Interannual Variability of Wintertime Monthly Surface Air Temperature in China

Based on observed and reanalysis data, this study analyzes the spatiotemporal variations of monthly surface temperature in winter in China, their interrelationship, and the related anomalous circulation on the interannual timescale. The atmospheric internal mechanisms for the interannual variation of surface temperature is also discussed. The dominant interannual mode is uniform across China, except in the Tibetan Plateau, for all winter months, while the second mode is a north–south dipole mode with opposite sign. The dominant interannual modes of surface temperature in January and February are closely correlated to each other in phase, but are to some extent negatively correlated with that in the prior December. The dominant interannual modes of monthly surface temperature in winter are also linked to the opposite-sign dipole anomalous patterns of surface temperature in the Eurasian continent. The anomalous temperature signals associated with the nationwide winter surface temperature anomalies may extend up to high levels in the troposphere, with the most intense signals at the surface. The surface temperature anomalies may induce the air temperature anomalies from the near surface to the upper troposphere via the upward longwave radiation flux anomalies emitted from the underlying surface. In all winter months, the intensified westerly over the northern Eurasian continent hinders the southward intrusion of cold air from high latitudes, and then results in a deep warm anomaly over China in the winter, and an even larger part of the Eurasian continent.