Hi,
I have a question regarding the characteristic of cloud type and visibility.
The question is: which are characteristics of a cold air mass moving over a warm surface?
a. cumuliform clouds turbulence and poor visibility
b. cumuliform clouds turbulence and good visibility
c. stratiform clouds smooth air and poor visibility
d. stratiform clouds turbulence air and good visibility
I think the correct answer is C because cold is stable and it will subside underneath the warm air forming stratus cloud, and since the air is stable the visibility will be poor.
Am I on the right path here?
Cheers

If a cold air mass moves across a warm surface, the temp difference between the bottom layer of the air mass and the top of the air mass is greater. This is because air is a poor conductor of heat, so only the bottom layers of the cool air mass in contact with the warm ground will be heated, leaving the "higher" layers to still be cold.

As a result, the lower parts of the air mass now becomes warmer than the top layers.
As we know, air warmer than the environment will rise due to its greater bouyancy i.e. convection. Convection produces cumuliform clouds. So i would be inclined to choose B from your options. Obviously there is turbulence associated with the convection and visibility should also be better as the convection takes the particles with it.

A cold air mass moving over warmer grounds is typically known as Latitudinal Heating, as cooler polar air moves northwards towards the equator and becomes warmer through conduction from the ground/sea.


This is all greatly explained in Bob's Met Book

Thanks a lot for your explanation. I totally understand it now. I am actually reading the Aviation Theory Center Met book which does not say anything about latitudinal heating at all. If the warm air mass moving over a cold surface, the warm air mass will be cooled from below and sink which will form stratus cloud, smooth air, and poor visibility?

As a warm air mass moves over a cool surface, such as that when a warm front moves in to replace a cold air mass, the air mass will be cooled from below, effectively reducing the temp difference between the bottom and top layers of the air mass - making it more stable than the previous case of the cold air mass moving over the warm surface.

Obviously at the air mass fronts there will be greater weather, but generally once the warm front has passed, the warmer air behind gets cooled as it moves over the cooler ground once occupied by the cooler air that it replaced.

As for the exact cloud type that will form, i am unsure, but Bob explained in his book that the weather after the passage of the warm front is generally quite good.

But i would hazard a guess that if the air mass become more stable, then any cloud that would form would more likely be stratus type cloud.