METEOSAT SECOND GENERATION (MSG) APPLICATIONS OF METEOSAT SECOND GENERATION (MSG) FOG DETECTION Author: Jochen Kerkmann (EUMETSAT) (kerkmann@eumetsat.de) Contributors: H. J. Lutz (EUMETSAT), P. Pylkkö (FMI), HP. Roesli (MeteoSwiss), D. Rosenfeld (HUJ)

Day-time Fog over Southern Germany 24 February 2003

IR10.8 channel not very useful for fog detection MSG-1 24 Feb 2003 11:00 UTC Channel 09 (IR10.8) 1 2 2 1= low-level fog or stratus 2= snow 3 = snow-free ground 3 1 1 1 1 3 IR10.8 channel not very useful for fog detection

MSG-1 24 Feb 2003 11:00 UTC Channel 04 (IR3.9) 1 2 2 1= low-level fog or stratus 2= snow 3 = snow-free ground 3 1 1 1 1 3 Detection of fog during day-time much better with IR3.9 channel

MSG-1 24 Feb 2003 11:00 UTC Channel 04r (IR3.9r) 1 2 2 1= low-level fog or stratus 2= snow 3 = snow-free ground 3 1 1 1 1 3 Detection of fog during day-time also good with solar component of IR3.9

MSG-1 24 Feb 2003 11:00 UTC Difference IR3.9 - IR10.8 1 2 2 1= low-level fog or stratus 2= snow 3 = snow-free ground 3 1 1 1 1 3 … or with the brightness temperature difference IR3.9 - IR10.8

Detection of fog over snow surfaces with SEVIRI NIR 1 Detection of fog over snow surfaces with SEVIRI NIR 1.6 channel 24 Feb 2003, 11:00 UTC 1 2 1 High reflectance (water clouds) Lower reflectance (ice clouds) Low reflectance (snow, sea) 3 1 2 1 3 1

Detection of fog over snow surfaces with SEVIRI NIR 1.6 channel Animation 1/5 Detection of fog over snow surfaces with SEVIRI NIR 1.6 channel 2 1 2 1 1= low-level fog or stratus 2= snow 3= thin mid-level cloud with water droplets (supercooled cloud) 4= lakes 2 3 4 MSG-1 24 Feb 2003 11:00 UTC Channel 03 (NIR1.6)

Detection of fog over snow surfaces with SEVIRI NIR 1.6 channel Animation 2/5 Detection of fog over snow surfaces with SEVIRI NIR 1.6 channel 2 1 2 1 1= low-level fog or stratus 2= snow 3= thin mid-level cloud with water droplets (supercooled cloud) 4= lakes 2 3 4 MSG-1 24 Feb 2003 11:15 UTC Channel 03 (NIR1.6)

Detection of fog over snow surfaces with SEVIRI NIR 1.6 channel Animation 3/5 Detection of fog over snow surfaces with SEVIRI NIR 1.6 channel 2 1 2 1 1= low-level fog or stratus 2= snow 3= thin mid-level cloud with water droplets (supercooled cloud) 4= lakes 2 3 4 MSG-1 24 Feb 2003 11:30 UTC Channel 03 (NIR1.6)

Detection of fog over snow surfaces with SEVIRI NIR 1.6 channel Animation 4/5 Detection of fog over snow surfaces with SEVIRI NIR 1.6 channel 2 1 2 1 1= low-level fog or stratus 2= snow 3= thin mid-level cloud with water droplets (supercooled cloud) 4= lakes 2 3 4 MSG-1 24 Feb 2003 11:45 UTC Channel 03 (NIR1.6)

Detection of fog over snow surfaces with SEVIRI NIR 1.6 channel Animation 5/5 Detection of fog over snow surfaces with SEVIRI NIR 1.6 channel 2 1 2 1 1= low-level fog or stratus 2= snow 3= thin mid-level cloud with water droplets (supercooled cloud) 4= lakes 2 3 4 MSG-1 24 Feb 2003 12:00 UTC Channel 03 (NIR1.6)

