Interdecadal Variability of the Seasonal-scale Persistence in the Tropical Mean Tropospheric Temperature

Abstract

After the climate shift of 1976/1977, associated with the interdecadal variability in the tropical Pacific Ocean, persistence barriers of El Nino/Southern Oscillation (ENSO) and tropical mean tropospheric temperature (TMTT) variations are detected in the boreal spring and autumn, respectively. Prior to the climate shift, however, the TMTT persistence barrier is almost non-existent, despite the prominence of the ENSO persistence barrier. Thus, the phase lag between ENSO and the TMTT variations is not fixed prior to the climate shift, while there is a fixed lag after the climate shift. This interdecadal variability is most remarkable for the TMTT anomalies in December. After the climate shift, the TMTT anomalies in December tend to persist 4 months later than prior to the climate shift. This is further examined in the comparison to the SST averaged over the strongly precipitating regions only, that is, the rainy-region SST. The SST variations in the rainy-region well correspond to those over the remote ocean basins, such as the Indian Ocean and the Western Pacific, that show a lagged response to the equatorial eastern Pacific SST anomalies. The TMTT anomalies are positively correlated with the rainy-region SST anomalies in both periods, prior to and after the climate shift. The interdecadal variability of the rainy-region SST persistence is similar to that of the TMTT persistence, although the variability is not as distinct as that of the TMTT.