engleski

Impact of tropical SSTs on the monthly signal over the North Atlantic-European region

Targeted numerical simulations were designed to test the potential impact of tropical sea surface temperatures (SSTs) on the geopotential heights at 200 hPa (GH200) signal over the North Atlantic-European region. Five experiments with SST anomalies prescribed in different areas, acting as lower boundary forcing, were created with an intermediately complex atmospheric general circulation model of the atmosphere (ICTP AGCM). In the AGCM experiments, the SST forcing was prescribed globally, in the tropical zone of all oceans, in the tropical Atlantic, in the tropical Indian Ocean and limited to the tropical Pacific. All of the simulations cover a 156-year-long period. The monthly GH200 signal variance was calculated based on the difference between the ensemble mean of each experiment and the climatological mean for the considered period. The monthly signal variance from each experiment was sorted into two categories according to the value of the late-winter Niño3.4 index to inspect the impact of the El Niño-Southern Oscillation (ENSO). Results have shown that the GH200 signal variance is the strongest in the late-winter months in all experiments. The AGCM experiment with SST boundary forcing prescribed only in the tropical Atlantic consistently had the smallest amplitude. The strongest signal linked to ENSO events was found in the experiment with the SST forcing prescribed only in the tropical Pacific.

teleconnections ; climate modelling ; North Atlantic ; ENSO

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