# Presentation: 796204

## Ocean NPP  MOD 27  Status

- Wayne E. Esaias
- Code 971, GSFC
- Kevin R. Turpie
- SAIC, GSC
- December 18, 2001

## Outline

- Product Summary
- Performance of Provisional - Version 3
- Input Dependencies
- Comparison with SeaWiFS
- Quality Flags
- Remaining Issues
- Schedule for Promotion

## Slide 3

## Slide 4

## SCIENCE QUESTIONS (Ocean NPP)

- This Product Derives Ocean Net Primary Production and Annual Export Production from Chlorophyll, Light (PAR), SST, and Mixed Layer Depth
- Carbon fixed/m2/day - Needed to understand:
-  Magnitude and Variability of ONPP, and uncertainties.
-  Ecosystem dynamics (coupling with physical forcings)
-  Food chain effects  (_fisheries resources_)
-  Carbon cycle (carbon export, pCO2 and hence air sea C flux)
- (Ocean NPP is 40-50% of global total production.  ONPP shows greater interannual variability than TNPP - Behrenfeld et al, 2000)
- RELEVANT SCIENCE QUESTIONS for MODIS Oceans
- Variability  - How are global ecosystems changing?
- Response - How do ecosystems respond to and affect global
- 	environmental change and the carbon cycle?
- Consequences - What are the consequences of climate and sea level
-  	changes and _increased human activities in the coastal regions_?
- Prediction - How well can cycling of carbon through the Earth system be
- 	 modeled, and how reliable are predictions...
- _WHAT IS THE PRESENT UNCERTAINTY OF ONPP?_

## Slide 6

## ONPP a Level 4 product

- P1 = Behrenfeld & Falkowski
- 	NPP = f(Chl *a*, PAR, Pb opt)
- 	Integrated over the Euphotic zone
- 	Pb opt = f (SST)    7th order polynomial
- P2 = Howard, Yoder, Ryan
- 	NPP = f (Chl *a*, PAR, Pmax)
- 	Integrated over the upper Mixed Layer Depth (MLD)
- 	Pmax (Platt) = f (SST)   Eppley Peterson exponential
- Annual = Iverson/Esaias
- 	Empirical relationship

## Input Dependencies

- Chlorophyll
- Current archive product uses Chlor_a_3.
- Investigate differences with Chor_MODIS, Chlor_a_2.
- Flags are independent, can account for some differences in test runs.
- Freshwater, inland seas.
- MLD
- No comparisons - Carr PPARR
- PAR
- Comparisons with SeaWiFS, DAO, B-R  PAR Products
- Currently use the same PAR used by Land NPP
- Spatial, Temporal resolution issues
- May impact SeaWiFS/MODIS comparisons.

## MODIS best quality

- MODIS coverage is greater due to
- Wider swath, greater duty cycle (50 vs 40 min/orbit),
- Less cloud obscuration (1 km pixels), morning orbit.  Product dependent.

## Weekly PAR    December 10, 2000

- Derived from GSFC Data Assimilation Office  3 hr retrievals.

## OPP P1    December 10, 2000

- Falkowski Behrenfeld depth  integrated model calculates total euphotic zone productivity to 1% surface irradiance.  Primary inputs are PAR, SST, Chlor_a_3.  Units gm Carbon/m2/yr.

## Mixed Layer Depth  Dec. 10, 2000

- Mixed Layer Depth is averaged from daily values retreived by Fleet Numerical Monterey Oceanographic Center’s (FNMOC) OTIS model, obtained through NOAA-Navy net by GES DAAC.

## OPP P2    December 10, 2000

- Howard Yoder Ryan model for productivity in the upper mixed layer.

## QL=BEST

- This period is not highly impacted by
- Earth-sun double correction.

## Percent Differences in NPP estimates

- From MODIS Chlorophylls and SeaWiFS

## Steps to Validation

-  Algorithms are validated, published.
-  PGE 51 code computes the correct ONPP for given inputs.
-  Requires “validation” of Chlor_a_3, SST.
- Acceptance” of higher global means from Chlor_a_3.
-  Investigating issues with how quality flags are propagated.
-  Can be accomplished in 1 month from a stable input.
-   Expect to meet spring schedule for code readiness.
-  Initial uncertainties will be based on:
-  Heritage (SeaWiFS and Published Literature)
-  Consistency
-  Comparison with Ocean Time Series
-   Participant in PP Round Robin - M.E. Carr, JPL.
-   Expect a validated status ~ 1 month after Chlor_a_3.

## Developments that have been Deferred

- P1 Evolution to Behrenfeld Photo-Acc approach
- 	Prod. Efficiency = f(MLD, Nut, Fe)
- Run at daily scales
- 	coverage is better than expected,
- 	less filling/extrap is needed
- 	major processing load
- MODIS PAR