Intraseasonal variability and predictability of the subtropical Asian summer rain band

The climatological intraseasonal oscillations (CISOs) of the subtropical Asian summer rain band (SASRB) are found significantly related with the CISO in the atmospheric circulation over extratropical Eurasian continent, which is dominated by an intraseasonal North Pacific oscillation (ISNAO) pattern and its associated wave trains. The anomalous trough (ridge) of the eastward propagating wave train of the ISNAO pattern affects active (break) rainfall of SASRB and modulates the CISO of SASRB, together with the anomalous active (suppressed) convection northward propagating from the tropics and the subtropics. Moreover, the anomalous trough (ridge) around the Lake Baikal bridges the CISO in the mid-high latitudes and that of SASRB. The NCEP Climate Forecast System version 2 (CFSv2) depicts the spatial-temporal features, principal modes, and propagation of the CISO of SASRB reasonably well. However, the mean state of precipitation and the variance of CISO are overestimated. In the model, the ISNAO pattern is too weak and its fluctuating frequency is too high. Moreover, the CFSv2 only shows marginal skills in simulating the ISNAO pattern and the propagation of its associated wave trains, and underestimates the relationship between the atmospheric circulation in the mid-high latitudes and the CISO of SASRB. In addition, overestimation of the intensity of CISO in the tropical-subtropical and higher-latitude atmosphere may cause overestimation of the CISO of SASRB.