“…The 1000-mb heights may then be determined from the surface pressures and temperatures with the aid of a nomogram like the one printed on the Skew-T diagram [5]. The "representative" sea-level temperatures, as computed by Arnason and Vuorela [6], may also be used as the temperature parameter. __ haps the one most frequently used indica-visibility being less than one mile if the spread is tor for forecasting fog by objective methods.…”