Sensitivity of Hydrological Simulations of Southeastern United States Watersheds to Temporal Aggregation of Rainfall

Abstract

This study investigates the sensitivity of the performance of hydrological models to certain temporal variations of precipitation over the southeastern United States (SEUS). Because of observational uncertainty in the estimates of rainfall variability at subdaily scales, the analysis is conducted with two independent rainfall datasets that resolve the diurnal variations. In addition, three hydrological models are used to account for model uncertainty. Results show that the temporal aggregation of subdaily rainfall can translate into a markedly higher volume error in flow simulated by the hydrological models. For the selected watersheds in the SEUS, the volume error is found to be high (;35%) for a 30-day aggregation in some of the selected watersheds. Hydrological models tend to underestimate flow in these watersheds with a decrease in temporal variability in precipitation. Furthermore, diminishing diurnal amplitude by removing subdaily rainfall corresponding to times of climatological daily maximum and minimum has a detrimental effect on the hydrological simulation. This theoretical experiment resulted in the underestimation of flow, with a disproportionate volume error (of as high as 77% in some watersheds). Observations indicate that over the SEUS variations of diurnal variability of rainfall explain a significant fraction of the seasonal variance throughout the year, with especially strong fractional variance explained in the boreal summer season. The results suggest that, should diurnal variations of precipitation get modulated either from anthropogenic or natural causes in the SEUS, there will be a significant impact on the streamflow in the watersheds. These conclusions are quite robust since both observational and model uncertainties have been considered in the analysis.

Simulating diurnal variations over the southeastern United States

“…It is obvious from Figure that RMSE is significantly higher in 20CR‐RAS and 20CR‐KF in nearly all months, while the rest of the model simulations seem to display far more comparable RMSE. It should be however noted that observed diurnal variations over the SEUS in the winter and spring months are significantly lower than the rest of the year [ Bastola and Misra, ]. The monotonic decrease in RMSE from the summer months to December likely stems from the model's ability to simulate well the strong diurnal pattern of precipitation in the wet season.…”

“…In the Southeastern United States (SEUS), diurnal variation of precipitation accounts for nearly 40% of the total seasonal variation in the summer [ Bastola and Misra, ]. In fact, the diurnal variation of rainfall is a considerably strong and persistent feature of SEUS climatology [ Dai et al, ].…”

Terrestrial and Ocean Climate of the 20th Century

“…(Lin and Mitchell, 2005). From Bastola and Misra (2013). Seasonality in the temporal correlations between precipitation and surface temperature over Florida reveal that they change from positive correlations in the winter to negative correlations in the summer (Trenberth and Shea 2005;Misra and Dirmeyer 2009). In the winter time, surface evaporation that leads to cooling of the surface temperature is not an important contributor of moisture for local precipitation (Misra and Dirmeyer 2009).…”

Modeling flash floods in southern France for road management purposes

“…The high time frequency of radar data is also a determining factor (Michaud and Sorooshian, 1994;Bouilloud et al, 2010or Wetterhall et al, 2011. Results are sensitive to the radar time-step (Atencia et al, 2011;Anquetin et al, 2010;Bastola and Misra, 2013). O'Loughlin et al (2012) suggested that the calibration depends on the QPE time-step.…”