Explore the vast range of titles available.

This study investigates the dominant characteristics of winter Arctic tropospheric thickness (1000–200 hPa), the variations of winter atmospheric circulation in the Northern Hemisphere, and the related winter North Pacific storm track (NPST) variabilities during 1979–2018 under the combined effects of the La Niña events with different periods of Arctic tropospheric thermal conditions. Results show that the leading mode (42.7%) exhibits prominent warm anomalies centered on Greenland and Baffin Bay. The winter Arctic tropospheric thickness experienced a phase shift from a cold period of the Arctic tropospheric temperature in 1979–1999 to the warm period after 2000. During the La Niña events with Arctic tropospheric warm anomalies, a wave train is shown in the mid-high latitudes with alternative anticyclonic, cyclonic, and anticyclonic anomalies over the Ural Mountains, Lake Baikal, and North Pacific, respectively. This atmospheric circulation pattern not only intensifies the linkage between the Arctic and mid-low latitudes but also induces the winter NPST shifting poleward. The possible physical mechanism is attributed to the large-scale circulation change and the local baroclinic energy conversion (BCEC). The enhanced anticyclonic anomaly in the North Pacific alters the climatological mean flow, further influencing the local BCEC through the interaction between the mean flow and eddies. The significantly robust BCEC over the North Pacific possibly induces the poleward shift of winter NPST during the La Niña events under the warm period.

Studies have indicated regime shifts in atmospheric circulation, and associated changes in extratropical storm tracks and Arctic storm activity, in particular on the North Atlantic side of the Arctic Ocean. To improve understanding of changes in Arctic sea ice mass balance, we examined the impacts of the changed storm tracks and cyclone activity on Arctic sea ice export through Fram Strait by using a high resolution global ocean–sea ice model, MITgcm–ECCO2. The model was forced by the Japanese 25-year Reanalysis (JRA-25) dataset. The results show that storm-induced strong northerly wind stress can cause simultaneous response of daily sea ice export and, in turn, exert cumulative effects on interannual variability and long-term changes of sea ice export. Further analysis indicates that storm impact on sea ice export is spatially dependent. The storms occurring southeast of Fram Strait exhibit the largest impacts. The weakened intensity of winter (in this study winter is defined as October–March and summer as April–September) storms in this region after 1994/95 could be responsible for the decrease of total winter sea ice export during the same time period.

Using the lagged maximum covariance analysis (MCA), the present study investigates the interannual variability of the storm track in the Southern Hemisphere and the Antarctic sea ice throughout the year. The results show that the two are most tightly coupled in the austral cold seasons. Specifically, storm track anomalies in June and July are associated with a zonal dipole structure of the sea ice concentration (SIC) anomalies in the western Hemisphere, with centers in the Antarctic Peninsula and the Amundsen-Bellingshausen Seas. The storm track can modulate the large-scale atmospheric circulations, which induces anomalous meridional heat transport, downward longwave radiation, and mechanical forcing to further influence the SIC anomalies. The resultant SIC anomalies can last for several months and have the potential to feed back to the storm track. According to the MCA, the influence of the SIC anomalies to the storm track is most evident in August. The SIC dipole along with the SIC anomalies in the Indian Ocean sector have large impact on the storm track activities downstream. The SIC anomalies alters the near-surface temperature gradient and subsequently atmospheric baroclinicity. Further energetic analysis suggests that the enhanced atmospheric baroclinicity facilitates the baroclinic energy conversion from mean available potential energy to eddy available potential energy, and then to eddy kinetic energy, strengthening the storm track activities over the midlatitude Indian Ocean.

Air–sea interactions in mid-latitudes and their climatic effects have long been a research focus. However, the influence of the variability of the Southern Oceanic Front (SOF) on atmospheric processes at interannual timescales remains somewhat ambiguous from existing studies. Using reanalysis data, our findings reveal that the SOF reaches its maximum intensity during the austral summer, characterized by pronounced interannual variability and an insignificant trend. On the one hand, an enhanced SOF intensifies the meridional temperature gradient and atmospheric baroclinicity, accompanied by increased local and downstream baroclinic energy conversion. This amplifies storm track activities in both the lower and upper troposphere. On the other hand, the atmospheric circulation in mid- and high-latitudes exhibits an equivalent barotropic response. This is attributed to the feedback of storm tracks on the mean flow, dominated by the transient eddy vorticity forcing. Moreover, we compare the relative contributions of the South Indian Oceanic Front (SIOF) and South Atlantic Oceanic Front (SAOF) variability to storm track and atmospheric circulation. Results indicate that the SIOF variability dominates the downstream development of storm track response and modulates the anomalous atmospheric circulation around the Antarctic, while the SAOF variability produces only a limited local atmospheric response.

