# Presentation: 558739

## Using Satellite Data to Improve Flight Safety and Aviation Weather

- Gary Ellrod (NOAA/NESDIS)
- Camp Springs, Maryland

## Outline	

- Weather Impacts on Aviation
- Aviation Weather Providers
- Review of NOAA Satellites
- Satellite Detection of Aviation Hazards
- Low ceilings/visibility
- Aircraft icing
- Jet streams
- Turbulence & mountain waves
- Thunderstorm hazards (winds, lightning)
- Aerosols (volcanic ash / smoke / haze)

## Weather as a Factor in Aviation

- $6B annual socio-economic impact (ATA)
- 40% due to fog and low clouds
- Accident costs (MCR Federal)
- Ceiling & visibilities account for 50% of $690M
- Weather-related accident causes (GAO)
- Airliners – turbulence
- General aviation – winds & wind shear
- Contingency fuel loads based on forecasts
- Average cost: $2.25M daily

## Aviation Weather Providers

- Pre-flight
- NWS forecasts
- Tailored forecasts
- Airline dispatchers
- Commercial providers
- Flight Service Stations (FAA)
- Inflight
- NWS Aviation Weather Center (SIGMETs)
- Center Weather Service Units (at ARTCC’s)

## NOAA Satellites - Review

- Geostationary (GOES)*
- Visible (1 km)
- 4 Infrared (4 km)
- Shortwave (3.9 m)
- Water vapor (6.7m)
- Window IR (11 m)
- Split window (12 m)

- Polar-orbiting (NOAA)
- Visible (1 km)
- 2 Near-IR (1.1 & 1.6 m)
- 3 Infrared
- Shortwave (3.7 m)
- Window IR (11 m)
- Split window (12 m)

- *  Preferred by aviation users

## Low Ceilings / Visibilities

- Fog/stratus caused by:
- Radiational cooling
- Saturation by rainfall
- Flow of moist air over cold surface (snow cover, lake)
- Upslope flow
- Not all fog detectable via satellite

## Daytime: Fog in Visible Satellite Imagery

**Notes:**
Fog is easily identified in visible satellite images due to its smooth texture and relatively bright reflectance.  It is also constrained by surrounding terrain.  Higher clouds have rougher texture, and shadows.

## Night:  Two-Band Fog Product vs IR Image

**Notes:**
Single IR channel images do not provide sufficient contrast to delineate fog, so we must use the difference between the shortwave (3.9 um) and longwave window (10.7 um) channels.

## http://orbit-net.nesdis.noaa.gov/arad/fpdt/fog.html

**Notes:**
This animation of the GOES two-channel difference imagery shows stratus and fog developing and moving inland from the Gulf of Mexico.

## Fog Detection in Remote Regions (Alaska)

- GOES-10
- Imager

- NOAA-16
- AVHRR

**Notes:**
At northern latitudes, GOES resolution degrades to 8-10 km resulting in poor depiction of cloud coverage compared to the 1 km resolution of NOAA Advanced Very High Resolution Radiometer (AVHRR).

## Slide 11

**Notes:**
An estimate of fog depth can be obtained from the amount of temperature difference between the 11um and 3.9 um IR channels.  Thicker fog areas tend to clear slower than shallow fog.

## http://orbit-net.nesdis.noaa.gov/arad/fpdt/fog.html

**Notes:**
The experimental product at right highlights areas where cloud bases are likely to be less than 1000 ft as red, with higher cloud bases as green.  Cirrus is black and blue.  The information is determined from the difference between the GOES cloud top temperature and the surface temperature.

##         Resolution vs Fog Detection

**Notes:**
The resolution of NOAA AVHRR allows excellent detection of valley fog in the Ohio River region of OH, KY & WV.  GOES IR resolution will improve to about 2 km by the year 2013.

