sea surface temperature gradient comparisons from modis and avhrr sensors ed armstrong 1, grant...

Sea surface temperature gradient comparisons from MODIS and AVHRR sensorsEd Armstrong1, Grant Wagner, Jorge Vazquez, Mike Chin, Gregg Foti,

Ben Holt, Melissa Haltuch2, Carrie Holt3

1NASA Jet Propulsion Laboratory, California Institute of Technology2NOAA-Fisheries, Northwest Fisheries Science Centre, Seattle, WA

3Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, Canada

NASA Sea Surface Temperature Science Team Meeting

Seattle, WA8-10 Nov 2010

Copyright 2010 California Institute of Copyright 2010 California Institute of Technology. Government Sponsorship Technology. Government Sponsorship

Acknowledged.Acknowledged.

GoalsCompare and contrast SST gradients extracted from

daily L3 MODIS Aqua and AVHRR Pathfinder (N17, N18)

4 km, seasonal scales. Time series is 2003-2009

Gulf Stream and California Current study areas

Builds off previous SST gradient and frontal probability time series work for AVHRR PathfinderUses a Sobel filter applied to daily daytime and nighttime

data and averaged to monthly and seasonal scalesPathfinder gradient products currently available online

from 1982-2009 in netCDF

Seasonal gradient study areas• MODIS Aqua and AVHRR Pathfinder seasonal SST

gradient and frontal probability. 2003-2009.

A comparison of gradients

Monterey Bay

Average gradients in CC study region

Cloud free coverage

Gradients near C. Mendocino

Average gradients in CC study region

Average gradients in Gulf Stream study region

Cloud free coverage

SST Gradient variability

SST gradient correlation (pixel-to-pixel)

Gradient differences (pixel-to-pixel)

MODIS/AVHRR comparisonMODIS: more channels for improved cloud

screening

MODIS 12 bit vs 10 bit data telemetry

MODIS: 50% lower noise equivalent temperature

MODIS: 4 km pixels averages all 1 km pixels while AVHRR GAC sub samples in along-track and only averages in crosstrack

Yet: Same channels, similar algorithm for SST derivation for both radiometers

MODIS SST gradient products

2003-2009 available at seasonal interval for Aqua

Monthly products and Terra product not yet processed

“Bias” adjustment to Pathfinder products ?? More research is needed, ideally with some in situ

SST dataSimilar issues may be apparent when comparing L2

to L3 derived gradients Ideally we want to work with the channel brightness

temperatures. But not available globally.

Applications

18

Improving the management of Pacific hake (Merluccius productus) by integrating satellite information into models of spatial distribution

Melissa Haltuch1 and Carrie Holt2

1NOAA-Fisheries, Northwest Fisheries Science Centre, Seattle, WA, USA2Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, BC, Canada

Peterson Field Guide to Pacific Coast Fishes, 1983

19

Hake Survey

1995 1998 2001 2003 2005 2007

20

00.010.020.030.040.050.060.070.080.090.10.110.120.130.140.150.160.170.180.190.20.210.220.230.240.25

Results

Contour of relative hake abundance

SSTs gradients (ΔºC)

2005

Hypothesis 1: mesoscale features

21

Results

Hypothesis 1: mesoscale features

Model predicting log(abundance)

AIC ΔAIC LogL

~ 1 + depth + age 3028 16 -1507

~1 + depth + age + Fronts

3023 12 -1504

~1 + depth + age + Fronts + Fronts*depth

3011 0 -1496

Additional SST products1980s-present Level 2 AVHRR Pathfinder for US

Coast at 1 km (P. Cornillon)

Pathfinder v6 Level 3

MUR Level 4 (blended) SST at 1 km daily. Presently 2008-present but eventually 1980s-present (M. Chin)

SummaryDifferences in satellite radiometer derived SST gradients

are likely due to a number of factors Instrument differences (e.g., noise)Processing artifacts (e.g., cloud clearing, gridding)Oceanographic features

MODIS appears to have significantly improved sensitivity in comparison to AVHRR seriesBut what is the real truth ? There are challenges to sorting

out the various effects (processing, instrument) on the gradient calculation.

Need comparisons to other radiometers including in situ data

There is a growing community for SST applications