Post on 13-Dec-2015
20/1/2004 Dr. J.J. Remedios, Leicester. ACAW, 21/1/2004 1
GMES-GATO: Atmospheric correction using atmospheric composition satellite data
J.J. Remedios
EOS-SRC, Dept. of Physics and Astronomy, University of Leicester, U.K.
http://www.leos.le.ac.uk/home
20/1/2004 Dr. J.J. Remedios, Leicester. ACAW, 21/1/2004 2
Structure
Influence of the atmosphere on surface observations
– Atmospheric correction
– Issues requiring surface and atmosphere information
Requirements for atmospheric correction
What are the technical issues?
Current developments?
Rational system needs (existing data/systems)
What is missing (future systems)?
GMES objectives
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Atmospheric influence on Systems Observing the Earth’ s Surface I
1. Satellite observations of the surface must intrinsically account for the atmosphere (atmospheric correction)
Atmospheric effects are present at almost all wavelengthsExample of 1. is correction of phytoplankton (ocean colour) data for
ozone contribution.
2. Atmospheric composition may also affect surface properties and also the reverse
– Direct e.g., chemical action, deposition, emitted flux of gases.
– Indirect, e.g., control of surface temperature or photosynthetic radiation.
User requirements include combined surface and atmosphere datasets, e.g., forestation and carbon dioxide, vegetation and water vapour, U/V radiation.
Example of 2. is dependence of phytoplankton concentrations on U/V radiation (and hence ozone)
Concentrate on 1 here: atmospheric correction
20/1/2004 Dr. J.J. Remedios, Leicester. ACAW, 21/1/2004 4
SOURCES OF RADIATION AT THE TOP OF THE ATMOSPHERE; RADIATION BALANCE
20/1/2004 Dr. J.J. Remedios, Leicester. ACAW, 21/1/2004 5
ATMOSPHERIC GASES AND THE SOLAR SPECTRUM
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Infra-red emission spectrum to space[Nadir signal for an i/r instrument
10 m 4 m20 m 5 m
Wavenumber = 1/ but in cm-1. Ref. pt. 10 m = 1000 cm-1
12 m window
8 m window
CO2O3
N2O, CH4
H2O
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I/R EMISSION SPECTRA
Sahara
Mediterranean
Antarctic
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Atmosphere influence on surface systems II
Policy issues in this area arise from two sources:• Requirements for atmospheric correction to surface data• Requirements for atmosphere data relevant to interpretation
of surface measurements. [cross-cutting BICEPS level]
Concentrate on 1 here.
User requirements for surface data can be grouped into three areas, for which a number of key issues can be identified.
• Environmental hazards [GMES]• Environmental monitoring [GMES]• Commercial remote sensing
20/1/2004 Dr. J.J. Remedios, Leicester. ACAW, 21/1/2004 9
Volcanic Activity
20/1/2004 Dr. J.J. Remedios, Leicester. ACAW, 21/1/2004 10
MODIS/AQUA – FIRES/AEROSOLMAY 9 2003
RUSSIA FIRES 2003
MOPITT CO. MAY 3-8 2003
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VEGETATION
ATSR-2 IMAGE:
VEGETATION DIFFERENCES AT THE BORDERS OF ISRAEL
ATSR-2 IMAGE:
DERIVED VEGETATION COVER (06/09/95)
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Atmospheric correction?