## Slide 14

**Notes:**
The daytime reflectance of stratus clouds and fog at 3.9 um wavelength allows easy detection over snow cover.

## Fog Clearing Case – 14 June 2001 / 6:45 AM – 2:15 PM

**Notes:**
Animation of GOES visible showing clearing of fog in Middle Atlantic States and New England.  Sea fog and thicker inland fog persists the longest.

## Aircraft Icing

**Notes:**
Severe icing on the wing of a research aircraft.  Icing causes increased drag and loss of lift, and is especially dangerous for general aviation or commuter class aircraft

## Factors Conducive to Aircraft Icing

- Temperature (0 to -20C)
- Liquid Phase (supercooled clouds)
- Drizzle-size cloud droplets
- High Liquid Water Content
- Weak vertical motion
- Embedded convection
- Large areal extent

## GOES Icing Risk Product	

- Multiple threshold technique (Vis + 3 IR)
- Product available hourly day and night
- Strengths
- Good detection (~70%), low false alarm rate
- Good spatial, temporal coverage
- Weaknesses
- Obscuration by high clouds
- No information on heavy icing

## Slide 19

**Notes:**
Severe icing caused the crash of a commuter aircraft near Chicago on 31 October 1994.  The GOES icing product indicates icing was likely in this area.

## Turbulence Mechanisms 

- Wind shear along jet and upper fronts
- Flow over obstacles
- Mountains
- Thunderstorms
- Rough terrain
- Convection (thunderstorms, dry thermals)
- Wake turbulence from other aircraft

## Slide 21

**Notes:**
Well-defined transverse cloud bands are a good indicator of moderate to severe turbulence along the jet stream.

## Slide 22

**Notes:**
Closeup of cloud bands.

## Extreme Turbulence Scenarios

- Environmental conditions:
- Strong jet intersects:
- Cold front with:
- Low top convection
- Extreme turbulence possible over and downwind from convection

**Notes:**
Severe to extreme turbulence can occur downwind from thunderstorms in the presence of strong winds aloft.

## Slide 24

**Notes:**
Water vapor channel images (6.7 um) can detect mountain wave patterns not seen in visible or infrared.  These waves in western North Carolina were associated with severe low level turbulence below 10 thousand feet.

## Slide 25

**Notes:**
The longer the wavelength (distance between crests), the more likely there will be severe turbulence with mountain wave clouds.

## Satellite-Derived Motion Fields:	Geostationary Visible, IR, WV Channels

**Imagery types**
- Water vapor  (6.7um)
- Window IR  (11um)
- Visible  (0.65um)
- Frequency
- 30 min x 3
- Coverage
- Global
- Automatic production & quality control

**Notes:**
Show viewgraph of weighting functions

## GOES Water Vapor / IR  Winds

- http://orbit-net.nesdis.noaa.gov/arad/fpdt/winds.html

**Notes:**
Strong winds detected by GOES cloud motion in the North Pacific between Hawaii and the U. S. mainland.  Turbulence was reported in the banded cloud regions due to the decelerating flow.

## Thunderstorm Hazards

- “Microburst”

**Notes:**
The microburst/downburst can lead to sudden changes in headwinds/tailwinds as an aircraft lands or takes off.

## Microburst/Downburst Detection with GOES

**Arc – shaped gust fronts**
**Warming in anvil cloud top**
**Rapid storm motion**
**Indices from GOES Sounder**

## “Bow Echo” with Strong IR Gradients (WV)9 August 2000

- GOES-8 Infrared

- GOES-8 Visible

**Notes:**
Damaging winds occurred over much of Ohio and West Virginia along the leading edge of this storm system.  There were rapid horizontal changes in IR cloud top temperature (gradients) along the front portion of the storm.

## Maximum Thunderstorm Gust Potential

- GOES Sounder Profiles – 3 Aug 2002

**Notes:**
The Wind Index is calculated using temperature and moisture profiles from the GOES Sounder, a separate 19 channel instrument.  It shows maximum possible wind gusts if thunderstorms occur.

