Interpretation of Dust Clouds
using Visible and Infrared
Satellite Images
Dust Training Week
2 March 2010
Centra Conference Briefing to be Broadcast by EUMETSAT from
Darmstadt Germany
Thomas F. Lee
Naval Research Laboratory
Why should I learn to interpret Visible and Infrared
images when I can get color RGB products?
• Some regions are not covered by
multispectral imagers; or RGB products
from those imagers might not be available
• Understanding Visible and Infrared images
will enable you to understand RGB
products better
• Visible and Infrared images help you
understand why/how/when satellites can
detect dust clouds.
Behavior of Dust Clouds
• Tend to form during the daytime due to
increased wind and instability.
• Few dust clouds form at night but dust
often remains in suspension.
• Just because it is difficult to detect dust on
nighttime infrared images, it doesn’t mean
that the dust cloud has dissipated or
moved out of the area.
Mostly Boring (?) Black and White
Images
• Visible – 0.6 micrometer
• Infrared – 10.8 micrometer
COMET:
Forecasting Dust Storms
Arabian Peninsula SW. of Arabian Gulf
Daytime Dust Interpretation
Infrared Window Channels
Red
Sea
Dust Clouds
Channel 07 (8.7 m)
Channel 09
(10.8 m)
MSG IR imagery on 25 June 2003 at 10:00 UTC
showing a dust cloud over the Arabian Peninsula.
From Presentation by J. Kerkmann
Solar Channels
Dust Clouds
Channel 01 (0.6 m)
Channel 02 (0.8 m)
Channel 03 (1.6 m)
MSG VIS imagery on 25 June 2003 at 10:00 UTC
showing a major dust cloud over the Red Sea. The dust cloud over the
Arabian Peninsula is not visible in VIS imagery.
From Presentation by J. Kerkmann
Dust early morning HRV
Italy
Africa
07 28 2005 0600
Dust at midday HRV
Italy
07 28 2005 1200
Morning Dust Cloud
DMSP Visible
Arabian
Peninsula
Nighttime Dust Interpretation
• At night without visible images, dust
detection is quite difficult (must use
Infrared).
• In Infrared images, dust detection is
difficult because it blends thermally with
the cool desert surface.
• Infrared-based RGBs (later in the course)
offer more hope for dust detection at night.
Guidelines for Interpretation
• Use Loops
• Look at both Visible and Infrared Images
• If you have interactive processing (contrast
stretch) use it, IR: +30 C to -20 C.
Subtle IR contrast
?
Dust
Background
11 24 2004 0700 UTC
IR Daytime Loop
11 24 2004 0400 – 1330 UTC
Visible Loop
Dust
11 24 2004 0700 UTC Put in range
Daytime Image
Dust ?
2
1
3 05 2005 0900
Dust
IR Daytime Image
Dust?
3 05 2005 0900
Dusty Cyclone
17 April 2001
COMET – Visible and Infrared
Techniques
COMET – Visible and Infrared
Techniques
Dust at Night (IR)
07 14 2003 0200
Dust at Night IR
Diff. 8.7 m - 10.8 m
07 14 2003 0200
Gravity waves in the lee
of Fuerteventura
Dust flows around Gran
Canaria and Tenerife
African
Dust Storm
MSG-1
3 March 2004
17:00 UTC
Channel 12
(HRV)
Slide from EUMETSAT
Snow
African
Dust Storm
Africa
Dust flows around Gran
Canaria and Tenerife
MSG-1
3 March 2004
17:00 UTC
RGB Composite
R = NIR1.6
G = VIS0.8
B = VIS0.6
Slide from EUMETSAT
Major African Dust Storm
with near-full Moon
Minimal Signal – 64 Grayshades
Night Visible Dust
MODIS Capabilities
Oklahoma
NM
Texas
= Smoke
= Dust
NexSat
Southern CA Fires
California
MODIS Dust RGB
vs MSG Dust RGB
7:30 UTC
10:30 UTC
4 March 2010 (Dust training week)
Over land: MSG RGB better
Over Sea. MODIS RGB better (use of vis channels)
0300 LST
0800 LST
1300 LST
1800 LST
0100 LST
0500 LST
1000 LST
1300 LST
1700 LST
0000 LST
0230 LST
Loop
Conclusions
• Viewing dust on Visible and Infrared
Images is often difficult but rewarding.
• Infrared and Visible Interpretation varies
whether we’re over Land vs. Sea
• Important Differences occur Day to Night
• If we understand these differences we can
understand RGB multispectral images
better.