This research is supported by the National Oceanic and Atmospheric Administration, Office of Global Programs, Paleoclimatology Program through Grants NA36GP0139 and NA66GP0251, and is an outgrowth of previous support by the National Science Foundation, Grant ATM 88-14675 and the U.S. Geological Survey, Biological Resources Division, Agreement CA-8012-2-9001. The PDSI data were kindly obtained from Ned Guttman of NOAA. Most of the tree-ring chronologies used here came from the International Tree-Ring Data Bank (ITRDB) at the NGDC in Boulder. Others not in the ITRDB were kindly contributed by a number of scientists, including Hal Fritts, Lisa Graumlich, Tom Swetnam, Connie Woodhouse, Laura Haston, Joel Michaelsen, and Glen MacDonald.
Akaike, H., 1974: A new look at the statistical model identification. IEEE Trans. Autom. Control,AC-19, 716–723.
Barnston, A. G., and R. E. Livezey, 1987: Classification, seasonality, and persistence of low-frequency atmospheric circulation patterns. Mon. Wea. Rev.,115, 1083–1126.
Bergman, K. H., C. F. Ropelewski, and M. S. Halpert, 1986: The record Southeast drought of 1986. Weatherwise,39, 262–266.
Blasing, T. J., and D. N. Duvick, 1984: Reconstruction of precipitation history in North American corn belt using tree rings. Nature,307, 143–145.
Box, G. E. P., and G. M. Jenkins, 1970: Time Series Analysis: Forecasting and Control. Holden-Day, 553 pp.
Bretherton, C. S., C. Smith, and J. M. Wallace, 1992: An intercomparison of methods for finding coupled patterns in climate data. J. Climate,5, 541–560.
Briffa, K. R., P. D. Jones, T. M. L. Wigley, J. R. Pilcher, and M. G. L. Baillie, 1986: Climate reconstruction from tree rings: Part 2, Spatial reconstruction of summer mean sea-level pressure patterns over Great Britain. J. Climatol.,6, 1–15.
Broadbrooks, W. J., and P. B. Elmore, 1987: A Monte Carlo study of the sampling distribution of the congruence coefficient. Educ. Psychol. Meas.,47, 1–11.
Cole, J. E., and E. R. Cook, 1998: The changing relationship between ENSO variability and moisture balance in the continental United States. Geophys. Res. Lett.,25, 4529–4532.
Cook, E. R., and G. C. Jacoby Jr., 1977: Tree-ring–drought relationships in the Hudson Valley, New York. Science,198, 399–401.
——, M. A. Kablack, and G. C. Jacoby, 1988: The 1986 drought in the southeastern United States: How rare an event was it? J. Geophys. Res.,93, 14 257–14 260.
——, D. W. Stahle, and M. K. Cleaveland, 1992: Dendroclimatic evidence from eastern North America. Climate Since AD 1500, R. S. Bradley and P. D. Jones, Eds., Routledge, 331–348.
——, K. R. Briffa, and P. D. Jones, 1994: Spatial regression methods in dendroclimatology: A review and comparison of two techniques. Int. J. Climatol.,14, 379–402.
——, D. M. Meko, D. W. Stahle, and M. K. Cleaveland, 1996: Tree-ring reconstructions of past drought across the coterminous United States: Tests of a regression method and calibration/verification results. Tree Rings, Environment, and Humanity, J. S. Dean, D. M. Meko, and T. W. Swetnam, Eds., Radiocarbon, 155–169.
——, ——, and C. W. Stockton, 1997: A new assessment of possible solar and lunar forcing of the bidecadal drought rhythm in the western United States. J. Climate,10, 1343–1356.
——, J. E. Cole, R. D. D’Arrigo, D. W. Stahle, and R. Villalba, 1999:Tree ring records of past ENSO variability and forcing. El Niño and the Southern Oscillation: Multiscale Variability and its Impacts on Natural Ecosystems and Society, H. F. Diaz and V. Markgraf, Eds., Cambridge University Press, in press.
Cramer, J. S., 1987: Mean and variance of R2 in small and moderate samples. J. Econometrics,35, 253–266.
