SAFESEAS WorkshopSAFESEAS Workshop

Wednesday, August 04

and

Thursday, August 05

2004

National Weather Service Headquarters

Silver Spring, Maryland

SAFESEAS OverviewSAFESEAS Overview

Key Terms Localization Customizing Your Monitoring Area Customizing Your Monitor Thresholds The SAFESEAS Monitor Customizing Your Display Thresholds The SAFESEAS Display

SAFESEAS OverviewSAFESEAS OverviewKey TermsKey Terms

Area of Responsibility

An office’s area of responsibility (AOR) consists of all the zones and counties for which it normally has the responsibility of issuing forecasts, watches, and warnings.

Monitoring Area

An office’s monitoring area (MA) consists of its AOR plus the AOR of each adjacent office having marine responsibilities. For offices along the borders with Canada and Mexico, the MA also includes all Canadian/Mexican area within 125 statute miles of the “centroid” of any zone/county in the MA. Finally, for moving platforms (ships and drifting buoys), the MA includes all area within 200 nautical miles of the “centroid” of any marine zone in the MA.

Nominal Hour

The nominal hour is the whole hour with which a report is associated. Reports associated with a nominal hour are those from 30 minutes before the hour to 29 minutes after the hour. As an example, all reports from 14:30 to 15:29 are considered 15Z nominal hour reports.

SAFESEAS OverviewSAFESEAS OverviewLocalizationLocalization

determines the default MA.* which zones and counties are included in the MA.* which fixed stations are in the MA.* in which zone/county is each fixed station located.

generates the default (factory setting) monitor thresholds. generates the default (factory setting) display thresholds. (starting with OB-4) merges previously done customizations with

the results of the above.

SAFESEAS OverviewSAFESEAS OverviewLocalization (continued)Localization (continued)

SAFESEAS localization uses US county “shape” files, marine zone “shape” files, (OB-5 and beyond, oconus site only) forecast zone “shape” files, the “metarStationInfo.txt” file, and the “maritimeStationInfo.txt” file.It is the responsibility of each office to make sure it has the currentversions of these files before localization is run.

SAFESEAS OverviewSAFESEAS OverviewLocalization (concluded)Localization (concluded)

(OB-3 and OB-4)In addition, for mesonet stations, SAFESEAS localization uses the following files in directory “/awips/fxa/ldad/data/”:* “LDADinfo.txt”.* one location information file for each external data source. these files have names

of the form “xxxStation.txt”, where “xxx” is a data_root value from “LDADinfo.txt”.

* one dataset information file for each external data source. these files have names ofthe form “yyy.desc”, where “yyy” is a data_type value from “LDADinfo.txt”.

It is the responsibility of each office to make sure these files are correct and up-to-date before localization is run. See the documentation in file “/awips/fxa/data/localization/scripts/SS_mesonetStationInfo.sh” for more information.

(OB-5 and beyond)Current OB-5 SAFESEAS localization code for mesonet, maritime, and METAR stations is the same as OB-4. But we are seriously considering using “*.spi” files instead of the “metarStationInfo.txt”, “maritimeStationInfo.txt”, “LDADinfo.txt”, “xxxStation.txt”, and “yyy.desc” files.

SAFESEAS OverviewSAFESEAS OverviewCustomizing Your Monitoring AreaCustomizing Your Monitoring Area

add and delete zones and counties. add and delete fixed stations. customize the association of fixed stations with zones and

counties, that is, which stations are monitored to determine each zone’s / county’s threat level.

SAFESEAS provides a GUI for customizing the MA. Specifically,the office can:

SAFESEAS OverviewSAFESEAS OverviewCustomizing Your Monitor ThresholdsCustomizing Your Monitor Thresholds

SAFESEAS provides a GUI for customizing the monitor thresholds. Thresholds are zone-specific, and so may be customized for each zone individually.

SAFESEAS OverviewSAFESEAS OverviewThe SAFESEAS MonitorThe SAFESEAS Monitor

The SAFESEAS monitor is a persistent background process, much like the SCAN and FFMP processors. Currently, it monitors METARs, C-MAN reports, buoy reports, ship reports, and mesonet reports. Only reports from within the MA are monitored. From these reports, wind speed, wind direction, wave height, and visibility are monitored. Starting with OB-4, swell height, swell direction, and swell period are also monitored.

Once every four minutes, it gets all new point observation reports. Based on the observation values and the monitor thresholds, an overall MA threat level is determined. The result is the threat level of the most severe observation from within the MA during the past two hours. The threat level is written to the file read by the SAFESEAS D-2D threat level button (the anchor). Finally, the anchor and the SAFESEAS display are signaled to update themselves.

