Anomalous Winter Temperature and Precipitation Events in Southern China
我国南方冬季异常低温和异常降水事件分析

This paper analyzed the anomalous low-temperature events, and the anomalous rain-abundant events over southern China for Januaries since 1951 and for winters since 1880, there anomalous events are defined using ±1σ thresholds. And 12 cold temperature Januaries are identified where temperature anomaly is below - 1σ, and 10 wet Januaries are identified where precipitation anomaly is above +1σ.Among these events there are 3 cold-wet Januaries, namely 1969, 1993 and 2008. Using NCEP/NCAR reanalysis data, the authors checked the atmospheric circulation changes in association with the anomalous temperature and precipitation events. The results show that the strong Siberian high (SBH), East Asian Trough (EAT) and East Asian Jet Stream (EAJS) are favorable conditions for low temperature in southern China. While the anomalous south-wind at 850 hPa, the weak EAT at 500 hPa, and the strong Middle East Jet Stream (MEJS) and the weaker EAJS are found to accompany a wetter southern China. The cold-wet winters in southern China, such as January of 2008, are mainly related to a stronger Siberian High, and at the same time the circulation anomalous in middle to upper troposphere is precipitation-favorable. In wet winters, the water vapor below 500 hPa are mainly transported by the anomalous southwesterly flow and the anomalous southern flow over the Indo-China Peninsula and the South China Sea area. The correlation coefficients of MEJS, EAMW (East Asian Meridional Wind), EU (Eurasian pattern) to southern China precipitation in January are +0.65, - 0.59 and - 0.48 respectively, and the correlation for the high-pass filtered data are +0.63, - 0.55 and - 0.44, respectively, their correlations are all significant at the 99% level. MEJS, EAMW and EU together can explain 49.4% of the variance in January precipitation. Explained variance for January and winter temperature by Siberian High, EU, WP (Western Pacific pattern) and AO (Arctic Oscillation) are 47.2% and 51.5%, respectively. There are more precipitation in southern China during El Nino winters, and less precipitation during La Nina winters. And there is no clear evidence that occurrences of anomalous temperature events in winter in southern China are closely linked with ENSO events.