Temporal variability of precipitation in the Upper Tennessee Valley

Upper Tennessee River Basin, United States. The temporal variation of precipitation in the Upper Tennessee River Basin was investigated by utilizing datasets from the Tennessee Valley Authority (TVA) rain gauge network consisting of 56 rain gauges (1990–2010), and the National Weather Service (NWS) analyzing mean areal precipitation values for 78 subbasins (1950–2009). The Mann–Kendall trend test, Mann–Kendall–Sneyers test, Yamamoto Method, and Morlet's wavelet were applied to reveal precipitation trends and abrupt changes in annual precipitation volumes. Analyses indicated that: (a) 11% of the 78 subbasins experienced statistically significant increasing or decreasing precipitation over a 50-year period; (b) seasonal precipitation trends based on monthly volumes varied, with the summer and autumn series showing the largest significant increases; (c) abrupt changes in annual precipitation volumes were detected among subbasins corresponding to strong El Niño events; and (d) several subbasins displayed significant periodicities of 1, 6, 18, and 22 years in monthly volumes. These findings provide key information for regional precipitation down-scaling from global climate change models where the Appalachian mountainous terrain greatly impacts down-scaling results.