… close-up view over the Alps MSG-1, 24 Feb 2004, 11:00 UTC, VIS0.8 … close-up view over the Alps Non-detection of fog over snow surfaces with SEVIRI VIS0.6 amd VIS0.8 channels

… close-up view over the Alps MSG-1, 24 Feb 2004, 11:00 UTC, HRV … close-up view over the Alps Non-detection of fog over snow surfaces with SEVIRI HRV channel

Recommended RGBs for Monitoring of Day-time Fog 1 MSG-1 24 Feb 2003 11:00 UTC RGB Composite R = NIR1.6 G = VIS0.8 B = VIS0.6 1 2 2 1 1= low-level fog or stratus 2= snow 3= thin mid-level cloud with water droplets (supercooled cloud) 2 1 1 3 Recommended RGBs for Monitoring of Day-time Fog

Recommended RGBs for Monitoring of Day-time Fog 1 MSG-1 24 Feb 2003 11:00 UTC RGB Composite R = VIS0.8 G = IR3.9r B = IR10.8 1 2 2 1 1= low-level fog or stratus 2= snow 3= thin mid-level cloud with water droplets (supercooled cloud) 2 1 1 3 Recommended RGBs for Monitoring of Day-time Fog

Recommended RGBs for Monitoring of Day-time Fog 1 MSG-1 24 Feb 2003 11:00 UTC RGB Composite R = VIS0.8 G = NIR1.6 B = IR3.9r 1 2 2 1 1= low-level fog or stratus 2= snow 3= thin mid-level cloud with water droplets (supercooled cloud) 2 1 1 3 Recommended RGBs for Monitoring of Day-time Fog

Recommended RGBs for Monitoring of Day-time Fog MSG-1 24 Feb 2003 11:45 UTC RGB Composite R = NIR1.6 G = HRV B = HRV 1 2 1 1= low-level fog or stratus 2= snow 3= thin mid-level cloud with water droplets (supercooled cloud) 2 3 Recommended RGBs for Monitoring of Day-time Fog

Night-time Fog over France 14 July 2003

Detection of fog at night (and day) with IR3.9 - IR10.8 brightness temp. diff. Animation 1/4 2 1= low-level fog or stratus 2= clear ground 3= high-level clouds 1 3 MSG-1 14 July 2003 03:00 UTC Difference Image IR3.9 - IR10.8

Detection of fog at night (and day) with IR3.9 - IR10.8 brightness temp. diff. Animation 2/4 2 1= low-level fog or stratus 2= clear ground 3= high-level clouds 1 3 MSG-1 14 July 2003 04:00 UTC Difference Image IR3.9 - IR10.8

Detection of fog difficult at dawn/dusk ! Detection of fog at night (and day) with IR3.9 - IR10.8 brightness temp. diff. Animation 3/4 Detection of fog difficult at dawn/dusk ! 2 1= low-level fog or stratus 2= clear ground 3= high-level clouds 1 3 MSG-1 14 July 2003 05:00 UTC Difference Image IR3.9 - IR10.8

Detection of fog at night (and day) with IR3.9 - IR10.8 brightness temp. diff. Animation 4/4 2 1= low-level fog or stratus 2= clear ground 3= high-level clouds 1 3 MSG-1 14 July 2003 06:00 UTC Difference Image IR3.9 - IR10.8

MSG-1, 14 July 2003 Difference IR3.9 - IR10.8, 2:00 UTC HRVIS for comparison, 08:45 UTC

Night-time Fog over S. Africa 24 April 2003

IR10.8 channel not useful for fog detection 3 IR10.8 channel not useful for fog detection during night-time 1= low-level fog or stratus 2= clear ground 3 = thin mid-level clouds 4 = thick high-level clouds 1 2 MSG-1 24 April 2003 02:00 UTC Channel 09 (IR10.8) 4

