APPLICATIONS OF
METEOSAT SECOND
GENERATION (Meteosat-8)
AIRMASS RGB
Jochen Kerkmann
Satellite Meteorologist, Training Officer
jochen.kerkmann@eumetsat.int
Contributors: G. Bridge (EUM), C. Georgiev (Bulgaria)
P. Chadwick (Canada)
Objectives
 Learn how to generate the Airmass RGB (Recipe)
 Learn how to use/interpret the WV6.2 - WV7.3 and the
IR9.7 - IR10.8 brightness temperature difference (BTD)
 In particular, understand the relationship between the IR9.7 IR10.8 BTD and the total ozone content
 Short overview of WV image interpretation
 Interpretation of colours of the Airmass RGB
 Usage of the Airmass RGB composite for monitoring jet
streams, cyclogenesis, PV maxima etc.
THE "AIRMASS" RGB
R = Difference WV6.2 - WV7.3
G = Difference IR9.7 - IR10.8
B = Channel WV6.2
Applications:
Area:
Time:
Rapid Cyclogenesis, Jet Stream Analysis, PV Analysis
Full MSG Viewing Area
Day and Night
Airmass RGB: Recipe
Recommended Range and Enhancement:
Beam
Channel
Red
Green
Blue
WV6.2 - WV7.3
IR9.7 - IR10.8
WV6.2
Range
-25 … 0 K
-40 … +5 K
+243 … +208 K
Gamma
1.0
1.0
1.0
Airmass RGB Example
combines the best three MSG features
for the early detection of rapid
cyclogenesis !
MSG-1, 07 January 2005, 03:00 UTC, RGB Composite
WV6.2-WV7.3, IR9.7-IR10.8, WV6.2
Airmass RGB: Colour Inputs
Red = WV6.2 - WV7.3
Blue = WV6.2i
Green = IR9.7 - IR10.8
RGB
Airmass RGB: Colour Inputs
Red = WV6.2 - WV7.3
Blue = WV6.2i
Green = IR9.7 - IR10.8
RGB
Red Colour Beam: WV6.2 - WV7.3
Recommended Range and Enhancement:
Beam
Channel
Range
Red
WV6.2 - WV7.3
-25 … 0 K
Gamma
1.0
Channel 05 (WV6.2)
MSG-1, 07 January 2005, 03:00 UTC, Channel 05 (WV6.2)
Range: 253 K (black) to 213 K (white)
Channel 06 (WV7.3)
MSG-1, 07 January 2005, 03:00 UTC, Channel 06 (WV7.3)
Range: 273 K (black) to 213 K (white)
BTD WV6.2 - WV7.3
MSG-1, 07 January 2005, 03:00 UTC, Difference WV6.2 - WV7.3
Range: -35 K (black) to 0 K (white)
BTD WV6.2 - WV7.3
For cloud-free scenes, the BTD between WV6.2 and WV7.3 depends
on (in order of priority):
I. temperature and humidity profile
II. satellite viewing angle
BTD WV6.2 - WV7.3
For cloudy scenes, the BTD between WV6.2 and WV7.3 depends on
(in order of priority):
I. temperature and humidity profile (above the cloud)
II. satellite viewing angle
III. emissivity of cloud at WV6.2 and WV7.3
BTD WV6.2 - WV7.3
Case I:
Very Dry
Atmosphere
very small BTD
6.2 m
7.3 m
0
-10
-20
T(850 hPa)
Moist Layer: opaque to the radiation at WV6.2 and WV7.3
(Planetary Boundary Layer)
-25
BTD WV6.2 - WV7.3
Case II:
Moist Layer
at 700 hPa
small BTD
6.2 m
7.3 m
0
-10
T(700 hPa)
T(850 hPa)
Moist Layer: opaque to the radiation at WV6.2
less opaque to the radiation at WV7.3
-20
Moist Layer: opaque to the radiation at WV6.2 and WV7.3
(Planetary Boundary Layer)
-25
BTD WV6.2 - WV7.3
Case III:
Moist Layer
at 500 hPa
large BTD
6.2 m
7.3 m
0
-10
