ITSC 12, Melbourne, Australia
27 Feb. – 6 Mar. 2002
NOAA-TOVS 23 Year Total Column Ozone Product by
Neural Network Retrieval System (NNORSY)
Anton K. Kaifel, Martin D. Müller
Center for Solar Energy and Hydrogen Research (ZSW)
Stuttgart, Germany
Outline
•Approach and processing
• Validation
• Comparison
• Trend analyses
• Conclusions
• Movie (09/79-12/01)*
*) mpeg movie of total ozone data (total 1.2GB) available on ftp-site: ftp.zsw-bw.de /pub/NNORSY/TOVS
ITSC12 Melbourne 2002: ZSW 1
Satellite Ozone retrievals
Neural Network Ozone Retrieval System
(NNORSY)
Current available:
• NNORSY-TOVS
• NNORSY-GOME
• NNORSY-GOME
(total ozone column)
(total ozone column)
(profile)
Planned:
• NNORSY-SEVIRI
• NNORSY-OMI
(total ozone column)
(profile and total column)
ITSC12 Melbourne 2002: ZSW 2
NNORSY Scheme
Operation
Retrieved
ozone
operational
real-time
processing
Level 1
data
extraction
Ozone
data
collocation
Suppl.
data
Preprocessing
collocated
spectra/
ozone
network
param.s
quality
check
neural
network
training
training
data
test
data
eval.
data
data
mixing
Training
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WOUDC/Virtual Station Distribution
ground
stations
virtual TOMS
stations
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Climatological Correction of TOMS Data
EPT-Ground fit over latitude and time (DU)
(Bodeker et al., 2001 )
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NOAA-TOVS Data at ZSW
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NNORSY-TOVS: Input Data
• Timerange 09/1979 to 01/2002
• Satellites TIROS-N, NOAA-6 to NOAA-14
• Collocation radius 75 km
• yields:
~ 1.5 million training datasets
~ 200000 test datasets
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Input
Layer
Output
Layer
Retrieved Ozone
Input Data
Feed-Forward Neural Network
Hidden
Layer
Signal Propagation
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NNORSY-TOVS: Input Data
Neural Network Input (28 neurons):
•HIRS channels 1-19
•MSU channels 1-4
•HIRS scan angle
•Solar & satellite zenith angle
•Latitude
•Elevation
Retrieved Total Ozone
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NNORSY-TOVS: Ground validation over time
Potsdam, Germany
monthly mean total ozone [DU]
500
450
400
350
300
250
40
20
0
-20
-40
1979
Potsdam
RMS:
Bias:
WOUDC
TOVS
TOMS
WOUDC-TOMS
WOUDC-TOVS
TOVS
7.2 D.U.
1.9 D.U.
1983
TOMS
6.5 D.U.
-0.9 D.U.
1987
1991
1995
1999
2003
year
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NNORSY-TOVS: Ground validation monthly mean 1/5
NNORSY-TOVS: Ground validation monthly mean 2/5
NNORSY-TOVS: Ground validation monthly mean 3/5
NNORSY-TOVS: Ground validation monthly mean 4/5
NNORSY-TOVS: Ground validation monthly mean 5/5
NNORSY-TOVS L3 (09/79 –12/02)
Monthly mean values of
56 WOUDC ground stations
also used for TOMS validation
global
RMS:
Bias:
TOVS
9.1 D.U.
2.0 D.U.
TOMS
8.0 D.U.
-2.8 D.U.
Comparison of monthly mean with NOAA
operational product 1/2
TOMS – NOAA-TOVS, Jan. 2000
TOMS – TOVS-NN, Jan. 2000
TOMS – NOAA-TOVS, Mar. 2000
TOMS – TOVS-NN, Mar. 2000
D. U.
Comparison of monthly mean with NOAA
operational product 1/2
TOMS – NOAA-TOVS, Oct. 2000
TOMS – TOVS-NN, Oct. 2000
TOMS – NOAA-TOVS, Dez. 2000
TOMS – TOVS-NN, Dez. 2000
D. U.
Examples of NNORSY-TOVS zonal mean values
Year 1987 - 1990
Year 1991 - 1994
Year 1995 - 1998
Comparison of zonal mean: NNORSY-TOVS - TOMS
Year 2001
Year 2000
TOVS
TOMS
TOVS-TOMS
D. U.
D. U.
NNORSY-TOVS: Global trends
mean
maximum
mimimum
daily global total column ozone [DU]
600
550
trends:
500
14.6 DU/decade
450
400
350
300
7.12 DU/decade
250
200
17.5 DU/decade
150
100
50
1979
1983
1987
1991
1995
1999
2003
year
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NNORSY-TOVS: Global trends
zonal mean total ozone
zonal mean total ozone [DU]
350
SH
NH
gobal
300
trends:
5.30 DU/decade
7.12 DU/decade
8.94 DU/decade
250
1979
1983
1987
1991
1995
1999
2003
year
ITSC12 Melbourne 2002: ZSW 21
NNORSY-TOVS: Global trends
0
ozone trend zonal mean [DU/decade]
zonal mean total ozone trend (10 lat. band)
25
trend
20
15
10
5
0
-80
-60
-40
-20
0
20
40
60
80
latitude
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Conclusions
NNORSY-TOVS
• is very fast
• needs no cloud corrections or a priori information
• needs no limb correction for scan angle
• compares well with other sensors and ground data
• supplement for TOMS data gaps and night time retrieval
• is in real time operation for NOAA 14 at DWD
Future work
• support for NOAA KLM (15,16)
• MSG SEVIRI real time ozone retrieval
• OMI in co-operation with KNMI
• MetOp
MOVIE: NNORSY-TOVS 09/79 to 01/02
Still image of movie