www.ncof.gov.uk near real time forecasting of biogeochemistry in global gcms rosa barciela, ncof,...
TRANSCRIPT
www.ncof.gov.uk
Near real time forecasting of biogeochemistry in global GCMs
Rosa Barciela, NCOF, Met Office
www.ncof.gov.uk
The Talk
• What are the aims?
• What tools are we using?
• What have we developed so far?
• Some preliminary results
• Assimilation of satellite-derived chlorophyll
• What will we be doing next?
• Are there any issues to be addressed?
• Conclusions
www.ncof.gov.uk
What are the aims?
- NERC-CASIX:
- estimates of air-sea fluxes of CO2
- decadal re-analysis (1997-2006) with/without ocean colour DA
- Royal Navy- water clarity forecasts in the open ocean (5 to 7 days ahead)- improvement of light attenuation estimates: SST, MLD, sea-ice- minimise risks to maritime environment when deploying active sonar systems
• Different users have different needs:
• Pre-operational coupled physical-biogeochemical model by 2008
www.ncof.gov.uk
The Talk
• What are the aims?
• What tools are we using?
• What have we developed so far?
• Some preliminary results
• Assimilation of satellite-derived chlorophyll
• What will we be doing next?
• Are there any issues to be addressed?
• Conclusions
www.ncof.gov.uk
What tools are we using?
– FOAM
Forecasting Ocean Assimilation Model
– HadOCC Hadley Centre Ocean Carbon Cycle Model
• Coupling together two models …
www.ncof.gov.uk
Forecasting the open ocean: the FOAM system
• Operational real-time deep-ocean forecasting system
• Daily analyses and forecasts out to 6 days
• Low resolution global to high resolution nested configurations
• Relocatable system deployable in a few weeks
• Hindcast capability (back to 1997)
• Assimilates T and S profiles, SST, SSH, sea-ice concentration
FOAM = Forecasting Ocean Assimilation Model
Real-time data
Obs QC
Analysis
Forecast to T+144
NWP 6 hourly fluxes
Automatic verification Product
delivery
Input boundary
data
Output boundary
data
www.ncof.gov.uk
Hadley Centre Ocean Carbon Cycle Model (HadOCC)
Model description:
- Variable C:Chl ratio
- Coupled to carbon & alkalinity
- Normally used for climate studies
- Transported around the ocean by physical processes
- ‘NPZD’ ecosystem model
www.ncof.gov.uk
The Talk
• What are the aims?
• What tools are we using?
• What have we developed so far?
• Some preliminary results
• Assimilation of satellite-derived chlorophyll
• What will we be doing next?
• Are there any issues to be addressed?
• Conclusions
www.ncof.gov.uk
What have we developed so far?
• HadOCC embedded into FOAM at different resolutions (1º, 1/3º & 1/9º)
1/3º North Atlantic
– Initial tests have been run with 1˚ global, 1/3˚ N Atlantic and Arctic and 1/9˚ N Atlantic FOAM configurations.
– Nested system running successfully
• Data assimilation scheme for derived chlorophyll (ocean colour)
www.ncof.gov.uk
The Talk
• What are the aims?
• What tools are we using?
• What have we developed so far?
• Some preliminary results
• Assimilation of satellite-derived chlorophyll
• What will we be doing next?
• Are there any issues to be addressed?
• Conclusions
www.ncof.gov.uk
The impact of a phytoplankton bloom on air-sea CO2 flux
FOAM-HadOCC at 1º resolution, April 29th – May 19th 2000
www.ncof.gov.uk
Validation of FOAM-HadOCC results
Validation of surface chlorophyll against SeaWiFS dataDaily mean North Atlantic fields for 20th April 2003
1º Global 1/3º North
Atlantic & Arctic
1/9º North Atlantic
SeaWiFS 5-day
composite
www.ncof.gov.uk
Validation of FOAM-HadOCC results
Validation of subsurface structure vs AMT cruise data
Temperature Salinity Chlorophyll
32.6W, 24.3N, 6th June 2003Temperature Salinity Chlorophyll
20.0W, 41.5N, 11th June 2003
AMT obs
1/9º
1/3º
1º
www.ncof.gov.uk
The Talk
• What are the aims?
• What tools are we using?
• What have we developed so far?
• Some preliminary results
• Assimilation of satellite-derived chlorophyll
• What will we be doing next?
• Are there any issues to be addressed?
