Seasonal predictability of primary East Asian summer circulation patterns by three operational climate prediction models

Abstract

Seasonal predictability of the Primary East-Asian Summer Circulation Patterns (PEASCPs), including the Western Pacific Subtropical High (WPSH), South Asian High (SAH), anomalous Philippine Sea AntiCyclone (PSAC) and East Asian Summer Monsoon (EASM), are investigated by using the hindcasts from the three operational climate prediction models, including BCC_CSM1.1(m), NCEP CFSv2 and ECMWF System 4. We show that prediction skills of the indices for representing these PEASCPs are sensitive to the initial calendar month of model prediction, and the ensemble mean of the three models provides relatively higher and more stable skills than forecasts from an individual model. In general, the indices of intensity and area have high prediction skills while the position indices have relatively low skills. Specifically, the skills of the WPSH intensity, area, SAH centre intensity, PSAC and EASM are higher, while the skills of the WPSH western boundary and SAH centre latitude are lower, and the skills of WPSH ridge line and SAH centre longitude are the lowest. Further analysis shows that the El Niño/Southern Oscillation (ENSO) has a large contribution to these prediction skills, and these patterns of atmospheric circulation anomalies in response to ENSO can be well captured by models, which is the major predictability source of the skills.