Analysis on the Cause of Cold and Warm Transition in Beijing- Tianjin-Hebei during November-December 2022

During November-December of 2022， the climate of Beijing-Tianjin-Hebei （BTH） showed significant cold and warm transition， and the average air temperature difference between November and December was 10.6 °C， ranked first with 1971 and 1980 since 1961.Based on NCEP/NCAR reanalysis and multiple climate index data， the possible causes of the air temperature transition in November and December 2022 in BTH was explored from the perspective of the interdecadal influence of atmospheric circulation transition， ENSO and AO on variation of temperature anomalies.The results show that the weak strength of the Ural Mountains Blocking High and the Siberian High， as well as the strong strength of the Western Pacific Subtropical high led to the abnormally warm climate in the BTH region in November.But the turning of the atmospheric circulation in December， the strengthening of the Ural Blocking high， the deepening of the East Asia Great trough， the strengthening of the Siberian high， and the northerly air flow in BTH， resulting in the abnormally cold December.The temperature anomaly difference of these two months showed obvious interdecadal changes， positive in 1961-1985， negative in 1986 -2003， and positive again in 2004 -2022.Compared to the cold and warm transition events in 1971， 1980， and 2005， there were interdecadal changes observed in atmospheric circulation transitions.The weak cold air activity in the north and the southern warm air flow influenced by the strengthening of the Western Pacific subtropical high acted together to cause the warm November of 2022 and 2005.However， the weak cold air activity in the north was mainly influence factor for warm November 1971 and 1980.The combination of significant Arctic warming and a significantly stronger Siberian high led to unusually cold Decembers in 2022 and 2005.The correlation between ENSO and November temperature in the BTH， as well as the correlation between AO and December temperature， exhibited a significant increase during the 2000s.In the context of La Nin ̃a， AO transitioned from a positive phase in November to a negative phase in December， resulting in a high likelihood of temperature inversion.Given that 2022 was the year of La Niña and influenced by an AO shift， a cold to warm transition event occurred in the BTH from November to December.