Visibility lrg

Grunt Productions 2008

VisibilityVisibility

A brief by Lance GrindleyA brief by Lance Grindley


VisibilityVisibilityRule 6Rule 6Safe SpeedSafe SpeedEvery vessel shall at all times proceed at a safe speed so that she can take Every vessel shall at all times proceed at a safe speed so that she can take

proper and effective action to avoid collision and be stopped within a proper and effective action to avoid collision and be stopped within a distance appropriate to the prevailing circumstances and conditions. distance appropriate to the prevailing circumstances and conditions.

In determining a safe speed the following factors shall be among those In determining a safe speed the following factors shall be among those taken into account:taken into account:

(a) By all vessels:(a) By all vessels:(i) The state of visibility;(i) The state of visibility;(ii) The traffic density including concentrations of fishing vessels or any (ii) The traffic density including concentrations of fishing vessels or any

other vessels;other vessels;(iii) The manageability of the vessel with special reference to stopping (iii) The manageability of the vessel with special reference to stopping

distance and turning ability in the prevailing conditions;distance and turning ability in the prevailing conditions;(iv) At night the presence of background light such as from shore lights or (iv) At night the presence of background light such as from shore lights or

from back scatter from her own lights;from back scatter from her own lights;(v) The state of wind, sea and current, and the proximity of navigational (v) The state of wind, sea and current, and the proximity of navigational

hazards;hazards;(vi) The draft in relation to the available depth of water.(vi) The draft in relation to the available depth of water.


-is a -is a cloudcloud in contact with the in contact with the ground.ground. -is a cloud (stratus) which has its -is a cloud (stratus) which has its cloud base on or close to ground, cloud base on or close to ground, and reduces visibility to less than and reduces visibility to less than 10001000

FogFog



MistMist

is a phenomenon of small droplets suspended is a phenomenon of small droplets suspended in in airair. It can occur as part of natural . It can occur as part of natural weatherweather or or volcanicvolcanic activity, and is common in cold air activity, and is common in cold air above warmer water, in above warmer water, in exhaledexhaled air in the cold, air in the cold, and in a steam room of a and in a steam room of a saunasauna. It can also be . It can also be created artificially with created artificially with aerosol canistersaerosol canisters if the if the humidity conditions are right. humidity conditions are right.


MistMist


HazeHaze

is caused when sunlight encounters tiny is caused when sunlight encounters tiny pollution pollution particles in the airparticles in the air. Some light is absorbed by the . Some light is absorbed by the particles. Other light is scattered before it reaches an particles. Other light is scattered before it reaches an observer. More pollutants in the air mean more observer. More pollutants in the air mean more absorption and scattering of light, which reduce the absorption and scattering of light, which reduce the clarity and color of what we see. Some types of clarity and color of what we see. Some types of particles, such as sulfates, scatter more light than particles, such as sulfates, scatter more light than others, particularly during humid conditions. others, particularly during humid conditions.



is a kind of is a kind of air pollutionair pollution; the word "smog" is a ; the word "smog" is a portmanteau of smoke and fog. Comes from portmanteau of smoke and fog. Comes from vehicular and industrial emissions that are vehicular and industrial emissions that are acted on in the atmosphere by sunlight to form acted on in the atmosphere by sunlight to form secondary pollutants that also combine with secondary pollutants that also combine with the primary emissions to form photochemical the primary emissions to form photochemical smog smog

SmogSmog


SmogSmog


Sea SmokeSea Smoke

Evaporation fog or steam fog which is formed Evaporation fog or steam fog which is formed when water vapor is added to air which is when water vapor is added to air which is much colder than the vapor's source; most much colder than the vapor's source; most commonly, when very cold air drifts across commonly, when very cold air drifts across relatively warm water. relatively warm water.

cold air moves over warmer water. cold air moves over warmer water.


Sea SmokeSea Smoke


Fog: Fog:

TypesTypes Radiation FogRadiation Fog Advection FogAdvection Fog Upslope FogUpslope Fog Steam FogSteam Fog


How they formHow they form

Radiation fogRadiation fog shallow, moist air near shallow, moist air near

surface surface clear/calm nights clear/calm nights although light winds will although light winds will

bring more air in contact bring more air in contact with ground with ground



Advection FogAdvection Fog

Common off the west coast of the U.S.

Cold current along coastlinewarm water further to the westwesterlies moving in from the warmer water to the colder water


Advection FogAdvection Fog


Technology

Visibility lrg