13 



Other overcast conditions also tend to decrease in 

 February and March from those noted in January. In February, 

 21% of the mornings and 21% of the afternoons (6 days) are 

 overcast and the stratus layer is continuous through 24 hours 

 12% of the month (4 days). Broken clouds show a marked 

 decrease in occurrence in both months with none lasting 24 

 hours in February and only one recording in March. 



Because of the decrease in overcasts there is a great 

 increase in the number of clear days in the first two months 

 of the period. In February, the sky is clear all day 62% of 

 the time (21 days), and in March, 667o of the month is clear 

 for 24 hours. 



In April, the "summer sea fogs" begin to intrude the 

 southern California coast, although these low stratus layers 

 are more frequent in May, June, and August. The ! 8 sea fogs" 

 are actually low-lying stratus layers of varying thickness 

 and are called "high fogs" by the general public in the Los 

 Angeles Basin area. Usually the stratus dissipates or 

 "burns off" before noon, but there may be perioas during which 

 a continuous overcast persists for a week or ten days. Although 

 it is uncommon, the morning occurrence of stratus may be 

 remarkably regular. There have been summer months during which 

 an overcast occurred through most of the forenoon for 21 of 

 the 30 days. In 1948, from the first of June to the first of 

 September, only 18 of 93 mornings were clear. In July 1948, 

 19 consecutive mornings were foggy or cloudy, and from the 

 11th of August through the 4th of September, every morning 

 was overcast, a total of 25 consecutive days. The ceilings of 



