Seasonal Predictability of Summertime Asian Jet Deceleration near Japan in JMA/MRI-CPS2

抄録

Seasonal predictability of summertime Asian jet deceleration near Japan is examined using monthly mean data of hindcasts based on an operational seasonal prediction system of the Japan Meteorological Agency. Interannual variabilities of the Asian jet deceleration averaged during July–August are generally well predicted with moderate to high forecast skill starting from initial months from January to June. The seasonal predictability of the Asian jet deceleration in specific years is, by contrast, limited with large forecast errors. An inter-member regression analysis for the forecast errors of the Asian jet deceleration using ensembles shows that the forecast errors of the Asian jet are associated with those of the Asian jet deceleration near Japan. Furthermore, the forecast errors of El Niño Southern Oscillation (ENSO)-related excessive upper-tropospheric divergence near Southeast Asia can account for the errors of the northward shifted Asian jet. The above-mentioned results indicate that more accurate seasonal prediction of ENSO can further improve the seasonal prediction skill of the Asian jet deceleration and summer climate near Japan.