IR8.7 channel also not useful for fog detection 3 IR8.7 channel also not useful for fog detection during night-time 1= low-level fog or stratus 2= clear ground 3 = thin mid-level clouds 4 = thick high-level clouds 1 2 MSG-1 24 April 2003 02:00 UTC Channel 07 (IR8.7) 4

IR3.9 channel also not useful for fog detection during night-time 1= low-level fog or stratus 2= clear ground 3 = thin mid-level clouds 4 = thick high-level clouds 1 2 MSG-1 24 April 2003 02:00 UTC Channel 04 (IR3.9) 4

3 1 2 4 Fog at night visible in IR3.9 - IR10.8 brightness temperature difference images 3 1= low-level fog or stratus 2= clear ground 3 = thin mid-level clouds 4 = thick high-level clouds 1 2 MSG-1 24 April 2003 02:00 UTC Difference Image IR3.9 - IR10.8 4

3 1 2 4 Fog at night less visible in IR8.7 - IR10.8 brightness temperature difference images 3 1= low-level fog or stratus 2= clear ground 3 = thin mid-level clouds 4 = thick high-level clouds 1 2 MSG-1 24 April 2003 02:00 UTC Difference Image IR8.7 - IR10.8 4

3 1 2 4 Fog at night not visible in IR12.0 - IR10.8 brightness temperature difference images 3 1= low-level fog or stratus 2= clear ground 3 = thin mid-level clouds 4 = thick high-level clouds 1 2 MSG-1 24 April 2003 02:00 UTC Difference Image IR12.0 - IR10.8 4

Recommended RGB for Monitoring of Night-time Fog MSG-1 24 April 2003 02:00 UTC RGB Composite R = IR12.0 - IR10.8 G = IR10.8 - IR3.9 B = IR10.8 3 1 1= low-level fog or stratus 2= clear ground 3 = thin mid-level clouds 4 = thick high-level clouds 2 Recommended RGB for Monitoring of Night-time Fog 4

Night-time Fog over Central Europe 25 October 2003

IR10.8 channel not useful for fog detection during night-time 3 1 1 2 2 1= low-level fog or stratus 2= clear ground 3 = thin Cirrus clouds 3 MSG-1 25 October 2003 02:00 UTC Channel 09 (IR10.8)

IR8.7 channel also not useful for fog detection during night-time 3 1 1 2 2 1= low-level fog or stratus 2= clear ground 3 = thin Cirrus clouds 3 MSG-1 25 October 2003 02:00 UTC Channel 07 (IR8.7)

IR3.9 channel a bit better for fog detection during night-time, but ... 3 1 1 2 2 1= low-level fog or stratus 2= clear ground 3 = thin Cirrus clouds 3 MSG-1 25 October 2003 02:00 UTC Channel 04 (IR3.9)

… fog at night very well visible in IR3. 9-IR10 … fog at night very well visible in IR3.9-IR10.8 temperature difference images 3 1 1 2 Fog: -8/-10 K (black) Ground: -4/-5 K (grey) 2 1= low-level fog or stratus 2= clear ground 3 = thin Cirrus clouds 3 MSG-1 25 October 2003 02:00 UTC Difference Image IR3.9 - IR10.8

… fog at night also well visible in IR8. 7-IR10 … fog at night also well visible in IR8.7-IR10.8 temperature difference images 3 1 1 2 Fog: -4 K (dark grey) Ground: -2 K (light grey) 2 1= low-level fog or stratus 2= clear ground 3 = thin Cirrus clouds 3 MSG-1 25 October 2003 02:00 UTC Difference Image IR8.7 - IR10.8

… fog at night not visible in IR12. 0-IR10 … fog at night not visible in IR12.0-IR10.8 temperature difference images 3 1 1 2 2 1= low-level fog or stratus 2= clear ground 3 = thin Cirrus clouds 3 MSG-1 25 October 2003 02:00 UTC Difference Image IR12.0 - IR10.8