Fritts, H. C., 1965: Tree-ring evidence for climatic changes in western North America. Mon. Wea. Rev.,93, 421–443.
——, 1976: Tree Rings and Climate. Academic Press, 567 pp.
——, 1991: Reconstructing Large-Scale Climate Patterns from Tree-Ring Data. The University of Arizona Press, 286 pp.
——, T. J. Blasing, B. P. Hayden, and J. E. Kutzbach, 1971: Multivariate techniques for specifying tree-growth and climate relationships and for reconstructing anomalies in paleoclimate. J. Appl. Meteor.,10, 845–864.
Gilman, D. L., F. J. Fuglister, and J. M. Mitchell Jr., 1963: On the power spectrum of “red noise.” J. Atmos. Sci.,20, 182–184.
Glahn, H. R., 1968: Canonical correlation and its relationship to discriminant analysis and multiple regression. J. Atmos. Sci.,25, 23–31.
Graumlich, L. J., 1993: A 1000-year record of temperature and precipitation in the Sierra Nevada. Quat. Res.,39, 249–255.
Guttman, L., 1954: Some necessary conditions for common-factor analysis. Psychometrika,19, 149–161.
Guttman, N., 1991: Sensitivity of the Palmer hydrologic drought index to temperature and precipitation departures from average conditions. Water Res. Bull.,27, 797–807.
Haston, L., and J. Michaelsen, 1994: Long-term central coastal California precipitation variability and relationships to El Niño–Southern Oscillation. J. Climate,7, 1373–1387.
——, and ——, 1997: Spatial and temporal variability of southern California precipitation over the last 400 yr and relationships to atmospheric circulation patterns. J. Climate,10, 1836–1852.
Haugh, L. D., and G. E. P. Box, 1977: Identification of dynamic regression (distributed lag) models connecting two time series. J. Amer. Stat. Assoc.,72, 121–130.
Helland, I. S., 1987: On the interpretation and use of R2 in regression analysis. Biometrics,43, 61–69.
Hendrickson, A. E., and P. O. White, 1964: Promax: A quick method for rotation to oblique simple structure. Br. J. Stat. Psychol.,17, 65–70.
Hurvich, C. M., and C. Tsai, 1989: Regression and time series model selection in small samples. Biometrika,76, 297–307.
Kaiser, H. F., 1960: The application of electronic computers to factor analysis. Educ. Psychol. Meas.,20, 141–151.
Karl, T. R., and A. J. Koscielny, 1982: Drought in the United States. J. Climatol.,2, 313–329.
——, and W. E. Riebsame, 1984: The identification of 10- to 20-year temperature and precipitation fluctuations in the contiguous United States. J. Climate Appl. Meteor.,23, 950–966.
——, C. N. Williams Jr., and F. T. Quinlan, 1990: United States Historical Climatology Network (HCN) serial temperature and precipitation data. Environmental Sciences Division Publ. 3404, 371 pp. [Available from Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831.].
Kutzbach, J. E., and P. J. Guetter, 1980: On the design of paleoenvironmental data networks for estimating large-scale patterns of climate. Quat. Res.,14, 169–187.
LaMarche, V. C., Jr., and H. C. Fritts, 1971: Anomaly patterns of climate over the western United States, 1700–1930, derived from principal component analysis of tree-ring data. Mon. Wea. Rev.,99, 138–142.
Langbein, W. B., and J. R. Slack, 1982: Yearly variations in runoff and frequency of dry years for the conterminous United States, 1911–79. U.S. Geological Survey Open-File Rep. 82-751, 85 pp. [Available from Branch of Distribution, USGS, Box 25425, Denver Federal Center, Denver, CO 80225.].
Lorenz, E. N., 1956: Empirical orthogonal functions and statistical weather prediction. Statistical Forecasting Scientific Rep. 1, Department of Meteorology, Massachusetts Institute of Technology, Cambridge, MA, 57 pp.
Mann, M. E., R. S. Bradley, and M. K. Hughes, 1998: Global-scale temperature patterns and climate forcing over the past six centuries. Nature,392, 779–787.
