Jerome Fiechter, Andy Moore, Gregoire Broquet Ocean Sciences Department
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Transcript of Jerome Fiechter, Andy Moore, Gregoire Broquet Ocean Sciences Department
Jerome Fiechter, Andy Moore, Gregoire Broquet
Ocean Sciences Department
University of California, Santa Cruz
ROMS Workshop, Sydney, April 2009
Improving Ecosystem Model Predictions
through Data Assimilation
Outline
• Physical/biological properties of Coastal Gulf of Alaska (CGOA)
• Ocean circulation, ecosystem, and iron limitation models
• Simulation results for 1998-2002 without data assimilation
• Simulation results for 2001 with data assimilation
CGOA Physical and Biological Properties
Physical Variability• Downwelling-favorable wind regime (Stabeno et al., 2004)
• AS intrinsic mesoscale variability (Combes and Di Lorenzo, 2007)
• Anticyclonic (Yakutat) eddy passages (Okkonen et al., 2003)
Biological Variability• CGOA: high-productivity shelf, fisheries
• Subarctic Gyre: HNLC region (Lam et al., 2006)
• Iron limitation on primary production (Strom et al., 2006)
Interannual Variability• 1997-1998 El Niño; 1999 La Niña
• 1999 NEP “Cold” Regime Shift (Peterson and Schwing, 2003)
• 2002 NEP Subsurface Cold Event (Curchitser et al., 2005)
Coastal Gulf of Alaska Ocean Circulation Model
• ROMS: ~10 km horizontal resolution, 42 vertical levels
• One-way offline nesting with North East Pacific ROMS
• Monthly mean atmospheric and open boundary forcing
• Macro Nutrients from monthly WOA01 climatology
• Dissolved iron from VERTEX (Martin et al., 1989)
Lower Trophic Level Ecosystem Models
• NPZD+Fe (Powell et al., 2006; Fiechter et al., 2009)
• NEMURO+Fe (Kishi et al., 2007; Fiechter and Moore, 2009)
(from Kishi et al., 2007)
Strom et al., 2007
NPZD
PS: Nano P
PL: Diatoms
ZS: Ciliates
ZL: Copepods
ZP: KrillFe
RESULTS: PART I
INTERANNUAL VARIABILITY (1998-2002)
ROMS + NEMURO/NPZD + Fe-limitation
WITHOUT DATA ASSIMILATION
Surface Chlorophyll EOFs: Models vs. Observations
NEMURO+Fe NPZD+Fe SeaWiFS
NEMURO/NPZD Surface Chlorophyll, 1998-2002
Taylor diagrams with respect to SeaWiFS based on monthly means
(NEMURO+Fe, NPZD+Fe)
20012001
LACK OF VARIABILITY
Sea Surface Height: GAK Line, 1995-2004
ROMS AVISO
GAK Line GAK Line GAK Stations
ROMS vs. AVISO
RESULTS: PART II
SEASONAL VARIABILITY (2001)
ROMS + NPZD + Fe-limitation
WITH DATA ASSIMILATION
IS4DVAR Data Assimilation
CASE NAME7-DAY SSH
(AVISO)
5-DAY SST
(Pathfinder)
IN SITU T/S
(GLOBEC)
8-DAY CHL
(SeaWiFS)
FREE NO NO NO NO
SSHT YES YES YES NO
SSHTP (AD, PASS) YES YES YES YES
SSP (AD, PASS) NO NO NO YES
• Configuration: ROMS+NPZD+Fe, adjoint/passive biology
• Assimilation: 7-day cycle, 1 outer (NL) loop, 10 inner (TL/AD) loops
• Strong constraint (no model error), adjust IC only, model space search
• Univariate background error covariance:a) isotropic, homogeneous correlations (50km horiz., 30m vert.)b) std deviations based on 10-year non-assimilated solution
• Observation std deviations: SSH=2cm; T=0.25C; S=0.1; Chl=0.5mg/m3
Sea Surface Height, 2001
RMS errors and correlations with AVISO based on weekly means
FREE SSHT SSHTP-BIOAD SSP-BIOAD
Sea Surface Temperature, 2001
RMS errors and correlations with Pathfinder based on weekly means
FREE SSHT SSHTP-BIOAD SSP-BIOAD
Sea Surface Height, 2001
Taylor diagrams with respect to AVISO based on weekly means
NPZD Surface Chlorophyll, 2001
RMS errors and correlations with SeaWiFS based on monthly means
FREE SSHT SSHTP-BIOAD SSHTP-BIOPASS
NPZD Surface Chlorophyll, 2001
RMS errors and correlations with SeaWiFS based on monthly means
SSHT-BIOAD SSHT-BIOPASS SSP-BIOAD SSP-BIOPASS
NPZD Surface Chlorophyll, 2001
Taylor diagrams with respect to SeaWiFS based on monthly means
NO BIO ASSIM
NO BIO ASSIM
PASSIVE BIO ASSIM
PASSIVE BIO ASSIM
ADJOINT BIO ASSIMADJOINT
BIO ASSIM
NPZD Surface Chlorophyll: Seasonal Means, 2001
FREE SSHT SSHTP-BIOAD SeaWiFS
AP
R-J
UN
JUN
-AU
GA
UG
-OC
T
Surface Chlorophyll and Nutrients: GAK Stations, 2001
Comparisons between model, SeaWiFS, and in situ chlorophyll
RESULTS: PART III
SEASONAL VARIABILITY (2001)
ROMS + NEMURO + Fe-limitation
WITH DATA ASSIMILATION
NEMURO Surface Chlorophyll, 2001
RMS errors and correlations with SeaWiFS based on monthly means
FREE SSHT SSHTP-BIOPASS SSP-BIOPASS
NEMURO Surface Chlorophyll: Seasonal Means, 2001
FREE SSHT SSHTP-BIOPASS SeaWiFS
AP
R-J
UN
JUN
-AU
GA
UG
-OC
T
Summary
Interannual variability, no data assimilation, 1998-2002• Models reproduce spring bloom, underestimate fall bloom• Models good on “normal” years, not so good on “abnormal” years
Seasonal variability, data assimilation, 2001• Chlorophyll not improved by assimilation of physical data only• Chlorophyll improved by assimilation of biological data• Chlorophyll assimilation improved by using adjoint biology• Assimilation incompatibilities between physics and biology
Future work• Adjoint vs. passive NPZD solutions (sensitivity studies)• Assimilation with NEMURO (Chl to small/large phytoplankton)• Forecast skill assessment for physics and biology
Collaborators:
H. Arango (Rutgers), K. Bruland (UC Santa Cruz),
E. Curchitser (Rutgers), E. Di Lorenzo (Georgia Tech),
C. Edwards (UC Santa Cruz), K. Hedstrom (ARSRC),
A. Hermann (NOAA/PMEL), B. Powell (U. Hawaii),
T. Powell (UC Berkeley)
Funding:
National Science Foundation (U.S. GLOBEC)
Iron Limitation on Phytoplankton Growth
Nitrate-limited phytop. growth rate:
Dissolved (available) Iron:
Phytop.-associated Iron:
Iron uptake: Optimal Fe:C:
Realized Fe:C:
Iron-limited phytop. growth:
FeNmFepd IUp
P
GZRF
t
F
FeNpp Ip
P
GZUF
t
Fm
Fe
Fe t
NCP-RRI
:0adbFR 0
NCP
FR p
:
),min( *22
2
NFe
N UkR
RU
)(* Pz
NmN
PWekN
NVU
Chlorophyll Vertical Profiles: GAK Stations, 2001