山西宁武地区1686年以来年降水重建*

根据山西北部宁武地区的树轮宽度指标,建立了该地区过去318年的树轮STD,RES和ARS年表,发现上年8月至当年7月 (全年)的降水与差值年表(RES)显著相关 (r=0.71, n=50),在此基础上设计了转换方程,重建了宁武地区1686年以来的全年降水,方差解释量达到 48.6％(调整自由度后为46.8％, r=0.697,F=26.471, p<0.0001)。降水量较少的时段为1693~1710年,1720~1764年,1825~1841年,1873~1882年,1901~1930年,1966~1972年和1988~2003年,降水量较多的时段为1711~1720年, 1765~1824年,1842~1872年,1883~1886年和1931~1987年。 历史文献记录的干旱年份在重建序列上均有所反映。重建序列与贺兰山1~7月降水显著相关 (99％置信度下, r=0.312)。功率谱分析表明山西宁武上年8月至当年7月降水含有2.34~2.68年,4.92年,5.26年的显著周期,可能与ENSO活动有关。

RECONSTRUCTION OF ANNUAL PRECIPITATION SINCE 1686A.D. FROM NINGWU REGION, SHANXI PROVINCE

The annual precipitation from last August to current July was reconstructed based on tree-ring width analyses since 1686A.D.33 cores from 19 Chinese pine trees(Pinus tabulaeformis)have been collected in Ningwu region (38°50'N,112°05'E), Shanxi Province. Tree-ring samples were prepared, cross-dated and measured following conventional procedures. There are two meteorologic stations near the sampling site, the Wuzhai station (38°55'N,111°49'E,ca.1401m ) and the Yuanping station (38°44'N,112°43'E,ca.828.2m ), which is 42km and 46km to the sampling site respectively. We chosed the Yuanping station data for the following analysis. It is evident that ring-width indices respond pronouncedly to AJ (last August to current July) precipitation. The correlation coefficient was 0.71. In this paper, climatic record data from the Yuanping meteorologic station is divided into two phases: verification phase (1974~2003) and calibration phase (1954~1973). From these data, using simple linear regression, a transfer function was build to reconstruct total precipitation from last August to current July since 1686 A.D.: P₈₇=331.315RES_t+88.454, (n=30, r=0.697, R²=48.6 ％, R²_adj=46.8 ％, F=26.471, p<0.0001). In this function, P₈₇ was total precipitation from last August to current July, RES_t was current residual chronology.The explained variance of reconstruction is 48.6 ％ (adjusted explained variance is 46.8 ％, F=26.471, p<0.0001). Dry periods in the reconstruction include 1693~1710,1720~1764,1825~1841,1873~1882,1901~1930,1966~1972,1988~2003, and wet periods include 1711~1720, 1765~1824,1842~1872,1883~1886 and 1931~1987. The dry/wet years are well identified by historical documents. The reconstructed precipitation of Ningwu series was significantly correlated with precipitation of January to July (P₁₇) from the Mt. Helan (at 99 ％ confidence level, n=230, r=0.312). Ningwu and Mt. Helan are both located in the environmentally sensitive zone; the precipitations in this zone are controlled by the East Asian monsoon. Power spectrum analysis shows that there exist periods of 2.34~2.68, 4.92, and 5.26 years in last August to current July precipitation that respond to ENSO event. It suggests that climate variations in Ningwu region are driven not only by local events, but also by the global climate.