Using multiple reanalysis datasets, this study reveals that the variability in the western Pacific pattern (WP) in boreal winter has shown notable changes during recent decades. The variability in the winter WP exhibited a marked weakening trend before the early 2000s and increased slightly thereafter. Two epochs with the highest and lowest WP variabilities are selected for a comparative analysis. Winter WP-related meridional dipole atmospheric anomalies over the North Pacific were stronger and had a broader range during the high-variability epoch than during the low-variability epoch. Correspondingly, the winter WP had larger impacts on surface temperature variations over Eurasia and North America during the high-variability epoch than that during the low-variability epoch. We find that the shift in the winter WP variability is closely related to changes in the connection between the winter WP and the El Niño-Southern Oscillation (ENSO) and to changes in the amplitude of the North Pacific storm track. Specifically, ENSO had a closer connection with the WP during the high-variability epoch, when the amplitude of the North Pacific storm track was also stronger. During the high-variability epoch, the extratropical atmospheric anomalies generated by the tropical ENSO shifted westward and projected more on the WP-related atmospheric anomalies, thus contributing to an increase in WP variability. In addition, the larger amplitude of the North Pacific storm track that occurred during the high-variability epoch led to the stronger feedback of synoptic-scale eddies to the mean flow and contributed to stronger WP variability. Further analysis indicates that the change in the connection of ENSO with the WP may be partly related to the zonal shift of the sea surface temperature anomaly in the tropical Pacific associated with ENSO.

Previous studies have found inconsistent responses of the North Atlantic jet to Arctic sea‐ice loss. The response of wintertime atmospheric circulation and surface climate over the North Atlantic‐European region to future Arctic sea‐ice loss under 2°C global warming is analyzed, using model output from the Polar Amplification Model Intercomparison Project. The models agree that the North Atlantic jet shifts slightly southward in response to sea‐ice loss, but they disagree on the sign of the jet speed response. The jet response induces a dipole anomaly of precipitation and storm track activity over the North Atlantic‐European region. The changes in jet latitude and speed induce distinct regional surface climate responses, and together they strongly shape the North Atlantic‐European response to future Arctic sea‐ice loss. Constraining the North Atlantic jet response is important for reducing uncertainty in the North Atlantic‐European precipitation response to future Arctic sea‐ice loss. Plain Language Summary Variations in the North Atlantic jet affect temperature, precipitation, and storminess in Europe. It is not well understood how the jet and European climate will respond to future sea‐ice loss in the Arctic under human‐caused increases in global temperature. We study how atmospheric circulation and surface climate in winter over the North Atlantic‐European region would respond to future Arctic sea‐ice loss under 2°C global warming, using an unprecedented number of coordinated simulations from different climate models. In many models the North Atlantic jet stream in winter responds by shifting southward, but the response of its speed is less clear. These jet stream changes are found to strongly shape the responses in precipitation and storm track activity. More precise estimates of the jet stream response are key to reducing uncertainty in the North Atlantic‐European precipitation response to future Arctic sea‐ice loss. Key Points Projected Arctic sea‐ice loss causes a robust equatorward shift of the North Atlantic jet across models, but no robust change in jet speed Changes in jet position and speed strongly shape the European winter surface climate response to projected Arctic sea‐ice loss Constraining the jet response is important for reducing uncertainty in the European precipitation response to future Arctic sea‐ice loss

