The Characteristics and Evolution of Orographic Snow Clouds under Weak Cold Advection

Abstract

Abstract On 25 February 1999, on the western side of the central mountain range of Japan, orographic snow clouds had formed under conditions of weak cold advection due to a winter monsoon after a cyclonic storm. The data from Ka-band Doppler radar, microwave radiometer, hydrometeor videosondes, and 2D Grey imaging probe provided unique datasets that were used to analyze the evolution of meso- and microscale structures, especially ice and supercooled liquid water (SLW) evolutions associated with variations in surrounding conditions. In the present case, four stages were identified in the evolution of the clouds: stratiform (I), transition (II), shallow convective (III), and dissipating (IV). During stage I, substantial blocking of the low-level flow occurred. The echo top was relatively flat and the echo pattern was stratiform with a bright band. The clouds were considered to be almost glaciated, primarily by the deposition growth of ice crystals. The wind speed up the slope gradually increased in the latt...