Laserfiche WebLink
including a number of reconstructions from the Four <br />Corners region (the junction of Arizona, New Mexico, <br />Utah, and Colorado) (Rose et al. 1982; D'Arrigo and <br />Jacoby 1991, 1992; Grissino -Mayer 1996). In their <br />1000 -yr -long reconstruction of winter precipitation <br />D'Arrigo and Jacoby (1991, 1992) found the 1950s <br />drought was surpassed only by a 22 -yr drought in the <br />late 1500s. The reconstruction of Colorado River flow <br />for 1520 -1961 shows the period 1579 -98 to reflect the <br />longest and most severe drought in this record (Stock- <br />ton and Jacoby 1976; Meko et al. 1995). In the White <br />Mountains of eastern California, precipitation recon- <br />structed from bristlecone pine shows a moderate <br />drought in the late sixteenth century (Hughes and <br />TABLE 3. Variance in observed precipitation and drought series explained (r') or shared (r) by tree -ring chronologies. <br />Variance explained (0) <br />Study Region Variable* Years or shared- (r) ** <br />Weakly (1965) Western NE Annual precipitation at 1210 -1965 r =0.63 (ring widths) <br />North Platte r = 0.75 (ring area) <br />Stockton and Eastern MT Annual regional 1700 -1977 rzadt= 0.52 <br />Meko (1983) Eastern WY precipitation rzadj= 0.54 <br />IA r2��= 0.44 <br />rz,d�= 0.40 <br />OK <br />Stahle et al. (1985) AK June PDSI 1531 -1980 r2 di= 0.40 <br />Cleaveland and IA July PDHI 1640 -1982 ..dj= 0.67 <br />Duvick (1992) <br />*PDSI: Palmer Drought Severity Index; PHDI: Palmer Hydrological Drought Index (Palmer 1965), <br />* *The use of r2 or r' di depends on how results were reported in specified studies. <br />Bulletin of the American Meteorological Society 2701 <br />