FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological...
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Transcript of FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological...
![Page 1: FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological Satellite Data Gary P. Ellrod NOAA/NESDIS, Camp Springs,](https://reader035.fdocuments.in/reader035/viewer/2022062422/56649eb15503460f94bb7df5/html5/thumbnails/1.jpg)
FRAM, Montreal, Que15 June 2005
Analysis of Hazardous Fog and Low Clouds Using
Meteorological Satellite Data
Gary P. EllrodNOAA/NESDIS, Camp Springs, MD
![Page 2: FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological Satellite Data Gary P. Ellrod NOAA/NESDIS, Camp Springs,](https://reader035.fdocuments.in/reader035/viewer/2022062422/56649eb15503460f94bb7df5/html5/thumbnails/2.jpg)
FRAM, Montreal, Que15 June 2005
Outline• Benefits/limitations of remote sensing• Detection of low clouds
– Night: Longwave – Shortwave IR– Day: Visible and Shortwave IR
• Determination of low ceilings• Fog depth estimates• Technology upgrades needed• Summary
![Page 3: FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological Satellite Data Gary P. Ellrod NOAA/NESDIS, Camp Springs,](https://reader035.fdocuments.in/reader035/viewer/2022062422/56649eb15503460f94bb7df5/html5/thumbnails/3.jpg)
FRAM, Montreal, Que15 June 2005
Nighttime GOES Infrared Fog
Detection Capabilities• Advantages:
– High frequency (15-30 min)– Good spatial coverage, resolution (4km)
• Limitations– Obscuration by higher clouds– Some fog too narrow, thin to detect– False signatures (sandy soils)– Is it fog or stratus?
![Page 4: FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological Satellite Data Gary P. Ellrod NOAA/NESDIS, Camp Springs,](https://reader035.fdocuments.in/reader035/viewer/2022062422/56649eb15503460f94bb7df5/html5/thumbnails/4.jpg)
FRAM, Montreal, Que15 June 2005
Remote Sensing of Fog
• Radiative studies (Hunt 1973)
• Experience with AVHRR in U.K. (Eyre et al 1984)
• GOES investigations– Gurka 1978, 1980– Ellrod 1991, 1994– Lee (NRL) et al 1997
• METEOSAT– Cermak, Bendix
Nighttime fog product from GOESSounder, June 1987
![Page 5: FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological Satellite Data Gary P. Ellrod NOAA/NESDIS, Camp Springs,](https://reader035.fdocuments.in/reader035/viewer/2022062422/56649eb15503460f94bb7df5/html5/thumbnails/5.jpg)
FRAM, Montreal, Que15 June 2005
Radiative Properties of Clouds
![Page 6: FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological Satellite Data Gary P. Ellrod NOAA/NESDIS, Camp Springs,](https://reader035.fdocuments.in/reader035/viewer/2022062422/56649eb15503460f94bb7df5/html5/thumbnails/6.jpg)
FRAM, Montreal, Que15 June 2005
Nighttime Fog Detection Using GOES Multi-spectral Image Data
![Page 7: FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological Satellite Data Gary P. Ellrod NOAA/NESDIS, Camp Springs,](https://reader035.fdocuments.in/reader035/viewer/2022062422/56649eb15503460f94bb7df5/html5/thumbnails/7.jpg)
FRAM, Montreal, Que15 June 2005
Features Observed in Nighttime Fog Images
Yellow = T4 – T2 > 2C
![Page 8: FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological Satellite Data Gary P. Ellrod NOAA/NESDIS, Camp Springs,](https://reader035.fdocuments.in/reader035/viewer/2022062422/56649eb15503460f94bb7df5/html5/thumbnails/8.jpg)
