Key Laboratory of Meteorological Disaster,Ministry of Education KLME/Joint International Research Laboratory of Climate and Environment Change ILCEC/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters CIC–FEMD,Nanjing University of Information Science and Technology,Nanjing,China
Based on the nationwide records of cold weather hazards combined with the high-precision reanalysis data NASA MERRA2 during wintertime (November-March) in the period of 1980-2020, a daily dataset of low-temperature disasters (low temperature, abrupt temperature drop, freezing, rain&snow, and snowstorm) in China has been constructed. Using linear trend analysis, ensemble empirical mode decomposition (EEMD) method, and wavelet analysis, the temporal and spatial distribution characteristics of various kinds of cold hazards in China are studied. Results show that cold hazards without precipitation (low temperature, abrupt temperature drop, and freezing) are often co-caused by two or more kinds of cold hazards, while cold hazards with precipitation (rain&snow and snowstorm) are mostly caused by a single kind. The occurrence frequency of different kinds of cold hazards has significant regional and seasonal differences: the low temperature hazard had the widest affected area in January, and the occurrence frequency presents a "high-low-subhigh" distribution pattern from south to north; The frequency of abrupt temperature drop hazard occurred the most in December, whose occurrence frequency is "high in the East and low in the west"; Rain& snow hazard occurred most in southern China from January to February; The occurrence of snowstorm hazard is significantly more frequent than the other four kinds of cold hazards, mostly distributed in susceptible regions such as pastoral areas. As far as the whole country is concerned, the frequency and affected area of most cold hazards (except snowstorm) show a long-term increasing trend. The snowstorm hazard, however, has an increasing trend in the affected area, mainly contributed from January, and a decreasing trend in the frequency, mainly contributed from March. The interdecadal variability of the occurrence and affected area of most cold hazards (except snowstorm) increased after 2000s, while the interdecadal variability of snowstorm is greater before 2000s; The interannual variability of the frequency of cold hazards (except snowstorm) increased significantly after 2005. For single-kind disasters, only the affected area of abrupt temperature drop hazard showed a significant increasing trend, mainly due to January. For the compound-kind cold hazards, the combination of abrupt temperature drop and cold hazards with precipitation increased significantly.