The first EOF mode (EOF1) of summer storm track activity over the North Atlantic is characterized by a dipole structure, with negative storm track anomalies over the south coast of Greenland extending northeast across Iceland to the Norwegian Sea and positive anomalies over coastal western Europe. This study shows that a significant interdecadal change in the North Atlantic storm track during boreal summer occurred around the mid-2000s. After the mid-2000s, the EOF1 occurs more frequently at its positive phase, which is associated with an interdecadal increase in the geopotential height anomalies around Greenland. On the intra-seasonal timescale, the anticyclonic anomalies around Greenland are crucial for the occurrence of positive EOF1 events via triggering eastward propagating Rossby waves. Therefore, the interdecadal increase in the geopotential height anomalies around Greenland tends to facilitate the occurrence of the positive EOF1 event and is therefore a key driver of the interdecadal change in the summer storm track activity over the North Atlantic. Further analysis indicates that the development of anticyclonic anomalies around Greenland is maintained by the self-interaction among the low- and high-frequency transients themselves. Moreover, the anomalous synoptic eddy activities associated with the change in storm tracks can in turn amplify and maintain the Rossby waves triggered by the anticyclonic anomalies around Greenland in the synoptic-scale eddy feedback process.

The strong East Asian winter monsoon (EAWM) frequently brings severe cold weather and heavy snowfall to East Asia, emphasizing the needs for a comprehensive understanding of its underlying mechanisms. This study investigates how midlatitude atmosphere–ocean interactions, as a feedback process, influence EAWM variability. Strong EAWM brings lower‐tropospheric cold air in early winter, enhancing upward surface heat fluxes over the midlatitude western North Pacific (WNP) around 30°N. These anomalous fluxes progressively cool sea surface temperature (SST) south of Japan until late winter. Atmospheric general circulation model experiments revealed that the resulting cold SST anomalies modulate storm‐track activity and transient eddy‐mean flow interaction, facilitating an EAWM‐related cyclonic anomaly east of Japan in late winter. This circulation response acts to reinforces the EAWM, leading to further lower‐tropospheric cooling around Japan. These findings highlight the active role of the midlatitude WNP and importance of the atmosphere–ocean interactions in driving the EAWM variability.

ABSTRACT The most active synoptic‐scale disturbances in Eurasia are embedded within the Siberian storm track. This paper investigates the linkage between the winter Siberian storm track (WSST) and the winter precipitation in China and explores the underlying physical processes. The results show that an intensified WSST is associated with a decrease in winter precipitation along the southeast coast of China and in the East China Sea on the interannual scale. The anomalous low‐level northerly winds over eastern China and upper‐level positive vorticity anomalies over the East China Sea, accompanied by the subsidence, exert an inhibitory effect on precipitation. The anomalous moisture flux divergence related to northerly winds reduces the moisture supply. The interaction between WSST and mean flow may sustain the anomalous large‐scale atmospheric circulation and baroclinicity. In addition, synoptic‐scale disturbances originating from the WSST region propagate to the East China Sea, forming cyclonic circulation anomalies that are unfavorable for precipitation. The winter precipitation anomalies related to the Siberian storm track. Climatological winter‐mean standard deviation of filtered geopotential height at 500 hPa (left). Composite differences in precipitation between strong and weak Siberian storm track winters (right).

After approaching 0°C owing to an Atlantic storm at the end of 2015, the Arctic temperature approached freezing again in 2022, indicating that Arctic daily warming events remain a concern. The NCEP/NCAR Reanalysis dataset was used to investigate the influence of the NAO on the Arctic winter daily warming events induced by Atlantic storms, known as the Atlantic pattern-Arctic Rapid Tropospheric Daily Warming (Atlantic-RTDW) event. Atlantic-RTDW events are triggered by Atlantic storms that transport warm and humid air masses moving into the Arctic. Furthermore, an interdecadal change in the influence of NAO on Atlantic-RTDW-event frequency was observed around the mid-1980s. Specifically, before the mid-1980s (pre-transition period), 500-hPa southerly (northerly) wind anomalies occupied the North Atlantic (NA) in the positive (negative) phase of NAO, which increased (decreased) the Atlantic-RTDW events occurrence by steering Atlantic storms into (away from) the Arctic; thus, the NAO could potentially influence the Atlantic-RTDW-event frequency. However, the relationship between the NAO and the Atlantic-RTDW-event frequency has weakened since the mid-1980s (post-transition period). In the post-transition period, such 500-hPa southerly (northerly) wind anomalies over the NA hardly existed in the positive (negative) phase of NAO, which was attributed to a stronger Atlantic Storm Track (AST) activity intensity than that in the pre-transition period. During this period, the strong AST induced an enhanced NAO-related cyclone via transient eddy-mean flow interactions, resulting in the disappearance of southerly and northerly wind anomalies over the NA.