Reversing hydrology: quantifying the temporal aggregation effect of catchment rainfall estimation using sub-hourly data

Abstract

Inferred rainfall sequences generated by a novel method of inverting a continuous time transfer function show a smoothed profile when compared to the observed rainfall, however, streamflow generated using the inferred catchment rainfall is almost identical to observed streamflow (Rt2 > 97%). This paper compares the effective rainfall inferred by the regularised inversion process (termed inferred effective rainfall (IER)) proposed by the authors with effective rainfall derived from the observed catchment rainfall (termed observed effective rainfall (OER)) in both time and frequency domains in order to confirm that, by using the dominant catchment dynamics in the inversion process, the main characteristics of catchment rainfall are being captured by the IER estimates. Estimates of the resolution of the IER are found in the time domain by comparison with aggregated sequences of OER, and in the frequency domain by comparing the amplitude spectra of observed and IER. The temporal resolution of the rainfall estimates is affected by the slow time constant of the catchment, reflecting the presence of slow hydrological pathways, for example, aquifers, and by the rainfall regime, for example, dominance of convective or frontal rainfall. It is also affected by the goodness-of-fit of the original forward rainfall–streamflow model.