Recommended RGB for Monitoring of Night-time Fog 3 MSG-1 25 Oct 2003 02:00 UTC RGB Composite R = IR12.0-IR10.8 G = IR10.8-IR3.9 B = IR10.8 1 1 2 2 1= low-level fog or stratus 2= clear ground 3 = thin Cirrus clouds 3 Recommended RGB for Monitoring of Night-time Fog

Night-time Fog over Southern Finland 29 October 2003

Fog at night not visible in IR10.8 images 2 1 3 1= low-level fog or stratus 2= clear ground 3 = high-level frontal clouds 3 1 MSG-1 29 October 2003 02:00 UTC Channel 09 (IR10.8) 2

Fog at night not visible in IR8.7 images 1 2 1 3 1= low-level fog or stratus 2= clear ground 3 = high-level frontal clouds 3 1 MSG-1 29 October 2003 02:00 UTC Channel 07 (IR8.7) 2

Fog at night hardly visible in IR3.9 images 1 2 1 3 1= low-level fog or stratus 2= clear ground 3 = high-level frontal clouds 3 1 MSG-1 29 October 2003 02:00 UTC Channel 04 (IR3.9) 2

Night-time fog is not well visible in IR3. 9-IR10 Night-time fog is not well visible in IR3.9-IR10.8 temperature difference images over Scandinavia 1 2 1 3 1= low-level fog or stratus 2= clear ground 3 = high-level frontal clouds 3 1 MSG-1 29 October 2003 02:00 UTC Difference Image IR3.9 - IR10.8 2

The IR8.7-IR10.8 temperature difference images give better results for fog detection at high latitudes 1 2 1 3 1= low-level fog or stratus 2= clear ground 3 = high-level frontal clouds 3 1 MSG-1 29 October 2003 02:00 UTC Difference Image IR8.7 - IR10.8 2

Recommended RGB for Monitoring of Night-time Fog at high Latitudes MSG-1 29 Oct 2003 02:00 UTC RGB Composite R = IR12.0-IR10.8 G = IR10.8-IR8.7 B = IR10.8 1 2 1 3 3 1= low-level fog or stratus 2= clear ground 3 = high-level frontal clouds 1 2 Recommended RGB for Monitoring of Night-time Fog at high Latitudes

Night-time Fog over Central Europe 5 November 2003

Fog at night not visible in IR window channels 3 3 Fog at night not visible in IR window channels 2 1= low-level fog or stratus 2= clear ground 3 = high-level clouds 1 1 3 MSG-1 5 November 2003 03:00 UTC Channel 04 (IR3.9) 1 2

Fog at night not visible in IR window channels 3 3 Fog at night not visible in IR window channels 2 1= low-level fog or stratus 2= clear ground 3 = high-level clouds 1 1 3 MSG-1 5 November 2003 03:00 UTC Channel 07 (IR8.7) 1 2

Fog at night not visible in IR window channels 3 3 Fog at night not visible in IR window channels 2 1= low-level fog or stratus 2= clear ground 3 = high-level clouds 1 1 3 MSG-1 5 November 2003 03:00 UTC Channel 09 (IR10.8) 1 2

Fog at night well visible in IR3.9 - IR10.8 difference images 2 Fog: -7/-10 K (black) Ground: -4 K (grey) 1= low-level fog or stratus 2= clear ground 3 = high-level clouds 1 1 3 MSG-1 5 November 2003 03:00 UTC Difference Image IR3.9 - IR10.8 1 2

Fog at night also well visible in IR3.9 - IR12.0 difference images Fog: -8/-10 K (black) Ground: -5 K (grey) 1= low-level fog or stratus 2= clear ground 3 = high-level clouds 1 1 3 MSG-1 5 November 2003 03:00 UTC Difference Image IR3.9 - IR12.0 1 2

