Statistical Characteristics Of The Northeast Cold Vortex In The Past 30 Years And Its Prediction And Evaluation By The S2S Model

Based on NCEP 6h reanalysis data and ERA5 observation data provided by China Meteorological Administration,the northeast cold vortex generated and maintained from may to september in 1989-2018 was statistically analyzed.Combined with ECMWF-CF and JMA model data provided by S2 S data center,the prediction ability and error sources of northeast cold vortex were evaluated with the help of different indicators.The results show that:(1)221 northeast cold vortex processes occurred in northeast China from may to september in 1989-2018,with a total of 1044 days,mainly moving eastward.The northeast cold vortex has a two-year cycle before 2010.The northeast cold vortex has the greatest influence in late spring and early summer.The strong north vortex and the weak middle vortex appear at high frequency in late spring and early autumn(may and september).In the late spring and early autumn,the north vortex and the strong upper level jet strengthen the divergence of the upper troposphere,cooperate with the circulation field of the middle and lower troposphere,cooperate with the obvious cold trough and strong upward movement,and have strong dry invasion,which is conducive to the strengthening of the cold vortex;in summer,the middle vortex is on the contrary.(2)ECMWF-CF S2 S model can well simulate the life history,intensity index and location of the northeast cold vortex,and the error of dry intrusion mainly comes from meridional wind.The first 2-5 forecast time models predicted the westerly jet branching and blocking situation ahead of time,the northeast cold vortex entered the mature period ahead of time,except the northeast cold vortex.The forecast results of strong/weak cold vortex NECVI are credible 15 / 10 days ahead of time,and the NECVI decreases / increases with the increase of forecast time.If the wind field is forecasted 20 days in advance,the upper air wind field is weak;if the wind field is forecasted 30 days in advance,the error of height field and temperature field is large.(3)JMA S2 S model has better prediction ability for north vortex than middle vortex,and stronger prediction ability for strong cold vortex than weak cold vortex.The prediction of the background circulation of the north vortex is credible 20 days in advance,the prediction of the dry intrusion mechanism is credible 1-10 days in advance,the simulation of the dry intrusion mechanism of the strong / weak north vortex is stronger / weaker,and the prediction of the vertical velocity field is credible 1-30 days in advance.The results show that the JMA model can predict the background circulation of meso vortex 10 days ahead of schedule,20 days ahead of schedule,the simulation error of height field and upper air wind field is large,and the intensity of strong / weak cold vortex is weak / strong.The accuracy of the dry intrusion mechanism is low.