Abstract
The optimum interpolation method, which allows ready estimates of the error of interpolation, is applied to a network of monthly mean surface air temperature at 370 stations to the north of 25°S, for 324 months from January 1951–December 1977. The temperature deviations from the 25-year mean at grid points on 30° longitude (45° longitude at 80°N only) and 10° latitude intersections are determined for each month. From a set of these grid-point values, time series of longitudinal distributions at 60 and 30°N, and of spatial means over 30° latitudinal zones 90–60°N, 60–30°N and 30–0°N are given. In addition 12- and 36-month running means of the Northern Hemisphere mean are presented, together with the 95% confidence limits for the error, which are estimated as less than 0.05 and 0.03°C, respectively. Some significant fluctuations are noticed.