Climate patterns in December
Pro Research Analysisby 
Searched over 200M research papers
December Climate Patterns: Global Temperature Anomalies and Atmospheric Circulation
Northern Hemisphere Dipole: Colder Eurasia, Warmer North America
In December 2023, a striking temperature pattern emerged across the northern mid-latitudes, with colder-than-normal conditions over northern Eurasia and warmer-than-normal conditions over North America. This dipole pattern is closely linked to atmospheric variability, such as the strength of the Siberian high and the Alaska ridge, as well as boundary conditions like Arctic sea ice and North Atlantic sea surface temperatures. A key precursor to this pattern was strong blocking activity over the Greenland-Eurasia sector in November, which weakened the stratospheric polar vortex and shifted it toward Eurasia. This led to stronger high pressure over Eurasia and weaker ridging over Alaska, reinforcing the cold Eurasia/warm North America pattern in December .
The Role of the Siberian High in Asia and Iran
The Siberian high is a dominant feature influencing December temperatures in Asia. When the Siberian high is weaker, as observed during the record-breaking warm spell in the North China Plain in December 2023, cold air from high latitudes is blocked, resulting in unusually high temperatures. This event was also associated with a strong polar front jet, which promoted zonal circulation and further weakened the winter monsoon, leading to widespread warmth across Asia . In Iran, the extension of the Siberian high is a major driver of low temperatures in December. Different pressure patterns, especially those dominated by the Siberian high, are linked to below-average temperatures across much of Iran, although a general warming trend has been observed in recent decades, likely due to global warming .
North Atlantic Oscillation (NAO) and European Climate
The North Atlantic Oscillation (NAO) is a key driver of December climate in Europe and the North Atlantic region. The NAO is particularly predictable in December, thanks to its strong relationship with North Atlantic sea surface temperature anomalies and stratospheric circulation patterns. When the NAO is in a positive phase, westerly winds dominate the mid-latitudes, leading to milder conditions in Europe. However, extreme cold events, such as the cold December of 2010 in the UK, can occur when the NAO interacts with other atmospheric patterns like the East Atlantic mode, highlighting the complexity of December climate variability in Europe Tian2019Moore2011.
ENSO and Teleconnections in December
The El Niño–Southern Oscillation (ENSO) has a notable impact on December climate patterns, especially in the Euro-Atlantic sector and East Asia. ENSO-related temperature anomalies in November and December can extend over large areas, influencing both temperature and precipitation. In East Asia, ENSO’s influence is strongest in December, affecting the East Asian trough and leading to persistent temperature anomalies. The persistence of sea surface temperature dipole patterns in the North Atlantic and Mediterranean also plays a role in sustaining these anomalies throughout winter Yu2023King2018.
East Asian Temperature Variability and Subseasonal Reversals
East Asia experiences significant subseasonal temperature variability in December. For example, in some years, December is colder than the following winter months, influenced by factors such as reduced Arctic sea ice and specific phases of the Pacific Decadal Oscillation. These conditions can accelerate the East Asian jet stream and trigger cold air outbreaks. In South Korea, December temperature patterns are closely linked to ENSO and monsoon circulation, with tropical Pacific sea surface temperatures providing predictive skill for December temperatures several months in advance Xu2018Lee2019.
Solar and Geomagnetic Influences
Solar activity and geomagnetic conditions also affect December climate, particularly in the North Atlantic. Geomagnetic activity strengthens the polar vortex and promotes a positive NAO-like circulation, while solar ultraviolet variability influences stratospheric winds and pressure gradients. These effects can operate independently and contribute to the variability of December climate patterns .
Conclusion
December climate patterns are shaped by a complex interplay of atmospheric circulation systems, oceanic conditions, and external forcings. Key features include the Eurasia-North America temperature dipole, the influence of the Siberian high, the predictability of the NAO, ENSO teleconnections, and the role of solar and geomagnetic activity. Understanding these drivers is crucial for improving seasonal climate predictions and anticipating extreme events in December across the Northern Hemisphere.
Sources and full results
Most relevant research papers on this topic