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

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?

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

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

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

Improvement Example  Registration GOES-12 vs. GOES-13 Registration GOES-12 vs. GOES-13 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 Hurricane FrancesHurricane 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

IR Enhancement

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)

Another Example

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

Cloud Streets

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

Identifying Cumuliform Clouds  Cumulus –Vis: Medium bright; lumpy –IR: Dark to medium gray; hard to see individual elements  Stratocumulus –Vis: Bright; often cellular –IR: Dark; can be hard to detect

Identifying Cumuliform Clouds  Cumulus –Vis: Medium bright; lumpy –IR: Dark to medium gray; hard to see individual elements  Stratocumulus –Vis: Bright; often cellular –IR: Dark; can be hard to detect  Cumulonimbus –Very bright in both Vis and IR

Identifying Cirriform Clouds  Cirrus –Vis: Dark/medium gray; wispy; thin –IR: Light gray; not as fibrous

Identifying Cirriform Clouds  Cirrus –Vis: Dark/medium gray; wispy; thin –IR: Light gray; not as fibrous  Cirrostratus –Vis: Smooth; light gray; thicker –IR: Light gray to white

Identifying Cirriform Clouds  Cirrus –Vis: Dark/medium gray; wispy; thin –IR: Light gray; not as fibrous  Cirrostratus –Vis: Smooth; light gray; thicker –IR: Light gray to white  Cirrocumulus

Identifying Cirriform Clouds  Cirrus –Vis: Dark/medium gray; wispy; thin –IR: Light gray; not as fibrous  Cirrostratus –Vis: Smooth; light gray; thicker –IR: Light gray to white  Cirrocumulus  Anvil Cirrus