• Conclusions
www.ncof.gov.uk
Chlorophyll data assimilation scheme
Two stage analysis scheme: Model chl vs. satellite obs: increments (ACS) Balancing increments to biogeochemical variables
Phytoplankton increments derived using model biomass:chlorophyll ratio
Increments constrained to conserve total nitrogen & carbon at each grid point (if sufficient nitrogen is available)
Increments to other pools depend on the likely contributions to phytoplankton error from errors in growth and loss
www.ncof.gov.uk
Phytoplankton background error before the first analysis.
Phytoplanktonanalysis error after the first analysis, with data everywhere.
Phytoplankton errors (mmolN/m3)
Assimilation of derived chlorophyllR
esu
lts fr
om 3
-D tw
in
exp
erim
ent
s
www.ncof.gov.uk
“True” run- start from a spun-up model state, - model run for 1 year (Jan 2003 – Jan 2004)- forced by NWP 6 hourly surface fluxes- with physical (T, S, SST) data assimilation
Observations of Chl are taken from this “true” model state once a day. Assimilation and control runs
- HadOCC initialised using the fields from March 2003- physical fields taken from true run from April 2003
Assimilation run assimilates chl observations from the “true” run Control run does not
Ocean colour DA: tests in 3-D win experiments
www.ncof.gov.uk
Phytoplankton (mmol N/m3) Zooplankton (mmol N/m3)
Detritus (mmol N/m3) Nutrients (mmol N/m3)
Control - truth Assimilation - truth
3-D Twin experiments: daily mean RMS errors in the North Atlantic
Total DIC (mmol C/m3)
air-sea exchange of CO2
significantly improved after assimilating ocean colour data
www.ncof.gov.uk
Real world experiments
Global average RMS (solid lines) and mean (dashed lines) errors compared to the satellite chlorophyll data.
Green: no DA Black: only physical DA Red: physical and biological DA
www.ncof.gov.uk
Real world experiments – on 1st July 2003
Log(chl) from model with no biological assimilation
Log(chl) observations
Log(chl) from model withbiological assimilation
www.ncof.gov.uk
The Talk
• What are the aims?
• What tools are we using?
• What have we developed so far?
• Some preliminary results
• Assimilation of satellite-derived chlorophyll
• What will we be doing next?
• Are there any issues to be addressed?
• Conclusions
www.ncof.gov.uk
What will be doing next?
The key next steps are:
further quantitatively validation to initial FOAM-HadOCC integrations
parameter tuning (required to improve performance)
further refinement of ocean colour assimilation scheme
explicit biological feedback to physical model: downward radiation
run a 10-year re-analysis of FOAM-HadOCC with ocean colour and physical assimilation
www.ncof.gov.uk
The Talk
• What are the aims?
• What tools are we using?
• What have we developed so far?
• Some preliminary results
• Assimilation of satellite-derived chlorophyll
• What will we be doing next?
• Are there any issues to be addressed?
• Conclusions
www.ncof.gov.uk
Issues …
Data assimilation: Impact of physical assimilation on biogeochemistry: vertical mixing?
Quality of chl product: target accuracy in open ocean ~ 35% !!!
Chlorophyll versus IOPs/absorption?
Validation:
Good temporal and spatial coverage for chlorophyll only (global – remotely sensed since 1997)
Other verifiable variables are: pCO2 (North Atlantic?-VOS), nutrient (climatology, cruise data, time-series from monitoring stations)
Lack of verification for remaining fields: biomass (P,Z), detritus.
www.ncof.gov.uk
The Talk
• What are the aims?
• What tools are we using?
• What have we developed so far?
• Some preliminary results
• Assimilation of satellite-derived chlorophyll
• What will we be doing next?
• Are there any issues to be addressed?
• Conclusions
www.ncof.gov.uk
an ocean colour data assimilation scheme has been designed and implemented within FOAM-HadOCC.
joint collaboration between University of Plymouth, NOC-Southampton and Met Office
real-world experiments show that the scheme is able to improve the chlorophyll: other biological fields are difficult to verify but some work is underway in this area
Conclusions
the FOAM-HadOCC system has been run for 1 year at three resolutions
the system appears to be effective at simulating the onset of the spring bloom (good qualitative agreement with SeaWiFS and AMT data) but chl levels subsequently appear to be over-estimated.
higher resolution provides improved representation of advective processes in particular. However, benefits masked by large scale errors
Model development
Data assimilation
