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

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. Scatter plots and linear regression lines of PCC skills for BCC_CSM1.1(m) (orange), NCEP CFSv2 (green), ECMWF System 4 (blue) models and the ensemble mean (red) initiated in May against the absolute value of former winter‐mean (December, January and February) Niño3.4 index: (a) geopotential height at 200 hPa over the South Asia region [10°N–50°N, 30°E–120°E], (b) geopotential height at 500 hPa over the western Pacific region [10°N–40°N, 90°E–180°E], (c) u–wind at 200 hPa over the South Asia region [10°N–50°N, 30°E–120°E], and (d) u‐wind at 850 hPa over the Southeast Asia region [10°N–20°N, 90°E–120°E]