The Influence of Atlantic Tropical Cyclones on Drought over the Eastern United States (1980-2007)

To assess the influence of Atlantic tropical cyclones (TCs) on the eastern U. S. drought regime, the Variable Infiltration Capacity (VIC) land surface hydrologic model was run over the eastern United States forced by the North American Land Data Assimilation System phase 2 (NLDAS-2) analysis with and without TCrelated precipitation for the period 1980-2007. Adrought was defined in terms of soil moisture as a prolonged period below a percentile threshold. Different duration droughts were analyzed-short term (longer than 30 days) and long term (longer than 90 days)-as well as different drought severities corresponding to the 10th, 15th, and 20th percentiles of soil moisture depth. With TCs, droughts are shorter in duration and of a lesser spatial extent. Tropical cyclones variously impact soil moisture droughts via late drought initiation, weakened drought intensity, and early drought recovery. At regional scales, TCs decreased the average duration of moderately severe short-term and long-term droughts by less than 4 (10% of average drought duration per year) and more than 5 (15%) days yr(-1), respectively. Also, they removed at least two short-term and one longterm drought events over 50% of the study region. Despite the damage inflicted directly by TCs, they play a crucial role in the alleviation and removal of drought for some years and seasons, with important implications for water resources and agriculture.