Results of the US IOOS Testbed for Comparison of
Hydrodynamic and Hypoxia Models of Chesapeake Bay
Carl Friedrichs (VIMS) and the Estuarine Hypoxia Team
Federal partners
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David Green (NOAA-NWS) – Transition to operations at NWS
Lyon Lanerole, Rich Patchen, Frank Aikman (NOAA-CSDL) – Transition to operations at CSDL; CBOFS2
Lewis Linker (EPA), Carl Cerco (USACE) – Transition to operations at EPA; CH3D, CE-ICM
Doug Wilson (NOAA-NCBO) – Integration w/observing systems at NCBO/IOOS
Non-federal partners
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Marjorie Friedrichs, Aaron Bever (VIMS) – Metric development and model skill assessment
Ming Li, Yun Li (UMCES) – UMCES-ROMS hydrodynamic model
Wen Long, Raleigh Hood (UMCES) – ChesROMS with NPZD water quality model
Scott Peckham (UC-Boulder) – Running multiple ROMS models on a single HPC cluster
Malcolm Scully (ODU) – ChesROMS with 1 term oxygen respiration model
Kevin Sellner (CRC) – Academic-agency liason; facilitator for model comparison
Jian Shen (VIMS) – SELFE, FVCOM, EFDC models
John Wilkin, Julia Levin (Rutgers) – ROMS-Espresso + 7 other MAB hydrodynamic models
Presented at MABPOM
Horn Point, MD, October 12, 2011
Results of the US IOOS Testbed for Comparison of
Hydrodynamic and Hypoxia Models of Chesapeake Bay
Carl Friedrichs (VIMS) and the Estuarine Hypoxia Team
Federal partners
•
•
•
•
David Green (NOAA-NWS) – Transition to operations at NWS
Lyon Lanerole, Rich Patchen, Frank Aikman (NOAA-CSDL) – Transition to operations at CSDL; CBOFS2
Lewis Linker (EPA), Carl Cerco (USACE) – Transition to operations at EPA; CH3D, CE-ICM
Doug Wilson (NOAA-NCBO) – Integration w/observing systems at NCBO/IOOS
Non-federal partners
•
•
•
•
•
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•
•
Here today
Marjorie Friedrichs, Aaron Bever (VIMS) – Metric development and model skill assessment
Ming Li, Yun Li (UMCES) – UMCES-ROMS hydrodynamic model
Wen Long, Raleigh Hood (UMCES) – ChesROMS with NPZD water quality model
Scott Peckham (UC-Boulder) – Running multiple ROMS models on a single HPC cluster
Malcolm Scully (ODU) – ChesROMS with 1 term oxygen respiration model
Kevin Sellner (CRC) – Academic-agency liason; facilitator for model comparison
Jian Shen (VIMS) – SELFE, FVCOM, EFDC models
John Wilkin, Julia Levin (Rutgers) – ROMS-Espresso + 7 other MAB hydrodynamic models
Presented at MABPOM
Horn Point, MD, October 12, 2011
Results of the US IOOS Testbed for Comparison of Hydrodynamic
(and Hypoxia) Models of Chesapeake Bay
OUTLINE
• Methods: (i) Models, (ii) observations, (iii) skill metrics
• Results (i): What is the relative hydrodynamic skill of
these CB models?
• Results (ii): What is the relative dissolved oxygen skill of
these CB models?
• Summary and Conclusions
Presented at MABPOM
Horn Point, MD, October 12, 2011
Methods (i) Models: 5 Hydrodynamic Models (so far)
(& J. Wiggert/J. Xu,
USM/NOAA-CSDL)
Methods (i) Models (cont.): 5 Dissolved Oxygen Models (so far)
o ICM: CBP model; complex biology
o bgc: NPZD-type biogeochemical model
o 1eqn: Simple one equation respiration (includes SOD)
o 1term-DD: depth-dependent net respiration
(not a function of x, y, temperature, nutrients…)
o 1term: Constant net respiration
Methods (i) Models (cont.): 5 Dissolved Oxygen Models (so far)
o ICM: CBP model; complex biology
o bgc: NPZD-type biogeochemical model
o 1eqn: Simple one equation respiration (includes SOD)
o 1term-DD: depth-dependent net respiration
(not a function of x, y, temperature, nutrients…)
o 1term: Constant net respiration
Methods (i) Models (cont.): 8 Multiple combinations (so far)
o
o
o
o
CH3D
+
EFDC
+
CBOFS2
+
ChesROMS +
ICM
1eqn, 1term
1term, 1term+DD
1term, 1term+DD, bgc
Methods (ii) observations: S and DO from Up to 40 CBP station locations
Data set for model skill assessment:
~ 40 EPA Chesapeake Bay stations
Each sampled ~ 20 times in 2004
Temperature, Salinity,
Dissolved Oxygen
Map of
Late July 2004
Observed
Dissolved
Oxygen
[mg/L]
(http://earthobservatory.nasa.gov/Features/ChesapeakeBay)
Methods (iii) Skill Metrics: Target diagram
Dimensionless version of
plot normalizes by standard
deviation of observations
(modified from M. Friedrichs)
Results of the US IOOS Testbed for Comparison of Hydrodynamic
(and Hypoxia) Models of Chesapeake Bay
OUTLINE
• Methods: (i) Models, (ii) observations, (iii) skill metrics
• Results (i): What is the relative hydrodynamic skill of
these CB models?
• Results (ii): What is the relative dissolved oxygen skill of
these CB models?
