1.Key Laboratory of Mesoscale Severe Weather of Ministry of Education,School of Atmospheric Sciences,Nanjing University;2.China;3.Henan Key Laboratory of Agrometeorological Support and Applied Technique;4.Henan Meteorological Observatory
The idealized moist baroclinic wave simulation was performed to describe the rapid development of extratropical cyclone. Then the warm and cold conveyor belts were identified with the use of Lagrangian trajectory selection method and physical quantities along their trajectories were diagnosed, followed by the analysis of their impacts on the precipitation. The study reappears the previous conclusions of conveyor belts and find some more refined structures, especially for the cold conveyor belts. As the result shows that, the warm conveyor belts could generally split into “forward-sloping ascent” and “rearward-sloping ascent” branches. They originate in the warm sector ahead the cold front and low-level, and move respectively forward and rearward relative to the cyclone center when they spiral upward to the upper and middle level, generating negative PV disturbance upon the outflow region and promoting the development of upper system. They also transport abundant moisture upward and influence significantly the formation and maintenance of the precipitation extremum around the front. The cold conveyor belts are confirmed to represent two branches of ascent and remaining low-level as described by the previous researches, and then could be classified finely into four branches. The “forward-sloping ascent” and “rearward-sloping ascent” branches originate near the warm front and curve separately forward and rearward relative to the cyclone center when rising upon the middle level, benefiting to the rainfalls around the warm front. While the branches of “wrapping around the cyclone and forward-sloping” and “wrapping around the cyclone and rearward-sloping”, always staying in the lower level, move from east of the surface cyclone far from the warm front toward the cyclone center whenever their vapor content increases, and then descend respectively anticlockwise and clockwise to the downstream and upstream of the cyclone after travelling slowly upward west of the cyclone around the center, inducing the little precipitation northwest of the cyclone.