Image Interpretation for Weather Analysis

transcript

Image Interpretation for Image Interpretation for Weather AnalysisWeather Analysis

Part IPart I

18 October 201118 October 2011

Dr. Steve DeckerDr. Steve Decker

Two KindsTwo Kinds

Polar OrbitingPolar Orbiting– Polar-orbiting Operational Environmental Satellite Polar-orbiting Operational Environmental Satellite

(POES)(POES) NOAA-19 (2009) [NOAA-18 and older provide backup]NOAA-19 (2009) [NOAA-18 and older provide backup] MetOp-A (2006)MetOp-A (2006) Two in operation at one timeTwo in operation at one time

– Sun-synchronous - 1:30 PM and 9:30 AMSun-synchronous - 1:30 PM and 9:30 AM To be replaced by NPOESS in 2014To be replaced by NPOESS in 2014

GeostationaryGeostationary– Geostationary Operational Environmental Satellite Geostationary Operational Environmental Satellite

(GOES)(GOES)– How does a geostationary orbit work?How does a geostationary orbit work?

Meet the GOES SatellitesMeet the GOES Satellites

GOES 11, 2000/2006, 135GOES 11, 2000/2006, 135°W, 2°W, 2ndnd gen. gen.– Current GOES-WestCurrent GOES-West

GOES 12, 2001/2003, 60GOES 12, 2001/2003, 60°W, 2°W, 2ndnd gen. gen.– Was GOES-East, now covering South AmericaWas GOES-East, now covering South America

GOES 13, 2006/2010, GOES 13, 2006/2010, 7575°W, 3°W, 3rdrd gen. gen.– Current GOES-EastCurrent GOES-East

GOES 14, 2009, 3GOES 14, 2009, 3rdrd gen. gen. GOES 15, 2010, 3GOES 15, 2010, 3rdrd gen. gen. Fourth generation (GOES-R / GOES-NEXT) Fourth generation (GOES-R / GOES-NEXT)

scheduled for launch in 2014scheduled for launch in 2014

Improvement ExampleImprovement Example

Registration GOES-12 vs. GOES-13

GOES Image FrequencyGOES Image Frequency

Standard OperationsStandard Operations– Every 30 minutes for CONUSEvery 30 minutes for CONUS– Every three hours for full disk (takes 26 Every three hours for full disk (takes 26

minutes)minutes) Rapid Scan OperationsRapid Scan Operations

– Every 5 to 15 minutes for CONUSEvery 5 to 15 minutes for CONUS Super Rapid Scan OperationsSuper Rapid Scan Operations

– Every minute for small regionEvery minute for small region– Example: Example: Hurricane Frances

Common ChannelsCommon Channels

VisibleVisible– 0.65 0.65 μμm (red)m (red)

Infrared (IR)Infrared (IR)– 10.7 10.7 μμmm

Water VaporWater Vapor– 6.7 6.7 μμmm

Shortwave IRShortwave IR– 3.9 3.9 μμmm

Visible ChannelVisible Channel

Measures amount of sunlight reflectedMeasures amount of sunlight reflected– Approximates Earth’s albedoApproximates Earth’s albedo

CloudsClouds– Thick: High albedo Thick: High albedo White White– Thin: Moderate albedo Thin: Moderate albedo Light or medium gray Light or medium gray

Ocean: Low albedo Ocean: Low albedo Black Black Land: Variable albedo Land: Variable albedo Shades of gray Shades of gray

Sun Angle EffectsSun Angle Effects

Brightness varies by time of dayBrightness varies by time of day ““Terminator”: sunrise/sunset lineTerminator”: sunrise/sunset line Cloud shadowsCloud shadows

– Bumpy cloud top Bumpy cloud top lumpy depiction lumpy depiction– Flat cloud top Flat cloud top smooth depiction smooth depiction

SunglintSunglint– Brighter Brighter smoother sea smoother sea

Sun Angle EffectsSun Angle Effects

Brightness varies by time of dayBrightness varies by time of day ““Terminator”: sunrise/sunset lineTerminator”: sunrise/sunset line Cloud shadowsCloud shadows

– Bumpy cloud top Bumpy cloud top lumpy depiction lumpy depiction– Flat cloud top Flat cloud top smooth depiction smooth depiction

SunglintSunglint– Brighter Brighter smoother sea smoother sea

Infrared ChannelInfrared Channel

Amount of radiation received by satellite Amount of radiation received by satellite with with λλ=10.7 =10.7 μμmm

Combination of surface and cloud-top Combination of surface and cloud-top temperaturestemperatures

For monochrome images, colder For monochrome images, colder temperatures are brightertemperatures are brighter– Why?Why?