SAFESEAS OverviewSAFESEAS OverviewCustomizing Your Display ThresholdsCustomizing Your Display Thresholds

SAFESEAS provides a GUI for customizing the display thresholds. Thresholds are zone-specific, and so may be customized for each zone individually.

SAFESEAS OverviewSAFESEAS OverviewThe SAFESEAS DisplayThe SAFESEAS Display

the SAFESEAS Plot.* consists of D-2D METAR, fixed buoy, moving buoy, and mesonet plots bundled together.* includes reports for stations within the MA only.* report plotted for the nominal hour is that which is closest to the top of the hour.

the Zone Table.* observation values and threat levels for each zone and county.* values shown are from the most recent reports for the nominal hour for each station

associated with the zone.* sorted by user-selected product/variable (default is zone ID).

the Station Table.* observation values and threat levels for each station within a zone.* values shown are from the most recent report for the nominal hour .* sorted by user-selected product/variable (default is station ID).

the Trends* (OB-3) shows all observation values for most recent three hours.* (OB-4 and beyond) shows all values for a variable for most recent 24 hours.

the Single-Station 24-Hour Observation Table.* new to OB-5.* shows observations from all reports for the most recent 24 hours.* user can configure which variables’ values are shown.

Fog Monitor OverviewFog Monitor Overview

Theory and MethodTheory and Method LocalizationLocalization Customizing Your Monitoring AreaCustomizing Your Monitoring Area Customizing Your Monitor ThresholdsCustomizing Your Monitor Thresholds The Fog MonitorThe Fog Monitor Customizing Your Display ThresholdsCustomizing Your Display Thresholds The Fog Monitor DisplayThe Fog Monitor Display

Supporting theorySupporting theory

Spectral feature of fog in multiple satellite channels

1. Scattering radiation feature (Daytime) (a) VIS Channel (b) 10.7 (3.9) μm Channel 2. Emitting radiation feature (Nighttime) (a) 3.9 μm Channel (b) 10.7 μm Channel

Kinematic feature of fog

Fog monitoring is a kind of object-oriented processing

All we have to know is how to describe a fog object: its properties

and its behaviors

properties

behaviors

Scattering/Reflecting Radiation(1) Scattering/Reflecting Radiation(1) [1][1] Particle/channel Fog stratus Other cloud Long IR Short IR Vis

size vs wavelength 1~10 μm

5~6μm

>10μm

10.7μm

3.9μm

0.4-0.7μm

According to Mie scattering theory:In the VIS channel, reflectivity mainly is related to the depth of the cloud/fog. In channel 3.9µm, fog/stratus has maximum scatter rate with its size equivalent to 3.9 µm.

Scat t er i ng/ r efl ect i ng r adi at i on r at i o compar si on

VI S Channel 3. 9 μ m I R 11 μ m I R

f og/ st r at us

cl oud

Comments:Comments:•Here two differences can be used to distinguish fog and cloud: 1) VIS difference; 2) 3.9 µm IR difference.•The fog region in satellite image should be smooth, edge-clear&regular. •Snow cover and sea ice are bad reflectors in channel 3.9 µm, while fog and stratus are good.

Scattering/Reflecting Radiation(2)Scattering/Reflecting Radiation(2) [12][12]

Data Normalization of the VIS satellite data

Normalization with fine tuningNormalization with fine tuningScattering/Reflecting Radiation(3)Scattering/Reflecting Radiation(3)

Scattering/Reflecting Radiation(4) Scattering/Reflecting Radiation(4) [2][13][14][2][13][14]

Assumed that all objects are black bodies:so TBemit3.9 = TB11 = Treal , and according to the Planck radiation law,

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TBk

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TBk

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hc

e

hc

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This is how reflective product of RAMSDIS ONLINE is generated . Because of the assumption of black body and TBemit3.9 = TB11 , it is an approximated reflective product and it does not take the angular correction into consideration So in our algorithms, it is not adopted for fog detection but for sea ice/snow cover exclusion.http://www.cira.colostate.edu/RAMM/Rmsdsol/main.htmlhttp://www.nrlmry.navy.mil/~turk/intro.htmlAllen, R.C., P.A. Durkee, and C.H. Wash, 1994: Snow-cloud discrimination with multispectral satellite images. J. Appl. Meteor

Emitting Radiation(1)Emitting Radiation(1)[2][2]

Channel VIS (0.4 - 0.7μm) 3.9 μm IR 10.7 μm IR

Radiation received by satellite

Scattering radiation1Emitting radiation0

Scattering radiationEmitting radiation( Mix together)

Scattering radiation0Emitting radiation1

0 means “can be ignored” 1 means “major”

Without the presence of sun light, in fog region, a positive value with[10.7 μm channel - 3.9 μm channel]. This difference is caused by the emissivity difference of fog between 10.7 um and 3.9 μm.

