Relationships between ENSO and drought over the southeastern United States

[1] A long term precipitation ( P) data set over the United States and the sea surface temperature ( SST) data from 1915 to 2006 were used to examine the impact of El Nino Southern Oscillation ( ENSO) on drought and persistent wet spells over the southeastern United States. The meteorological droughts and wet spells were identified based on the 6- month standardized precipitation index ( SPI 6) calculated from P averaged over the Southeast. These events indicate that a drought ( or wet spell) over the Southeast is more likely to start during a cold ( warm) ENSO winter or early spring. The influence of ENSO on P is seasonally dependent. The P composites for cold ENSO events show positive P anomalies over the Southeast in winter but negative anomalies in summer. For warm ENSO events, the situation reverses. Therefore, a persistent cold ( warm) ENSO from winter to summer does not create favorable conditions for drought ( wet spells) to persist over the Southeast. While cold ENSO events are more likely to initiate droughts, droughts are likely to persist if the cold ( warm) ENSO winter is followed by an ENSO neutral summer.