Application Of Satellite Derived Retrievals Of Ocean Colour To The Modis/aster Airborne Simulator

Application of satellite derived retrievals of ocean colour to the MODIS/ASTER Airborne Simulator

A study over Monterey Bay, HelenCA Thomas Student Airborne Research Program, 2009

Overview •Why monitoring ocean colour properties (in particular, algal blooms) is important •Methods used to monitor blooms •Why Remote sensing methods are important! •Algorithms to retrieve Chlorophyll •Results •Conclusions - algorithm functionality and usefulness of methods

Why study algal blooms? Phytoplankton: ØBase of the oceanic food chain ØAre major producers of oxygen ØCan affect the atmosphere by production of DMS ØHarmful Algal Blooms production of toxins and oxygen depletion

“Red tide” bloom of Noctiluca scintillans in New Zealand Source:http://serc.carleton.edu/images/microbelife/t opics/red_tide_genera.v3.jpg

Methods

Objectives MASTER = MODIS/ASTER Simulator

Comparisons Are Important!

Overflight: 07/22/2009 1. Compare MASTER and MODIS Satellite data with in situ data 2. Apply satellite derived Chlorophyll –a algorithms to MASTER

Theoretical Basis Fluorescence line height

Letelier and Abbott (1996)

Theoretical Basis Fluorescence line height

Letelier and Abbott (1996)

Theoretical Basis Fluorescence line height

Letelier and Abbott (1996)

Theoretical Basis Fluorescence line height

C

FLH = Lc-(Lf+((LaLf)*y/(x+y)))

Fails under Low Chlorophyll conditions….

A

F

5

6

7

But might work in high chlorophyll concentrations

Letelier and Abbott (1996)

Theoretical Basis Chlorophyll-a

Band 1: 457 nm Band 2: 498 nm 1

2

3 O’Reilly, et al. (2000)

Results

1. Fluorescence Line Height FLH = Lc-(Lf+((La-Lf)*y/(x+y)))

Boat Chlorophyll

MASTER FLH

MASTER FLH

Results

2. SeaWIFS OC2v4

R=log10(R490/R555) or log10(R490/R565) Chl_oc2 = 10^(a0 + a1*R+a2*R^2+a3*R^3) + Boat Chlorophyll

MASTER Chloro.

MASTER Chloro.

Results

3. SeaWIFS OC4 R=log10(R443/R551) or log10(R488/R551) Chl_oc4 =10^(a0 + a1*R + a2*R^2+a3*R^3+a4*R^4)

Boat Chlorophyll

MASTER Chloro.

MASTER Chloro.

Results

4. MODIS Chl_a R=R443/R555 or R490/R555 Chl_a = 1o^(a0 +a1*R+a2*R^2+a3*R^3 + a4*R^4)

Boat Chlorophyll

MASTER Chloro.

MASTER Chloro.

Results

5. Polder Chl_a R=log10(R490/R555) Polder_chl = 10^(a0+a1*R+a2*R^2+a3*R^3)

Boat Chlorophyll

MASTER Chloro.

MASTER Chloro.

Results MODIS Time Series for July 2009

Results MODIS Chl -a

MODIS FLH

Results MODIS Chl -a

Boat Chlorophyll

Results MODIS FLH

Boat Chlorophyll

Issues Time lag Spatial Scales Interferences Algorithms Band Locations

Conclusions ØMASTER Bands are poorly positioned to retrieve FLH and Chlorophyll-a (in this case) ØMODIS Chlorophyll-a retrieval reveals little in this case ØMODIS FLH corresponds well to boat chlorophyll estimates

Future Work ØRescale MASTER data to MODIS spatial resolution – allow a direct comparison ØUse data where chlorophyll concentrations are high ØAdapt algorithms to be more specific to the spectral properties of MASTER

Acknowledgements