Variations in the Establishment Time and Eastern Boundary Position of the Somali Jet and Correlations with Summer Rainfall in China

The establishment time index and eastern boundary position index were set up to describe the characteristics of the Somali jet (SMJ) activity, and relationships between the indices and Chinese summer rainfall were also explored used NCEP/NCAR reanalysis data. The Somali jet established in the 24th pentad and retreated in the 62nd pentad, and the eastern boundary position was maintained at 45-65 degrees E. The establishment time sequence was characterized by an earlier tendency, and the eastern boundary position sequence exhibited the strong interannual variability. The intensity, establishment time and eastern boundary position indices were verified to describe the characteristics of the Somali jet activity from different angle and flank. The connection between these three indices and the Asian monsoon index seemed to be quite different. Both the intensity and establishment time were positively correlated with the third and second pattern of China summer rainfall, respectively. The eastern boundary position was negatively related to the first pattern of the summer rainfall in China. Additionally, the impact of the establishment time and eastern boundary position of the Somali jet on China summer precipitation were closely related to the Lake Baikal high and the western Pacific subtropical high as well as the equator warm wet airflow.