FRAM, Montreal, Que15 June 2005
Fog-related Highway AccidentWindsor, Ont., 3 Sep 1999 (Pagowski et al 2004)
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FRAM, Montreal, Que15 June 2005
Spread of Lake Fog – Time Lapse
![Page 10: FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological Satellite Data Gary P. Ellrod NOAA/NESDIS, Camp Springs,](https://reader035.fdocuments.in/reader035/viewer/2022062422/56649eb15503460f94bb7df5/html5/thumbnails/10.jpg)
FRAM, Montreal, Que15 June 2005
Daytime Fog Detection
• Visible images– Smooth texture, sharply defined borders,
moderate brightness
• 3.9 m IR (or 1.6m AVHRR)– Fog droplets are good reflectors at 3.9m
• Result is relatively warm Tb
– Snow is poor reflector at 3.9m– Result: Good contrast with snow or cold
ground
![Page 11: FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological Satellite Data Gary P. Ellrod NOAA/NESDIS, Camp Springs,](https://reader035.fdocuments.in/reader035/viewer/2022062422/56649eb15503460f94bb7df5/html5/thumbnails/11.jpg)
FRAM, Montreal, Que15 June 2005
Fog Clearing on 3 Sep 1999
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FRAM, Montreal, Que15 June 2005
Snow vs Fog Using Visible and Shortwave IR
MODIS m CH6MODIS Visible CH1
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FRAM, Montreal, Que15 June 2005
Snow vs Fog Using Visible and Shortwave IR
MODIS 3.9m CH6MODIS Visible CH1
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FRAM, Montreal, Que15 June 2005
RGB Depiction of Fog Over Snow-Covered Ground (MODIS)
Red = VisibleGreen= 1.6mBlue= 11m IR
Fog is yellowSnow is redBare surface is green
![Page 15: FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological Satellite Data Gary P. Ellrod NOAA/NESDIS, Camp Springs,](https://reader035.fdocuments.in/reader035/viewer/2022062422/56649eb15503460f94bb7df5/html5/thumbnails/15.jpg)
FRAM, Montreal, Que15 June 2005
Daytime Fog DiscriminationUsing Visible and IR Data
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FRAM, Montreal, Que15 June 2005
Estimation of Low Cloud Base Category from GOES
• When GOES IR cloud top is <4º K from surface temperature, low clouds (<1000 ft) likely
Brown 1987Ellrod 2003
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FRAM, Montreal, Que15 June 2005
Low Visibility Determination
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FRAM, Montreal, Que15 June 2005
GOES Low Cloud Base Product
Available for all regions of the U. S. and parts of southern Canada
at: http://www.orbit.nesdis.noaa.gov/smcd/opdb/fog.html
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Verification of LCB Product *Overall verification for low clouds detected but not
covered by cirrus clouds (N = 2381): • POD = 72 %• FAR = 11 %
Regional Statistics
* Completed in 2001-2002
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FRAM, Montreal, Que15 June 2005
San Francisco Fog Project (Terabeam Inc, 2001)GOES Ceiling Categories
Categories created to compare satellite data with ceilometer data.
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Brightness values plotted against ceilometer ceiling heights. Top-left and bottom-right quadrants (separated by dashed lines) show category 1 and 2 agreement, respectively. Top-right shows false alarms, bottom-left shows under-detection.
