April-June precipitation reconstruction for Xi'an and drought assessment for the Guanzhong Plain from tree rings of Chinese pine

Variations in earlywood width (EWW) of Chinese pine in the Nanwutai Mountain were used to develop high-resolution climate proxy data to extend existing climate records in Guanzhong Plain, Shaanxi Province, China. Growth-climate response analyses showed the EWW series in Nanwutai Mountain are mainly influenced by spring and early summer precipitation. Based on the EWW series derived from the Nanwutai Mountain, we developed an April-June precipitation reconstruction for Xi'an for the period 1800-2009. The climate/tree-growth model accounts for 36.4% of the instrumental precipitation variance during the period 1951-2009. Spatial climate correlation analyses with the gridded precipitation data revealed that our precipitation reconstruction contains a strong regional precipitation signal for the Guanzhong Plain. Our reconstruction successfully captured recent climatic changes and agreed, in general, with other tree-ring-based precipitation reconstructions from nearby regions on a decadal timescale. The rainfall/drought series in northern China also showed highly synchronous decreasing trends since the 1970s, suggesting that precipitation related to the East Asian summer monsoon has decreased by large spatial and temporal (decadal) scales. In addition, wavelet analysis revealed the existence of some decadal (13.3-year) and interannual (9.1-, 5.4-, 3.1-, and 2.1-year) cycles, which may potentially be the fingerprints of some proposed climate change forcings, such as El Nino-Southern Oscillation and solar activities.