Temporal Patterns of Drought Frequency and Severity in North Carolina, 1920–2019 and the Drought Gap of the 1960s–1970s

abstract:Residents of North Carolina have endured the negative impacts of droughts for centuries. In this study, I examine spatiotemporal aspects of drought across North Carolina's eight climate divisions over a recent 100–year period (1920–2019). Using the Palmer Drought Severity Index, I define a drought event as any period of three or more consecutive months recording moderate to extreme drought conditions. I compare drought frequency, intensity, and length between early (1920–1969) and late (1970–2019) 50–year periods and test for trends in drought severity for the full 100–year study period and the most recent 50– and 30–year periods. For the majority of climate divisions, droughts are more frequent and longer in the late period. However, these differences were not statistically significant (p > 0.05) in any climate division or for the entire state. Similarly, trends in drought severity were generally absent, with only two climate divisions recording a significant trend toward drier conditions. Temporally, the long-term patterns reveal that droughts were largely absent statewide during the 1960s and 1970s. Considerable spatial variability exists within the state, with the southern coastal plain and Piedmont climate divisions the most anomalous for frequency and intensity.