What causes the summer fog in California?

[seriously disabled]

I've never been to California but based on what I've seen on BBC's Natural History Unit television series called Planet Earth, coastal California is home to the largest trees in the world, called douglas firs and giant redwoods.

 

But the funny thing is that these giant trees in coastal California are only there because of the heavy summer fog and heavy winter rains. There is no rain during the summer months in California so even if the winter rains fail these kind of trees can extract enough moisture from the fog.

 

So my question is: What actually causes the heavy summer fog in coastal California which allows for the growth of such big trees as opposed to other coastal areas (like coastal Portugal or coastal France for example) which do not support such trees like in coastal California?

Edited July 2, 2013 by seriously disabled

[Phi for All]

I don't know why other similar coastal regions are different. Typically, cooler air from offshore mixes with the warmer air inland, which condenses to form fog. Southern California has the Santa Ynez mountains that trap the fog to make it linger, so maybe it's all about the geography.

 

I remember hearing that the inland fogs are different from the "marine layer" that forms over the water when warm winds from inland get trapped over the cooler offshore winds. That can also travel inland, but it forms over the water first.

[arc]

It is caused by several factors, one being the ocean current called the California current that runs east to British Columbia where it then turns south and continues along the coast down to California. This is a cold current to begin with but is lowered additionally when the north easterly winds produce up-welling of cold deep waters along the California coast.

 

Another factor is that warm air holds more water molecules than cold air, so as the summer progresses the warming atmosphere incrementally holds more moisture in its expanding gasses. When these two thermal content bodies meet along the coast the cold waters of the current cause the warm air to cool quickly. As the air molecules thermally contract the water molecules are forced out of the atmosphere, forming the famous California fog. arc