# Presentation: 896337

## Estimating Chlorophyll Concentrations  using MODIS Fluorescence: A Preliminary Evaluation in Coastal Waters 

- Ricardo Letelier, Mark Abbott,
- Jasmine Nahorniak
- College of Oceanic and Atmospheric Sciences
- Oregon State University

- Acknowledgment:  Robert Evans et al.  University of Miami

## Natural (passive) Fluorescence

- 	where 	F = fluorescence
- 			[chl] = chlorophyll concentration
- 			PAR = photosynthetically available 				  radiation
- 			a* = chlorophyll specific absorption
- 			F = fluorescence quantum yield
- Absorbed Radiation by Phytoplankton
- 		ARP = a* x [chl] x PAR (calculated independently from [chl])
- F/ARP = Chl Fluor. Efficiency (CFE)  F
- ARP / ([chl] x PAR) = a*

## If  p + f + h = 1  &   h = const.  

- then  p = const. – f
- 
- PP = [chl] x (PAR x a*) x (const. – f)
- or     PP    ARP x (const. - FLH/ARP)
- 	   (const./ARP) - FLH

## Can we use FLH to tell us about chlorophyll?

- Absorption-based algorithms fail in waters where there are other materials that absorb and scatter and are not correlated with chlorophyll
- Sediment
- Dissolved organic matter
- Chlorophyll fluorescence is specific to chlorophyll
- But it also depends on physiology

## Goddard DACC weekly declouded 36 km starting 12/02/2000 (Quality=0 L2 V 4.2.2)

- MODIS ARP

- MODIS FLH

## Goddard DACC weekly declouded 36 km starting 12/02/2000 (Quality=0 L2 V 4.2.2)

- MODIS CHL

- MODIS CFE

## Chlorophyll December 4, 2000

## FLH December 4, 2000

## Chlorophyll June 25, 2002

## FLH June 25, 2002

## A

- B

- C

- (From Frank Hoge)

## MODIS_Chl           MODIS_FLH           MODIS_CFE        MODIS_ARP

- OSU Direct Broadcast  October 04, 2001

## Field Approach

- Mesoscale Surveys (Cowles/Barth)

## Some Survey Measurements

- -Continuous from Flow-through system
- 	-Temperature/ Salinity
- 	- Active Fluorometry
- 	- Fast Repetition Rate Fluorometry
- 	- Total and dissolved absorption
- 	  and attenuation
- -Discrete
- 	- Pigments (Fluor/HPLC)
- 	- Nutrients (autoanalyzer)
- 	- Particulate absorption
- - Other Platforms
- 	- Optical Drifters, tethered
-                 buoys
- 	- Moorings
- 	- Satlantic MicroSAS
-                 underway reflectance
- 	- Satellites (SeaWiFS,
- 	  MODIS, AVHRR,...)

## Comparison between field measurements 

- Comparison between field measurements
- and Remote Sensing data
- (Mesoscale Survey August 2000
- And MODIS Image from August 2nd)

- (In situ chl derived from the calibration of the flow through fluorometer with
- HPLC chlorophyll determinations )
- -Blue = all mesoscale survey data (July 31st – August 7th)
- -Red =  Within 0.5 days of the MODIS Image Time stamp

- In situ chl (mg m-3)

- In situ chl (mg m-3)

- MODIS chl_2 (mg m-3)

- MODIS FLH, W m-2 um-1 sr-1

## East Coast Image 2001095.1605

- Range covering most
- oceanic regions
- (Gordon, 1979;
- Carder & Steward,
- 1985; and others)

- Oregon Coast DB Image 2001150

- # occurences

- # occurences

- CFE

- CFE

- , mg m-2

- , mg m-2

## East Coast Image 2001095.1605

- Oregon Coast DB Image 2001150

## Chlorophyll biomass proxy                     Optimum photosynthesis max yield

- (From Rachel Sander’s work)

## Slide 19

## Photoprotective:Photosynthetic pigment ratio

- Latitude

- Longitude

- PP/PS

- PP/PS

- Other alternatives :
- 		- Changes in ARP (We just finished analyzing the filter
- 		   pad particulate absorption samples)
- 		- Heat dissipation processes not accounted for

## However:

- FLH and CFE are very different MODIS products in terms of validation.
- 		- FLH is based on nLw at 678 nm after 	  baseline correction
- 		- CFE is a proxy for f (a physiological
-            parameter) that requires the previous
- 		   validation of ARP ([chl] x a*).
- 		- Further use of f to infer p requires
-            the characterization of  the variability
- 		   in energy distribution within the
- 		   photosystem.

## Thalassiosira weissflogii 

*Thalassiosira weissflogii*
- Chemostat results 2001-2002

- After 3 days of constant
- cell counts
- After 14 days

## Summary

- Fluorescence and chlorophyll
- Generally a linear relationship between absorption-based estimates and fluorescence-based estimates of chlorophyll
- Exceptions are apparent, for example near the coast
- Slope of line relating FLH to chl is related to CFE
- Can we estimate chlorophyll from FLH?
- Challenge is that many processes affect F
- Photoprotective pigments, absorption cross-section
- Appears, though, that CFE appears to fall into 2 clusters so problem may be tractable
- High values of CFE appear to be associated with communities far from equilibrium
- Time history of CFE may be key