1

Introduction into the Absorption Channels

Description of characteristics and content of the Ozone channel:

Ch08: 9.7

Contact person:Veronika Zwatz-Meisezwatz-meise@zamg.ac.atVersion 1.0. 13 July 2004

2

All MSG channels• Channel 01: VIS 0.6

• Channel 02: VIS 0.8

• Channel 03: NIR 1.6

• Channel 04: MIR 3.9

• Channel 05 WV 6.2

• Channel 06: WV 7.3

• Channel 07: IR 8.7

• Channel 08: IR 9.7 („Ozon“)

• Channel 09: IR 10.8

• Channel 10: IR 12.0

• Channel 11: IR 13.4 („CO2“)

• Chanell 12: HRV (High Resolution Visible)

3

„Ozone channel“

Ch08: 9.7 m

4

Sun radiation Earth radiation

Ch08: 9.7

Wavelength (micron)

Watt/m2 andmicron

Ozone

Carbondioxid

Watervapour

5

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

only VIS

VIS +IR

only IR

• 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 radiationWatt/m2

andmicron

6

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

7

8

• Ch08 is in the centre of the O3 absorption band around 9

EnergyspectrumSource:EUMETSAT

Ch08

9

Figure 3c

Signals from lower parts of troposphere;But:Secondary maximum from higher than 100 hPa

WeightingfunctionsSource:EUMETSAT

10Figure 3d

Signals from lower parts of troposphere;But:Secondary maximum from higher than 100 hPa

WeightingfunctionsSource:EUMETSAT

11

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

12

„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 Ozone in upper tropopsheric heights

13

Case 4 December 2002

• Black stripe in WV: Belgium - W-Alps -W-Switzerland - 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

14

MTP: WV

15

WV 6.2

04 December 02/ 12.30 UTC

MSG: Ch05, WV

16

O3 9.7

04 December 02/ 12.30 UTC

MSG: Ch08,Ozone

17

18

Maximum ofshear vorticity

at 300

19

PV = 2 (tropopause)lower than

450 hPa

20

Confluence at 500

and 300 hPa

21

Case 9 July 03/0600 UTC

• 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

22

MSG: Ch08,Ozone

23

MSG: Ch09, IR

24

MSG: Ch05, WV

25

At cyclonic sideof jet streak

at 300

26

Maximum ofshear vorticity

at 300

27

PV = 2 (tropopause)lower than

450 hPa