The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC,...
-
Upload
howard-oconnor -
Category
Documents
-
view
231 -
download
1
Transcript of The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC,...
![Page 1: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/1.jpg)
The Eta Model: Design, History, Performance, What Lessons have
we Learned?
Fedor Mesinger
NCEP/EMC, and UCAR, Camp Springs, MD;[email protected]
15 June 2004
![Page 2: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/2.jpg)
Early history:Design of the Eta ancestor code started in Belgrade, first code written beginning of 1973 (Notes on my code worksheets:
started January 24, done March 2.
In the same time period, on 7 February 1973, for the first time fcst BCs incorporated in the NMC’s first operational PE LAM, the
LFM)
Aim: use the Arakawa approach• Maintenance of chosen integral properties;• Avoidance of computational modes;• . . .
The very first code: some of each
![Page 3: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/3.jpg)
Originalflow-chart:
![Page 4: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/4.jpg)
Some of the features of this very first code that survive in today’s Eta
• Choice of the E horizontal grid;
• Lateral BC schemeBCs prescribed (or, extrapolated from the inside) along a single outer line of grid points (consistent with the mathematical nature of our initial-boundary value problem)
![Page 5: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/5.jpg)
Some of the features of this very first code that survive in today’s Eta
• Choice of the E horizontal grid;
• Lateral BC schemeBCs prescribed (or, extrapolated from the inside) along a single outer line of grid points (consistent with the mathematical nature of our initial-boundary value problem)
Many milestones (see the pdf !) A few:
• gravity-wave coupling scheme (Mesinger 1973,1974)• E-grid enstrophy, energy conservation, “”,(Janjic 1977)• Janjic (1984) Arakawa C-grid enstrophy … conserving scheme;• eta coordinate (Mesinger 1984);
Eta dynamical core code: Belgrade (Dushka Zupanski), GFDL, NMC (1984), ….
![Page 6: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/6.jpg)
Why eta?
I convinced myself (Mesinger 1982) the sigma system problem• seems to have no acceptable solution;• should become more serious as we increase resolution;
Quasi-horizontal coordinates are needed !
![Page 7: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/7.jpg)
Back to NMC: more milestones:• physics package (Janjic, Black; acknowledgements: Betts-Miller, Mellor-Yamada, Harshvardhan);
• testing, removal of physics problems identified;
• analysis system (Rogers, …)• …
Operational implementation: 12z 8 June 1993,as a replacement of the LFM
![Page 8: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/8.jpg)
Challenges, and an inadvertent experiment:
• Comparisons against the NGM and the RSM;
• The “Early” vs the “Meso” Eta;
• Eta vs the Avn/GFS
![Page 9: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/9.jpg)
Eta vs the NGM, 1st 24 months of the Eta, NGM and Avn precip scores:(Both Eta and NGM ~80 km resolution, physics packages of similar/ not too different complexity) “All Periods”: 00-24, 12-36, 24-48 h forecasts
Recall: NGM 4th order formal accuracy, Eta never more than 2nd
![Page 10: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/10.jpg)
Eta vs the RSM,
2 years of scores, 1996-1997, at ~50 km resolution:
Note: Eta is using 12 h “old” Avn LBCs, RSM is using current Avn LBCs
![Page 11: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/11.jpg)
The “Early” vs the “Meso” Eta“Early”: 48 km, 12 h old Avn LBCs,“Meso”: 29 km, current Avn LBCs;
Domains:
![Page 12: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/12.jpg)
2 years of scores:
Scores of the the “Early” and the “Meso” Eta about the same!The benefit of the large domain compensates the combined
benefit of more accurate LBCs and higher resolution
![Page 13: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/13.jpg)
Eta vs the Avn/GFS2nd 24 months of the Eta, NGM and Avn scores:
Eta is using 12 h old LBCs; can one detect the impact of the advection of the error?
![Page 14: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/14.jpg)
Not at that time. But what about today?
Both models have increased resolution;Eta has been extended to 84 h as of April 2001;
Can one now detect the the impact of the advection of the LB error?