Fog at night also visible in IR8.7 - IR10.8 difference images 3 3 Fog at night also visible in IR8.7 - IR10.8 difference images 2 Fog: -3/-4 K (dark grey) Ground: -1 K (light grey) 1= low-level fog or stratus 2= clear ground 3 = high-level clouds 1 1 3 MSG-1 5 November 2003 03:00 UTC Difference Image IR8.7 - IR10.8 1 2

Fog at night not visible in difference IR12.0 - IR10.8 3 3 Fog at night not visible in difference IR12.0 - IR10.8 2 Fog: 0/+1 K (light grey) Ground: 0/+1 K (light grey) 1= low-level fog or stratus 2= clear ground 3 = high-level clouds 1 1 3 MSG-1 5 November 2003 03:00 UTC Difference Image IR12.0 - IR10.8 1 2

3 3 2 1 1 3 1 2 Recommended RGB for Monitoring of Night-time Fog MSG-1 5 November 2003 03:00 UTC RGB Composite R = IR12.0-IR10.8 G = IR10.8-IR3.9 B = IR10.8 2 1 1 1= low-level fog or stratus 2= clear ground 3 = high-level clouds 3 1 2 Recommended RGB for Monitoring of Night-time Fog

Day-time Fog over Central Europe 5 November 2003

River Valley Fog as seen by Meteosat First Generation (MFG) Met-7, 5 November 2003, 08:00 UTC, VIS channel

River valley fog can be better detected with the MSG HRV channel Mosel Valley Danube Valley MSG-1 5 November 2003 08:45 UTC Channel 12 (HRV)

… and the MSG HRV channel gives more details Kaiserstuhl (557 m) MSG-1 5 November 2003 08:45 UTC Channel 12 (HRV)

3 2 1 1 4 1 2 4 Recommended RGBs for Monitoring of Day-time Fog MSG-1 5 November 2003 09:00 UTC RGB Composite R = NIR1.6 G = VIS0.8 B = VIS0.6 2 1 1 1= low-level fog or stratus 2= clear ground 3 = high-level clouds 4 = snow 4 1 2 4 Recommended RGBs for Monitoring of Day-time Fog

3 2 1 1 2 4 1 4 Recommended RGBs for Monitoring of Day-time Fog MSG-1 5 November 2003 09:00 UTC RGB Composite R = VIS0.8 G = IR3.9r B = IR10.8 2 1 1= low-level fog or stratus 2= clear ground 3 = high-level clouds 4 = snow 1 2 4 1 4 Recommended RGBs for Monitoring of Day-time Fog

3 2 1 1 2 4 1 4 Recommended RGBs for Monitoring of Day-time Fog MSG-1 5 November 2003 09:00 UTC RGB Composite R = VIS0.8 G = NIR1.6 B = IR3.9r 2 1 1= low-level fog or stratus 2= clear ground 3 = high-level clouds 4 = snow 1 2 4 1 4 Recommended RGBs for Monitoring of Day-time Fog

Recommended RGBs for Monitoring of Day-time Fog 3 MSG-1 5 November 2003 08:45 UTC RGB Composite R = HRV G = HRV B = IR3.9i 2 1= low-level fog or stratus 2= clear ground 3 = high-level clouds 4 = snow 1 1 4 Recommended RGBs for Monitoring of Day-time Fog 4 2 1

Night-time Fog over Europe 9 November 2003

Fog at night not visible in IR window channels 1 3 1 2 1= low-level fog or stratus 2= cold clear ground 3 = warm clear ground (mountains) 4 = thin, high-level clouds 3 4 1 MSG-1 09 November 2003 03:15 UTC Channel 04 (IR3.9)

Fog at night not visible in IR window channels 1 3 1 2 1= low-level fog or stratus 2= cold clear ground 3 = warm clear ground (mountains) 4 = thin, high-level clouds 3 4 1 MSG-1 09 November 2003 03:15 UTC Channel 07 (IR8.7)

