Assessment of Atmospheric Circulation Regimes in the Atlantic-Eurasian and Arctic Regions Using Climate Indices. The Perspectives of Applications in the Seasonal Weather Forecasts
Mikhail M. Latonin
Department of Meteorology, Climatology and Environmental Protection, Russian State Hydrometeorological University, Malookhtinsky prospect 98, 195196, Saint-Petersburg, Russian Federation.
Ocean-atmosphere interaction is a very important chain when considering the elements of general circulation of the atmosphere, which essentially defines the everyday weather that we experience. And climate index is one of the tools used to describe the state of ocean-atmosphere interaction. Between the known climate indices, significantly characterizing weather in the Atlantic-Eurasian region, we can name the North Atlantic Oscillation and Arctic Oscillation indices.
Polar air outbreaks from the Arctic can be categorically considered as extreme weather events because monthly temperature anomalies both in the Arctic and middle latitudes may exceed 20 degrees. It was found out that both the North Atlantic Oscillation and the Arctic Oscillation indices are not sensitive to the two completely different types of polar air outbreaks in terms of distinguishing them. The physical origins of polar air outbreaks were highlighted, and the classification of them was carried out. Based on this classification, a conclusion about the existence of the North Siberian anomaly was made. And, according to many features, this anomaly can be treated as the one more action center of the atmosphere. This finding has allowed us to introduce a new climate index, which was called as the Atlantic Arctic Oscillation index. It is related to the normalized difference of sea level pressure anomalies between Reykjavik (Iceland) and Ostrov Dikson (Russia) weather stations. This index permits us to identify the two types of polar air outbreaks with the high level of recognition probability.
An interrelation between the new climate index and temperatures in the investigated (lat-lon) regions was analyzed. Summer season in the middle latitudes is becoming colder, while winter season in the Arctic is becoming warmer, and the Atlantic Arctic Oscillation index shows it.
One of the most important reasons of Arctic sea ice melting is related to the domination for the past 20 years of the second type of polar air outbreaks that cause high positive air temperature anomalies in the eastern sector of the Arctic. In contrast, during 1960s the first type of arctic air outbreaks prevailed.
Keywords: climate index, Arctic, sea ice, season, polar air outbreaks, sea level pressure, surface air temperature, Atlantic Arctic Oscillation, Arctic Oscillation, North Atlantic Oscillation.
Pages: 241 – 264 | Full PDF Paper