San Francisco Fog Project (Terabeam)
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FRAM, Montreal, Que15 June 2005
Estimation of Fog Depth
• Based on BTD for 3.9m and 10.7m IR
• Developed using cloud top heights from aircraft pilot reports (PIREPs)
Brightness count difference (GOES-7 Sounder) vsfog depth estimated from PIREPs
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FRAM, Montreal, Que15 June 2005
Fog Depth Verification
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FRAM, Montreal, Que15 June 2005
Fog Depth Product – 3 Sep 99
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FRAM, Montreal, Que15 June 2005
Fog Depth Estimation• Application of fog depth to forecast burnoff time
GOES Fog Depth, 1045 UTC
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FRAM, Montreal, Que15 June 2005
Results for 3 Sep 99 Case
GOES Fog Depth, 1045 UTC GOES visible, 1415 UTC
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FRAM, Montreal, Que15 June 2005
Visible Brightness DifferencesFog vs Cloud-Free to Estimate Clearing Time
• Requires visible (CH1) imagery >1.5 hours after sunrise (Gurka 1974)– Uses following data:
• Digital brightness count difference (fog vs clear region)
• Obtain incoming solar radiation
– Larger brightness difference = longer clearing time after sunrise
![Page 28: FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological Satellite Data Gary P. Ellrod NOAA/NESDIS, Camp Springs,](https://reader035.fdocuments.in/reader035/viewer/2022062422/56649eb15503460f94bb7df5/html5/thumbnails/28.jpg)
FRAM, Montreal, Que15 June 2005
Depth Threshold for GOES Detection270 m
~160 m
~100 m ?
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FRAM, Montreal, Que15 June 2005
Technology Upgrades
Needed for Better Fog Detection from GOES
![Page 30: FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological Satellite Data Gary P. Ellrod NOAA/NESDIS, Camp Springs,](https://reader035.fdocuments.in/reader035/viewer/2022062422/56649eb15503460f94bb7df5/html5/thumbnails/30.jpg)
FRAM, Montreal, Que15 June 2005
1. Optimal SWIR wavelengths
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FRAM, Montreal, Que15 June 2005
2. Improved ResolutionBased on AVHRR IR (3.7 m and 11.0 m)
![Page 32: FRAM, Montreal, Que 15 June 2005 Analysis of Hazardous Fog and Low Clouds Using Meteorological Satellite Data Gary P. Ellrod NOAA/NESDIS, Camp Springs,](https://reader035.fdocuments.in/reader035/viewer/2022062422/56649eb15503460f94bb7df5/html5/thumbnails/32.jpg)
FRAM, Montreal, Que15 June 2005
3. Improved Signal to Noise
MODIS Fog Depth GOES Fog Depth
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FRAM, Montreal, Que15 June 2005
Summary and Conclusions• GOES can effectively detect fog/low
clouds and show areal extent– Problems with small scale, shallow fog
• Able to estimate fog depth, ceilings– Good correlation with SFO visibility data
• GOES needs to be complemented by surface data to be most effective
• GOES-R will have major upgradeshttp://www.orbit.nesdis.noaa.gov/smcd/opdb/fog.html
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FRAM, Montreal, Que15 June 2005
References
• Hunt, G. E., 1973: Radiative properties of terrestrial clouds at visible and IR thermal window wavelengths. QJRMS, 99, 346-369.
• Eyre, J. R., J. L. Brownscombe, and R. J. Allam, 1984: Detection of fog at night using AVHRR imagery. Meteor. Mag., 113, 266-271.
• Ellrod, G. P., 1994: Advances in the detectio of fog at night using GOES multispectral IR imagery, Wea. Forecasting, 10, 606-619.
• Pagowski, M., I. Gultepe, and P. King, 2004: Analysis and modeling of an extremely dense fog event in Southern Ontario. J. Appl. Meteor., 43, 3-16.
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FRAM, Montreal, Que15 June 2005
References• Brown, R., 1987: Observations of the structure of a
deep fog. Meteorological Magazine, 116, 329-338.• Ellrod, G. P., 2002: Estimation of low cloud base
heights at night from satellite infrared and surface temperature data. Nat. Wea. Digest, 26, 39-44.
• Fischer, K. et al, 2003: Validation of GOES Imager experimental low cloud data products for terrestrial free space optical telecommunications. 12th AMS Conference on Satellite Meteor. and Oceanography, Long Beach, California, 9-13 Feb 2003.
• Gurka, J., 1974: Using satellite data for forecasting fog and stratus dissipation. Preprints, 5th Conf. on Weather Forecasting and Analysis, March 4-7, 1974, St. Louis, MO, AMS, Boston, 54-57.