Impact of tropical SSTs on the late-winter signal over the North Atlantic-European region and contribution of midlatitude Atlantic

The impact of tropical sea surface temperatures (SSTs) on the signal of geopotential heights (GH200) over the North Atlantic-European (NAE) region is analysed from the aspects of seasonality, the contribution of individual tropical basins and midlatitude North Atlantic, El Nino-Southern Oscillation (ENSO) effect and spatial pattern of the atmospheric response. For this purpose, ensembles of targeted numerical simulations with SST forcing prescribed in various ocean basins are performed and examined. A clear atmospheric response is obtained in the late winter months. The strongest signal is linked to ENSO events during late winter. The competitive influences of individual tropical basins are indicated. At the same time, the superposition effect of the extratropical North Atlantic SSTs, which is established through the modulation of storm tracks, is demonstrated. Both, the modelled signal and the NOAA-CIRES-DOE 20th Century Reanalysis variance reveal the ENSO signature as a pattern in the North Atlantic projecting onto the East Atlantic pattern.

Automated summary

This study analyzes the impact of tropical sea surface temperatures (SSTs) on the signal of geopotential heights (GH200) over the North Atlantic-European (NAE) region. The results show that in late winter, the association between ENSO events and geopotential heights is the strongest. The influences of individual tropical basins are also competitive. Additionally, the superposition effect of extratropical North Atlantic SSTs is demonstrated through the modulation of storm tracks. The ENSO signature in the North Atlantic is projected onto the East Atlantic pattern.