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