Harbin, located in northeast China (NEC), has obvious monsoon climate characteristics due to the influence of its geographical environment. Under the control of the polar continental air mass, winter in Harbin is exceedingly cold and long, with the frequent invasion of the cold and dry air from the north. Because of its intensely cold climate in winter, Harbin has created a local form of tourism with its own characteristics: the snow and ice landscape attracts a large number of tourists. Therefore, the anomalies of air temperature and precipitation in winter have an important impact on the livelihood of the local people and economy. In the winter of 2018/2019, the ice and snow tourism in Harbin was harshly affected by the extreme weather, and the direct cause is the anomalies of atmospheric circulation. There is a center of strong positive geopotential height anomalies over east China, which favors the movement of warm air northwards to the NEC, resulting in warmer-than-normal air temperature. Anomalous precipitation is largely controlled by the anomalies of local water vapor and air temperature. The aim of this study was to determine whether the warmer-than-normal temperature, which made the atmosphere more resistant to saturation, was the primary cause of the reduced snowfall. The relative importance of water vapor and air temperature anomalies to the anomalous precipitation was compared. The results suggest that the warmer-than-normal temperature affected all levels, but its impact on the near-surface level was greater. At the middle and upper levels (above 850 hPa), in addition to the warmer-than-normal temperature, the amount of water vapor was less than normal. These conditions both reduced the amount of snow; however, by comparison, the dryness of the air contributed more significantly.

Northeast China (NEC) is an agricultural base of the country. It suffered a severe drought in 2014. During the drought, the western Pacific subtropical high is stronger than normal and stretches to the west. The warm and moist air in the southwest edge of the high transports northwestwards and thus cannot affect NEC. Over high latitudes, in the regions west and east to NEC, there are large anomalies in geopotential height, which favour meridional exchange and may lead to stronger-than-normal cold air intrusions. Because of the lack of warm and moist air supply from the south while the invasion of the cold and dry air from the north, the atmosphere over NEC is finally drier and colder than normal in saturation levels. Based on the physical relation between seasonal precipitation and relative humidity, along with the defined C q and C T , indicators for measuring the changes in moisture and temperature, the effects of water vapour and air temperature on the drought can be linearly separated, and thus compared. Results reveal that, at middle and high levels, the dryness of the air, which plays a positive role in the drought, can offset the negative effect of the coldness, and the atmosphere over NEC then maintains a lower-than-normal relative humidity. In the near-surface level, the air is drier and warmer than normal, which facilitates the drought.