Earth Observation Science

Recent and potential scientific achievements of the (A)ATSR Series

- and some possibilities for synergy with MERIS

David Llewellyn-JonesSpace Research CentreUniversity of Leicester

AATSR Science – and MERIS

• What can AATSR do?

• Some Scientific Highlights

• AATSR and MERIS

– What can AATSR do for MERIS?

– What can MERIS do for AATSR?

• The Future prospects

– Archive

– Data continuity

What does AATSR do?• It is an imager co-registered with MERIS

• Spatial Resolution of 1Km

• Swath width 500km

• Dual angle view: at nadir, like MERIS and at 55º to nadir

• Three thermal IR channels, at 3.7.10.5 7 12 µm

• Tour reflected infrared channels

• High quality on-board calibration systems

Scientific Highlights of the ATSR-1, ATSR-2, AATSR

programmesOcean Science Tropical Instability Waves Observation of thermal signature of Rossby Waves Global change in SST

Atmospheric Science Atmospheric Water Vapour Aerosols and clouds ATSR-2 cloud data key to retrieval of GOME Ozone

Land Applications Enhanced atmospheric correction from dual-angle view Improved calibration of AVHRR and MODIS visible channels

Rossby waves detected also in the SST anomaly field (Hill et al, 2000)

Tropical Instability Waves (2½ Years)

(Allen et al 1995)

AVHRR (solid): 0.09°K/decadeATSR (dashed): 0.13°K/decade

Residual Trends in ATSR and AVHRR SST recordsMeasurement of Residual Trends in Global SSTfrom AVHRR and ATSR data

Lawrence et al

Western Boundary Currents of the Northern HemisphereGulf Stream

Kuroshio

Thermohaline Ocean Circulation

http://oceansjsu.com/105d/exped_circulation/21.html

The Gulf Stream in 2003 (Biweekly Averages, Feb - July)

KuroShio from AATSR on ENVISAT: 2002-2005

Movements of the Kuroshio: 1995-2005

data source: ATSR-2 and AATSR

KuroShio Position and Wind-field curl

From ATSR-2 and AATSR

From ECMWF wind-fields

KuroShio meanders – preliminary conclusions

• Kuroshio position can be quantitatively monitored using (A)AATSR data

• study of 10-year time series suggests some possibility of correlation between wind-stress curl and Kuroshio position

• However, other possible mechanisms (including ocean gyres) must be investigated

• Cloud contamination a problem – need for a new approach?

Recent applications of AATSAR

data•See Simon Good’s poster

•Precursor work to investigation of W Boundary Currents

•Compares AATSR SSTs with SSTs from other satellites

•Demonstrates the value of Medspiration/GHRSST

AATSR and MERIS

• Main differences & similarities

• Potential synergy:

–What can MERIS do for AATSR?

–What can AATSR do for MERIS?

Main differences & similarities

• Co-registered 250km each side of nadir

• Swath width: MERIS has over twice AATSR’s

– MERIS 1150km; AATSR 500km

• Pixel size – over 10 MERIS pixels per AATSR

– MERIS 0.29km; AATSR 1km

• AATSR has thermal channels

• AATSR has dual-angle view

Overlapping ChannelsMERIS Ch.

Wavelength ± BW (nm)

AATSR channels

MERIS Application

55 556600 ±± 1100

555500 ±± 1100

CChhlloorroopphhyyllll aabbssoorrppttiioonn mmiinniimmuumm

77 666655 ±± 1100

665599 ±± 1100

CChhlloorroopphhyyllll aabbssoorrppttiioonn aanndd fflluuoorreesscceennccee

rreeffeerreennccee

1133 886655 ±± 2200

886655 ±±1100

VVeeggeettaattiioonn,, wwaatteerr vvaappoouurr rreeffeerreennccee

11661100 ±± 3300

AAAATTSSRR cclloouudd ddeetteeccttiioonn ((ddaayyttiimmee))

AATSR/MERIS – potential synergy

Ocean productivity:• Temperature has influence on bio-activity

(biophysical interactions)

Atmospheric water vapour• MERIS product, can also be derived from A ATSR

Atmospheric aerosols• AATSR can detect aerosols but cannot constrain

all the variables• MERIS aerosol product would elucidate this• Along-track view has potential for atmos

correction over land

ENVISAT 2003 - Monthly means

AATSR SST MERIS Chlorophyll

Separation of Bi-directional Reflectance from atmospheric effects using dual view

Top ofatmosphere

= 555nm

Forward and Nadir ToA reflectancesGerund reflectance

Optical Depth

Retrieved ground reflectance

North et al

Total Atmosphe

ricWater

Vapour from ATSR

I J Barton, CSIRO

Atmospheric Aerosols - from ATSR dual-nadir SST

difference

ATSR2 SST (dual-nadir) vs TOMS Aerosol

Comparison

AATSR/MERIS – potential synergy -

2AATSR cloud detection• Analysis and refinement of AATSR cloud-

clearance scheme could benefit from MERIS ‘sub-pixel resolution

• AATSR Land-surface temperature

Land non-uniformity is a major issue• MERIS could provide indication of non-

umiformity at AATSR sub-pixels scale

Summary and Conclusions• AATSR exploitation programme now mature

• Co-registration of MERIS offers great opportunities

• Several projects already exist with strong need or alternative. Co-registered aerosol measurements.

• AATSR has archive (15+ years of SST/LST; 10+ of land reflectivity) can, in principle, allow MERIS records to extrapolated backwards.

• Data continuity is an urgent issue

• GMES-1 and Sentinel 3 satellite are key to future data availability.