This study investigates interannual variations of surface air temperature (SAT) over mid- and high latitudes of Eurasia during boreal spring and their association with snow, atmospheric circulation, and sea surface temperature (SST) changes. The leading mode of spring SAT variations is featured by same-sign anomalies over most regions. The second mode features a tripole anomaly pattern with anomalies over the central part opposite to those over the eastern and western parts of Eurasia. A diagnosis of surface heat flux anomalies suggests that snow change contributes partly to SAT anomalies in several regions mainly by modulating surface shortwave radiation but cannot explain SAT changes in other regions. Atmospheric circulation anomalies play an important role in spring SAT variability via wind-induced heat advection and cloud-induced surface radiation changes. Positive SAT anomalies are associated with anomalous westerly winds from the North Atlantic Ocean or with anomalous anticyclone and southerly winds. Negative SAT anomalies occur in regions of anomalous cyclone and northerly winds. Atmospheric circulation anomalies associated with the first mode have a close relationship to spring Arctic Oscillation (AO), indicating the impact of the AO on continental-scale spring SAT variations over the mid- and high latitudes of Eurasia. The atmospheric circulation anomalies associated with the second mode feature a wave pattern over the North Atlantic and Eurasia. Such a wave pattern is related to a tripole SST anomaly pattern in the North Atlantic Ocean, signifying the contribution of the North Atlantic Ocean state to the formation of a tripole SAT anomaly pattern over the mid- and high latitudes of Eurasia.

The Indian and East Asian summer monsoons are two components of the whole Asian summer monsoon system. Previous studies have indicated in-phase and out-of-phase variations between Indian and East Asian summer rainfall. The present study reviews the current understanding of the connection between Indian and East Asian summer rainfall. The review covers the relationship of northern China, southern Japan, and South Korean summer rainfall with Indian summer rainfall; the atmospheric circulation anomalies connecting Indian and East Asian summer rainfall variations; the long-term change in the connection between Indian and northern China rainfall and the plausible reasons for the change; and the influence of ENSO on the relationship between Indian and East Asian summer rainfall and its change. While much progress has been made about the relationship between Indian and East Asian summer rainfall variations, there are several remaining issues that need investigation. These include the processes involved in the connection between Indian and East Asian summer rainfall, the non-stationarity of the connection and the plausible reasons, the influences of ENSO on the relationship, the performance of climate models in simulating the relationship between Indian and East Asian summer rainfall, and the relationship between Indian and East Asian rainfall intraseasonal fluctuations.

Boreal winter and spring snow cover extent and snow water equivalent over Eurasia experienced an obvious decrease in late 1980s. A concurrent surface warming is observed over the North Atlantic and Eurasia. The present study documents the relationship among the interdecadal changes in snow, surface air temperature, and wind and the plausible reason for this change. Analysis shows that the snow decrease contributes to the temperature increase only in some limited regions and that the surface warming is largely related to the change in atmospheric circulation. The effect of atmospheric circulation change on surface warming is manifested in wind‐induced heat advection and cloud‐radiation changes. The wind changes over the North Atlantic and Eurasia feature a wave train with an anomalous anticyclone over Europe and anomalous southerly winds over midlatitude east Europe and Asia. The anomalous southerly winds contribute to surface warming through advection of warmer air from lower latitudes. The anomalous anticyclone contributes to surface warming over Europe through anomalous warm advection by bringing warmer air from ocean and enhanced downward shortwave radiation by suppressing upward motion. The wave pattern appears to be connected to equatorial Atlantic warming. Warmer sea surface temperature (SST) in the equatorial Atlantic Ocean enhances convection and induces a lower level anomalous cyclone to the northwest of the SST warming. The role of equatorial North Atlantic SST increase in the formation of the wave train over Eurasia is supported by numerical experiments with an atmospheric general circulation model.

This study investigates interdecadal changes in the relationship between interannual variations of boreal spring sea surface temperature (SST) in the North Atlantic and surface air temperature (SAT) over the mid-to-high latitudes of Eurasia during 1948–2014. Analyses show that the connection between the spring North Atlantic tripole SST anomaly pattern and the Eurasian SAT anomalies has experienced marked interdecadal shifts around the early 1970s and mid-1990s. The connection is strong during 1954–72 and 1996–2014 but weak during 1973–91. A diagnosis indicates that interdecadal changes in the connection between the North Atlantic SST and Eurasian SAT variations are associated with changes in atmospheric circulation anomalies over Eurasia induced by the North Atlantic tripole SST anomaly pattern. Further analyses suggest that changes in atmospheric circulation anomalies over Eurasia are related to changes in the position of atmospheric heating anomalies over the North Atlantic, which may be due to the change in mean SST. Marked atmospheric heating anomalies appear over the tropical western North Atlantic during 1954–72 and 1996–2014 but over the subtropical central-eastern North Atlantic during 1973–91. Barotropic model experiments confirm that different background flows may also contribute to changes in anomalous atmospheric circulation over Eurasia.

A strong cold event hit eastern China around 24 January 2016 with surface air temperature reaching more than 10°C below the climatological mean in most regions of eastern China south of 40°N. A total of 37 strong cold events similar to the January 2016 event with temperature anomalies over eastern China exceeding −5°C have been identified during the winters from 1979/80 to 2015/16. A comparative analysis of events with surface temperature anomalies of the same intensity but limited to north of 40°N indicates that the southward invasion of cold air to eastern China south of 40°N is related to two factors. One is the latitudinal location of the upper-level wave train, the surface Siberian high, and the midtropospheric East Asian trough over the mid- to high-latitude Eurasian continent. The other is a subtropical upper-level wave train emanating from the midlatitude North Atlantic. The emergence of the subtropical wave train is related to the positive phase of the North Atlantic Oscillation (NAO). When the mid- to high-latitude wave train is located too far northward and the subtropical wave train induces an anomalous midtropospheric high over southern China, the East Asian trough does not extend southwestward and the Siberian high does not expand southeastward. In such a case, the cold air mainly affects northeastern China and northern Japan.