A 396-year reconstruction of precipitation in southern Jordan

Water resources are the lifeblood of the Near East region. Careful planning and management of water resources in dry land regions requires information on the likelihood of extreme events, especially prolonged drought. It is e ssential to understand the variability of climate on time scales of decades to centuries to assign reasonable probabilities to such events. Tree-ring analysis is one way to increase our knowledge of the climate variability be yond the short period covered by the instrumental data. In this paper, we r econstruct October-May precipitation from a Juniperus phoenicia tree-ring c hronology in southern Jordan to gain a longterm (A.D. 1600-1995) perspectiv e on runs of dry years and on time series fluctuations in precipitation ave raged over several years. The reconstruction equation derived by regression of log-transformed precipitation on tree-ring indices explains 44 percent of the variance of observed precipitation. The longest reconstructed drough t, as defined by consecutive years below a threshold of 217.4 mm, was four years, compared with three years for the 1946-95 instrumental data. A Monte Carlo analysis designed to account for uncertainty in the reconstruction i ndicates a lower than 50 percent chance that the region has experienced dro ught longer than five years in the past 400 years.