Synoptic Climate Settings and Moisture Supply for the Extreme Heavy Snowfall in Northern China during 6–8 November 2021

A record-breaking extreme heavy snowfall(EHS)event hit northern China during 6–8 November 2021,with two maximum snowfall centers in North China(NC)and Northeast China(NEC),which inflicted severe socioeconomic impacts.This paper compares the differences in the synoptic processes and moisture supply associated with the EHS event in NC and NEC,as well as the atmospheric circulation anomalies before the event,to provide a reference for better prediction and forecasting of EHS in northern China.Synoptic analyses show that a positively tilted,inverted 500-hPa trough channeled cold-air outbreaks into NC,while dynamic updrafts along the front below the trough promoted moisture convergence over this region.In NEC,the dynamic updraft south of the frontogenesis region firstly triggered a low-level Yellow–Bohai Sea cyclone,which then converged with the 500-hPa trough to ultimately form an NEC cold vortex.Calculation of the vorticity tendency indicates that absolute vorticity advection was a better indicator than absolute vorticity divergence for the movement of the trough/ridge at the synoptic scale.Moreover,NOAA’s HYSPLIT(Hybrid Single-Particle Lagrangian Integrated Trajectory)model results reveal that the moisture for the EHS over NC mainly originated from the mid-to-low levels over the Asian–African region and the Eurasian mid-to-high latitudes,accounting for 32%and 31%,respectively.In contrast,the source of water vapor for the EHS over NEC was mainly the Eurasian mid-to-high latitudes and East Asia,with contributions of 38%and 28%,respectively.The findings of this study shed some fresh light on the distinctive contributions of different moisture sources to local precipitation.Further analyses of the atmospheric circulation anomalies in October reveal that a phase shift in the Arctic Oscillation related to the weakening of the polar vortex could have served as a useful indicator for the cold-air outbreaks in this EHS event.

Surface energy budget diagnosis reveals possible mechanism for the different warming rate among Earth’s three poles in recent decades

With the introduction of the‘‘Third Pole'[1],the Arctic,Antarctic,and Tibetan Plateau(TP)can be collectively referred to as the‘‘three poles of the Earth'.The cryosphere is an important component of the climate system because of its effect on Earth’s surface albedo and its role in reducing the amount of heat exchanged between the atmosphere and ocean or land(2)As the dominant parts of the cryosphere,the Arctic,Antarctic,and TP are pivotal and sensitive areas of global climate change.Global warming will weaken the inherent stability of the cryosphere,such as its ice shelves,glaciers and permafrost[3,4].

Atmospheric heat source/sink dataset over the Tibetan Plateau based on satellite and routine meteorological observations

The Tibetan Plateau(TP),acting as a large elevated land surface and atmospheric heat source during spring and summer,has a substantial impact on regional and global weather and climate.To explore the multi-scale temporal variation in the thermal forcing effect of the TP,here we calculated the surface sensible heat and latent heat release based on 6-h routine observations at 80(32)meteorological stations during the period 1979–2016(1960–2016).Meanwhile,in situ air-column net radiation cooling during the period 1984–2015 was derived from satellite data.This new data-set provides continuous,robust,and the longest observational atmospheric heat source/sink data over the third pole,which will be helpful to better understand the spatial-temporal structure and multi-scale variation in TP diabatic heating and its influence on the earth’s climatic system.