Subjectivity in evaluation of forecasts for intermittent streamflow - an information-theoretical perpective

Information-theoretical evaluation of probabilistic hydrological forecasts has several advantages. Firstly, forecasts in terms of probability put the onus for correct expression of uncertainty on the forecaster, as opposed to the recipient of the forecast. Secondly, formulating the evaluation of forecast quality in terms of information-measures enables consistency with the principle of minimum description length. 

When applying the information-theoretical evaluation framework to forecasts of mixed-type variables, such as streamflow in rivers with intermittent flow regimes, subjectivity is introduced through the choice of units in which streamflow is measured. This can lead to preference reversals between forecasts when using certain information measures.  

At the hand of some examples, we explore the origins of this subjectivity, possible interpretations, as well as avenues for its resolution. Among others, the role of observation uncertainty and the physical meaning of zero flow are discussed.