Fog over coastal region

[AirCanuck]

Folks,

This one is totally wracking my brain. I have thought about it from all the angles of 'types of fog' and how sea and land breezes work. I'm sure it's a very simple question. What am I missing here?

I'm quite comfortable in my fogs, methods of cooling etc as well as land and sea breeze so I'm not sure why I can't get it.

it is from a friend, a question he remembers from his A exams. Perhaps he is misremembering the wording but...

Fog is occurring over water near a coastline but not over land, why?
air mass is
a) warm, dry, land breeze
b) warm, wet, sea breeze
c) cold, wet, sea breeze
d) cold, dry, sea breeze

Could be C, a sea breeze goes from a cooler water to warmer land. If the air warms then it can hold more moisture, so perhaps it wouldn't form fog? I assume it would be 'wet' as it is coming from a region of fog.

I'm fairly sure sea breeze is part of it. Warm sea breeze I'll . since the water is cooler than land for a sea breeze.. definitely not sure though.

Thoughts?

[Schooner69A]

Saint John NB I'm thinking warm, moist air over cold Bay of Fundy.

"The most conspicuous weather condition produced by the Bay is fog. Thick, damp, murky fog that can chum and wisp across the shores to permeate the lands and forests for miles. The fog is formed when warm, moist air moves off the land and over the cold Fundy waters. As the air cools, it condenses to form millions of microscopic water droplets in the air. Indeed, Saint John, New Brunswick is officially Canada’s second-most foggy city (the dubious top honour going to St. John’s, Newfoundland)."

Flew out of there for fifteen years. Got very adept at landing in fog moving at 15-20 knots, 90 degrees to runway.

[pelmet]

Maybe....(a)

[AirCanuck]

Saint John NB I'm thinking warm, moist air over cold Bay of Fundy.

"The most conspicuous weather condition produced by the Bay is fog. Thick, damp, murky fog that can chum and wisp across the shores to permeate the lands and forests for miles. The fog is formed when warm, moist air moves off the land and over the cold Fundy waters. As the air cools, it condenses to form millions of microscopic water droplets in the air. Indeed, Saint John, New Brunswick is officially Canada’s second-most foggy city (the dubious top honour going to St. John’s, Newfoundland)."

Flew out of there for fifteen years. Got very adept at landing in fog moving at 15-20 knots, 90 degrees to runway.

yes, but there's no warm, wet, land breeze option!

[AirCanuck]

Maybe....(a)

if a, why is there fog at all?

[JasonE]

Option E? Warm wet land breeze

[co-joe]

It's A, you have to break it down into the criteria for causing fog. Moisture (air in contact with the water), warm air being cooled to it's saturation point, and something to "mix things up". Without that light breeze the fog can't happen. In this case the land breeze (aka Katabatic wind if the land is mountainous like in CYAZ)

There's a scenario where you have moist air over cool ground, but zero wind, so it's clear. The first aircraft takes off and mixes things up literally and fog forms. Condensation nuclei can be a factor in this example as well in the form of exhaust particles.

Arctic sea smoke is another such case, the wiki explanation is better than mine: https://en.wikipedia.org/wiki/Sea_smoke

[co-joe]

B is what happens on the east coast when the warm moist air over the gulf stream meets the cold land of Canada, cools, condenses, and it very much drifts inland.

the other 2 are diversions.

[yhz41]

On the exam the answer is warm moist offshore flow. Those are the exact words they use.

[AirCanuck]

On the exam the answer is warm moist offshore flow. Those are the exact words they use.

maybe my buddy misquoted the options, because definitely I can see THAT being a reason for this scenario. It would be advection fog then, plain and simple.

[pelmet]

Folks,

This one is totally wracking my brain. I have thought about it from all the angles of 'types of fog' and how sea and land breezes work. I'm sure it's a very simple question. What am I missing here?

I'm quite comfortable in my fogs, methods of cooling etc as well as land and sea breeze so I'm not sure why I can't get it.

it is from a friend, a question he remembers from his A exams. Perhaps he is misremembering the wording but...

