Seasonal Palmer drought severity index reconstruction using tree-ring widths from multiple sites over the central-western Da Hinggan Mountains, China since 1825 AD

Many evidences indicate that the drought in Northern China has progressively intensified, threatening people's lives and properties. Drought has become one of the most severe environmental problems in Northern China, and thus has serious impacts on the regional social and economic development. The present study investigated the seasonal Palmer drought severity index (PDSI) over the central-western Da Hinggan Mountains (CW-DHM), northeastern China. 283 cores of Mongolian pine trees from 6 locations were used to generate a regional ring-width chronology. The chronology in CW-DHM was significantly correlated with the May-July PDSI, with an explained variance of 49% (r = 0.700, 1951-2013, p < 0.0001). The regional May-July PDSI (PDSI5-7) from the CW-DHM was reconstructed from 1825 to 2013 AD. The ensemble empirical mode decomposition method (EEMD) and multi-taper method (MTM) spectral analyses revealed that the cycles in the reconstructed PDSI5-7 were close to those of the ENSO and solar activity. This suggests that both the ENSO and solar activity have strong influence on the PDSI5-7 variation in the CW-DHM region. In addition, EEMD also revealed that the Pacific decadal oscillation and the Atlantic multi-decadal oscillation influenced the drought variation in this region. The PDSI5-7 reconstruction showed a long-term declining (dry) trend during the period of the 1950s-2010s. This drying trend was also detected in the PDSI data of other parts of China after the 1950s. We believe that these phenomena may be related to a large extent with the weakening of the East Asian summer monsoon