Page 167 - 《高原气象》2025年第6期

6 期 郑 皎等：昆明准静止锋冰冻天气过程的雨雪转化特征 1575

Characteristics of a Rain-Snow Transition for a Kunming

Quasi-Stationary Frontal Freezing Weather Process

ZHENG Jiao ， SHI Yuanhao ， LI Yingfa ， GUO Xueliang 2
1
1
1
（1. Honghe Meteorological Bureau， Mengzi 661199， Yunnan， China；
2. Institute of Atmospheric Physics， Chinese Academy of Sciences， Beijing 100029， China）

Abstract： The low-temperature rain-snow freezing weather always has multiple precipitation phases， which
greatly increases the difficulty of weather forecasting. Based on data from C-band dual-polarization radar and pre‐
cipitation particle spectrum in Honghe， Yunnan， the characteristics of atmospheric circulation， the vertical struc‐
ture of cloud microphysical structure and the spectral distribution of precipitation particles for a freezing weather
event occurred on February 22， 2022 are investigated. The main results are summarized as following： （1） the
strengthen and westward of the Kunming quasi-stationary front and its combination with the southern westerly
trough of Tibet Plateau should be responsible for the freezing weather event. The alternative changes of the front
and cold-warm atmospheric stratification directly induced the rain-snow phase transition on the ground.（2） when
precipitation occurred， at -15 ~ -10 ℃ layer， there were sudden increases in Z and K ， and a decrease in CC，
DP
DR
showing a significant growth of dendritic ice crystals. There was also obvious bright band property at the melting
layer， indicating an increase in melting process.（3） There were apparent differences in spectral distributions for
different precipitation-phase particles. The formation of large snowflakes mainly depends on frost and collision
growth of small snowflakes. The average particle number concentration of snowflakes reached the highest during
snowfall， and corresponded the falling velocity of 1. 1 m·s ， which was smaller than that of rain or sleet
-1
-1
（2. 2 m·s ）. The average spectra display a single-peak mode， with a spectral width of 0. 312~7. 5 mm for sleet
and snow， which was wider than that of rain （0. 312~5. 5 mm）. When sleet occurred， the particle size had a turn‐
ing point at 5. 5 mm， as it turned into snow， the concentration of large-sized particles increased significantly.
The results of this study can provide an important reference for the nowcasting of precipitation phase in winter.
Key words： Kunming quasi-stationary front； rain-snow transition； dual polarization radar； precipitating particle
spectrum