Areas with missing data

Abstract

In the case of Spain, lack of radiometric stations other than Madrid precluded the use of the method just described for defining “satellite” stations. Instead, the coefficients a_m and b_m for each heliographic station in Spain were determined by the method of Dogniaux and Lemoine (29) who proposed a linear dependence of a_m and b_m on geographical latitude ϕ, corrected by a site-specific index for the atmospheric transparency. Similar procedures were adopted in certain other countries where the observational record was inadequate, for example Turkey.