Add instantaneous PET

[leoglonz]

Problem

The parameterization LSTM and HBV model in dHBV 2.0 currently rely on a daily Hargreaves PET formulation. For hourly PET, this requires aggregating all daily data for a daily PET, then discretizing to hourly. Therefore, forward runs of ngen and datastream requires preprocessing this input, which may not always be supported.

Proposed Solution

For full compatibility with hourly simulation settings, we need to evaluated and add a new instantaneous PET calculation to the dhbv2 BMIs. This may be, for example, Penman-Monteith, which could also levarage additional AORC observation data like wind speed and solar radiation. We will also need to evaluate whether the parameterization network will require retraining in such a case.

Additional context