A comparative analysis of the first snowfall and freezing rain in 2015,Guizhou

Based on the reanalysis of data of NCEP 1.0°latitude×1.0° longitude and on the routine observational data,the differences and similarities of the atmospheric circulation,temperature and moisture vertical structure,dynamic lifting condition and the water vapor condition between the first snow from January 8th(1.8) and the first regional freezing from January 28th (1.28) rain process in 2015 have been analyzed comprehensively.The results show that the southern trough and the convergence of cold and warm air were more significant in the “1.8” snowfall process.The frontal inversion appeared at both cases.For the “1.28” freezing rain process,the inversion layer was deeper,and the vertical temperature distribution presented “cold-warm-cold” pattern and the moisture layer was shallow. For the “1. 8” snowfall process,before the snow started the inversion layer was shallow,and when it started to snow the inversion layer disappeared,while the characteristic of vertical temperature distribution was consistently cold and the moisture layer was deep.The front at lower layer is more stronger and the water vapor convergence region centralized at lower layer in the “1.28” freezing rain process.While the southwest airflow appeared at the middle and upper layer,and the north airflow appeared at the low layer in the “1.8” snowfall process.The abundant supplying of water vapour,distinct updraft at middle layer and the front at lower-layer contributed to the snowfall.