Neural Network Ozone Retrieval System
First Result on Ozone Profile Retrieval
From GOME-2 and IASI
Anton Kaifel, Roger Huckle, Martin Felder
Center for Solar Energy and Hydrogen Research (ZSW)
Baden-Württemberg
Outline
• What do we not need
• What do we need
• Collocation GOME-2 and IASI
• NNORSY-GOME-2 ozone profile retrieval
• First results on NNORSY-GOME-2/IASI
-2-
Not Needed for NNORSY
Compared to classical retrievals schemes based on
Optimal Estimation
• No a-priori profiles
• No forward model
• No spectroscopic database
• No high performance computers for real-time
application
-3-
Needed for NNORSY
• A representative training database
• A good neural network training algorithm
Neural network input:
• selected parts of GOME-2 spectra
• selected parts of IASI spectra
• space-time info
• observation geometry
• Temperature profiles data helps
-4-
Some Results on NNORSY-GOME-2
sonde
satellite
-5-
sonde
satellite
satellite
sonde
NNORSY-GOME-2
Profile Comparison
with Ozone Sonde
Station
NNORSY
HOHENPEISSENBERG
(mid latitudes)
sonde
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
rel. comparison
-6-
GOME-2/IASI Collocation
• GOME‐2 footprints are base grid for retrieval
• Collocation in cooperation with NWP‐SAF (Nigel)
• Collocation of AVHRR with GOME‐2 pixels for cloud mask Scan characteristics
IASI
GOME-2
-7-
pixels / scan
line
scan time
[sec]
time / pixel
[sec]
forward scan
viewing time
[sec]
30x4
8
0.216
6.48
24
6
0.1875
4.5
Approach for GOME-2/IASI Collocation
Right hand rule for
cross products
Æ3 steps
for
collocation
-8-
GOME-2/IASI Collocation: Step 1
Cross product AP1 x AB
Cross product CP1 x CD
Æ 2 resulting vectors orthogonal on pixel plain
AP
AB
B
-9-
1
P1
.
C
C
P1
P2
.
CD
A
D
GOME-2/IASI Collocation: Step 2
Scalar product of resulting vectors
Æ point is outside lines (e.g. P2)
Æ point is between lines (e.g. P1)
If parallel > 0
If antiparalle < 0
A
C
P1
P2
.
B
- 10 -
.
D
GOME-2/IASI Collocation: Step 3
Same procedure for vertical line pair
P2 is outside the first line pair, further
investigation is therefore not necessary
A
C
P1
P2
.
B
.
D
Collocation is 5x faster than file reading (updated EUMETSAT readers)
- 11 -
Testorbit GOME-2/IASI Collocation
- 12 -
Testorbit GOME-2/IASI Collocation
(magnified)
GOME-2/AVHRR collocation almost finished
- 13 -
altitude [km]
First Results on Combined Retrieval
GOME-2
GOME-2
without
without
IASI
IASI
¾ IASI improves
retrieval mainly
below ozone peak
relative bias and stddev
- 14 -
¾ Plots show relative
errors on test data
GOME-2
set
GOME-2
&&
IASI
¾ No ECMWF
IASI
temperatures were
used here
¾ Probably obviates
need for temperature
profiles from NWP
analyses
Conclusion
• NNORSY-GOME-2 ozone profile retrieval available
• New fast collocation scheme for GOME-2/IASI
• Collocation GOME-2 with AVHRR for cloud mask
• Combined one-step NNORSY-GOME-2/IASI
retrieval improves ozone profile quality
• Easily adaptable for real-time application
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