O Cl««.r O H'i^KC«i(mj\ 



rrs 



0\/£R- 



76<7 



• 1^^ 



«?-!? *"^''"'- r-o^og 



in<t'icates Wi'ni Force. 



J ® l_ow 



® Haje ?tBS6ore mMillinietet-i 



Fig, 1. — Example of pressure distribution favourable to the occurrence of sea 

 fogs of advection type at the sea along the Kuril Islands and the Pacific 

 coasts of Hokkaido. 



radiation fogs on land, because the latter are also caused directly by 

 cooling of the air from below. But the observations do not show such 

 identity at all. 



Later Professor S. Petterssen has suggested the convection theory 

 on the formation of sea fogs of advection type along the west coast of 

 California. The theory is as follows : a stratus layer will be formed 

 under the inversion by vertical mixing or convection in the air under the 

 inversion, the base of the stratus layer coinciding with the condensation 

 level of the surface air. When the condensation level comes down to 

 the surface, or other fog-producing factors are present in the lower 

 portion of the layer, the stratus builds down to the surface and forms 

 a dense fog. 



The theory of Professor Petterssen might be much better than the 

 old theory to explain the nature of sea fogs, but the theory is still doubtful 

 on account of the following reason : sea fogs are often accompanied by 



70 



