Aviation and Marine Applications

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Aviation and Marine Applications

• COMET Satellite Meteorology
• Gary Ellrod (NOAA/NESDIS)
• Camp Springs, Maryland

SatMet 99-2 Thursday, 29 April 1999
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Aviation/Marine Outline

• Aviation
• Stratus and fog
• Aircraft icing
• Jet streams / Clear Air Turbulence (CAT)
• Mountain waves
• Microbursts / gust fronts
• Marine
• Sea fog
• Oceanic convection
• Surface winds / cyclones

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Is it fog or Sc/Ac?

• Fog looks smoother
• Sc/Ac is mottled
• Fog is brighter (if depth equal)
• Fog has distinct edges
• Higher clouds may have shadows
• Fog is warmer in CH4 IR (10.7 mm)
• Fog moves/develops more slowly

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Resolution vs Fog Detection
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Meteorological Factors Conducive to Icing

• Temperature (0 to -20C)
• Liquid Phase (supercooled droplets)
• Large drop sizes (gt50 mm)
• High Liquid Water Content (gt0.25 gm-3)
• Weak vertical motion (1 mbar s-1)
• Embedded convection
• Large areal extent

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GOES Channels Useful in Icing Detection

• Visible (0.6 mm)
• Thickness, coverage, phase, convection
• IR2 (3.9 mm)
• Cloud phase, drop size
• IR4 (10.7 mm)
• Cloud top temperatures, thickness, coverage
• IR5 (12.0 mm)
• Thin cirrus detection

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GOES Icing Risk Product

• Multiple channel screening technique
• Product available hourly day and night
• Strengths
• High POD (70), low FAR
• Good spatial, temporal coverage
• Weaknesses
• Obscuration by high clouds
• No data 2 hr after sunrise / before sunset

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Turbulence-Generating Mechanisms

• Shear instability along jet and upper fronts
• Flow over obstacles
• Mountains
• Thunderstorms
• Convection (thunderstorms, dry thermals)
• Low level mechanical (strong winds over rough
  terrain)
• Wake turbulence from other aircraft

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Detection of Turbulence Using Satellite Imagery

• Clear Air Turbulence (CAT)
• Water vapor imagery (8 km)
• Subsidence warming with time along fronts
• Infrared (4 km)
• Transverse cirrus cloud bands
• Deformation zone cloud boundaries
• Visible (1 km)
• Billow wave clouds (K-H instability)
• Mountain waves
• Transverse cloud bands (IR/Vis)
• Lee-of-mountain cirrus with lee gap (IR/WV)

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Extreme Turbulence Scenario

• Environmental conditions
• Strong jet intersects
• Cold front with
• Low top convection
• Extreme turbulence possible downwind from
  convection

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Pilot Reports - 4 Feb 99/15-18Z
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Microburst/Downburst Detection with GOES

• Leading Edge (IR) Gradients (LEG) - mirrors
  WSR-88D reflectivity gradients
• Anvil warming to rear of storm (IR) - evidence of
  rear inflow jet
• Extensive clouds to rear of gust fronts
• Rapid storm motion
• GOES Sounder products
• WIND Index (WINDEX)
• Dry Microburst Potential (DMPI)
• Max. Theta-e Difference (Sfc-300mb)

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Hazards of Volcanic Ash

• Reduced engine performance, possible stalls
• Abrasion, pitting of leading edges
• Electrical discharges (St. Elmos fire)
• Ash difficult for pilots to see at night
• Volcanoes in remote areas (North Pacific) where
  few alternate airfields available
• Height/depth of ash difficult to determine

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Smoke as an Aviation Hazard
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Marine Applications

• Sea fog
• Oceanic convection
• Cyclones
• Strong wind zones
• Quantitative surface wind data

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Cloud Streets/ Open Cell Convection
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Gulf Stream Convection
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Strong Wind Zones in Oceanic Cyclones

• Indicators of Rapid Cyclogenesis
• Cloud pattern evolution (leaf to 360o comma in lt
  18 hours)
• Strong dry slot subsidence (warming in WV)
• Mesoscale Cloud Features
• Closely spaced cloud streets
• Open cell convection / arc lines
• Ring Cloud feature at storm center
• Hooking or sharply-tapered comma head

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Ring Cloud Thermal Structure
Nieman, et al., 1993
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Ocean Surface Winds from Satellite Data

• IR/Visible Cloud Drift (cloud base motion)
• Passive microwave (SSM/I, AMSU)
• 16v GHz, 22v GHz, 37vh GHz
• Valid at 20 m height upper limit 25 m/sec
• Scatterometer radar (ERS-2)
• Correlates backscattered energy to surface wind
  direction and speed
• Valid at 10 m height

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ERS-2 Scatterometer Swaths
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