A correlation between visual observations and instrumental records of cloudiness in Mexico

Abstract

This paper develops an empirical relationship between visual point cloudiness observations and mean monthly values of daily bright sunshine measured by Campbell-Stokes recorders in Mexico. We use 56 observation points over the period from 1951 to 1980. The statistical fit obtained from the total data base including all stations and all months is better than the fit for data grouped by month, climatological type or latitude. This model is useful for estimating the mean monthly bright sunshine in sites with visual cloudiness observations.