Effect of the Marine Layer in Lowering Sunshine in Southern California
One thing bothering me about May Gray and June Gloom morning cloudiness from the coastal marine layer was how to extend the names into July and August of this year. Google, of course, found the names No Sky July and Fogust. It also supplied “Summer Bummer” and referred to a seasonal affective disorder. It also supplied quantitative data on the amount of cooling caused.
The data are from Los Angeles, measured at USC, and besides temperatures measured mean monthly sunshine hours, and percent possible sunshine, averaged over a 16-year period, from 1961 to 1977. Coming from UCLA, USC is far inland. However, even UCLA is inland from beach towns along the coast. So, this is not 100% relevant to Laguna Beach. The data are from the Wikipedia article “June Gloom”.
The mean monthly sunshine hours for May and June were 276.2 and 275.8, compared to the July and August values of 364.1 and 349.5, respectively. The percent possible sunshine for May and June were 64% and 64%. For July and August, the percentages were 83% and 84% respectively. So, there is a reduction of 20% in the possible sunshine during May and June over July and August. But you can also focus on the reductions in total sunshine over all four months, since there are also marine layers in July and August.
The same NOAA table that the Wikipedia article used also contained data for San Diego, which is a little more beachy. For May and June, mean monthly sunshine hours were 250.5 and 242.4, compared to July and August at 304.7 and 295.0. The May and June values of mean monthly sunshine hours for San Diego are 11% lower than the values for Los Angeles at USC. The July and August values for San Diego are lower by 16% than the USC values.
Percent possible sunshine ranged from 70% to 78% during the other months of the year. This shows how exceptional the lows in May and June were, as well as the highs in July and August.
Any homeowner who keeps track of generated solar power can provide data comparing the sunshine for the four summer months in a specific location. We know that even the beach or downtown areas can be shaded, while the upper hills are sunny.
