fog
Let an agent handle fog through its type, visibility and duration, which matter for transport safety and forecasting.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
written by Claude from model knowledge without web access - no source was read, every claim is a lead to verify
Researched by: Claude
Purpose and description
Let an agent handle fog through its type, visibility and duration, which matter for transport safety and forecasting.
A cloud of tiny water droplets or ice crystals suspended in the air at or near the ground, reducing horizontal visibility below 1 km.
What it is for: Describing and forecasting a weather condition that disrupts transport and affects health and ecosystems.
It can be forecast it, especially radiation fog overnight; observe it, as visibility in weather reports; plan around it, for aviation, shipping and roads; harvest water from it, with fog collectors in dry regions.
Distinguishing features
Defined by visibility below 1 km at the surface
A liquid aerosol, a kind of cloud at ground level
Classified by formation process: radiation, advection, upslope, evaporation
Distinct from smog and haze, which are pollution aerosols
What it looks like
A grey or white veil near the ground that hides distant objects; freezing fog leaves rime on surfaces.
Physical character
visibility: below 1000 m - dense fog below 50-200 m depending on the service
droplet diameter: 1-40 micrometres
liquid water content: 0.05-0.5 g/m3
How it is recognised
Visibility below 1 km near the ground
Mist is similar but thinner, with visibility of 1 km or more
Low cloud touching high ground is fog to people on the hill
Related models
is a kind of - water droplets suspended in air
is a kind of - cloud at the surface
is confused with - mist is thinner; haze is dry particles
disrupts - visibility limits for roads, aviation and shipping
In practice
Families and kinds
radiation fog
advection fog
upslope fog
freezing fog
ice fog
steam fog
Identifiers
WMO present weather code codes 40-49 in SYNOP fog reports
METAR code FG, BR, FZFG aviation weather reports
Standards and regulation
WMO Manual on Codes
ICAO Annex 3 meteorological service for aviation
Road traffic rules on fog lights and speed in fog
Failure modes and hazards
Multi-vehicle collisions in sudden fog
Flight delays and diversions
Ship collisions in reduced visibility
Icing from freezing fog
Also called
Where this came from
wikidata · CC0 1.0
Also registered as vr.tr.fog
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 4 bundles · 8 layers · 8 findings · 16 questions.
Formation How the fog formed.
Formation type predicts how long fog lasts and how it clears.
Type
Radiation, advection, upslope.
Fog type
The formation process.
- What type of fog is this? definition
- What conditions formed it? definition
Lifecycle
Onset and dissipation.
Timing
When it formed and when it will clear.
- When did it form, and when is it expected to clear? measurement
- What would make it persist? boundary
Observation Measuring visibility.
Visibility is the defining measurement.
Visibility
Measured visibility.
Visibility reading
The visibility value and instrument.
- What is the visibility, and how was it measured? measurement
- How patchy is the fog? measurement
Reports
METAR and SYNOP codes.
Coded report
The coded reports.
- How is this fog reported in METAR or SYNOP? provenance
- What does the report miss? boundary
Transport impact Effects on travel.
Fog is mainly a transport hazard.
Roads
Driving in fog.
Road guidance
Rules and advice for drivers.
- What rules apply to driving in fog here? provenance
- When should travel be avoided? action
Aviation and shipping
Visibility minima.
Operational minima
Minima and procedures.
- Which visibility minima apply at this airport or port? measurement
- What procedures apply below them? action
Other effects Health, ecosystems and water.
Fog also matters for health, ecosystems and water supply.
Health
Fog and pollution.
Health effects
Interaction with pollutants.
- Does this fog trap pollutants, forming smog? boundary
- Who should be advised? action
Fog water
Fog collection and ecosystems.
Water yield
Water gathered from fog.
- How much water can fog collectors yield here? measurement
- Which ecosystems depend on fog? definition
What the second pass must settle
- Should fog types be separate entries?
- How should visibility thresholds differ by service and jurisdiction?
- How should fog forecasts be expressed for agents advising drivers?