Tropical influence on Euro-Asian autumn rainfall variability |
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| Authors: | A Mariotti J Ballabrera-Poy N Zeng |
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| Institution: | (1) ENEA, Rome, Italy and ESSIC, University of Maryland, College Park, MD, USA;(2) ESSIC, University of Maryland, College Park, MD, USA;(3) Department of Meteorology and ESSIC, University of Maryland, College Park, MD, USA |
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| Abstract: | The connection between autumn rainfall variability in the Euro-Asian domain and tropical climate is documented using state-of-the-art global observational datasets and re-analyses. Results suggest a robust statistical relationship between the El Niño Southern Oscillation (ENSO) and autumn rainfall in parts of southwest Europe, northern Africa and southwest Asia. The correlation between area-mean anomalies over this region (Pea) and the NIÑO3.4 index is 0.68, stationary over the last 50 years. Global ENSO-like tropical climate anomalies are observed in conjunction with Pea anomalies confirming the relationship found with the NIÑO3.4 index. Overall, the connection with Indo-Pacific variability is stronger than that with the eastern Pacific.While rainfall anomalies in southwest Europe and southwest Asia appear to largely co-vary as one pattern under the influence of ENSO, our results suggest that different mechanisms may be contributing to the observed anomalies. In the North Atlantic/European region, it is speculated that while a PNA-like mode maybe the prevailing teleconnection mechanism for high Pea, for low Pea tropical Atlantic ENSO related SST anomalies may be playing a more relevant role forcing northeastward propagating Rossby waves. Over southwest Asia, a more direct connection to the Indo-Pacific region is suggested by the upper air anomaly observed over southern Asia, possibly the Rossby wave response to enhanced heating in the Indian Ocean. |
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