Soil-moisture-atmosphere coupling hotspots and their representation in seasonal forecasts of boreal summer

This paper examines soil-moisture-atmosphere coupling "hotspots" in the Northern Hemisphere during the summer months and evaluates their representation in seasonal forecasts. Using hindcasts from the Copernicus Climate Change Service (C3S) multi-model seasonal forecast system the study explores the predictability of land-atmosphere interactions based on soil moisture anomalies. The results show that regions with strong soil-moisture-atmosphere coupling exhibit considerable potential for predicting seasonal temperature and precipitation patterns a season or more in advance. However, significant uncertainty exists in estimates of the soil-moisture initial conditions and soil-moisture persistence timescales. While some regions show realistic coupling, others, including the Central USA and Eastern Europe, display exaggerated coupling, leading to errors in temperature and precipitation forecasts. This study underscores the potential for predicting the atmosphere in summer based on memory of soil-moisture initial conditions whilst highlighting areas for further forecast system improvement.