Fog at night not visible in IR window channels 1 3 1 2 1= low-level fog or stratus 2= cold clear ground 3 = warm clear ground (mountains) 4 = thin, high-level clouds 3 4 1 MSG-1 09 November 2003 03:15 UTC Channel 09 (IR10.8)

Fog at night visible in IR3.9 - IR10.8 Animation 1/6 Fog at night visible in IR3.9 - IR10.8 difference images 1 Fog: -7/-10 K (black) Ground: -4/-5 K (grey) 3 1 2 1= low-level fog or stratus 2= cold clear ground 3 = warm clear ground (mountains) 4 = thin, high-level clouds 3 4 1 MSG-1 09 November 2003 03:15 UTC Difference Image IR3.9 - IR10.8

Fog at night visible in IR3.9 - IR10.8 Animation 2/6 Fog at night visible in IR3.9 - IR10.8 difference images 1 Fog: -7/-10 K (black) Ground: -4/-5 K (grey) 3 1 2 1= low-level fog or stratus 2= cold clear ground 3 = warm clear ground (mountains) 4 = thin, high-level clouds 3 4 1 MSG-1 09 November 2003 04:15 UTC Difference Image IR3.9 - IR10.8

Fog at night visible in IR3.9 - IR10.8 Animation 3/6 Fog at night visible in IR3.9 - IR10.8 difference images 1 Fog: -7/-10 K (black) Ground: -4/-5 K (grey) 3 1 2 1= low-level fog or stratus 2= cold clear ground 3 = warm clear ground (mountains) 4 = thin, high-level clouds 3 4 1 MSG-1 09 November 2003 05:15 UTC Difference Image IR3.9 - IR10.8

Fog at dawn/dusk not visible in IR3.9 - IR10.8 difference images Animation 4/6 Fog at dawn/dusk not visible in IR3.9 - IR10.8 difference images 1 Fog: -3/-4 K (grey) Ground: -4/-5 K (grey) 3 1 2 1= low-level fog or stratus 2= cold clear ground 3 = warm clear ground (mountains) 4 = thin, high-level clouds 3 4 1 MSG-1 09 November 2003 06:15 UTC Difference Image IR3.9 - IR10.8

Fog at daytime visible in IR3.9 - IR10.8 Animation 5/6 Fog at daytime visible in IR3.9 - IR10.8 difference images 1 Fog: +2/+6 (light grey) Ground: -4/-5 K (dark grey) 3 1 2 1= low-level fog or stratus 2= cold clear ground 3 = warm clear ground (mountains) 4 = thin, high-level clouds 3 4 1 MSG-1 09 November 2003 07:15 UTC Difference Image IR3.9 - IR10.8

Fog at daytime visible in IR3.9 - IR10.8 Animation 6/6 Fog at daytime visible in IR3.9 - IR10.8 difference images 1 Fog: +6/+12 (light grey) Ground: -2/-3 K (dark grey) 3 1 2 1= low-level fog or stratus 2= cold clear ground 3 = warm clear ground (mountains) 4 = thin, high-level clouds 3 4 1 MSG-1 09 November 2003 08:15 UTC Difference Image IR3.9 - IR10.8

Fog at night also visible in difference IR8.7 - IR10.8 Fog: -3/-4 K (black) Ground: -1/-2 K (grey) 3 1 2 1= low-level fog or stratus 2= cold clear ground 3 = warm clear ground (mountains) 4 = thin, high-level clouds 3 4 1 MSG-1 09 November 2003 03:15 UTC Difference Image IR8.7 - IR10.8

Fog at night not visible in difference IR12.0 - IR10.8 Fog: 0/+1 K Ground: 0/+1 K Ocean: -1 K 3 1 2 1= low-level fog or stratus 2= cold clear ground 3 = warm clear ground (mountains) 4 = thin, high-level clouds 3 4 1 MSG-1 09 November 2003 03:15 UTC Difference Image IR12.0 - IR10.8

