Transcript Introduction into the Absorption Channels

Introduction into the
Absorption Channels
Description of characteristics and
content of the Ozone channel:
Ch08: 9.7 
Contact person:
Veronika Zwatz-Meise
[email protected]
Version 1.0. 13 July 2004
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All MSG channels
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Channel 01:
Channel 02:
Channel 03:
Channel 04:
Channel 05
Channel 06:
Channel 07:
Channel 08:
Channel 09:
Channel 10:
Channel 11:
Chanell 12:
VIS 0.6 
VIS 0.8 
NIR 1.6 
MIR 3.9 
WV 6.2 
WV 7.3 
IR 8.7 
IR 9.7  („Ozon“)
IR 10.8 
IR 12.0 
IR 13.4  („CO2“)
HRV (High Resolution Visible)
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„Ozone channel“
Ch08: 9.7 m
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Ch08: 9.7
Sun radiation
Earth radiation
Watt/
m2 and
micron
Ozone
Carbon
dioxid
Water
vapour
Wavelength (micron)
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Comparison of radiation sources
sun - earth
• For wave length < 5 m solar radiation is dominant
• For wave length > 5 m radiation of earth is dominant
• Ch01, 02, 03, 12: only sun radiation
• Ch04: both: radiation from sun and earth
• Ch 05, 06, 07, 08, 09, 10, 11: only thermal earth radiation
Sun radiation
Earth radiation
Watt/
m2
and
micron
only
VIS
VIS +
IR
only
IR
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Application areas for the Ozone channel
• Qualitative application of images:
– No well-known additional features compared to the IR
window channels
• But new feature detected: White stripes
– Stripes are „white“ in case of the inverted presentation of
the image
– They are a measure for high stratospheric Ozone
concentrations which have protruded relatively far down
into the troposphere
• Quantitative applications:
– The computation of quantitative Ozone values will be a
future task
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Energy
spectrum
Source:
EUMETSAT
Ch08
• Ch08 is in the centre of the O3 absorption band around 9 
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Weighting
functions
Source:
EUMETSAT
Signals from lower parts of troposphere;
But:
Secondary maximum from higher than 100 hPa
Figure 3c
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Weighting
functions
Source:
EUMETSAT
Signals from lower parts of troposphere;
But:
Secondary maximum from higher than 100 hPa
Figure 3d
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Ch08: Ozonechannel, 9.66
• Ozone concentration
in the lower
stratosphere
• is not regarded as a
channel with optically
applicable structures
– But: there are in some
situations white stripes
in the areas of the
black stripes in WV
– Further: there are
structures in the cloud
free sea, best seen in
this channel
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„White Stripes“
• White stripes can only be seen in Ch08, not in Chs 09, 10
• They appear in areas of dark stripes in WV (Ch05 and 06)
• They are accompanied by NWP paramaters typical for low
tropopause (tropopause folding):
– PV low down (for instance 500 hpa)
– Maximum of shear vorticity at 300 hpa
– on the cyclonic side of a jet streak
• Physical meaning of white stripes:
– high content of Ozone which absorbs the radiation from below and
emitts radiation according to 2 nd law of Kirchhoff
• There are many more situations with low tropopause
(tropopause folding) without the white stripe;
consequently:
• White stripes are an optical indication of high stratospheric
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Ozone in upper tropopsheric heights
Case 4 December 2002
• Black stripe in WV: Belgium - W-Alps -WSwitzerland - Western Mediterranean
• Same area shows white stripe in Ch08
• Model parameters:
– PV = 2 unit lower than 400, partly 450 hPa
– confluence area at 500 and 300 hPa
– maximum of shear vorticity
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MTP: WV
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WV
6.2Ch05, WV
MSG:
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04 December 02/ 12.30 UTC
O3
9.7 Ch08,Ozone
MSG:
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04 December 02/ 12.30 UTC
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Maximum of
shear vorticity
at 300
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PV = 2
(tropopause)
lower than
450 hPa
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Confluence
at 500
and 300 hPa
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Case 9 July 03/0600 UTC
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Black stripe in WV: Atlantic; huge low system
Same area shows white stripe in Ch08
white stripe not seen in the other IR channels
Model parameters:
– close to jet axis (zeroline of shear vorticity) on cyclonic
side
– maxima of cyclonic shear vorticity
– PV = 1 lower than 450
– in vertical cross section convergence at these levels
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MSG: Ch08,Ozone
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MSG: Ch09, IR
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MSG: Ch05, WV
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At cyclonic side
of jet streak
at 300
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Maximum of
shear vorticity
at 300
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PV = 2
(tropopause)
lower than
450 hPa
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