Estuarine Hypoxia Component of Testbed 2

Marjorie Friedrichs, VIMS, leadCarl Friedrichs, VIMS, co-lead

Wen Long and Raleigh Hood, UMCESMalcolm Scully, ODU

FY12 Testbed 2 Kick-off Telecon

Compare relative skill of various hydrodynamic and dissolved oxygen models in reproducing observations on seasonal time scales in Chesapeake Bay, by examining:

bottom/surface temperaturebottom/surface salinitybottom/surface dissolved oxygenmaximum stratificationdepth of maximum stratificationhypoxic volume

Provide information to managers such that results of these analyses could be transitioned to operational/scenario models

Objectives

Five Hydrodynamic Models Configured for the Bay

CH3DCerco & Wang

USACE

ChesROMSLong & Hood

UMCES

UMCES-ROMSLi & Li

UMCES

CBOFS (ROMS)Lanerolle & Xu

NOAA

EFDCShenVIMS

• ICM: CBP model; complex biology• BGC: NPZD-type biogeochemical model• 1eqn: Simple one equation respiration

(includes SOD)• 1term-DD: depth-dependent respiration

(not a function of x, y, temperature, nutrients…)

• 1term: Constant net respiration

Five biological models

Data from 40 CBP stations

mostly 2004some 2005 results

bottom T, bottom S, stratification = max dS/dz,

depth of max dS/dz

bottom DO, hypoxic volume

= ~40 CBP stations used inthis model-data comparison

Stratification (max dS/dz; 2004)

Stratification is a challenge; CH3D, EFDC reproduce seasonal/spatial variability best

unbiasedRMSD

[psu/m]

bias [psu/m]

Stratification is insensitive to grid resolution and changes in atmospheric forcing

CH3D, EFDC

ROMS

Sensitivity ExperimentsMaximumStratification

Stratification (max dS/dz; 2004)

Adjusting the minimum TKE parameter reduces the bias in ChesROMS

unbiasedRMSD

[psu/m]

bias [psu/m]

ROMS withnew TKEparameter

Hypoxic Volume

unbiasedRMSD[km3]

bias [km3]

Several simple DO models reproduce seasonal variability of hypoxic volume about as well as ICM

Hypoxic Volume

unbiasedRMSD[km3]

bias [km3]

5-model average does better than any single model

1. Compared 5 different hydrodynamic modelswith 5 different DO models (examined 12 different combinations of hydrodynamics+DO for 2004, subset of these for 2005)

Density stratification at pycnocline is a challengeSimplest DO models reproduce seasonal variability

as well as most complex modelsMulti-model average for hypoxic volume does better

than any single model

Models do much better in our wet year (2005) than our

dry year (2004)2. Began to examine sensitivity experiments with individual models

Strong sensitivities to wind, min TKE, advection scheme

Weak sensitivities to river discharge, coastal BC, grid resolution

Overall Progress from Testbed 1

3. Transitioning information to federal agencies

• Simple DO model incorporated into the research version of NOAA CSDL’s Chesapeake Bay Operational

Forecast System• Participated in Eco-Forecasting workshop at

NOAA/ NCEP to further hammer out transition steps for

moving to fully operational version of the DO model• Provided advice to the CBP on future estuarine

and hypoxia modeling strategies, in support of federally mandated environmental restoration, via a STAC workshop report

Overall Progress from Testbed 1(cont.)

We are on track to provide all deliverables as promised by Dec. 31, 2011

Update on Testbed 1 Deliverables

1. Improve modeled density stratificationExamine choice of turbulence closure scheme and advection scheme

2. Idealized sensitivity experiments with all modelsConcentrating on wind, may also include river

discharge

3. Additional skill metricAveraged Discrete Frechet Distance

4. Presentations/publicationsFive publications are in preparationMultiple presentations to managers and

scientific community

Plans for Testbed 2 Year 1

1. Unstructured GridsSELFEFVCOM

2. Potential for < 10 day operational forecastsNeed to examine skill of models in reproducing

high frequency data sets

3. Interannual/Interdecadal skillWe have simulations from 1991-2005 from

multiple models, but we do not yet have the resources to make these comparisons

“Wish List” for Testbed 2