1 3 1 2 3 4 1 Recommended RGB for Monitoring of Night-time Fog MSG-1 9 November 2003 03:15 UTC RGB Composite R = IR12.0-IR10.8 G = IR10.8-IR3.9 B = IR10.8 1 3 1 2 3 1= low-level fog or stratus 2= cold clear ground 3 = warm clear (mountains) 4 = thin, high level clouds 4 1 Recommended RGB for Monitoring of Night-time Fog

Day-time Fog over Europe 9 November 2003

Low Stratus and River Valley Fog as seen by MFG Met-7, 9 November 2003, 08:00 UTC, VIS channel

MSG HRV channel gives more details on the fog ... Fog/low stratus MSG-1 9 November 2003 08:15 UTC Channel 12 (HRV) River Valley Fog

… closer look at Denmark MSG-1 9 November 2003 08:15 UTC Channel 12 (HRV) Fog/Low stratus with Gravity Waves

MSG-1 9 November 2003 08:15 UTC RGB Composite R = NIR1.6 G = VIS0.8 B = VIS0.6 1 3 1 2 4 1 1= low-level fog or stratus 2= clear ground 3 = high-level thick clouds 4 = high-level thin clouds 5 = snow 4 5 4 3 1 2 Recommended RGBs for Monitoring of Day-time Fog

MSG-1 9 November 2003 08:15 UTC RGB Composite R = VIS0.8 G = IR3.9r B = IR10.8 1 3 1 2 4 1 1= low-level fog or stratus 2= clear ground 3 = high-level thick clouds 4 = high-level thin clouds 5 = snow 4 5 4 3 1 2 Recommended RGBs for Monitoring of Day-time Fog

MSG-1 9 November 2003 08:15 UTC RGB Composite R = VIS0.8 G = NIR1.6 B = IR3.9r 1 3 1 2 4 1 1= low-level fog or stratus 2= clear ground 3 = high-level thick clouds 4 = high-level thin clouds 5 = snow 4 5 4 3 1 2 Recommended RGBs for Monitoring of Day-time Fog

3 MSG-1 9 November 2003 08:15 UTC RGB Composite R = HRV G = HRV B = IR3.9 - IR10.8 1 1 2 1 4 4 2 1= low-level fog or stratus 2= clear ground 3 = high-level thick clouds 4 = high-level thin clouds 5 = snow 5 4 1 1 2 Recommended RGBs for Monitoring of Day-time Fog

Night-time Fog over Central Europe 11 November 2003

Recommended RGB for Monitoring of Night-time Fog MSG-1 11 Nov 2003 03:00 UTC RGB Composite R = IR12.0 - IR10.8 G = IR10.8 - IR3.9 B = IR10.8 1 2 4 5 3 3 1. Sea surface 2. Land surface 3. Warm fog 4. Cool fog + stratus (-3oC) 5. Supercooled water stratus (-13oC) 6. Highly supercooled water stratus (-18oC) 7. Cb with lightning 8. Thick cirrus 9. Thin cirrus 6 1 7 8 7 9 Recommended RGB for Monitoring of Night-time Fog

Recommended RGB for Monitoring of Night-time Fog 1 3 5 4 2 6 7 8 9 MSG-1 11 Nov 2003 03:00 UTC Difference Image R = IR12.0 - IR10.8 1. Sea surface 2. Land surface 3. Warm fog 4. Cool fog + stratus (-3oC) 5. Supercooled water stratus (-13oC) 6. Highly supercooled water stratus (-18oC) 7. Cb with lightning 8. Thick cirrus 9. Thin cirrus Recommended RGB for Monitoring of Night-time Fog