(Eta is now driven by the GFS forecast of 6 h ago. At 00 and 12z, in view of the “off” times, this is considered equivalent to about an 8 h error)
For an answer, I have looked into, Eta vs the Avn/GFS:
• precip scores, 24 accumulations, 00-48 h vs 36 to 84 h, May 2001-April 2002;
• rms fist to raobs as a function of time;
• position forecast errors of “major lows” at 60 h,December 2000-February 2001
![Page 15: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/15.jpg)
00-24, 12-36, 24-48 h
EtaAvn
![Page 16: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/16.jpg)
36-60, 48-72, 60-84 h
![Page 17: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/17.jpg)
“Warm Season”
![Page 18: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/18.jpg)
“Cold Season”
![Page 19: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/19.jpg)
In cold season, 250 mb winds, for a 6 months sample, the Eta is
• ~10-11 h behind the GFS at 60 h;
• ~9 h behind the GFS at 84 h
![Page 20: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/20.jpg)
In cold season, 250 mb winds, for a 6 months sample, the Eta is
• ~10-11 h behind the GFS at 60 h;
• ~9 h behind the GFS at 84 h
Position forecast errors: winter 2000-2001, rules, 31 cases;(see the pdf for #s) the Eta was significantly more accurate !
E.g.: Average errors: Eta 244 km, Avn 324 km# of wins: Eta 20, Avn 10
![Page 21: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/21.jpg)
In cold season, 250 mb winds, for a 6 months sample, the Eta is
• ~10-11 h behind the GFS at 60 h;
• ~9 h behind the GFS at 84 h
Position forecast errors: winter 2000-2001, rules, 31 cases;(see the pdf for #s) the Eta was significantly more accurate !
E.g.: Average errors: Eta 244 km, Avn 324 km# of wins: Eta 20, Avn 10
In relative terms, the Eta is doing best in winter, and,if anything, it improves with time !
Ingredient(s)/ component(s) must exist in the Eta that compensate for the inflow of the LB error !
![Page 22: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/22.jpg)
Strong case can be made that the primary candidate for this role is the eta coordinate
Some of the arguments:
• One eta/ sigma experiment;• Precip scores for the 1st 12 months of the availability
of three model scores on NMM domains(ConUS “East”, …, “West”, …)
![Page 23: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/23.jpg)
The experiment: Eta (left), 22 km, switched to use sigma (center), 48 h position error of a major low increased
from 215 to 315 km:
![Page 24: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/24.jpg)
Three-model precipitation scores, on NMM ConUS domains ("East" ,…,
"West"),available since Sep. 2002
• Operational Eta: 12 km, driven by 6 h old GFS forecasts;
• NMM: “Nonhydrostatic Mesoscale Model” nonhydrostatic, 8 km, most other features same or similar to Eta, but switched back to sigma, driven by the Eta;
• GFS (Global Forecasting System) as of the end of Oct. 2002 T254 (55 km) resolution
![Page 25: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/25.jpg)
![Page 26: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/26.jpg)
GFSEta
NMM
Bias normalized eq. threats
![Page 27: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/27.jpg)
Eta
NMM
GFS
(Five very heavy el Niño precip events)
![Page 28: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/28.jpg)
Eta vs NMM:East, no major topography: 12-km Eta about the same as the 8-km NMM, even a tiny bit better;West, complex topography: 12-km Eta much better than the 8-km (sigma system) NMM !!
GFS vs Eta: East: GFS (when corrected for bias) uniformly better;West: Eta much better (overcoming handicaps of the 6 h lateral boundary error, and less successful data assimilation) !
![Page 29: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/29.jpg)
However: what about a lot of bad press the eta had lately:
Schär et al., Mon. Wea. Rev., 2002;Janjic, Meteor. Atmos. Phys., 2003; Steppeler et al., Meteor. Atmos. Phys., 2003; Mass et al., Bull. Amer. Meteor. Soc., 2003;Zängl, Mon. Wea. Rev., 2003;
the eta coordinate system is
"ill suited for high resolution prediction models” ?
![Page 30: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/30.jpg)
The Eta ProblemFlow separation on the lee side (à la Gallus and Klemp 2000)
![Page 31: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/31.jpg)
Suggested explanation
pS
pS
pS
T 3
T 5 T6
T 1
T 9
T 2
v
v
v
vv v
v
v
vv
Flow from left: from the box 1 the flow enters box 2 to the right of it.
When conditioned to move downward, it will move downward via the interface between boxes 2
and 5. Some of the air that entered box 2 will continue to move horizontally into box 3.
Missing: the flow directly from box 1 into 5 !
