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