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Image Interpretation for Weather Analysis. Part I 29 October 2009 Dr. Steve Decker. Two Kinds. Polar Orbiting Polar-orbiting Operational Environmental Satellite (POES) NOAA-17 (2002), NOAA-18 (2005), NOAA-19 (2009) MetOp-A (2006) Two in operation at one time 2:00 and 7:30 Geostationary
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Image Interpretation for Weather Analysis Part I 29 October 2009 Dr. Steve Decker
Two Kinds • Polar Orbiting • Polar-orbiting Operational Environmental Satellite (POES) • NOAA-17 (2002), NOAA-18 (2005), NOAA-19 (2009) • MetOp-A (2006) • Two in operation at one time • 2:00 and 7:30 • Geostationary • Geostationary Operational Environmental Satellite (GOES) • How does a geostationary orbit work?
Meet the GOES Satellites • GOES-8, 1994 • Was GOES-East, now decommissioned • GOES-9, 1995 • Was GOES-West, then operated by Japan, now decommissioned • GOES-10, 1997, 60°W • Was GOES-West, now providing coverage for South America • GOES-11, 2000, 135°W • Current GOES-West • GOES-12, 2001, 75°W • Current GOES-East • GOES-13, 2006 • GOES-14, 2009
Meet the GOES Satellites • GOES-8, 1994 • Was GOES-East, now decommissioned • GOES-9, 1995, 160°E • Was GOES-West, now operated by Japan • GOES-10, 1997, 60°W • Was GOES-West, now providing coverage for South America • GOES-11, 2000, 135°W • Current GOES-West • GOES-12, 2001, 75°W • Current GOES-East • GOES-13, 2006 • GOES-14, 2009
Meet the GOES Satellites • GOES-8, 1994 • Was GOES-East, now decommissioned • GOES-9, 1995, 160°E • Was GOES-West, now operated by Japan • GOES-10, 1997, 60°W • Was GOES-West, now providing coverage for South America • GOES-11, 2000, 135°W • Current GOES-West • GOES-12, 2001, 75°W • Current GOES-East • GOES-13, 2006 • GOES-14, 2009
Improvement Example • Registration GOES-12 vs. GOES-13
GOES Image Frequency • Standard Operations • Every 30 minutes for CONUS • Every three hours for full disk (takes 26 minutes) • Rapid Scan Operations • Every 5 to 15 minutes for CONUS • Super Rapid Scan Operations • Every minute for small region • Example: Hurricane Frances
Common Channels • Visible • 0.65 μm (red) • Infrared (IR) • 10.7 μm • Water Vapor • 6.7 μm • Shortwave IR • 3.9 μm
Visible Channel • Measures amount of sunlight reflected • Approximates Earth’s albedo • Clouds • Thick: High albedo White • Thin: Moderate albedo Light or medium gray • Ocean: Low albedo Black • Land: Variable albedo Shades of gray
Sun Angle Effects • Brightness varies by time of day • “Terminator”: sunrise/sunset line • Cloud shadows • Bumpy cloud top lumpy depiction • Flat cloud top smooth depiction • Sunglint • Brighter smoother sea
Sun Angle Effects • Brightness varies by time of day • “Terminator”: sunrise/sunset line • Cloud shadows • Bumpy cloud top lumpy depiction • Flat cloud top smooth depiction • Sunglint • Brighter smoother sea
Infrared Channel • Amount of radiation received by satellite with λ=10.7 μm • Combination of surface and cloud-top temperatures • For monochrome images, colder temperatures are brighter • Why? • Snow vs low clouds vs land
Geographic Features • Background for the weather features • Coasts • Vis: Sudden change from dark (ocean) to light (land) • IR: At night, land is often colder (brighter) than water. Vice versa during daytime. • Lakes • Vis: Shows ice-cover (bright)
Geographic Features • Background for the weather features • Coasts • Vis: Sudden change from dark (ocean) to light (land) • IR: At night, land is often colder (brighter) than water. Vice versa during daytime. • Lakes • Vis: Shows ice-cover (bright)
Geographic Features • Background for the weather features • Coasts • Vis: Sudden change from dark (ocean) to light (land) • IR: At night, land is often colder (brighter) than water. Vice versa during daytime. • Lakes • Vis: Shows ice-cover (bright)
Geographic Features • Land type • Wooded Darker on Vis • Sandy; little vegetation Brighter on Vis • Heat islands • Dark spots in IR at night • Snow • Vis: Distinguishable from clouds in animations • Vis: Brighter in treeless areas
Geographic Features • Land type • Wooded Darker on Vis • Sandy; little vegetation Brighter on Vis • Heat islands • Dark spots in IR at night • Snow • Vis: Distinguishable from clouds in animations • Vis: Brighter in treeless areas
Geographic Features • Land type • Wooded Darker on Vis • Sandy; little vegetation Brighter on Vis • Heat islands • Dark spots in IR at night • Snow • Vis: Distinguishable from clouds in animations • Vis: Brighter in treeless areas
Cloud Patterns • Cloud shield • Broad pattern with similar width in any direction • Cloud band • Continuous formation with a distinct long axis • Cloud line • Narrow cloud band (less than 60 n mi wide) • Cloud street • Narrow cloud band with distinct elements • Often come closely packed in parallel • Cloud element • Smallest resolvable cloud in imagery • Comma cloud • Spiraling cloud with at least one band, often shaped like a comma
Animation for Comma Cloud • Comma.fli
Cloud Identification • Compare visible and infrared images • Brightness • Height and thickness • Texture • Visible only; shadows • Pattern • Edge definition • Size • Shape
Identifying Stratiform Clouds • Stratus • Smooth, flat tops; low altitude • IR: Difficult to see • Vis: Often quite bright • Altostratus • Fog • Difficult to distinguish from stratus using Vis and IR • Motionless; evaporates from outside in • Valley fog
Identifying Stratiform Clouds • Stratus • Smooth, flat tops; low altitude • IR: Difficult to see • Vis: Often quite bright • Altostratus • Fog • Difficult to distinguish from stratus using Vis and IR • Motionless; evaporates from outside in • Valley fog
Identifying Cumuliform Clouds • Cumulus • Vis: Medium bright; lumpy • IR: Dark to medium gray; hard to see individual elements