A Cool Season Precipitation Reconstruction for Saltillo Mexico

Abstract

Old Douglas-fir (Pseudotsuga menziesii) trees were sampled in the Sierra Madre Oriental of northeastern Mexico and used to develop a 219-year chronology of earlywood width. This chronology is correlated with monthly precipitation totals from January to June recorded at Saltillo some 55 km northwest of the collection site. The chronology was used to reconstruct winter-spring precipitation (January-June total) from 1782-2000. The reconstruction indicates large interannual, decadal, and multidecadal variability in winter-spring precipitation over Saltillo. This variability is vaguely apparent in the short and discontinuous instrumental record from 1950-1998, with January-June totals ranging from 15 to 310 mm, multiyear droughts, and a negative trend in January-June precipitation over the last 50 years. The reconstruction indicates that severe dryness was prevalent over a 24-year period from 1857-1880. This mid-19th century drought exceeds the duration of any droughts witnessed during the 20th century. However, three episodes of winter-spring dryness have prevailed in the Saltillo region after 1950, a much higher frequency of decadal drought than estimated over the past 219 years and aggravating the regional water supply problems associated with this booming manufacturing and ranching center.