Seasonal precipitation in the south-central Helan Mountain region, China, reconstructed from tree-ring width for the past 224 years

Chinese pine (Pinus tabulaeformis Carr.) trees from the Helan Mountain range in central China have been used to reconstruct total January-July precipitation from AD 1775 to 1998. For the calibration period R-adj(2) = 0.52. Narrow rings are associated with below-average precipitation from March through August. Wide rings are produced in years when the East Asian summer monsoon front arrives early. We use local historical writings over the last 300 years about extreme climatic conditions between spring and early summer to verify the extreme years. Most of the extreme dry years could be identified in local historical documents. Another East Asian summer monsoon front related precipitation reconstruction from northern Helan Mountain is also used to verify this reconstruction. They are well correlated from year to year, with a correlation coefficient of 0.52 (N = 218), and the wet or dry extreme events are well matched in many cases. This comparison could indicate a spatial and temporal connection of spring to early summer climatic conditions for the southern to northern portion of the Helan Mountain region. The sustained wet period before the 20th century lasts from the 1850s to the 1890s, and the longest dry period before the 20th century is in the 1830s and 1840s, largely coinciding with a spring-summer drought in Kashmir. Overall, multiyear fluctuations, such as the spectacular large-scale drought of the late 1920s and droughts in the 1830s-1840s and the 1970s, are well captured in this reconstruction, but only the 1970s drought is in the instrumental period. The reconstruction shows increasing variance from the 18th to the late 20th century.