Above will be good only during the night time:Other water/ice clouds like AC/AS also look similar to Fog in fog product [7]. But in 10.7 μm channel , the brightness temperature of fog is higher than that of higher water/ice cloud (AC/AS). This can in a degree help distinguish them.

Emitting Radiation(2) Emitting Radiation(2) [2][3][2][3]

R(satellite) = R(ground) - R(absorbed) + R(cloud)

Different emissivities of different cloud typesAbsorptivity is related to emissivity and the depth of the cloud/fogPlanck radiation law

Thin cloud (night) : TB(10.7 μm ) - TB(3.9 μm ) < 0Thick cloud (night) : TB(10.7 μm ) - TB(3.9 μm ) ~ 0Fog (night) : TB(10.7 μm ) - TB(3.9 μm ) > 0ice cloud (night) : TB(10.7 μm ) - TB(3.9 μm ) < 0Water/ice cloud (night) : TB(10.7 μm ) - TB(3.9 μm ) > 0

Comment: So fog product should be checked to eliminate other higher water/ice cloud (AC/AS) by using TB derived from 10.7 μm channel.Sea Fog Discrimination Chart from Gary Elrod

SAFESEAS Fog Monitor SAFESEAS Fog Monitor

NighttimeNighttime use 3.9 and 10.7 um infra-red images to use 3.9 and 10.7 um infra-red images to

produce night time fog product.produce night time fog product. Apply feature extraction to identify fog Apply feature extraction to identify fog

area based on night time fog product area based on night time fog product thresholdthreshold

Filter out high cloud using channel 10.7 um Apply a filter to eliminate very tiny size area as noise. (optional) Apply a filter to eliminate edge-irregular detected area (Optional)

process only those parts of the images that cover the monitoring area.

DaytimeDaytime use the visible image use the visible image Based on thresholds, apply feature extraction Based on thresholds, apply feature extraction

algorithm to identify fog areas.algorithm to identify fog areas. apply smoothness filter to eliminate noise. (optional)apply smoothness filter to eliminate noise. (optional) Apply a filter to eliminate snow/ice (optional)Apply a filter to eliminate snow/ice (optional)Twilight

No Detection

SAFESEAS Fog Monitor SAFESEAS Fog Monitor

Smoothness Definition:

Smoothness = (1- deviation/mean) * 100%

n

ii

n

ii

xn

x

x

xxn

smoothness

1

1

2

1

%100)(

1

1

X denotes the gray value at the VIS pixeland n is the number of pixels

SAFESEAS Fog Monitor SAFESEAS Fog Monitor Fog Monitor D2D displayFog Monitor D2D display

SAFESEAS Fog Monitor SAFESEAS Fog Monitor Fog Monitor D2D Display (Twilight)Fog Monitor D2D Display (Twilight)

Limitations (1)Limitations (1)

When the sky is overcast with high level (thick) cloud, fog can not be seen through by When the sky is overcast with high level (thick) cloud, fog can not be seen through by

satellite.satellite.

During the transition of daytime and nighttime, neither VIS product nor fog product is During the transition of daytime and nighttime, neither VIS product nor fog product is

good. And twilight is exactly the time when fog mostly affects marine interests.good. And twilight is exactly the time when fog mostly affects marine interests.

Lack of observations in marine zones causes problem for verificationLack of observations in marine zones causes problem for verification

No effective approach to distinguish fog from stratus just using satellite dataNo effective approach to distinguish fog from stratus just using satellite data

Limitations (2)Limitations (2)Data normalizationData normalization

At very low solar elevation, in the clear air region , there will still be small brightness values. After normalization, they will be enhanced to look like fog areas and will be detected by the Fog Monitoring Processor.

Limitations (3)Limitations (3)Radiation from the ground goes through thin cirrus/high cloud ,which makes cirrus look like fog in VIS

Limitations (3) (continue) Limitations (3) (continue) [14][14]

Use fractal dimension to try to reduce the detection of the irregular areaThis is still not a good solution but supplied as an optional filter for user

FD = 2ln(P/4)/ln(A)P= perimeter A=

Area• Count the outside edges of the grid boxes as the perimeter• Amount of the grid boxes as the area.

