Temperature and precipitation during winter in Ny?lesund, Svalbard and possible tropical linkages

摘要

Winter (DJF) temperature and precipitation variability in an Arctic Archipelago, Svalbard is investigated for an extreme event during December 2015 as well as on interannual time scales. During December 2015–16, a strong high pressure anomaly over northern Europe channelised warm and moist air into Ny ?lesund (～79°N and ～11°E) resulting in extreme temperature and precipitation. This high pressure anomaly was a result of wave trains associated with the Madden Julian Oscillation (MJO). On interannual time scales, the observation site, Ny ?lesund was characterised by an increasing trend in precipitation and temperature. A composite of SLP anomalies associated with the temperature and precipitation anomalies was characterised by a high pressure anomaly over northern Europe. The second mode in the EOF of SLP anomalies during winter (DJF) also indicated the presence of a high pressure anomaly over northern Europe, extending into the Pacific. The mode was correlated significantly with the ENSO. During the study period, more than 50% of the ENSO events influenced temperature and precipitation in Ny Alesund. In the present study, the EOF-2 temporal pattern correlated strongly with La Nina in the Pacific, suggesting the generation of a high/low pressure anomaly during negative/positive ENSO phases. On interannual timescales, extremes were conspicuous, particularly when La Nina coincided with active MJO. This may be due to the fact that both processes generate similar pressure anomalies in northern Europe and reinforce each other. This study also suggests that the influence of El Nino is weaker than La Nina. It is also noted that decadal oscillations in the Pacific, particularly the Interdecadal Pacific Oscillation (IPO) also enhance the high-pressure anomalies over northern Europe. Thus, the temperature and precipitation in a high Arctic location, Ny ?lesund is interconnected, at least hemispherically and is defined by processes of different time scales.