NOAA/WDS Paleoclimatology - Díaz et al. 2002 Chihuahua Winter-Spring Precipitation Reconstruction 1647-1992

The state of Chihuahua lies in an arid to semiarid zone in the NW central plain of Mexico. Its agricultural economy is highly vulnerable to frequent droughts. In this study, we reconstruct winter-spring precipitation from 1647-1992 using 6 earlywood width chronologies of Douglas fir from around Chihuahua. The tree-ring data explain 56% of the winter-spring precipitation variance in a linear regression for 1949-1992, and there is strong correlation between the tree-ring reconstructed precipitation data and the observed precipitation data not used for calibration (r = 0.74, p < 0.01). The 5 driest years in the reconstructed precipitation record were 1974, 1954, 1742, 1980, and 1820 in order of severity, and the longest dry period in the 346 yr record lasted about 17 yr (1948-1964) during the severe 1950s drought that also affected the SW United States. The reconstructed precipitation record has a statistically significant 4 yr spectral peak in the El Niño/Southern Oscillation (ENSO) frequency band and is significantly correlated with indices of ENSO (tropical rainfall index; r = 0.58, p = 0.001). The correlation between the ENSO and Chihuahuan reconstructed precipitation varied in strength when computed for non-overlapping 18 yr sub-periods (ranging from r = 0.43 to r = 0.68), which may reflect changes in the ENSO teleconnection to climate in northern Mexico.

奇瓦瓦州（Chihuahua）地处墨西哥中北部西北平原的干旱至半干旱地带，其农业经济极易受频发干旱的影响。本研究利用奇瓦瓦州周边6个花旗松（Douglas fir）的早材宽度年表，重建了1647-1992年的冬春季降水序列。该树轮数据在1949-1992年的线性回归分析中可解释56%的冬春季降水方差，且未用于校准的树轮重建降水序列与实测降水序列之间存在极强相关性（相关系数r=0.74，p<0.01）。重建降水序列中干旱程度由高到低的前5个年份依次为1974年、1954年、1742年、1980年和1820年；该346年序列中最长的干旱期持续约17年（1948-1964年），这一时期正是同时影响美国西南部的20世纪50年代严重干旱期。重建降水序列在厄尔尼诺-南方涛动（El Niño/Southern Oscillation, ENSO）频段存在统计学意义显著的4年周期峰值，且与ENSO指数（热带降雨指数）显著相关（r=0.58，p=0.001）。当以不重叠的18年亚时段计算相关性时，ENSO与奇瓦瓦州重建降水序列之间的相关强度存在变化（相关系数r介于0.43至0.68之间），这可能反映了ENSO遥相关对墨西哥北部气候影响的变化。