The Quantitative Research on Cold Vortex in Summer over Northeast China

Using daily reanalysis data, released by NCEP/NCAR, about geopotential height from 1981 to 2010 (30 years in total) to retrieve and analyze the cold vortex over Northeast China (CVONC), to extract and analyze the average state of CVONC, the authors define a deviation index on CVONC and discuss its rationality to depict the intensity of CVONC. It shows that: (1) the probability distribution of CVONC's geopotential height of occlusive center at 500 hPa is similar to the Gaussian normal distribution, and the average state of CVONC extracted by the expected value of Gaussian normal distribution hold general characters of CVONC; (2) the definition of deviation index on CVONC based on its average state could represent not only the deflected degree from the average state of CVONC, but also some information about the areas of low pressure, which means that it could indicate the intensity characteristics of CVONC directly.