Image Interpretation for Weather Analysis

1. Image Interpretation for Weather Analysis Part I 11 November 2008 Dr. Steve Decker

2. Two Kinds • Polar Orbiting • Polar-orbiting Operational Environmental Satellite (POES) • NOAA-18 (2005) • Two in operation at one time • 2:00 and 7:30 • Geostationary • Geostationary Operational Environmental Satellite (GOES) • How does a geostationary orbit work?

3. 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

5. 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

7. 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

9. Improvement Example • Registration GOES-12 vs. GOES-13

10. 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

11. Common Channels • Visible • 0.65 μm (red) • Infrared (IR) • 10.7 μm • Water Vapor • 6.7 μm • Shortwave IR • 3.9 μm

12. 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

13. 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

15. 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

17. 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

18. IR Enhancement

19. IR Enhancement

20. IR Enhancement

21. IR Enhancement

22. IR Enhancement

23. IR Enhancement

24. 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)

26. 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)

29. 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)

30. Another Example

32. 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

34. 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

36. 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

38. 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

40. Cloud Streets

41. Animation for Comma Cloud • Comma.fli

42. Cloud Identification • Compare visible and infrared images • Brightness • Height and thickness • Texture • Visible only; shadows • Pattern • Edge definition • Size • Shape

43. 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

46. 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

49. Identifying Cumuliform Clouds • Cumulus • Vis: Medium bright; lumpy • IR: Dark to medium gray; hard to see individual elements