A Kilometer-Scale Coupled Atmosphere-Wave Forecasting System for the
European Arctic
Abstract
Accurately simulating the interactions between the components of a
coupled Earth modelling system (atmosphere, sea-ice, and wave) on a
kilometer-scale resolution is a new challenge in operational numerical
weather prediction. It is difficult due to the complexity of interactive
mechanisms, the limited accuracy of model components and scarcity of
observations available for assessing relevant coupled processes. This
study presents a newly developed convective-scale atmosphere-wave
coupled forecasting system for the European Arctic. The HARMONIE-AROME
configuration of the ALADIN-HIRLAM numerical weather prediction system
is coupled to the spectral wave model WAVEWATCH III using the OASIS3
model coupling toolkit. We analyze the impact of representing the
kilometer-scale atmosphere-wave interactions through coupled and
uncoupled forecasts on a model domain with 2.5 km spatial resolution. In
order to assess the coupled model’s accuracy and uncertainties we
compare 48-hour model forecasts against satellite observational products
such as Advanced Scatterometer 10 m wind speed, and altimeter based
significant wave height. The fully coupled atmosphere-wave model results
closely match both satellite-based wind speed and significant wave
height observations as well as surface pressure and wind speed
measurements from selected coastal station observation sites.
Furthermore, the coupled model contains smaller standard deviation of
errors in both 10m wind speed and significant wave height parameters
when compared to the uncoupled model forecasts. Atmosphere and wave
coupling reduces the short term forecast error variability of 10m wind
speed and significant wave height with the greatest benefit occurring
for high wind and wave conditions.