What Leads to Persisting Surface Air Temperature Anomalies from Winter to Following Spring over Mid- to High-Latitude Eurasia?

Abstract

Surface air temperature (SAT) anomalies tend to persist from winter to the following spring over the mid- to high latitudes of Eurasia. The present study compares two distinct cases of Eurasian SAT anomaly evolution and investigates the reasons for the persistence of continental-scale mid- to high-latitude Eurasian SAT anomalies from winter to following spring (termed persistent cases). The persisting SAT anomalies are closely associated with the sustenance of large-scale atmospheric circulation anomaly pattern over the North Atlantic and Eurasia, featuring a combination of the North Atlantic Oscillation/Arctic Oscillation (NAO/AO) and the Scandinavian pattern, from winter to spring. The combined circulation anomalies result in SAT warming over most of mid- to high-latitude Eurasia via anomalous wind-induced temperature advection. The sustenance of atmospheric circulation anomaly pattern is related to the maintenance of the North Atlantic triple sea surface temperature (SST) anomaly pattern due to air–sea interaction processes. The Barents Sea ice anomalies, which form in winter and increase in spring, also partly contribute to the sustenance of atmospheric circulation anomalies via modulating thermal state of the lower troposphere. In the cases that notable SAT warming (cooling) in winter is replaced by pronounced SAT cooling (warming) in the subsequent spring—termed reverse cases—the North Atlantic SST anomalies become small and the Greenland Sea ice change is a response to atmospheric change in spring. Without the support of lower boundary forcing, the atmospheric circulation anomaly pattern experiences a reverse in the spatial distribution from winter to spring likely due to internal atmospheric processes.

The 2020 Siberian heat wave

“…The high geopotential heights over Asia contributed to the set up for the record June Arctic Siberian temperature. The SPV and jet stream congruence was associated with a record AO during January–April that contributed to heat wave persistence (Deser et al ., 2007; Wu and Chen, 2020).…”

“…The multi-year regression shows the main features of winterearly spring 2020: an extensive positive relation from Europe through East Asia and a bimodal maxima distribution over Europe and East Asia. Eurasian surface air temperature anomalies have also been shown to be (Gong et al, 2019;Wu and Chen, 2020). NAO was greater than 1.0 for January-March 2020 and SCA was strongly negative (negative heights over Scandinavia and correlated with positive Siberian temperatures) for January-May 2020.…”

“…The multi‐year regression shows the main features of winter‐early spring 2020: an extensive positive relation from Europe through East Asia and a bimodal maxima distribution over Europe and East Asia. Eurasian surface air temperature anomalies have also been shown to be associated with the persistence of large‐scale atmospheric circulation anomaly patterns over the North Atlantic and Eurasia, featuring a combination of the North Atlantic Oscillation (NAO)/AO and the Scandinavian pattern (SCA), from winter to spring (Gong et al ., 2019; Wu and Chen, 2020). NAO was greater than 1.0 for January–March 2020 and SCA was strongly negative (negative heights over Scandinavia and correlated with positive Siberian temperatures) for January–May 2020.…”

A GA-Based BP Artificial Neural Network for Estimating Monthly Surface Air Temperature of the Antarctic during 1960–2019

“…Only three geographic factors (i.e., longitude, latitude, and elevation), which were found to be the main factors affecting monthly SAT distribution and variation at continental scales in several previous studies, were considered for estimating the Antarctic SAT fields in this study. However, the mechanisms driving SAT distribution and variation are very complicated in space and time domains [18,55,59], and there may be some other factors that have not yet been evaluated such as land surface type, air humidity, wind speed, wind direction, and distance from the coastline; particularly, sea surface temperature and atmospheric circulation have been regarded as important factors affecting the long-term trend of the monthly and annual mean SAT [62,63]. However, this issue is beyond the scope of this study and will be explored in future work.…”

A tripole pattern of summer surface air temperature anomalies over northern Eurasia and its precursory signals in the tropical Atlantic and northern Asian land

“…The El Niño–Southern Oscillation (ENSO) and related anomalous heating over the tropical Pacific and Atlantic can affect summer SAT over western Russia through exciting a Rossby wave extending northwestward to western Russia (Sun et al ., 2016). The North Atlantic SSTAs play an important role in inducing persisting atmospheric circulation pattern over Eurasia and in the maintenance of Eurasian SAT anomaly pattern from winter to spring (Wu and Chen, 2020).…”