Regional boreal summer intraseasonal oscillation over Indian Ocean and Western Pacific: comparison and predictability study

摘要: The boreal summer intraseasonal oscillation (BSISO) has two major activity centers, the northern Indian Ocean and tropical Western North Pacific, which dominate monsoon variability over South Asia East Asia, respectively. spatial–temporal structures of BSISO (10°S–30°N, 60°–105°E) (IOISO) Pacific 105°–150°E) (WPISO) are examined by corresponding leading modes daily OLR 850-hPa zonal wind (U850). IOISO features a northeastward propagation with 30–45 days energy peak first principal component (PC1) maximum variance in May, while WPISO propagates northward broad spectral on 10–60 days PC1 August. Because large regional differences, indices, index index, defined their PCs. combined IOISO–WPISO captures about 30 % (10 %) U850 (OLR) entire IO–WP region 60°–150°E), doubles that captured Madden–Julian Oscillation (MJO) (Wheeler Hendon 2004) is 50 % higher than (Lee et al. 2013). also shows superior performance representing biweekly pentad-mean variations Asian-Pacific (north 10°N). predictability/prediction skill simulated indices explored using data derived from Intraseasonal Variability Hindcast Experiment project. reasonably well captured, but forecasted fractional variances center’s locations exhibit significant deficiencies. multi-model mean estimate predictability 40–45 days for whereas 33–37 days index. less predictable likely due to existence its component. prediction significantly initial amplitude (~20 days indices) small (~11 days), suggesting development much more difficult mature disturbances’ propagation.