Matthai, H. F., 1979: Hydrologic and human aspects of the 1976–77 drought. USGS Prof. Paper 1130, U.S. Government Printing Office, 84 pp. [Available from U.S. Government Printing Office, Washington, DC 20402.].
Meko, D. M., 1981: Applications of Box-Jenkins methods of time series analysis to the reconstruction of drought from tree rings. Unpublished Ph.D. dissertation, The University of Arizona, 149 pp.
——, 1992: Dendroclimatic evidence from the Great Plains of the United States. Climate Since A.D. 1500, R. S. Bradley and P. D. Jones, Eds., Routledge, 312–330.
——, E. R. Cook, D. W. Stahle, C. W. Stockton, and M. K. Hughes, 1993: Spatial patterns of tree-growth anomalies in the United States and southeastern Canada. J. Climate,6, 1773–1786.
Mitchell, J. M., Jr., C. W. Stockton, and D. M. Meko, 1979: Evidence of a 22-year rhythm of drought in the western United States related to the Hale solar cycle since the 17th century. Solar–Terrestrial Influences on Weather and Climate, B. M. McCormac and T. A. Seliga, Eds., D. Reidel, 125–144.
Morrison, D. F., 1990: Multivariate Statistical Methods. 3d ed. McGraw-Hill, 480 pp.
Namias, J., 1955: Some meteorological aspects of drought with special reference to the summers of 1952–54 over the United States. Mon. Wea. Rev.,83, 199–205.
——, 1966: Nature and possible causes of the northeastern United States drought during 1962–65. Mon. Wea. Rev.,94, 543–554.
——, 1978: Multiple causes of the North American abnormal winter 1976–77. Mon. Wea. Rev.,106, 279–295.
Nash, J. E., and J. V. Sutcliffe, 1971: Riverflow forecasting through conceptual models 1, A discussion of principles. J. Hydrol.,10, 282–290.
Palmer, W. C., 1965: Meteorological drought. Weather Bureau Res. Paper 45, U.S. Department of Commerce, Washington, DC, 58 pp.
Rencher, A. C., and F. C. Pun, 1980: Inflation of R2 in best subset regression. Technometrics,22, 49–53.
Reyment, R., and K. G. Jöreskog, 1993: Applied Factor Analysis in the Natural Sciences. Cambridge University Press, 371 pp.
Richman, M. B., 1986: Rotation of principal components. J. Climatol.,6, 293–335.
Roos, M., 1994: Is the California drought over. Proceedings of the Tenth Annual Pacific Climate (PACLIM) Workshop, Interagency Ecological Studies Program for the Sacramento-San Joaquin Estuary, Tech. Rep. 36, 123–128.
Ropelewski, C. F., and M. S. Halpert, 1986: North American precipitation and temperature patterns associated with the El Niño/Southern Oscillation (ENSO). Mon. Wea. Rev.,114, 2352–2362.
Stahle, D. W., and M. K. Cleaveland, 1988: Texas drought history reconstructed and analyzed from 1698–1980. J. Climate,1, 59–74.
——, ——, and J. G. Hehr, 1985: A 450-year drought reconstruction for Arkansas, United States. Nature,316, 530–532.
——, ——, and ——, 1988: North Carolina climate changes reconstructed from tree rings: A.D. 372–1985. Science,240, 1517–1519.
Stockton, C. W., and D. M. Meko, 1975: A long-term history of drought occurrence in western United States inferred from tree rings. Weatherwise,28, 244–249.
——, and ——, 1983: Drought recurrence in the Great Plains as reconstructed from long-term tree-ring records. J. Climate Appl. Meteor.,22, 17–29.
Warrick, R. A., 1980: Drought in the Great Plains: A case study of research on climate and society in the U.S.A. Climatic Constraints and Human Activities, J. Ausubel and A. K. Biswas, Eds., Pergamon, 93–124.
Woodhouse, C., and D. Meko, 1997: Number of winter precipitation days reconstructed from southwestern tree rings. J. Climate,10, 2663–2669.