Fog Monitor User Training

Fog Monitor User Training

http://www.nws.noaa.gov/mdl/fog_monitor/

Mike ChurmaJason Taylor

May 2008

Fog Monitor User TrainingFog Monitor User TrainingTraining Objectives

Introduction and BackgroundIntroduction and Background Reviewing Station Observation FunctionalityReviewing Station Observation Functionality Reviewing Fog Monitor’s presence in GuardianReviewing Fog Monitor’s presence in Guardian Explaining Satellite AlgorithmsExplaining Satellite Algorithms Describing Satellite Algorithm LimitationsDescribing Satellite Algorithm Limitations

The Fog Monitor is an AWIPS application that:

Monitors and displays station observation data, to alert forecasters of low visibility conditions.

Uses GOES satellite imagery to identify and highlight potential areas of fog.

Allows users to configure alert thresholds, algorithm settings, and the application’s monitoring area.

Fog Monitor User TrainingFog Monitor User TrainingBackground

Fog Monitor User Training Fog Monitor User Training Fog Monitor Display Features in D-2D

D-2D fog threat level image

Interactive Table

Station Plot

Guardian Icon

Fog Monitor User Training The Fog Monitor Zone/County Table Displays worst-case scenarios for counties and marine zones. Sorts data by column to reflect worst-case threat level. Displays colors (green-yellow-red) based on user-selectable thresholds Similar “buttonology” to SCAN and FFMP. Clicking on a zone/county name will reveal station information for that

area


“Configure Thresholds” button activates an interface with which to modify color

threshold s in the table.

Fog Monitor User Training Fog Monitor Station Table

Invoked by clicking on the county/zone ID in the zone table. D-2D map will zoom to the corresponding area.

Displays attributes for individual stations within the area. Sorts data by column Additional graphing and tabular features


• Visibility – in statute miles; rankable with an emphasis on lower values.

• Ceiling – for METARS only – in hundreds of feet, ranked with emphasis on lower values; “CLR” and “SKC” will be presented as necessary.

• Present Weather – not rankable; “NM” (not monitored) at the zone level, text info available at the station level.

• Wind Direction – rankable according to user-specified azimuths (“NM” if no angle is specified.)

• Wind Speed, Gust, Peak -- in knots; rankable with an emphasis on higher values.

• Temperature, Dewpoint, Dewpoint Depression– in degrees Fahrenheit; rankable with an emphasis on higher values.

• Relative Humidity – In percent; rankable with an emphasis on higher values.

• Algorithm – Green/Yellow/Red worst-case thresholds in the zone; available at the zone level, but not at station level.

Fog Monitor User Training Fog Monitor Display Features in D-2D

24-Hour trend graphs are available for most parameters. Color levels correspond to those in the table.


Wind direction trend is represented

by a hodograph


Observation History Table. The parameters in the table will change depending on whether the site is land or sea-based,

and also by how the user configures it.

Fog Monitor User Training Station Plots in Fog Monitor

Fog Monitor provides a conventional observation display, differentiated in color by station type.

• METARS• Fixed Buoys• Ships and Moving Buoys• Mesonets• MAROBS


Monitoring Area Configuration Tool (Zone Mode)• Found under the Fog Monitor selection in the Apps Launcher.• Add and remove counties/zones from the monitoring area.• Associate stations with zones/counties.• Set a time window to determine the duration of time to be monitored.• Set a distance from the nearest zone than a ship can be included.• Set the Fog Monitor algorithm status in Guardian.


Monitoring Area Configuration Tool (Station Mode)• Add and remove stations from the monitoring area.• Associate zones/counties to the stations.• Manually add a new station to the monitoring area


Monitoring Area Configuration tool -- Additional Features• Time Window• Ship Distance• Fog Monitor/Guardian toggle.

Fog Monitor User Training Fog Monitor contribution to Guardian

Fog Monitor’s fog icon in Guardian is colored according to worst-case threat level in the monitoring area.

Scrolling the cursor over the icon reveals worst case visibility conditions, present weather obscurations, and satellite algorithm worst-case conditions.

Users can control the visibility thresholds for this icon with a tool invoked from the Fog Monitor section of the Apps Launcher.


black= this location is not within the Monitored Area.gray= insufficient data available (usually due to clouds).green= there is probably no fog at this location.yellow= there may be fog at this location.red= there is probably fog at this location.

Fog Monitor User Training View Blocked by Opaque Higher Clouds

Opaque high clouds can block the Fog Monitor’s view.

Fog Monitor User Training Algorithm Scenarios

Nighttime Use 3.9 and 10.7 m infra-red

images to produce night time fog product.

Fog areas based on night time fog product threshold

• Filter out high clouds using 10.7 m IR data.• Apply a filter to eliminate small-sized areas as noise. (Optional)• Apply a filter to eliminate rough-edged detected area (Optional)

DaytimeDaytime Use the visible image to identify areas

of brightness consistent with fog. Apply smoothness filter to eliminate

noise. (optional) Apply a filter to eliminate snow/ice

(optional)

TwilightNo

Detection

Fog Monitor User Training Fog Monitor Image from Default Thresholds Settings

Fog Monitor User Training Customizing Your Monitor Thresholds

The Fog Monitor GUI enables offices to customize the range of:

IR brightness temperature differences - fog in fog product images.

