A tree-ring-based drought index reconstruction for far-western Mongolia: 1565-2004

Tree-ring records can provide longer, high-resolution records of climate variability in remote regions such as western Mongolia, where recorded data are extremely limited. Here, we use three absolutely dated tree-ring-width chronologies to reconstruct the Palmer Drought Severity Index (PDSI) for a grid point in western Mongolia (48.75°N, 88.75°W). A reconstruction of the June-September PDSI for this region extends from 1565 to 2003 and explains 41% of the total variance in the instrumental PDSI. The 439-year reconstruction shows that starting in the 20th Century and continuing into the 21st Century there is a large-scale regional increase in growing-season moisture conditions compared to the prior centuries, a trend not seen in central or eastern Mongolian tree-ring reconstructions. This increasing trend in western Mongolia is consistent with station observations and other nearby proxy records. The wettest 5-year period of the reconstruction is 1741-1745 followed by 1993-1997, and the driest period is 1755-1759, followed by 1882-1886. Spectral analysis shows significant periodicities at approximately 22, 11, 7 and 5 years. The reconstruction shows similar trends to a PDSI reconstruction from NW China during the 20th Century and also correlates with lake-level data from nearby Khar-Us Nuur, Mongolia. Copyright © 2008 Royal Meteorological Society