Idealised framework to prescribe sea surface temperatures to investigate the atmospheric circulation response

Abstract. Midlatitude sea surface temperature (SST) fronts exert a strong influence on storm tracks and westerly jets by modulating lower‑tropospheric baroclinicity, moisture availability, and diabatic heating. Yet the sensitivity of the large‑scale atmospheric circulation to the detailed structure of these fronts remains difficult to isolate in realistic model configurations. We introduce an idealised SST framework for aquaplanet experiments that allows to prescribe the strength, width, and latitude of a midlatitude SST front. The SST profile is constructed from analytically derived meridional gradients, ensuring that changes to the front generate physically consistent moisture distributions through the Clausius–Clapeyron relation.

Using this framework, we conduct a suite of sensitivity experiments to quantify the influence from various aspects in the structure of the SST front on the climatological-mean energy and water cycles as well as the associated atmospheric circulation. Preliminary results demonstrate that increasing the frontal SST gradient or narrowing the frontal width systematically intensifies storm‑track activity and strengthens the midlatitude jet, whereas shifting the front meridionally alters the latitudinal position of the storm track in a non-linear way. Warm‑ and cold‑climate experiments further show that imposing a fixed freezing threshold in atmosphere‑only setups artificially reduces high‑latitude baroclinicity, whereas allowing SSTs to go below freezing produces a more realistic polar thermal structure.

Overall, our results demonstrate that the experimental framework developed in this study provides a useful basis for targeted process studies of how midlatitude SST‑front characteristics shape the atmospheric circulation, energy budget, and hydrological cycle.