Drought variations in Almaty (Kazakhstan) since AD 1785 based on spruce tree rings

摘要

While dendroclimatic studies have extended the knowledge of drought variations in Tien Shan, these have been almost exclusively based on tree-ring data from Tien Shan in China. We present a drought reconstruction for Almaty based on a tree-ring width chronology developed from sites of the Schrenk spruce in Tien Shan, Kazakhstan. The drought reconstruction, spanning AD 1785-2014, was developed by calibrating tree-ring series with the mean August to January standardized precipitation evapotranspiration index (SPEI). The drought reconstruction was verified with independent data and accounts for 41.9 % of the actual SPEI variance during the common period. The drought reconstruction compares well with some tree-ring-based drought/precipitation reconstructions from Western Tien Shan and reveals the large-scale drought signals of Western Tien Shan. The wavelet analysis indicates the existence of some decadal (60 and 11 years) and interannual (2.0-4.0 years) periodicities, which may potentially be the fingerprints of large-scale land-atmosphere-ocean circulations. This study provides the first long-term drought reconstruction and drought assessment for Almaty and will aid in future plans to address climate change of Kazakhstan.