• Summary and Conclusions
Presented at MABPOM
Horn Point, MD, October 12, 2011
Results (i): Hydrodynamic Model Comparison
(a) Bottom
Temperature
bias [psu]
bias [°C]
(b) Bottom
Salinity
Inner circle in (a) & (b) = error
from CH3D model
- All models do very well
hind-casting temperature.
unbiased
RMSD
[psu]
unbiased
RMSD
[°C]
- All do well hind-casting
bottom salinity with CH3D
and EFDC doing best.
- Stratification is a
challenge for all the
models.
bias [psu/m]
(c) Stratification
at pycnocline
bias [m]
Outer circle in each case = error
from simply using mean of all data
unbiased
RMSD
[psu/m]
(from A. Bever, M. Friedrichs)
(d) Depth of
pycnocline
unbiased
RMSD
[m]
- All underestimate
strength and variability of
stratification with CH3D
and EFDC doing slightly
better.
- CH3D and ChesROMS do
slightly better than others
for pycnocline depth, with
CH3D too deep, and the
others too shallow.
- All underestimate
variability of pycnocline
depth.
Results (i) Hydrodynamics: Temporal variability of stratification at 40 stations
ChesROMS
CH3D
- Model behavior for stratification
is similar in terms of temporal
variation of error at individual
stations
CBOFS2
Mean
salinity of
individual
stations
[psu]
EFDC
UMCES-ROMS
(from A. Bever, M. Friedrichs)
Results (i) Hydrodynamics (cont.): Sensitivity to model refinement
Used 4 models to test sensitivity of hydrodynamic skill to:
o
o
o
o
o
o
o
Vertical grid resolution (CBOFS2)
Freshwater inflow (CBOFS2; EFDC)
Vertical advection scheme (CBOFS2)
Choice of wind models (ChesROMS; EFDC)
Horizontal grid resolution (UMCES-ROMS)
Coastal boundary condition (UMCES-ROMS)
2004 vs. 2005 (UMCES-ROMS)
Results (i) Hydrodynamics (cont.): Sensitivity of pycnocline depth
CBOFS2
0.2
-0.8
-0.6
-0.4
-0.2
-0.2
-0.2
(from A. Bever, M. Friedrichs)
CBOFS2 model pycnocline depth is insensitive to: vertical grid resolution,
vertical advection scheme and freshwater river input
Results (i) Hydrodynamics (cont.): Sensitivity of stratification at pycnocline
Stratification
CH3D, EFDC
(from A. Bever, M. Friedrichs)
ROMS
2005
ROMS
2004
Stratification at pycnocline is not sensitive to horizontal grid resolution or
changes in atmospheric forcing. (Stratification is still always
underestimated)
Results (i) Hydrodynamics (cont.): Sensitivity of bottom salinity
Bottom Salinity
High horiz res
Low horiz res
Bottom salinity IS sensitive to horizontal grid resolution
(from A. Bever, M. Friedrichs)
Results of the US IOOS Testbed for Comparison of Hydrodynamic
and Hypoxia Models of Chesapeake Bay
OUTLINE
• Methods: (i) Models, (ii) observations, (iii) skill metrics
• Results (i): What is the relative hydrodynamic skill of
these CB models?
• Results (ii): What is the relative dissolved oxygen skill of
these CB models?
• Summary and Conclusions
Presented at MABPOM
Horn Point, MD, October 12, 2011
Results (ii): Dissolved Oxygen Model Comparison
- Simple models reproduce dissolved oxygen (DO) and hypoxic volume
about as well as more complex models.
- All models reproduce DO better than they reproduce stratification.
- A five-model average does better than any one model alone.
(from A. Bever, M. Friedrichs)
Results (ii) Dissolved Oxygen: Top-to-Bottom DS and Bottom DO in Central Chesapeake Bay
ChesROMS-1term
model
- All models reproduce DO better than they reproduce stratification.
- So if stratification is not controlling DO, what is?
(by M. Scully)
Results (ii) (cont.): Effect of Physical Forcing on Dissolved Oxygen
ChesROMS-1term model
Hypoxic Volume in km3
20
Base Case
10
0
Jan Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Date in 2004
(by M. Scully)
Results (ii) (cont.): Effect of Physical Forcing on Dissolved Oxygen
ChesROMS-1term model
Hypoxic Volume in km3
20
Base Case
10
0
Freshwater river input
constant
Jan Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Date in 2004
Seasonal changes in hypoxia are not a function of seasonal changes in freshwater.
(by M. Scully)
Results (ii) (cont.): Effect of Physical Forcing on Dissolved Oxygen
ChesROMS-1term model
Hypoxic Volume in km3
20
July wind year-round
Base Case
10
0
Jan Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Date in 2004
Seasonal changes in hypoxia may be largely due to seasonal changes in wind.
(by M. Scully)
Results (ii) (cont.): Effect of Physical Forcing on Dissolved Oxygen
ChesROMS-1term model
Hypoxic Volume in km3
20
Base Case
10
January wind year-round
0
Jan Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Date in 2004
Seasonal changes in hypoxia may be largely due to seasonal changes in wind.
(by M. Scully)
SUMMARY & CONCLUSIONS
• Available models generally have similar skill in terms of hydrodynamic quantities
• All the models underestimate strength and variability of salinity stratification.
• No significant improvement in hydrodynamic model skill due to refinements in:
– Horizontal/vertical resolution, atmospheric forcing, freshwater input, ocean forcing.
• In terms of DO/hypoxia, simple constant net respiration rate models reproduce
seasonal cycle about as well as complex models.
• Models reproduce the seasonal DO/hypoxia better than seasonal stratification.
• Seasonal cycle in DO/hypoxia is due more to wind speed and direction than to
seasonal cycle in freshwater input, stratification, nutrient input or respiration.
– Note: This does not mean than inter-annual variation in nutrient input/respiration is unimportant.
• Averaging output from multiple models provides better hypoxia hindcast than
relying on any individual model alone.