Normalized visible brightness values - fog in visible images.

Fog Monitor User Training Decreasing Maximum Cloud Temperature

Decreasing the Maximum Cloud Temperature Threshold will increase the potential areas considers as fog.

Fog Monitor ThresholdsIncreasing Maximum Cloud Temperature

Increasing the Maximum Cloud Temperature Threshold will decrease the potential areas considered as fog.

Fog Monitor User Training Daytime Ice/Snow vs. Fog Threshold

Fog Monitor ThresholdsCool Fog vs. Warm Surface Threshold

Fog Monitor User Training Decreasing the Daytime Smoothness Threshold

Decreasing the Daytime Smoothness threshold will increase the bright areas of depicted fog.

Fog Monitor User Training Increasing the Daytime Smoothness Threshold

Increasing the Daytime Smoothness Threshold will help to filter out bright areas which may not be fog.

Fog Monitor User Training Adjacency Threshold

The Adjacency Threshold determines a minimum pixel size for the potential fog areas.

Fog Monitor User Training Increasing Adjacency Threshold

Increasing the Adjacency Threshold will increase the minimum size at which an area of fog will be flagged.

Fog Monitor User Training Increasing the Twilight Angle Threshold

Increasing the Twilight Angle Threshold during twilight hours will allow Fog Monitor to apply an “unknown” determination to more areas illuminated by low angle sunlight.

Fog Monitor User Training Decreasing the Twilight Angle Threshold

Decreasing the Twilight Angle Threshold during twilight hours will allow Fog Monitor to apply an “unknown” determination to less areas illuminated by low angle sunlight.

Fog Monitor User Training Default Twilight Angle Settings and Image

Fog Monitor User Training Increasing Fractional Dimension Threshold

Increasing the Fractional Dimension Threshold will allow for shapes with more jagged edges.

Fog Monitor User Training Decreasing Fractional Dimension Threshold

Decreasing the Fractional Dimension Threshold will allow Fog Monitor to consider brightness areas with relatively straight edges.

Fog Monitor User Training Algorithm & Display Limitations

• Low sun conditions/Twilight • Brightness Averaging at Feature Boundaries• Brightness averaging between clouds and surface• Brightness averaging of cloud shadows• Sun Glint

Fog Monitor User Training Low Sun Conditions/Twilight

Decreasing sunlight at lower angles affects Fog Monitor’s ability to properly normalize the visible satellite images.

Fog Monitor User Training Brightness Averaging at Feature Boundaries

Satellite’s View(with pixel boundaries superimposed)

fog

altostratus

snow

ground

fog

ground

Actual Situation(with pixel boundaries superimposed)

(A) (B) (C)

Fog Threat Image(with pixel boundaries superimposed)

(A) Boundary between fog and dark ground. Top row of green pixels is too dark to recognize as fog. The fog area looks smaller.

(B) Boundary between dark ground and snow. Column of red pixels is false fog. (C) Boundary between fog and bright higher cloud. Left column of green pixels is too bright to

recognize as fog. The fog area looks smaller.

Fog Monitor User Training Brightness averaging between clouds and surface

Small mid-level or translucent

high-level clouds

ground fog

ActualSituation

Averaged brightnessmatches fog.

Averaged brightnesstoo high for fog.

Satellite’sView

(A) (B)Small bright clouds or high translucent clouds makes the ground below look brighter to the satellite, causing the Fog Monitor to:

(A) incorrectly identify the ground below the cloud deck as fog.(B) fail to recognize the fog below the cloud deck.

Fog Monitor User Training Brightness Averaging of Cloud Shadows

Satellite’s View

Fog Threat Image

snow-covered ground

fogground

(A) (B)

The red area is the ground directly under the cloud. The medium gray area is the ground obscured from the satellite’s view by the cloud. The blue area is the cloud’s shadow.

The area outlined in red is the ground directly under the cloud. The medium gray area is the area that is obscured from the satellite’s view by cloud. The area outlined in blue is the cloud’s shadow.

lenticular

cumulus

Satellite’s View

Fog Threat Image

Sun glint can cause the Fog Monitor to wrongly identify an area as having fog.

Sun Glint

Sun glint as it might be

interpreted by the Fog Monitor

Fog Monitor User Training Limitations -- -- Sun Glint

Fog Monitor User Training Web Site


Users Guides Technical Briefs Troubleshooting Tips SAFESEAS/Fog Monitor listserve information

Fog Monitor User Training Training Summary

During this training the user has been:

Introduced to the Fog Monitor. Informed about the Fog Monitor surface observation functionality. Informed about the Fog Monitor information available in Guardian. Informed about the Fog Monitor’s satellite algorithms. Informed about the limitations of the Fog Monitor’s satellite

algorithms.

Fog Monitor User Training


Michael ChurmaJason Taylor

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Fog Monitor User Training