Limitations (3) (continue)Limitations (3) (continue)

Before After

Application of Fractal Dimension to filter out irregular area

Limitations (4) Limitations (4)

Limitations (4) (continue)Limitations (4) (continue)

ReferencesReferences

[1] Liu Jian, Xu Jianmin, Fang Zongyi Analysis of the particle sizes at the top of cloud and fog with [1] Liu Jian, Xu Jianmin, Fang Zongyi Analysis of the particle sizes at the top of cloud and fog with NOAA/AVHRR data Quarterly Journal of MeteorologyNOAA/AVHRR data Quarterly Journal of Meteorology

[2] [2] http://www.cira.colostate.edu/ramm/visit/fog.htmlhttp://www.cira.colostate.edu/ramm/visit/fog.html fog product tutorial fog product tutorial [3] [3] http://http://meted.ucar.edu/topics_fog.phpmeted.ucar.edu/topics_fog.php Fog/stratus tutorials Fog/stratus tutorials [4] Chen Weimin, Satellite Meteorology (Chinese version) Beijing Meteorological publishing house[4] Chen Weimin, Satellite Meteorology (Chinese version) Beijing Meteorological publishing house [5] Ellrod G P. Advances in Detection and Analysis of Fog at night Using Advanced Very High [5] Ellrod G P. Advances in Detection and Analysis of Fog at night Using Advanced Very High

Resolution Radiometer(AVHRR) Imagery [J] Meteo. MagazineResolution Radiometer(AVHRR) Imagery [J] Meteo. Magazine [6] [6] http://http://meted.ucar.edu/topics_satellite.phpmeted.ucar.edu/topics_satellite.php satellite products on METED satellite products on METED [7] [7] http://meted.ucar.edu/satmet/goeschan/http://meted.ucar.edu/satmet/goeschan/ GOES channel selection on METED GOES channel selection on METED [8] [8] http://www.ssd.noaa.gov/http://www.ssd.noaa.gov/ satellite service division homepage satellite service division homepage [9] [9] http://aviationweather.gov/awc/aviation_weather_center.htmlhttp://aviationweather.gov/awc/aviation_weather_center.html Aviation Weather Center Aviation Weather Center [10] [10] http://www.cira.colostate.edu/http://www.cira.colostate.edu/ Cooperative Institute for Research in the Atmosphere, Colorado Cooperative Institute for Research in the Atmosphere, Colorado

State UniversityState University [11] [11] http://www.nrlmry.navy.mil/http://www.nrlmry.navy.mil/ Naval Research Laboratory Monterey Naval Research Laboratory Monterey [12] ALBERS S. 1992: Photometric correction of GOES visible satellite images. Preprints, Sixth conf. [12] ALBERS S. 1992: Photometric correction of GOES visible satellite images. Preprints, Sixth conf.

on Satellite Meteorology and Oceanography, Atlanta, GA, Amer. Meteor. Soc., 223-225. on Satellite Meteorology and Oceanography, Atlanta, GA, Amer. Meteor. Soc., 223-225. [13] Allen, R.C., P.A. Durkee, and C.H. Wash, 1994: Snow-cloud discrimination with multispectral [13] Allen, R.C., P.A. Durkee, and C.H. Wash, 1994: Snow-cloud discrimination with multispectral

satellite images. J. Appl. Meteor satellite images. J. Appl. Meteor [14] Olsen, E.R., R.D. Ramsey and D.S.Winn. 1993. A modified fractal dimension as a measure of [14] Olsen, E.R., R.D. Ramsey and D.S.Winn. 1993. A modified fractal dimension as a measure of

landscape diversity.Photogram. Eng. Remote Sens. 59: 1517-1520 landscape diversity.Photogram. Eng. Remote Sens. 59: 1517-1520 [15] [15] http://www.cira.colostate.edu/RAMM/Rmsdsol/main.htmlhttp://www.cira.colostate.edu/RAMM/Rmsdsol/main.html RAMSDIS ONLINE RAMSDIS ONLINE

Fog Monitor OverviewFog Monitor OverviewKey TermsKey Terms

Area of Responsibility

An office’s area of responsibility (AOR) will consist of all the zones and counties for which it normally has the responsibility of issuing forecasts, watches, and warnings.

Monitoring Area

An office’s monitoring area (MA) will consist of its AOR plus the AOR of each adjacent office.

Channel 2

Channel 2 refers to the 3.9 micrometer infra-red satellite image.

Channel 4

Channel 4 refers to the 10.7 micrometer infra-red satellite image.

