Abstract: The Northeast China is one of the regions with a high frequency of cold wave events. It is crucial to clarify the pattern of cold wave events to develop disaster prevention and mitigation strategies. Authors used the Chinese national standard "Cold Wave Levels" (GB/T 21987-2017) and daily minimum temperature data from 226 meteorological stations in Northeast China from 1981 to 2015 to calculate the times and days of different levels of cold wave events occurring annually and monthly at the stations during 35 years. Linear regression and climate trend analysis were used to derive the spatial and temporal characteristics of cold wave events in Northeastern China. The results showed that the three levels of cold wave events occur more frequently at high latitudes and altitudes than at low latitudes and altitudes. High-occurrence areas are located in high-altitude areas, such as Daxinganling, Xiaoxinganling, and the Changbai mountains. The times of cold wave, strong cold wave, and extreme cold wave events at the stations during the last 35 years ranged from 37 to 447, 2 to 213, and 0 to 190, and their days ranged from 81 to 894, 5 to 464, and 0 to 475, respectively. In January, February, March, November, and December, the average times of cold wave events were 1.41, 1.46, 1.09, 1.36, and 1.39, and the average days was 3.04, 3.15, 2.23, 3.13, and 3.20, respectively. There were fewer cold wave events in April, May, September, and October, with an average times of 0.18, 0.01, 0.02, and 0.36 and an average days of 0.30, 0.02, 0.03, and 0.74 respectively (average of all stations). A trend of decreasing cold wave events is observed in the Northeast. The times of cold wave and strong cold wave events decreased at low latitudes and increased at middle and high latitudes, and the times of extreme cold wave events decreased. Climate trend analysis shows that the monthly average times and days of cold wave events for all three levels was in the range of [-1, 1]. The cold wave events in January and May showed an increasing trend, and those in February and October showed a decreasing trend. The cold wave events in March occurred primarily in the central region. Those in April showed a decreasing trend in times and an increasing trend in days. The trend in September was opposite to that in April and in November in the middle and high latitudes. The trend of cold wave events in April and September is unfavorable for agricultural production. Thus, measures should be implemented to adjust to this trend. However, since the temperature affects different crops and agricultural activities to various degrees, the cold wave events have different effects. Subsequent studies should determine appropriate temperature indicators, evaluate the level of cold wave events, investigate the changing patterns of cold wave events, and provide practical and reliable information to formulate disaster prevention and mitigation strategies.

Key words: Northeast China, Cold wave events, Annual scale, Monthly scale, Characteristics