Region-dependent meteorological conditions for the winter cold hazards with and without precipitation in China

Abstract

Cold hazard is one of the major meteorological disasters in winter. However, the meteorological conditions for the cold hazard events vary significantly with both the feature of the event and the region of occurrence. This study divided winter cold hazard events in China into three categories based on the daily gridded dataset of cold hazards from November 1980 to March 2020: events without wintry precipitation (hazardous low temperature, abrupt temperature drop, and/or freezing), with wintry precipitation only (hazardous sleet and/or snowstorm), and with both. The region-dependent multivariate meteorological conditions for each category of cold hazards are investigated using ERA5 reanalysis data. Results show that the surface air temperature (T2m) and its anomaly (T2m_anom) are lower than climatology during cold hazards. But the difference in T2m among provinces exceeds 30°C, and even for the same province, the difference among different categories of cold hazards exceeds 10°C. The region- and category-dependent differences of T2m_anom and daily temperature drop (∆T24) are also large, about 5°C and 2°C d-1, respectively. The Multivariate Empirical Orthogonal Function analysis has further been applied to not only the abovementioned temperature-related variables but also the precipitation-related variables (i.e., daily accumulated total precipitation, daily accumulated snowfall, and daily mean snow depth) in the middle and lower Yangtze River region, which reveals the event-mean state and spatial-temporal coupling evolution during the progression of the event for the selected key meteorological variables. The meteorological conditions for cold hazards put forward by this study could provide region-dependent and category-dependent reference for the prediction and warning of cold hazards.

Region-dependent meteorological conditions for the winter cold hazards with and without precipitation in China

“…Based on the daily gridded dataset of winter cold hazards in China from November 1980 to March 2020 derived by Yu et al (2022), this study divided cold hazard events into three categories: DRY-C events (cold hazards without wintry precipitation including hazardous low temperature, abrupt temperature drop and freezing), WET-C events (cold hazards with wintry precipitation only including hazardous sleet and snowstorm), and BOTH-C events (both cold hazards without and with precipitation occur). And the disaster-caused capability of DRY-C events is relatively low than those of WET-C and BOTH-C events.…”

“…The cold hazard data used in this study is the daily gridded cold hazard occurrence dataset in the China domain derived by Yu et al (2022). The spatial resolution of the data elds is on 0.5° latitude × 0.66° longitude grids covering the period from November 1980 to March 2020.…”

“…For the occurrence of each subgroup of cold hazards (i.e., low temperature, abrupt temperature drop, freezing, sleet, and snowstorm), the corresponding variable value is set as 1 when the corresponding cold hazards occurred at this grid point, otherwise is set as 0. The values of occurrence are the same at all the grid points belonging to the same province, because of the limited level of detail in the o cial records (see details in Yu et al 2022).…”

“…(2015a) used the area percentage occupied by surface air temperature below climatology by at least half of the local standard deviations to detect the continental-scale cold events. The anomalous features of synoptic systems related to stronger East Asian winter monsoon and the strengthening of the equatorward cold air branch of isentropic meridional mass circulation are crucial to the cold air outbreak in East Asia ( Using the daily gridded cold hazard dataset in the China domain derived by Yu et al (2022), this study aims at revealing the region-dependent meteorological conditions for each subgroup of cold hazards in China. The remainder of this paper is organized as follows.…”