基于DETR模型的东亚冬季冷锋路径及结构特征研究OA

Cold fronts are among the primary synoptic-scale weather systems in the midlatitudes.Near frontal zones,meteorological variables such as wind speed and direction,temperature,and humidity often undergo rapid changes,frequently accompanied by severe weather,including sharp temperature decreases,strong winds,heavy precipitation,blizzards,and sandstorms.These weather events can pose substantial threats to human life,property,and socioeconomic activities.Therefore,accurate identification of cold fronts and a better understanding of their activity movement and structural characteristics are of considerable importance for weather forecasting and disaster prevention and mitigation.In recent years,deep-learning methods have been increasingly applied to the identifica-tion of atmospheric fronts.However,long-term climatological characteristics of cold-front activity and their associ-ated structural features in East Asia remain insufficiently understood.In this study,ERA-5 reanalysis data and de-tection transformer(DETR)deep-learning model are used to automatically identify winter cold fronts in East A-sia.A cold-front tracking algorithm is subsequently applied to construct a dataset of winter cold-front trajectories for the period 1994-2023.The K-Means clustering method is then used to classify the major cold-front tracks,and the circulation and structural characteristics associated with different track types,as well as their relationships with cold-front-induced blizzard events,are investigated.The results show that:1)The winter cold-front trajectories in East Asia can be classified into three major types:northwestern,southern,and northeastern tracks.Northeastern tracks account for the largest proportion(45.22%)and primarily affect Northeast China,North Chi-na,and Japan.Southern track account for 43.66%of all cases and mainly influence southern China.Northwestern tracks account for only 11.12%of the total but exhibit a relatively broad area of influence,primarily affecting northwestern China.2)The circulation and structural characteristics differ substantially among the three cold-front track types.For northwestern tracks,a shallow upper-level trough is typically located between western Mongolia and Xinjiang,China.At the surface,the southwestern flanks of a relatively weak Siberian high extends eastward,guiding the cold front eastward.The cold air is primarily transported toward northwestern China.Meanwhile,the prefrontal inverted trough does not develop into a well-defined cyclone,limiting the eastward progression of the cold front toward Northeast China.For southern tracks,much of the Eurasian continent is dominated by a strong Siberian high.Cold fronts propagate southeastward along the peripheral isobars of the high-pressure system.The frontal zone at 850 hPa is substantially stronger than that associated with northwestern tracks,and strong north-westerly winds within the frontal zone promote the southward transport of cold air toward southern China.For northeastern tracks,the upper-level circulation is relatively zonal,while the development of a cyclone over North-east China plays an important role in directing the cold air eastward.The formation and intensification of this cy-clone favor the eastward progression of the cold front and its subsequent influence on Northeast China.3)The cir-culation mechanisms associated with blizzard events also differ between the southern and northeastern track types.For blizzard events associated with southern tracks,strong northwesterly winds within the 850 hPa frontal zone play a key role in directing cold air southward.An anomalously strong Siberian high controls the movement of the cold front along the leading edge of the high-pressure system,and the associated rain and snow generally occur behind the cold front.In contrast,for blizzard events associated with northeastern tracks,strong southwesterly winds ahead of the 850 hPa frontal zone provide favorable conditions for moisture transport and contribute to the development of heavy snowfall.The formation and development of a Northeast China cyclone are key factors con-trolling the evolution of these events.During this process,the cold front transitions from the leading edge of the high-pressure system toward the developing low-pressure system,and the associated precipitation and snowfall are primarily located ahead of the cold front.However,the dynamical mechanisms governing the development of cold fronts along different tracks and the processes responsible for their associated severe weather have not been fully examined in this paper and warrant further investigation.