Fog Product

The fog product is the image derived by subtracting 10.7 micrometer image brightness temperatures from 3.9 micrometer image brightness temperatures.

Fog Monitor OverviewFog Monitor OverviewLocalizationLocalization

will determine the default MA.

* which zones and counties are included in the MA.

* (OB-6) which fixed stations are in the MA.

* (OB-6) in which zone/county is each fixed station located.

For the alpha test, the default MA will be based on the same “shape” files used for OB-4 SAFESEAS. It is the responsibility of each office to make sure its systems have the current versions of these files before localization is run.

will generate the “dummy” fog threat image to display for incomplete image sets.

will generate the default (factory setting) monitor thresholds. (OB-6) will generate the default (factory setting) display

thresholds.

Fog Monitor OverviewFog Monitor OverviewCustomizing your Monitoring AreaCustomizing your Monitoring Area

The Fog Monitor will provide a GUI for customizing the MA. Specifically, the office will be able to:

• add and delete zones and counties.• (OB-6) add and delete fixed stations.• (OB-6) customize the association of fixed stations with zones

and counties, that is, which stations are monitored to determine each zone’s / county’s threat level.

Fog Monitor OverviewFog Monitor OverviewCustomizing Your Monitor ThresholdsCustomizing Your Monitor Thresholds

The Fog Monitor will provide a GUI that will enable offices to

customize the range of: normalized brightness values that should be considered fog in

visible images. temperature differences that should be considered fog in fog

product images.

Fog Monitor OverviewFog Monitor OverviewCustomizing Your Monitor Thresholds (continued)Customizing Your Monitor Thresholds (continued)

The customization GUI will also allow offices to enable/disable filters in thefog recognition algorithm: in channel 2 images, each pixel colder than a customizable threshold

temperature should be considered snow/ice. in channel 2 images, each pixel having a brightness temperature colder

than a customizable threshold temperature should be considered cloud. in channel 2 images, each pixel having a brightness temperature warmer

than a customizable threshold temperature should be considered ground or water surface.

in visible images, a group of contiguous pixels having a brightness variation greater than a customizable threshold cannot be considered fog.

in visible images, a group of contiguous pixels having fewer than a customizable number of pixels cannot be considered fog.

a pixel within a configurable number of degrees from the terminator should not be monitored.

Fog Monitor OverviewFog Monitor OverviewCustomizing Your Monitor Thresholds (concluded)Customizing Your Monitor Thresholds (concluded)

In OB-6, a GUI will also be provided that will enable offices to customize the thresholds used for monitoring point observations (METARs, C-MAN reports, ship reports, buoy reports, and mesonet reports) for fog. We will “negotiate” details for this tomorrow!

Fog Monitor OverviewFog Monitor OverviewThe Fog MonitorThe Fog Monitor

The fog monitor will be a persistent background process, much like the SAFESEAS, SCAN, and

FFMP processors. The alpha test version will monitor: visible imagery at those times and in those places that the sun is sufficiently above the horizon; the fog product at those times and in those places that the sun is sufficiently below the horizon.

In all cases, channel 2 images are used for certain kinds of filtering (unless the office has disabled

the filters).

The OB-6 fog monitor will also monitor point observations. The details of this will be “negotiated”

tomorrow.

The fog monitor will determine a fog threat level for each zone/county in the MA, and an overall

fog threat level for the entire MA. The threat level is the most severe of all the individual pixel

(OB-6: and point observation fog) threat levels for the past two hours.

The fog monitor generates a fog threat level image and a zone fog threat file for use by the Fog

Monitor display. Finally, the Fog Monitor threat level indicator and the Fog Monitor display are

signaled to update themselves.

Fog Monitor OverviewFog Monitor OverviewThe Fog Monitor DisplayThe Fog Monitor Display

the Fog Monitor fog threat level image:

** blackblack = this location is not within the MA.= this location is not within the MA.

* gray = insufficient data is available for determining

the fog threat level for this location.

* green = there probably is not fog at this location.

* yellow = there may be fog at this location.

* red = there probably is fog at this location.

(OB-6) the Fog Monitor station plot:

* only reports from within the MA are plotted.

* variables to be plotted will be “negotiated” tomorrow.

Fog Monitor OverviewFog Monitor OverviewThe Fog Monitor Display (concluded)The Fog Monitor Display (concluded)

the alpha test Fog Monitor zone fog threat table:

* two columns: zone ID and fog threat level (color).

* click column header to sort by that column.

the OB-6 Fog Monitor zone/station fog threat tables and trends:

* except for variables, same as SAFESEAS.

* variables to be included will be “negotiated” tomorrow.