Southeastern Geographer Vol. 30, No. 2, November 1990, pp. 94-106 COMPARISON OF MOISTURE CONDITIONS IN PENINSULAR FLORIDA WITH OTHER SECTIONS OF THE SOUTHEASTERN UNITED STATES* James A. Henry and David W. LeRoutillier INTRODUCTION. Drought has been an extremely significant factor in the Southeastern United States. Wagner noted that the outstanding climate event in the United States in 1986 was probably the severe drought in the Southeast. (J) Drought again affected the southeastern portion of the country in 1988, (2) and the situation could be worse in the future. Although there is considerable variability in the predictions produced by different computer models, most simulations indicate that large sections of the United States, including the Southeast (with the exception of a portion of Florida), will likely experience more frequent droughts as CO2 and other greenhouse gases continue to accumulate in the atmosphere . (3) Noting that the present climate models are not adequate to confidently describe future climate changes on a regional scale, an even worse situation has been projected for the Southeast; one of these computer simulations predicted that, even at the present level of greenhouse gases, the trend for the 1990s is for above-average warming and below-normal precipitation in the region. Several recent studies have highlighted important facets of the spatial and temporal characteristics of droughts in the Southeast. The drought of 1986 was discussed in three recent articles. These showed that some locations in the Southeast received less than 40% of normal precipitation and that the drought was the worst in at least 99 years for the region as a whole. (4) Analysis of moisture conditions over the pe- * The authors very much appreciate comments concerning spectral analysis from Dr. Kenneth Portier of the Statistics Department of the Institute of Food and Agricultural Sciences at the University of Florida. All graphics were drafted by Jan Coyne of the Department of Geography, and Lee Lines was instrumental in the data analysis. Computer support was provided by the Northeast Regional Data Center (NERDC) ofthe State University System of Florida and by the IBM Corporation; the assistance of Dr. Virginia Hetrick of NERDC in acquiring this support is appreciated. Dr. Henry is Associate Professor ofGeography at the University ofFlorida in Gainesville, FL 32611, and Mr. LeBoutillier is Assistant Professor ofGeography and Geology at Indiana State University in Terre Haute, IN 47809. Vol. XXX, No. 2 95 riod 1931-1982 for the Southeast, excluding Florida, was detailed by Eder et al. (5) Another study of drought for seven Southeastern states, including Florida, found, however, that frequently the moisture conditions in Florida, as revealed by the Palmer Drought Severity Index, were out of phase with much ofthe remainder of the Southeast. Drought often occurred in Florida when most of the other six Southeastern states were experiencing normal or wet conditions; on the other hand, when non-Florida sections were very dry, Florida frequently received abovenormal precipitation. (6) The purpose of this paper is to study further the relationship between Florida moisture conditions and those in the remainder of the Southeast. The previous studies did not apply techniques to evaluate the strength of the relationship between time series for Florida and those of the other six Southeastern states. The present study employs techniques that can determine effectively the degree of correlation between times series (cross-correlation), the existence of periodicities or cycles in the data (spectral analysis), and whether moisture conditions in disparate sections of the Southeast were produced by the same generating processes or by unrelated atmospheric processes (cross-spectral analysis). These types of analyses allow the specification of the nature and strength of the relationships of moisture conditions in Florida relative to those in other sections of the region. DATA AND METHODS. The Palmer Drought Severity Index (PDSI) is the most commonly used measure of moisture abnormality (although it also indicates the occurrence of normal conditions) and has proven to be quite reliable for comparing dry/wet conditions in different climatic regions . It has been used in previous studies in the Southeast. (7) PDSI data are available for each month for all 344 climatic divisions of the country since 1895. For this study, data were obtained for the period 1895 to...