Divergence of tree-ring-based drought reconstruction between the individual sampling site and the Monsoon Asia Drought Atlas: an example from Guancen Mountain

To evaluate the applicability of the Standardized Precipitation-Evapotranspiration Index （SPEI） and the self-calibrated Palmer Drought Severity Index （scPDSI） to paleoclimate reconstructions in the east Asian summer monsoon region, we used a 194-year tree-ring width chronology from Guancen Mountain, Shanxi Province, China, to investigate its correlation with SPEI and scPDSI, respectively. The results indicated scPDSI as a robust drought index that could be reconstructed from tree-ring width on Guancen Mountain other hydroclimate-related Significant correlations with series illustrated that our reconstruction captured common variations of hydroclimate in the surrounding areas. Additionally, our reconstruction showed significant correlation with nearby grid points of the Monsoon Asia Drought Atlas （MADA）. However, while unprecedented drying trend existed during the past several decades in MADA, it was not represented in our reconstruction or in instrumental scPDSI/Dai-PDSI. This may imply that MADA overestimated drought severity during the past several decades in our study area; this overestimation was probably caused by an insufficient spatiotemporal distribution of the tree-ring network used by MADA. Therefore, more drought reconstructions based on individual sampling sites in eastern Asia are necessary to gain a thorough understanding of the Asian Monsoon climate variability.

THE SOUTHERN OSCILLATION RECONSTRUCTION AND DROUGHT/FLOOD IN CHINA

Variation of the Southern Oscillation (SO) is, though observed at low latitudes, an indication of anom- alies of the global atmospheric circulation. In this study, we found that the dryness/wetness in China is influenced significantly by variation of the SO, and that monsoon rainfall, prior to ENSO maybe affect large scale atmosphere motion at lower latitudes. Since the dryness/wetness grades appear to be responsive to climate anomalies related to the SO, it should be possible to reconstruct past value of SO directly from grade indices. Thus we attempted to reconstruct the seasonal SO indices back to 1472 A. D. using canonical correlation technique. The best cstimates were derived from the model in which the period 1851--1962 is used for calibration and then is tested over an independent period 1963--1986. These estimates calibrate about 37 percent of the SO variance with about 17 percent of the variance verified. Significant peaks are apparent at period in 2.5--3, 5--6, 10.3--25 year range in the spectrum of the reconstructións of the SO which seems to have relationship with QBO and solar activity. It is encouraging that ENSO event in 1982-- 1983 is very well identified, especially in three seasons JJA, SON and DJF.