Post on 12-Jan-2016
description
AATSR SST Validation using the M-AERI
Peter J. Minnett Rosenstiel School of Marine and
Atmospheric Science,University of Miami, Florida, USA
Marianne EdwardsSpace Research Centre, University of Leicester
Leicester, UK
ENVISAT Validation WorkshopFrascati
12 December 2002
OverviewOverview
• SST variability
• The M-AERI
• Validation cruises
• Past experience
• Future directions
M-AERI data for satellite SST M-AERI data for satellite SST validationvalidation
• Skin SST is source of signal detected by infrared satellite radiometers.
• Use of M-AERI for validation is comparing “like with like.”
• For example, satellite SST accuracy determined with buoy data includes near surface SST variability, which can be significant during the day.
Near surface temperature gradients –Near surface temperature gradients – reality reality
Profile measured at 12:51 local time on
4 October 1999. Off Baja California,
R/V Melville MOCE-5 cruise.
Blue line = SkinDeEP* profile
Blue circle = M-AERI skin temp.
Red cross = Float bulk SST at ~0.05m
Green star = Ship thermosalinograph at ~3m
From Ward, B. and P. J. Minnett, 2001. An autonomous profiler for near surface temperature measurements. Gas Transfer at Water Surfaces. M. A. Donelan, W.M. Drennan, E.S. Saltzmann and R. Wanninkhof (Eds.) American Geophysical Union Monograph 127. 167 - 172.
Time evolution of near-surface thermal gradientsTime evolution of near-surface thermal gradients
SkinDeEP profiles on 12 October 1999. Off Baja California, R/V Melville.
From Ward, B. and P. J. Minnett, 2001. An autonomous profiler for near surface temperature measurements. Gas Transfer at Water Surfaces. M. A. Donelan, W.M. Drennan, E.S. Saltzmann and R. Wanninkhof (Eds.) American Geophysical Union Monograph 127. 167 - 172.
Fourier Transform Interferometers
Michelson interferometer
Interference
Fourier transforms of interferograms are spectra
M-AERI spectra
From Minnett, P. J., R. O. Knuteson, F. A. Best, B. J. Osborne, J. A. Hanafin and O. B. Brown (2001). "The Marine-Atmospheric Emitted Radiance Interferometer (M-AERI), a high-accuracy, sea-going infrared spectroradiometer." Journal of Atmospheric and Oceanic Technology. 18(6): 994-1013.
Air Temperature Skin SST
Both temperatures measured by one instrument, one calibration.
The M-AERIThe M-AERI
M-AERI M-AERI black-black-body body
cavitiescavities
M-AERI calibration targetsM-AERI calibration targets
Marine-Atmospheric Emitted Radiance Marine-Atmospheric Emitted Radiance Interferometer (M-AERI)Interferometer (M-AERI)
Temperatures are traced to NISTTemperatures are traced to NIST
1. On-board black-body cavities have thermometers calibrated to NIST-traceable thermometers (SSEC)
2. Periodic calibration using a 3rd black body in M-AERI zenith view.
3. Periodic calibration of M-AERI system with a NIST-designed Water-Bath Black-Body target at RSMAS, using NIST-traceable reference thermometers.
4. RSMAS Water-Bath Black-Body target characterized with NIST EOS TXR
NIST EOS TXR
TXR characterizing the RSMAS WBBB
M-AERI at seaM-AERI at sea
M-AERI in the ArcticM-AERI in the Arctic
M-AERI in the MediterraneanM-AERI in the Mediterranean
One of a series of cruises in collaboration with CNR Institute of Atmospheric Physics and Climate, Rome.
Time-series of M-AERI measurements on Time-series of M-AERI measurements on Explorer of the SeasExplorer of the Seas
The Explorer of the Seas is a Royal Caribbean Cruise Liner, operating a bi-weekly schedule out of Miami. It is outfitted as an oceanographic and atmospheric research vessel, very suitable for satellite validation. For more details see http://www.rsmas.miami.edu/rccl/
M-AERI data from M-AERI data from Explorer of the SeasExplorer of the Seas
M-AERI data from M-AERI data from Explorer of the SeasExplorer of the Seas
Comparison of M-AERI with AATSRComparison of M-AERI with AATSR
• Over 140 M-AERI files (days) between May and September converted and uploaded to the NILU database.
