 [EPSG 6931 intended?], the NSIDC EASE-Grid 2.0 GeoTiff-compatible WGS84 ellipsoidal earth Lambert azimuthal equal area projection (EA), using the 0º meridian rather than the conformal polar stereographic EPSG 3413 projection used by WorldView and almost all satellite imagery in ’Greenland down’ orientation of the -45º meridian. (A rotation would degrade image quality.)
This is unfortunate because these two projections cannot be readily rescaled to match, meaning satellite imagery cannot be layered onto CMEMS products without passing through netCDF (not offered) and Panoply. While it is possible to invert a satellite image in PS coordinates back to how it looked on the curved earth before projection and then then re-project that back down to the equal area plane, that would considerably degrade image quality. It’s further unclear whether the net radial distortion is already implemented in Gimp by the ‘lens refractive index’ setting in the Filter —> Distort menu.
However the meridian in CMEMS could easily be changed and an area scale added to facilitate both approximate overlay rescaling and accurate conversion from pixel counts to accurate surface area, one of the main reasons for using an equal-area projection. Smap is apparently served in EASE 2.0 though that is nowhere stated and pngs are provided rather than GeoTiffs (unlike the more modern AMSR2_AWI). There does not seem to be an open source online tool to interconvert PS and EA.
https://www.mdpi.com/2220-9964/1/1/32/htmneXtSIM papers (reverse chronological order):
Presentation and evaluation of the Arctic sea ice forecasting system neXtSIM-F
T Williams A Korosov P Rampal E Olason 25 Jun 2019 submission
https://tc.copernicus.org/preprints/tc-2019-154/https://ui.adsabs.harvard.edu/abs/2020EGUGA..22.9136W/abstract“We assimilate OSISAF SSMI and AMSR2 sea ice concentration products and the SMOS sea ice thickness product by modifying the initial conditions daily and adding a compensating heat flux to prevent removed ice growing back too quickly. We present an evaluation of the platform over the period from November 2018 to present, looking at sea ice drift and concentration and extent, and thin ice thickness.”
Probabilistic forecasts of sea ice trajectories in the Arctic: impact of uncertainties in surface wind and ice cohesion
S Cheng, A Aydoğdu, P Rampal A Carrassi L Bertino 17 Nov 2020
https://arxiv.org/pdf/2009.04881.pdf“We suggest that in order to get enough uncertainties in a sea ice model with brittle-like rheologies to predict sea ice drift and
trajectories, one should consider using ensemble-based simulations where at least wind forcing and sea ice cohesion are perturbed.”
On the statistical properties of sea ice lead fraction and heat fluxes in the Arctic
E Olason P Rampal V Dansereau January 2020 preprint
https://tc.copernicus.org/preprints/tc-2020-13/tc-2020-13.pdfOn the multi-fractal scaling properties of sea ice deformation
P Rampall V Dansereau et al 2019
https://tc.copernicus.org/articles/13/2457/2019/Impact of rheology on probabilistic forecasts of sea ice trajectories: application for search and rescue operations in the Arctic
M Rabatel P Rampal et al 2018
https://tc.copernicus.org/articles/12/935/2018/Parallel implementation of a Lagrangian-based model on an adaptive mesh in C++: Application to sea-ice
A Samaké P Rampal S Bouillon E Olason 2017
https://www.sciencedirect.com/science/article/pii/S0021999117306368Wave–ice interactions in the neXtSIM sea-ice model
T Williams P Rampal S Bouillon 2017
https://d-nb.info/1142799980/34Probabilistic forecast using a Lagrangian sea ice model: application for search and rescue operations
M Rabatel P Rampal et al 2017
https://pdfs.semanticscholar.org/f7fc/b5551b8a352e271999ff736c5674b2d3afa9.pdfIce bridges and ridges in the Maxwell-EB sea ice rheology
V Dansereau J Weiss P Saramito et al 2017
https://tc.copernicus.org/articles/11/2033/2017/tc-11-2033-2017.pdfneXtSIM: a new Lagrangian sea ice model
P Rampal S Bouillon E Olason M Morlighem 2016
https://tc.copernicus.org/articles/10/1055/2016/tc-10-1055-2016.pdfhttps://tinyurl.com/yyz2xgwj large meeting poster
Sea ice diffusion in the Arctic ice pack: a comparison between observed buoy trajectories and the neXtSIM and TOPAZ-CICE sea ice models
P Rampal S Bouillon J Bergh E Olason 2016
https://tinyurl.com/y3vx5bmgA Maxwell elasto-brittle rheology for sea ice modelling
V Dansereau J Weiss et al 2016
https://tc.copernicus.org/articles/10/1339/2016/tc-10-1339-2016.pdfPresentation of the dynamical core of neXtSIM, a new sea ice model
S Bouillon P Rampal 2015
https://www.sciencedirect.com/science/article/abs/pii/S1463500315000694Scaling properties of sea ice deformation from buoy dispersion analysis
P Rampal J Weiss et al 2008
https://doi.org/10.1029/2007JC004143