Fog is occurring over water near a coastline but not over land, why?
air mass is
a) warm, dry, land breeze
b) warm, wet, sea breeze
c) cold, wet, sea breeze
d) cold, dry, sea breeze

Could be C, a sea breeze goes from a cooler water to warmer land. If the air warms then it can hold more moisture, so perhaps it wouldn't form fog? I assume it would be 'wet' as it is coming from a region of fog.

I'm fairly sure sea breeze is part of it. Warm sea breeze I'll . since the water is cooler than land for a sea breeze.. definitely not sure though.

Thoughts?

The only answer that seems logical to me is a).

Maybe....(a)

if a, why is there fog at all?

This question is a general one and may not apply to all scenarios. That is the problem. The person who asked the question may have only been familiar with certain scenarios or just accepted that one question can't cover it all and therefore wrote a question about one well known phenomenon. It is quite common for fog to be over the cool waters off the west coast. Start with that concept and then go on to the rest of the question.

Of course this is all general theory which is in general accurate but there are variables. The fog/low cloud forms over the cool water. It is not always there but it does frequently hang around offshore(especially in cooler waters such as off the west coast) just waiting for the chance to move back in over land. If it were a sea breeze(wind from the ocean), the fog would move in over the land to a certain extent(a little or a lot) depending on the overall conditions. In the question, it has not, so that alone eliminates three of the answers.

A land breeze, especially a warm, dry land breeze will dissipate the fog over land and to a certain distance over the water(push it away offshore), once again, the extent of this depending on all the variables of the local conditions. Of course, the further the warm, dry air gets from the shoreline, the more it is modified to eventually become cool, moist air resulting in it having less and less effect on the fog.

The relatively drier, warmer air over land may turn fog that rolled in from the ocean into a cloud layer with a base typically increasing in altitude further and further inland. Daytime heating lifts fog into a cloud base or raises the cloud base then it subsequently gets worse in the late day/evening/overnight hours as it cools down again.

I fly some aircraft in LA and SFO fairly regularly and this is the situation to think about for much of the year....will there be cloud/fog coming off the water and if so, how far inland will it go and will it burn off. Basically, the question is, when will it burn off during the day and when will it form again late in the day. In LA, it is more prevalent at certain times of the year and is known as June Gloom.....
https://en.wikipedia.org/wiki/June_Gloom

Looking at the LA basin, LAX being right at the shoreline itself is the worst but it is pretty much IFR flying out of there anyways . It does make for some interesting scenes out the window sometimes such as low cloud or fog covering the latter half the runway or good vis on touchdown followed by poor vis during the landing roll, CAT II approaches with low RVR but the runway lights in sight though a sort of tunnel in the clouds from previous aircraft, vis going up and down in short time periods, etc. I have mostly seen this on the early morning arrival/late evening operations.

But the clouds can make things such as VFR overflights in the two LAX overhead corridors something requiring planning. One requires ATC control while the other has no ATC control(seriously...right over LAX at 3500' and not talking to ATC). The clouds may be too low for the higher uncontrolled corridor but ATC is too busy to open the lower one. Or you may only have the upper corridor available with the lower one in the cloud.

Certain airports near the water like Torrance, Santa Monica and Hawthorne are on the front line for cloud consideration in the morning(for burnoff) or evening for clouding over upon return. Long Beach is better because it is further inland but has its issues. SFO bay has similar problems with Half Moon Bay frequently fogged in while my regular airport at Palo Alto is better but has its issues while inland is no problem. If it is IFR on return, I will just head down to San Jose.

Frequently, there is some sort of a balance between the warm air and the ocean air with the clouds/fog hovering nearby in view as one does their early afternoon walkaround which results in me making alternative plans of where to land if the field becomes marginal or IFR when I return. But....if there are warm, dry winds from the east(called Santa Ana winds in LA or Diablo winds in SFO) there will be no fog/cloud from the ocean to worry about and it will be warm. Mechanical turbulence may now be the thing to worry about and perhaps performance on short runways.