Recommended RGB for Monitoring of Night-time Fog 1 3 5 4 2 6 7 8 9 MSG-1 11 Nov 2003 03:00 UTC Difference Image G = IR10.8 - IR3.9 1. Sea surface 2. Land surface 3. Warm fog 4. Cool fog + stratus (-3oC) 5. Supercooled water stratus (-13oC) 6. Highly supercooled water stratus (-18oC) 7. Cb with lightning 8. Thick cirrus 9. Thin cirrus Recommended RGB for Monitoring of Night-time Fog

Recommended RGB for Monitoring of Night-time Fog 1 3 5 4 2 6 7 8 9 MSG-1 11 Nov 2003 03:00 UTC Difference Image B = IR10.8 1. Sea surface 2. Land surface 3. Warm fog 4. Cool fog + stratus (-3oC) 5. Supercooled water stratus (-13oC) 6. Highly supercooled water stratus (-18oC) 7. Cb with lightning 8. Thick cirrus 9. Thin cirrus Recommended RGB for Monitoring of Night-time Fog

Day-time Fog over the Po Valley 20 November 2003

MSG-1, 20 November 2003, 11:00 UTC, HRV Channel

1 to 2 critical slots at dawn/dusk MSG-1, 20 November 2003 Difference IR3.9 - IR10.8 Night Fog darker than clear ground Dawn Fog and clear ground equal Day Fog brighter than clear ground 1 to 2 critical slots at dawn/dusk

MSG-1, 20 November 2003, 00:00 - 15:00 UTC, IR3.9 - IR10.8 Click on the icon or on the image to see the animation (15068 KB) ! MSG-1, 20 November 2003, 00:00 - 15:00 UTC, IR3.9 - IR10.8

SUMMARY

Detection of Fog/Low Stratus during Daytime VIS0.6 and HRVIS: to disciminate between fog and ground (fog white, ground dark) VIS0.8: less useful because of less contrast to vegetated areas NIR1.6 and IR3.9: to discriminate between fog and snow (fog high reflectivity, snow low reflectivity) IR3.9 - IR10.8: fog large positive values; clear ground around 0 K (-5 K to +5 K)

Detection of Fog/Low Stratus during Daytime RGB 03-02-01: fog white-pinkish; clear ground greenish or reddish (depending in vegetation) RGB 03-12-12: fog white-pinkish; clear ground reddish RGB 02-04r-09: fog white-pinkish; clear ground blueish RGB 02-03-04r: fog whitish, clear ground greenish-bluish

Detection of Fog/Low Stratus during Nighttime (Low and Mid Latitudes) IR3.9-IR10.8: fog -10/-7 K; clear ground around -4 K (difficulties at high latitudes) RGB 10-09 / 09-04 / 09: fog light greenish-yellowish; clear ground dark pinkish

Detection of Fog/Low Stratus during Nighttime (High Latitudes) IR8.7-IR10.8: fog -4 K, clear ground around -1/-2 K RGB 10-09 / 09-07 / 09: fog light greenish-yellowish; clear ground dark pinkish

Detection of Fog/Low Stratus at Dawn/Dusk IR3.9-IR10.8: fog detection difficult because of compensating effects (fog colder in IR3.9 than in IR10.8 because of lower emissivity, but reflection of solar radiation) IR8.7-IR10.8: fog -4 K, clear ground around -1/-2 K (only small difference between fog and clear ground, but works also at dawn/dusk)

Detection of Fog/Low Stratus: Conclusion In operational applications, the difference IR8.7-IR10.8 may be the best to detect fog/low stratus (day- and night), because of: Less noisy than the difference IR3.9 - IR10.8 (works well also over Scandinavia) 24-hour capability with "constant" colour for fog/low stratus (unlike IR3.9-IR10.8 difference) High-level Cirrus above fog/low stratus can also be detected (combined with IR12.0-IR10.8 difference)

MSG-1, 9 November 2003, 00:15 - 08:15 UTC, Difference Image, IR8 MSG-1, 9 November 2003, 00:15 - 08:15 UTC, Difference Image, IR8.7 - IR10.8 Click on the icon or on the image to see the animation (10550 KB) !