1. Most common atmospheric factors are
a) Clouds (troposphere – optically thick, thin, broken)
b) Tropospheric Aerosols (lower 2-3 km)
c) Tropospheric water vapour (lower 2-3 km)
d) Tropospheric CO2, CH4 (near-surface)
e) Molecular density (ground to approximately tropopause)
f) Stratospheric ozone (above 15/20 km)
g) Stratospheric aerosols (volcanic eruption)
h) O4 complex
2. Would also include ionosphere for radio/microwave
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1x1 Block:
Dual SST Matchups
• 30 June 2003
• Overpass ± 60 min
Key - matchups:
- within ± 0.3 K
X - > ± 0.3 K
- AATSR cloud
Increasing time
PUERTO RICO
Colour indicates dual-view SST
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ATSR2 SST (dual-nadir) vs TOMS Aerosol
DUAL-NADIR ATSR-2 SST
TOMS AEROSOL
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ATSR SST-AEROSOL: 07/1999
ATSR-2 VS AVHRR
TOMS AEROSOL INDEX
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Dust Storm over Red Sea(MODIS) August 14th 2003
http://naturalhazards.nasa.gov/
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Box14 Red Sea
Mean SST difference versus Time
TOMS Aerosol Index versus Time
Correlation=0.79
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Scatter Plot of Mean SST Difference versus Aerosol Index Over the Red Sea
Pixel by Pixel Correlation=0.544
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Schroedter, M., 1997 Diplomarbeit and M. Schrodter, F. Olesen, H. Fischer, 2003 IJRS
TOVS versus ECMWF profiles
Difference between LST: TOVS - ECMWF
Atmospheric correction
AVHRR 16.09.1992 afternoon
Bias TOVS vs. ECMWF 0.23 KStdv. TOVS – ECMWF 0.27 K
Black:clouds,water,snow
AVHRR 17.09.1992 afternoon
Bias TOVS vs. ECMWF 0.82 KStdv. TOVS – ECMWF 0.82 K
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Table of Requirements
Parameter λ region Typical λ Typical spatial resn.
Atmospheric correction requirements
Sea/land surface temperature
Infra-red 11 μm, 12 μm 3.7 μm (night)
1 x 1 km2 Aerosol, water vapour (T)
Surface reflectance/imagery
visible 470 nm -2.2 μm (discrete channels or low spectral resn.)
30 x 30 m2
to 5 x 5 m2
Aerosol, water vapour, ozone,
O4
Vegetation indices (derived from reflectance)
visible 600 nm – 1 μm 1 x 1 km2 Aerosol, water vapour, ozone
Ocean colour visible 400-550 nm 1 x 1 km2 Aerosol, water vapour, ozone,
O4
Sea/land surface height (SH)[single channel]
microwave
13.575, 5.3, 3.2 GHz
<2 x 2 km2 Water vapour0 cm (poles)-40 cm (tropics)
Ocean salinity microwave
1.4 GHz 35-50 x 35-50 km2
Water vapour
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Current and future developments
Current:
Hyperspectral
Multi-angle
Dedicated channels for atmospheric correction
Future:
Future instruments: potential for joint surface/atmosphere measurements (e.g., aerosols from imagers, H2O from SAR)
Role of assimilation models, e.g., ECMWF, KNMI Ozone
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What are the technical issues?
1. The latest sensors often incorporate a spectral channel for determining atmospheric correction factors.
a) Are all the relevant atmospheric factors measured
b) Is vertical resolution required?
c) Is the information measured at the correct wavelengths – particularly aerosols?
2. Surface products and imagers often require a high spatial resolution ( < 5 x 5 km2 ) with specific temporal resolution. What is the ability of atmospheric GMES systems to deliver this information?
Spectral vs Spatial resolution
3. Will atmospheric instruments measure the “correct” (relevant) types of aerosol?
4. What is the accuracy of assimilation and the potential for improved spatial scales?
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Rational System Needs (European)
1. Communication between surface sensing and atmospheric sensing communities (network)
2. Research into the exploitation of independent atmospheric sensing information within surface sensors.
3. Establish accuracies of ECMWF/ other assimilation systems for ozone/water vapour
4. Research into radiative transfer systems and models of the atmosphere
5. Inter-instrument research on aerosol across the e/m spectrum.
6. Operational data processing for multi-system data, e.g. ENVISAT/Metop
7. Continuity in the observation of key atmospheric variables and intercalibrated datasets relevant to surface products
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What is missing (in European systems)?
1. Research into the derivation of atmospheric correction information at high spatial scales.
2. Development of synergistic mission system concepts – formation flying
3. Development of assimilation systems providing atmospheric information to surface sensing communities
4. High spatial resolution aerosol mission to establish aerosol climatology/radiative properties [air quality]
5. [“Quick reaction” system for volcanic eruption into stratosphere]
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Overall surface-atmosphere system
An integration of surface and atmosphere systems:
• Observation systems
Use of atmospheric sensors in other GMES (sub-) system.
Exploitation of atmospheric information derived from other GMES systems (two-way)
High spatial resolution aerosol mission
Continuity of measurements for water vapour, ozone.
• Accessible and linked databases /processing centres [*]
• NRT capabilities including data assimilation [*]
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Volcanic Activity
(c) Dr. A. Richter, IFE/IUP Bremen
Andreas Richter and John Burrows – IUP Bremen
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Mt Etna