## Forecasting Thunderstorm Formation

**Notes:**
Forecasters use satellite imagery to anticipate future thunderstorm development.  Outflow boundaries can trigger new storms when they intersect regions of instability, such as in northeast Mississippi.

## Thunderstorm Formation – 20 July 2000, 2:15 - 5:15 PM

**Notes:**
Four hour animation of GOES visible imagery showing development of storms along boundaries.

## The Collaborative Convective Forecast

**Notes:**
Collaborative Convective Forecast is updated every two hours during thunderstorm season.  Blue boundaries show extent of Air Route Traffic Control Center responsibility.

## Lightning from Space NASA Lightning Imaging Sensor (LIS)

- Provides _total flash rates_, land & sea, day and night
- Possible applications:
*Oceanic advisories*
*Severe storm forecasts*
- Could be flown on future GOES

**Supercell**
**Storm**

**Notes:**
NASA LIS instrument detects total cloud lightning from space, not just cloud to ground.  Useful for oceanic thunderstorm advisories, severe storm prediction over land.  Currently only on TRMM satellite.

## Volcanic Hazards

**Notes:**
Many hazards associated with volcanic eruptions.  Ash cloud is most dangerous to aircraft.  (Credit: USGS)

## Hazards of Volcanic Ash

- Reduced jet engine performance, possible stalls (KLM Flight 867 fell >2 miles in Alaska!)
- Abrasion, pitting of leading edges
- Electrical discharges (St. Elmo’s 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

## Slide 38

## Eruption of Mt. Clevelandin Alaska on March 19, 2001

- Popocatepetl, Mexico
- December 19, 2000

## Mt. St. Helens Eruption – GOES Visible

**Notes:**
GOES-3 visible animation showing eruption of Mt. St. Helens in 1980.  Shock wave shown by concentric ring.  Ash has darker appearance than other clouds.

## Volcanic Ash Advisory Centers (VAACs) Established by ICAO (1997)

## Slide 42

**Notes:**
Composite of GOES “two-band split window”  difference images over a two day period for Cleveland Volcano eruption.  Major air routes shown by white lines.  (Credit:  USGS)

## Smoke as an Aviation Hazard

## Haze Detection 

**Notes:**
Midday GOES visible image compared with MODIS true color showing haze in the North Atlantic.  Images in the blue portion of visible spectrum show more scattering by haze.  GOES image was at 18Z, MODIS image at 15Z.  (Credit: Fred Mosher, NWS Aviation Weather Center)

Look at the region off the coast of the upper-Atlantic states. Note that the GOES visible sensor was designed so as to minimize its ability to sense haze. (Of course 18Z is the worse time (due to view angles) for GOES to observe this.)

## Conclusions

- Weather satellites play an important role in supporting aviation forecasts & warnings
- Future satellites will have even greater capabilities
- This presentation available at:
- ftp://orbit-net.nesdis.noaa.gov/pub/arad/fpdt1/ncsu/

## Satellite Data Help With Situational Awareness

- But can’t help in every situation!

## Internet Resources

- March 14, 2003

**Internet Resources**

- This presentation available at:
- ftp://orbit-net.nesdis.noaa.gov/pub/arad/fpdt1/ncsu/
- Aviation Weather Products and Forecasts
- http://orbit-net.nesdis.noaa.gov/arad/fpdt/   (NESDIS)
- http://aviationweather.gov/   (NWS)
- http://adds.aviationweather.noaa.gov/  (NWS/NCAR)
- Tutorials
- http://ww2010.atmos.uiuc.edu/(Gh)/guides/rs/sat/home.rxml  (University of Illinois)
- http://rst.gsfc.nasa.gov/start.html  (NASA Goddard)
- http://meted.ucar.edu/topics_aviation.php (COMET/UCAR)
- General information
- http://www.fly.faa.gov/flyFAA/index.html (Airport status)