T(500 hPa)
Moist Layer: quasi opaque to the radiation at WV6.2
quite transparent to the radiation at WV7.3
-20
T(850 hPa)
Moist Layer: opaque to the radiation at WV6.2 and WV7.3
(Planetary Boundary Layer)
-25
BTD WV6.2 - WV7.3
Case IV:
Moist Layer
at 200 hPa
small BTD
T(200 hPa)
6.2 m
7.3 m
Moist Layer: quite transparent to the radiation at WV6.2
transparent to the radiation at WV7.3
0
-10
-20
T(850 hPa)
Moist Layer: opaque to the radiation at WV6.2 and WV7.3
(Planetary Boundary Layer)
-25
BTD WV6.2 - WV7.3
MSG-1, 07 January 2005, 03:00 UTC, Difference WV6.2 - WV7.3
Range: -30 K (black) to +5 K (white)
Green Colour Beam: IR9.7 - IR10.8
Recommended Range and Enhancement:
Beam
Channel
Range
Green
IR9.7 - IR10.8
-40 … +5 K
Gamma
1.0
Channel 08 (IR9.7)
MSG-1, 07 January 2005, 03:00 UTC, Channel 08 (IR9.7 (ozone channel))
Range: 263 K (black) to 213 K (white)
Channel 09 (IR10.8)
MSG-1, 07 January 2005, 03:00 UTC, Channel 09 (IR10.8)
Range: 293 K (black) to 213 K (white)
BTD IR9.7 - IR10.8
MSG-1, 07 January 2005, 03:00 UTC, Difference IR9.7 - IR10.8
Range: -50 K (black) to 0 K (white)
BTD IR9.7 - IR10.8
For cloud-free scenes, the BTD between IR9.7 and IR10.8 depends on
(in order of priority)*:
I.
II.
III.
IV.
temperature difference between T(surf) and T(ozone)
total ozone concentration
satellite viewing angle
emissivity of surface at IR9.7 and IR10.8
(e.g. desert surface has a 3% difference in emissivity,
water has a difference of 0.3 %)
==> strong diurnal/seasonal cycle due to
T(surf) variation
*neglecting WV absorption
BTD IR9.7 - IR10.8
For cloudy scenes, the BTD between IR9.7 and IR10.8 depends on (in
order of priority)*:
I.
II.
III.
IV.
temperature difference between T(cloud) and T(ozone)
total ozone concentration
Satellite viewing angle
emissivity of cloud at IR9.7 and IR10.8
For high-level clouds:
For mid/low-level clouds:
*neglecting WV absorption
T(cloud)  T(ozone)
T(cloud) > T(ozone)
BTD IR9.7 - IR10.8
9.7 m
10.8 m
T(ozone)
T(surf/cloud)
(surf/cloud)9.7
(surf/cloud)10.8
BTD IR9.7 - IR10.8
Case I:
Rich Ozone
Polar Airmass
large BTD
9.7 m
10.8 m
+5
T(ozone)
-20
T(surf)
-40
BTD IR9.7 - IR10.8
Case II:
Low Ozone
Tropical Airmass
smaller BTD
9.7 m
10.8 m
+5
T(ozone)
-20
T(surf)
-40
BTD IR9.7 - IR10.8: Effect of T(surf)
23 June 2004, 12:00 UTC
07 January 2005, 12:00 UTC
Difference IR9.7 - IR10.8
Range: -45 K (black) to +5 K (white)
BTD IR9.7-IR10.8: Effect of Ozone
260 DU  -25 K
320 DU  -33 K
400 DU  -40 K
Thumb rule:
BTD IR9.7-IR10.8 [K] = -TOZ [DU]/10
BTD IR9.7-IR10.8: Effect of Ozone
BTD IR9.7-IR10.8: Effect of Ozone
Source: MeteoSwiss
Annual cycle of the total ozone
amount above Arosa (CH)
BTD IR9.7-IR10.8: Effect of Ozone
Source: MeteoSwiss
BTD IR9.7-IR10.8: Effect of Viewing Angle
The larger the satellite
viewing angle, the
stronger the ozone
absorption effect
(limb cooling) !
