Ostalo
The effects of teleconnections on climate variability of the North Atlantic-European area
Sara Ivasić
Sažetak
Observed data, reanalysis and an intermediately complex general circulation model of the atmosphere (ICTP AGCM) have been employed to study the effects of teleconnections on the North Atlantic-European region as a part of this thesis. Modulation of the El Niño-Southern Oscillation (ENSO) teleconnection to the North Atlantic-European (NAE) region and its relationship with the North Atlantic Oscillation (NAO) have been tested via regression maps, running correlation, composite analysis and probability distributions. The impact of tropical ocean sea surface temperatures (SSTs) on the variability and predictable components of the late-winter atmospheric circulation over the NAE area has been investigated by employing advanced analysis techniques, such as the Empirical Orthogonal Functions (EOF) analysis and the signal-to-noise optimal patterns method. Targeted model simulations were designed to detect which ocean areas are the most important for establishing potentially predictable modes of atmospheric circulation in the NAE area. Finally, specific numerical model simulations were used to assess the impact of the warmer climate conditions on the variability and predictable components of the late winter circulation in the area of interest.
Results have shown that the ENSO teleconnection to the NAE region is not stationary. Its spatial pattern has changed from resembling the negative NAO at the surface to a different pattern with weak, statistically non-significant values after the 1970s. Meanwhile, targeted ICTP AGCM simulations confirmed the importance of sea-ice concentration and the background state of the sea surface temperatures in the modulation of the ENSO-NAE teleconnection. The change was detected at the surface and upper levels of the atmosphere in several variables and different datasets. Regarding the impact of tropical SSTs, it is suggested that the lower-boundary forcing originating from the tropics, especially the tropical Pacific, is essential for establishing the potentially predictable modes of atmospheric circulation over the North Atlantic on the seasonal and sub-seasonal scale.
Ključne riječi
climate variability; North Atlantic-European climate; Tropical-extratropical teleconnections, ENSO teleconnections, boundary-forced predictability
Hrčak ID:
318377
URI
Datum izdavanja:
12.6.2024.
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