C o -lo ca tio n p ro ce d ure to f indsp a tia l a nd te m p o ra l A A T S R /
M -A E R I d a ta m atch es
O u tp u t f ile o f m a tch e s fo rva lida tio n a n d a n a lys is
U p loa d ed toN IL U D a tab a se
C o n ve rs io n to s tan d a rd isedH D F fo rm at
D a ta e x trac tionp ro ced u re
D a ily M -A E R I d a tafro m P e te r M inn e tt,
M ia m i
G e o lo ca tio n ex trac tionp ro ced u re
A A T S R h igh re so lu tionG S S T d a ta fro m E S A
Explorer of the Seas cruise track
Past M-AERI results….Past M-AERI results….
• AVHRR Pathfinder
• MODIS
AVHRR-MAERI SST validation AVHRR-MAERI SST validation experienceexperience
Cruise Name N Mean K
St. Dev. K
CSP 1996 23 0.16 0.20
24N 1998 16 0.03 0.18
GASEX 1998 168 -0.01 0.25
FPO 1998 47 0.27 0.40
NOW 1998 (Arctic) 176 0.24 0.44
Total, all data 430 0.13 0.37
Total, excluding NOW data
254 0.06 0.29 254 0.06 0.29
M-AERI validation of Pathfinder SSTs
Using skin temperaturesreduces the uncertaintiesby about a factor of two.
See Kearns et al, 2000,Bull. Am. Met. Soc., 81, 1525-1536
MODIS SST Buoy and MAERI retrieval StatisticsMODIS SST Buoy and MAERI retrieval StatisticsVersion 4.5 (new delivery)Version 4.5 (new delivery)
BUOY M-AERI
• SST - new coefficients
Median StdDev Number
of Points
– Terra all -0.07 0.48 11027
– Terra night 0.01 0.42 4387– Terra day -0.14 0.51 6643– Aqua all 0.05 0.48
3821– Aqua night 0.00 0.43 1628– Aqua day 0.09 0.51
2203
• SST4 new coeffs, new formulation
– Terra night 0.00 0.41 1319
– Aqua night -0.01 0.39 4096
•SST - new coefficients Median StdDev Number
of Points
– Terra all
– Terra night 0.00 0.38 345
– Terra day
– Aqua all
– Aqua night 0.22 0.37 59
– Aqua day
•SST4 new coeffs, new formulation
– Terra night 0.02 0.34 278
– Aqua night -0.04 0.39 48
Terra MODIS SST ValidationTerra MODIS SST ValidationBoth SST and SST4 products show no trends with time (Jan 01-Sept 02),
satellite zenith angle (not shown) or latitude vs drifting buoys. Dotted lines are ± 0.2K and enclose 50% of the retrievals
Thermal, 10-11 µm SSTSST residual vs time by lat band
Mid-wave, 4 µm SSTSST4 residual vs time by lat band
IssuesIssues• Accuracy of M-AERI data well established.• M-AERI data-flow to Leicester, and to NILU,
established.• Narrow swath of AATSR is going to be a handicap
in developing a large M-AERI – AATSR validation data base (clouds cause ~90% data loss).
• Much larger numbers of buoys are an attractive proposition, especially at night, and can complement radiometer measurements.
• Inter-satellite comparisons should be made, e.g. AATSR and MODIS; EOS Terra is in a compatible orbit (overpass time).
Night-time behavior of the skin effect
T = -0.14 – 0.3 * exp(-U/3.7)
From Donlon, C. J., P. J. Minnett, C. Gentemann, T. J. Nightingale, I. J. Barton, B. Ward and J. Murray (2002). "Towards improved validation of satellite sea surface skin temperature measurements for climate research." J. Climate 15: 353-369.
Aqua-day
Aqua-dayTerra-day
Terra/Aqua Global DAY SST - Sept 29, 2002Terra/Aqua Global DAY SST - Sept 29, 2002
Wind speed Wind speed dependence dependence
of of diurnal & diurnal & skin effectsskin effects
Envisat, Terra and Aqua overpass times. Note, local time varies across the swath.
Future plansFuture plans
• Validate AATSR SSTs• 2003 cruises:
– Explorer of the Seas (2 weeks dry dock in January, 2003)
– Polar Sea: Melbourne – Yokohama – Seattle, March – April
– Urania: Mediterranean, April-May
– Franklin: Canadian Arctic, September 2003, for 12 months (?)
– Tangaroa: November, NZ SOLAS (?)
– Polar Star: Seattle – Sydney, November -December
• AVHRR, MODIS, AIRS, AMSR SSTs
pminnett@rsmas.miami.edu