Global and diffuse radiation and surface meteorological measurements at Edmonton, Montreal, Port Hardy, Toronto and Winnipeg for the years 1977-1984 are analyzed to yield estimates of atmospheric precipitable water and turbidity. Three methods of estimating the precipitable water and two methods of estimating the turbidity are used and compared. Laboratory measurements of pyranometer response as a function of zenith angle: are used to correct the global radiation measurements. Circumsolar radiation is removed from the direct radiation obtained from the difference of measured global and diffuse radiation. The magnitude of this circumsolar correction is discussed in the light of recent measurements and calculations of the circumsolar ratio. Turbidity time series are presented, showing a clearly defined El Chichon eruption signature in 1983-1984. A comparison with earlier results is included.