Gaoyuan qixiang (Oct 2023)
Characteristics of Warm Conveyor Belts in Extratropical Cyclones Causing Snowstorms in Northeastern China
Abstract
The role of warm conveyor belts （WCBs） on the development of cyclones and precipitation and their relationship to occluded fronts are investigated for extratropical cyclones causing snowstorms in northeastern China during 2006 -2021， using ERA5 reanalysis data and Lagrangian Analysis Tool （LAGRANTO）.Main results show that： （1） The correlation coefficient of 0.63 which could pass significance test of α=0.01 implies strong correlation between cyclone intensification and WCB strength.Most of cyclones have occluded in the 24 h period of strongest deepening， and these occluded fronts are mainly warm-type occlusions.（2） Rapidly intensifying occluded cyclones typically have strong WCBs， which low-level inflow mainly locates in the center and warm sector of cyclones， while the outflow has two branches： some trajectories rise to the high levels northwest of the cyclone， and others ascend to the downstream of cyclone following the upper westerly winds； the interaction between low-level potential vorticity （PV） and upper-level PV in cyclone occluding stage eventually forms a PV tower throughout the troposphere.（3） Non-occluded cyclones also have strong WCBs and positive low-level PV anomalies， but lack of significant upper-level PV forcing.The development of these cyclones is weak.Weakly intensifying occluded cyclones have a PV tower， but their WCBs and precipitation are weak.（4） Cyclones with strong （weak） warm conveyor belts cause more （less） precipitation， and the distribution of rainfall is closely related to the location of warm conveyor belts.The WCB trajectories moving towards to cyclone center play an important role for cyclone development.The warm advection and low-level diabatic PV production generated by these trajectories both enhance the low-level circulation and contribute to the cyclone intensification.
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