Analysis on Snow Particle Spectrum Characteristics of a Typical Cold-flow Blizzard in Shandong Peninsula
In order to study microphysical characteristics and changes of cold-flow snowstorms in Shandong Peninsula,the snow particle spectrum characteristics of a blizzard process caused by strong cold airflow after northeast cold vortex in Shandong Peninsula in the early winter of 2020 are analyzed based on the data of precipitation distrometer measurements(OTT Parsivel),new generation Doppler radar and conventional observation.The results show that:(1)The 850 hPa temperature over the Bohai Sea was-16 ℃ during the blizzard process.The surface winds were characterized by the convergence of northerly wind and westerly wind from Dalian to Shandong Peninsula,and the snowstorm occurred in the atmospheric stratification with convective instability.(2)The snow particle spectrum of the blizzard was distributed in a multi-peak pattern and differed in the stages of beginning,development and dissipation,i.e.the periods of development,maturation and weakening of a convective system of severe snowfall.The three-parameter characteristics of Gamma function of snow particles are that the shape factor μ is positive or negative near the zero,the slope λ is less than 1.0 mm-1,and the lgN0 is about 3 m-3·mm-1-μ.(3)During the bliz-zard process,the falling terminal velocities of snow particles corresponding to multiple number concentra-tion centers were all below 1.0 m·s-1,and the peak falling velocity of maximum number concentration of snow particles was 0.55 m·s-1.When the diameter of snow particle was about 1.0 mm,the falling veloc-ity spectrum of snow particles with large total concentration had a peak value,which was close to the ve-locity curve of non-frosting snow particles,indicating that the most snow particles of the cold-flow blizzard were dry and not easy to frost.The snow snowflake types were mainly the densely rimed dendrites and the assemblages of coalesced plates.The coefficient and exponents for the relationship between the terminal falling velocity V and particle diameter D of the two different snowfall types are 0.62 and 0.33 for den-drites,and 0.69 and 0.41 for coalesced plates,respectively.The fitting velocity-diameter relationships for dendrites and coalesced plates are V=0.62D0.33 and V=0.69D0.41,respectively.
snow particle spectrumcold-flow blizzardmicrophysical parametersnow particle type
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万方数据
