Seamless meteorological forecast production and evaluation towards hydrological decision-making in France : CIPRHES projet

Hydrological drought conditions have negative implications for environmental and socio-economic activities in France. Operational drought forecasts with adequate timing and quality can guide decision-makers to prepare and make informed decisions on water management. Available ensemble meteorological forecasting systems, used to force hydrological models, differ in configuration, resolution, timescale, release frequency, and accuracy. These differences in atmospheric forecasting systems limit their usefulness for operational drought forecasts. To address this challenge, we proposed an approach to produce seamless atmospheric forecasts (SeamF). SeamF were constructed from the extended- and long-range ensemble prediction systems (ECMWF and Météo-France, respectively) using a random concatenation member by member method in a first step.

The new SeamF system provides a 144-day outlook of hourly and daily precipitation and temperature variables, updated once a week, suitable for hydrological modelling over the country. In addition to the practicability of these integrated forecasts, as compared to stand-alone extended- or long-range forecasts, the level of deterministic and probabilistic verifications metrics suggests a promising improvement in hydrological applications. This approach builds a basis for more sophisticated seamless forecast production and application for hydrological decision-making in France.