The evolution of dry and wet periods in Asia and North America and its relationship with SSTA
亚洲和北美干湿变化及其与海表温度异常的关系

The Multichannel Singular-Spectrum Analysis (MSSA) was used to analyze the variability of Palmer Drought Severity Index (PDSI) across the Asia and North America, and the relation between PDSI and the Sea Surface Temperature Anomaly (SSTA) in the tropical and Northern temperate ocean. The results indicated that the interannual (3~6 years) and the quasi-decadal time scales (longer than 8 years) oscillations existing in the evolution of PDSI and SSTA. Further investigation indicated that the Asian PDSI showed significant 6~8 years time scales signal. It was found that the 3~6 years oscillation of SSTA displayed the characteristics of ENSO signal, while the ENSO-like or Pacific Decadal Oscillation (PDO) dominated the variability on the quasi-decadal timescale variation of SSTA. The results further presented the spatio-temporal characteristics of wet and dry signals in Asia and North America. The ENSO signal was more correlative to the wet-dry signals of Asia than those of North America on the interannual timescale (3~6 years). But on the quasi-decadal timescale, the ENSO-like seemed to have stronger influence in North America than other signals. From the spatial distribution of the correlation between the PDSI and SSTA, west Siberia, the north and south sides of Tibetan Plateau and the area east to Central Siberian Plateau had the strongest response to SSTA signals. Although the central parts of North America were influenced by SSTA on the interannual timescale, the west part of North America had stronger response to the quasi-decadal SSTA forcing signals.