It is not possible to override climate data within OverseerFM. OverseerFM uses a NIWA climate dataset, to understand the monthly temperature, PET, rainfall and sunshine hours in 500 square metre grids across New Zealand. This data represents an average taking into account the different weather conditions over 30 years (1991-2020), and any wet or dry periods.
Actual leaching from a farm block will vary year-on-year due to variations in weather — sometimes quite significantly. Using a long-term climate, removes short term variability (such as extreme weather events), which makes it possible to compare the effect of changes in farm management rather than reflecting changes in the weather each year. The model therefore estimates the nutrient leaching or gas emissions that are likely to occur in a typical year if the management system described remains in place. It is not a one-off prediction for a single year. This then allows comparisons with potential future management practices to inform farm planning and helps farms make good decisions for the long term.
For more information on the climate information the model uses see the Knowledge Base article here