Convert basin meteorological data to sub-basin level

Mean rainfall, PE and temperature are often provided at the basin scale. Semi-distributive model need to compute the runoff at the sub-basin level.

Create function ConvertMeteoSD.GRiwrm(InputsModel, tol) for converting meteorological data with:

• InputsModel a GRiwrmInputsModel
• tol the maximum deviation between the resulted meteo data and the initial one (A small downstream area can lead to aberrant values).

The feature is needed for solving #13 (closed)