第二届未来大气科学论坛

Freezing rain (FRZR) is one of the most hazardous disasters over southern China in winter, causing severe ice accretion on infrastructure and vegetation. This study analyzes the interannual variations of FRZR intensity, with a focus on the accumulated precipitation. The FRZR is diagnosed from the 5th generation of the European Centre for Medium-Range Weather Forecasts Reanalysis (ERA5) using the Ramer scheme. Results show that FRZR is most severe during January‒February (JF), accounting for approximately 87.1% of the total temporal variance in cold months (November–March). Stronger JF FRZR are significantly linked to intensified Siberian High (SH) and the northern component of the East Asian winter monsoon (EAWM), with correlation coefficients of 0.47 and 0.59, respectively (both significant at the 99% confidence level). These anomalies in the SH and northern component of the EAWM are likely driven by the strengthening of the Ural blocking high (UB). Furthermore, these changes in the UB are attributed to snow cover extent (SCE) over Eastern Europe during November‒December (ND). Specifically, the positive ND SCE anomalies over Eastern Europe are found to alter the vertically propagating Plumb fluxes, which may further manipulate the phase of stratospheric zonal wavenumber 2 through wave-mean flow interactions. The resulting positive geopotential height anomalies over the Ural region tend to propagate downward into the troposphere, thereby strengthening the UB in JF. These findings suggest that anomalous ND SCE over Eastern Europe can serve as an important indicator for JF FRZR variability over southern China, with a significant correlation coefficient of 0.65.

Freezing rain, Ural blocking high, snow cover extent, troposphere-stratosphere interaction