The Interannual Wintertime Climate Modes Over Mid-High Latitude Eurasia and Their Climate Impacts

Eurasian teleconnection pattern (EU) and its two variants (EU1 and EU2) are the representative wintertime atmospheric teleconnections over Eurasian continent. They are mainly indicative of the local features and closely related to other teleconnection patterns. What are the major interannual climate modes over mid-high latitude Eurasia in boreal winter is still an open question. With the ERA5 reanalysis data sets after removing the linear impact of El Nino-Southern Oscillation (ENSO), three wintertime climate modes over mid-high latitude Eurasia are identified by the first three empirical orthogonal function (EOF) modes of the anomalous relative tendency (ART) of 500 hPa geopotential height. They approximately explain 75% of the interannual variance in total. The three climate modes have combined features of EU-like patterns with Arctic Oscillation (AO), North Atlantic Oscillation (NAO) and West Atlantic (WA) teleconnections, respectively, and they are named EU-AO, EU-NAO and EU-WA climate modes accordingly. All the three climate modes originate mainly from the North Atlantic and demonstrate clear Rossby wave trains downstream to East Asia along the great circle route, and they can be primarily stimulated and maintained by positive air-sea feedback over North Atlantic regarding to the obvious North Atlantic tripole-like sea surface temperature patterns. Interannual climate variations over the most Eurasian continent are strongly linked to and well reproduced by the three ENSO-independent climate modes, which can be applied as the important signals for monitoring and predicting winter interannual climate variabilities over mid-high latitude Eurasia. The climate signals from mid-high latitudes have been getting more and more prominent for the extreme events in Eurasian continent during recent years, and they are generally demonstrated as the integrated features of multiple typical teleconnection patterns, which are usually interfered by El Nino-Southern Oscillation (ENSO). Filtering out the linear impact of ENSO, the first three empirical orthogonal function modes of the anomalous relative tendency of 500 hPa geopotential height are regarded as the major interannual ENSO-independent wintertime climate modes over mid-high latitude Eurasia. They have combined features of two typical teleconnection patterns, originating from the North Atlantic and exerting strong effects on Eurasian climate through downstream propagated planetary wave trains, and their spatial patterns are gradually shifted southwestward in order. Moreover, their generation and maintenance are primarily associated with the North Atlantic tripole-like sea surface temperature and its positive interaction with the local atmosphere. The three ENSO-independent climate modes are responsible for most of interannual variations of precipitation and temperature over Eurasian continent, and they can be applied as metrics for climate monitoring and climate prediction over Eurasia in boreal winter. Three ENSO-independent climate modes over mid-high latitude Eurasia are identified as the combination of two typical teleconnection patternsNorth Atlantic tripole-like sea surface temperature is the key factor causing the three ENSO-independent climate modes via its forced local Rossby wave sourceThe three ENSO-independent climate modes primarily determine the interannual variability over mid-high latitude Eurasia