The inflence of the sea surface temperature on the interannual variability and potential predictability of the mean seasonal atmospheric conditions

A climate simulation over a period of 20 years performed with the atmospheric general circulation model GEM-CLIM and forced by observational sea surface temperature (SST) and sea-ice extent was examined in terms of the variability of the seasonal mean 500hPa height (Z500) in the Northern Hemisphere. The external variability of Z500 due to forcing by the SST was estimated by a separation from the total variability through an SVD analysis. The residual is defined as internally generated variability and is by construction without temporal correlation with the forced variability. The maximum skill expected in seasonal forecasting - the potential predictability - is assumed to be an increasing function of the ratio of the SST-linked variability to the total variability. In winter, this potential is found to be high in the tropics as well as over the region of the Pacific / North American (PNA) pattern. The mid-latitudes are influenced by SST anomalies in the tropical Pacific through teleconnections. Although using a different approach of analysis the results support findings of previous studies and even go beyond them with representing statistically significant potential predictability over East Asia in winter and spring and over the North Atlantic in spring. In addition, the potential predictability of the surface air temperature associated with the signal of Z500 is examined.