MSG-1, 31 October 2003, 11:30 UTC
Difference IR9.7 - IR10.8
Blue Colour Beam: WV6.2
Recommended Range and Enhancement:
Beam
Channel
Blue
WV6.2
Range
+243 … +208 K
Gamma
1.0
Channel 05 (WV6.2)
MSG-1, 07 January 2005, 03:00 UTC, Channel 05 (WV6.2)
Range: 253 K (black) to 213 K (white)
Features seen in WV Images
United
Kingdom
Dry intrusion
France
Met-7, 26 December 1999, 06:00 UTC, WV Channel
(Storm "Lothar")
Source: DWD
Features seen in WV Images
Convex Deformation Zone
Saddle Point
X
N
X
N
GOES-12, 14 February 2004, 00:15 UTC, WV Channel
Source: NOAA & P. Chadwick
Features seen in WV Images
Stau cloud
Foehn
Mountain waves in
cloud-free areas
with possible Clear Air
Turbulence (CAT)
Italy
MSG-1, 21 January 2005, 12:15 UTC, Channel 05 (WV6.2)
Features seen in WV Images
Algeria
Mali
High-level gravity
waves caused by
thunderstorms
MSG-1, 25 June 2005, 14:15 UTC, Channel 05 (WV6.2)
Airmass RGB: Colour Interpretation
5
3 4
-25 K
4
5
-40 K
3
5
243 K
2
WV6.2 - WV7.3
3
0K
2
IR9.7 - IR10.8
2 4
WV6.2
1
1
+5 K
1
208 K
1 = high clouds (white)
2 = mid-level clouds (light ochre)
3 = rich ozone tropical airmass with high tropopause (greenish)
4 = low ozone polar airmass with low tropopause (bluish)
5 = rich ozone airmass of dry air
with a tropopause folding
Airmass RGB Example: Warm Airmass
MSG-1, 7 January 2005, 22:00 UTC
Airmass RGB Example: Cold Airmass
MSG-1, 7 January 2005, 22:00 UTC
Airmass RGB Example: Advection Jet
MSG-1, 7 January 2005, 22:00 UTC
Airmass RGB: Interpretation of Colours
Thick, high-level clouds
Thick, mid-level clouds
Jet (high PV)
Cold Airmass
Thick, low-level clouds
Thick, low-level clouds
(warm airmass)
(cold airmass)
Warm Airmass
Warm Airmass
High UTH
Low UTH
Airmass RGB: Colour Interpretation
1 = high clouds
2 = mid-level clouds
3 = warm airmass, high tropopause
4 = cold airmass, low tropopause
5 = dry descending stratospheric air
2
4
5
3
1
MSG-1
07 January 2005
15:00 UTC
RGB Composite
R = WV6.2 - WV7.3
G = IR9.7 - IR10.8
B = WV6.2
Airmass RGB: Colour Interpretation
1 = high cloud
(severe convective storm)
2 = mid-level clouds
3 = hot land surface
(high UTH)
4 = hot land surface
(low UTH)
1
3
4
2
2
MSG-1
21 August 2006
12:00 UTC
RGB Composite
R = WV6.2 - WV7.3
G = IR9.7 - IR10.8
B = WV6.2
Airmass RGB
Global View
Note: warm airmasses seen at
a high satellite viewing angle
appear with a bluish colour
(limb cooling effect) !
MSG-1
19 April 2005
10:00 UTC
Comparison Airmass RGB vs PV 300 hPa
MSG-1, 8 January 2005, 06:00 UTC
Comparison Airmass RGB vs TOZ
MSG-1, 8 January 2005, 06:00 UTC
Comparison Airmass RGB vs PV/TOZ
MSG-1, 08 January 2005, 06:00 UTC
PV 300 hPa
Total Ozone
Comparison Airmass RGB vs PV/TOZ
MSG-1, 08 January 2005, 06:00 UTC
PV 300 hPa
Total Ozone
Comparison Airmass RGB vs PV 300 hPa
reddish areas
high PV values
19 January 2005, 06:15 UTC
SUMMARY
• The "Airmass" RGB is a combination of 4 channels:
WV6.2, WV7.3, IR9.7 and IR10.8
• It helps to detect the position of jet streams and areas of
dry descending stratospheric air with high PV (red areas)
• It also helps to discriminate airmasses (rich ozone tropical
airmass, low ozone polar airmass)
• It is also useful to detect typical WV features like
deformation zones and wave features
• At the same time, through the use of the IR channels, it
allows to monitor cloud development at low, mid and high
levels