(It would have existed had the discretization accounted for the
terrain slope !) As a result: some of the air which should have moved slantwise from box 1 directly into 5 gets deflected
horizontally into box 3.
![Page 32: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/32.jpg)
Refined (sloping steps) eta discretization
Discretization accounting for slopes. Continuity equation ( at points not zero):
(3)
Effort in progress:
Define slopes at v points, based on four surrounding h points. Slopes discrete, valid on halves of the sides of h points, and halves of the eta layers. Slantwise transports calculated within the 1st term on the right of (3), and in other equations as appropriate.
Other possibilities available. However: keep the eta feature of having cells in horizontal of about equal volume (difference compared to shaved cells) ! This makes Arakawa-type conservation schemes, used in the Eta, approximately finite-volume schemes. Also, robust in the CFL sense.
€
∂pS
∂t= − ∇ ⋅ v
∂p
∂η
⎛
⎝ ⎜
⎞
⎠ ⎟
0
η S
∫ dη − ˙ η ∂p
∂η
⎛
⎝ ⎜
⎞
⎠ ⎟S€
˙ η
€
pS
€
pS
![Page 33: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/33.jpg)
The sloping steps, vertical gridThe central v box exchanges momentum, on its right side, with v boxes of two layers:
![Page 34: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/34.jpg)
Horizontal treatment, 3DExample #1: topography of box 1 is higher than those of 2, 3, and 4;
“Slope 1”
Inside the central v box, topography descends from the center of T1 boxdown by one layer thickness, linearly, to the centers of T2, T3 and T4
![Page 35: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/35.jpg)
Slantwise advection of mass, momentum, and temperature, and “”:
Velocity at the ground immediately behind the mountain increased from between
1 and 2, to between 7 and 8 m/s. Zig-zag features in isentropes at the upslope side removed.
![Page 36: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/36.jpg)
Thus,
12-km Eta: excellent QPF performance over complex topography ! Better than the sigma system 8-km NMM, and better than the GFS;
The Eta downslope windstorm problem: correctible, while keeping favorable Eta features:
• quasi horizontal coordinates (PGF !);• approximately finite-volume (because of the quasi-
horizontal coordinate and flux-type schemes);• robustness in the CFL sense
![Page 37: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/37.jpg)
Can one still significantly increase the skill of NWP ?Yes. How can we tell?
“The Future of NWP”:
![Page 38: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/38.jpg)
Can one still significantly increase the skill of NWP ?Yes. How can we tell?
Eta view of things:
• The Eta skill at NCEP – throughout its extended forecast range – is comparable to that of GFS, in spite of its handicaps of
1) absorbing a 6 (or, 8) h error advected at the lateral
boundaries;2) using a considerably less successful data assimilation system
“The Future of NWP”:
![Page 39: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/39.jpg)
Can one still significantly increase the skill of NWP ?Yes. How can we tell?
Eta view of things:
• The Eta skill at NCEP – throughout its extended forecast range – is comparable to that of GFS, in spite of its handicaps of
1) absorbing a 6 (or, 8) h error advected at the lateral
boundaries;2) using a considerably less successful data assimilation system
“The Future of NWP”:
The LB error, 1), is removed by• having a global Eta-like model, or• running a global model and the Eta simultaneously
![Page 40: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/40.jpg)
Eta rms wind fits to raobs vs same except in. cnd. interpolated from GFSOctober 2002-May 2003, 48 h fcsts:
At 250-300 mb, error reduced more than 10%
![Page 41: The Eta Model: Design, History, Performance, What Lessons have we Learned? Fedor Mesinger NCEP/EMC, and UCAR, Camp Springs, MD; fedor.mesinger@noaa.gov.](https://reader036.fdocuments.net/reader036/viewer/2022070413/5697bfa71a28abf838c98b39/html5/thumbnails/41.jpg)
Each on the order of 10% error at 48 h; both can be removed/ improved
upon !
• Numerous options to improve the Eta further.
Dynamical core:- Sloping steps;- Advection of scalars: piecewise linear, or biparabolic
(Rancic);- Gravity wave coupling: do momentum equation
forward;- Lateral boundaries: avoid space interpolation- …- …
The two operational Eta handicaps:
And: discretizations still more consistent with “physics”; and/or, physics that moves away from forcing at
individual grid points