Snow vs low clouds vs landSnow vs low clouds vs land

IR EnhancementIR Enhancement

Geographic FeaturesGeographic Features

Background for the weather featuresBackground for the weather features CoastsCoasts

– Vis: Sudden change from dark (ocean) to light Vis: Sudden change from dark (ocean) to light (land)(land)

– IR: At night, land is often colder (brighter) than IR: At night, land is often colder (brighter) than water. Vice versa during daytime.water. Vice versa during daytime.

LakesLakes– Vis: Shows ice-cover (bright)Vis: Shows ice-cover (bright)

Another Example

Land typeLand type– Wooded Wooded Darker on Vis Darker on Vis– Sandy; little vegetation Sandy; little vegetation Brighter on Vis Brighter on Vis

Heat islandsHeat islands– Dark spots in IR at nightDark spots in IR at night

SnowSnow– Vis: Distinguishable from clouds in animationsVis: Distinguishable from clouds in animations– Vis: Brighter in treeless areasVis: Brighter in treeless areas

Cloud PatternsCloud Patterns

Cloud shieldCloud shield– Broad pattern with similar width in any directionBroad pattern with similar width in any direction

Cloud bandCloud band– Continuous formation with a distinct long axisContinuous formation with a distinct long axis

Cloud lineCloud line– Narrow cloud band (less than 60 n mi wide)Narrow cloud band (less than 60 n mi wide)

Cloud streetCloud street– Narrow cloud band with distinct elementsNarrow cloud band with distinct elements– Often come closely packed in parallelOften come closely packed in parallel

Cloud elementCloud element– Smallest resolvable cloud in imagerySmallest resolvable cloud in imagery

Comma cloudComma cloud– Spiraling cloud with at least one band, often shaped like a commaSpiraling cloud with at least one band, often shaped like a comma

Cloud StreetsCloud Streets

Cloud IdentificationCloud Identification

Compare visible and infrared imagesCompare visible and infrared images BrightnessBrightness

– Height and thicknessHeight and thickness TextureTexture

– Visible only; shadowsVisible only; shadows PatternPattern Edge definitionEdge definition SizeSize ShapeShape

Identifying Stratiform CloudsIdentifying Stratiform Clouds

StratusStratus– Smooth, flat tops; low altitudeSmooth, flat tops; low altitude– IR: Difficult to seeIR: Difficult to see– Vis: Often quite brightVis: Often quite bright

AltostratusAltostratus FogFog

– Difficult to distinguish from stratus using Vis and IRDifficult to distinguish from stratus using Vis and IR– Motionless; evaporates from outside inMotionless; evaporates from outside in– Valley fogValley fog

Identifying Stratiform CloudsIdentifying Stratiform Clouds

StratusStratus– Smooth, flat tops; low altitudeSmooth, flat tops; low altitude– IR: Difficult to seeIR: Difficult to see– Vis: Often quite brightVis: Often quite bright

AltostratusAltostratus FogFog

– Difficult to distinguish from stratus using Vis and IRDifficult to distinguish from stratus using Vis and IR– Motionless; evaporates from outside inMotionless; evaporates from outside in– Valley fogValley fog

Identifying Cumuliform CloudsIdentifying Cumuliform Clouds

CumulusCumulus– Vis: Medium bright; lumpyVis: Medium bright; lumpy– IR: Dark to medium gray; hard to see individual IR: Dark to medium gray; hard to see individual

elementselements

StratocumulusStratocumulus– Vis: Bright; often cellularVis: Bright; often cellular– IR: Dark; can be hard to detectIR: Dark; can be hard to detect

elementselements StratocumulusStratocumulus

– Vis: Bright; often cellularVis: Bright; often cellular– IR: Dark; can be hard to detectIR: Dark; can be hard to detect

CumulonimbusCumulonimbus– Very bright in both Vis and IRVery bright in both Vis and IR

Identifying Cirriform CloudsIdentifying Cirriform Clouds

CirrusCirrus– Vis: Dark/medium gray; wispy; thinVis: Dark/medium gray; wispy; thin– IR: Light gray; not as fibrousIR: Light gray; not as fibrous

CirrostratusCirrostratus– Vis: Smooth; light gray; thickerVis: Smooth; light gray; thicker– IR: Light gray to whiteIR: Light gray to white

CirrocumulusCirrocumulus

CirrocumulusCirrocumulus Anvil CirrusAnvil Cirrus

Image Interpretation for Weather Analysis

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