THE ZONAL HARMONIC OF PENTAD MEAN 500 MB HEIGHT CONTOURS OVER THE NORTHERN HEMISPHERE AND THEIR PREDICTION

The power spectra of the zonal harmonic coefficients show that the quasiperiodic oscillations such as "Index Cycle",half-year rhythm and seasonal varialion are predominant.In terms of these quasi-periodic oscillations,a statistical forecast scheme has been designed,with which a set of eight successive pentad mean height forecast at 500 mb level over the Northern Hemisphere can be made.The results of sixty sets of forecasts for the period from 1976 throughout 1980 indicate that the mean forecast accuracy for the sign of deviations from the latitude average ρ=(n+-n-)/N is approximately 0.22,and for the sign of the sign of the anomalies from the climatic average gives ρ=0.08.