Potential vorticity inversion diagnosis of the impact of large scale physical processes on the intensity changes of typhoon Fitow(2013)
The typhoon Fitow(2013)is a typical long-term intensity-maintaining typhoon.Based on the analyses of the horizontal and vertical distribution characteristics of total potential vorticity disturbance of typhoon,this paper investigates the impacts of large-scale environmental conditions on the long-term maintenance of typhoon intensity,by using the piecewise potential vorticity inversion method.The study can help to better understand the typhoon dynamical issues and provide references for operational forecasting of typhoon intensity.The main conclusions are as follows:(1)The equilibrium physical fields that derived from the inversion of whole layer potential vorticity perturbation can accurately reflect the intensity variation and movement of Typhoon Fitow.Specifically,the average total potential vorticity perturbation in the middle troposphere is correlated well to the variation of typhoon intensity.(2)In the lower troposphere,the potential vorticity disturbance related to latent heat release plays a decisive role in the long-term maintenance of typhoon intensity,followed by the disturbance related to dry air.The geopotential height and vorticity fields that inverted from them correspond well with the typhoon intensity.Meanwhile,the potential vorticity disturbance related to unsaturated moist air and the disturbance in upper troposphere have negative contributions to the geopotential height disturbance,and the former had a reverse relationship with typhoon intensity.The negative contribution of upper-layer potential vorticity disturbance above 700 hPa weakened the positive contribution in the middle troposphere to a certain extent.3)In the middle troposphere,the contribution of potential vorticity disturbance related to latent heat release accounts for 65.2％to the development and intensity maintenance of typhoon.The contribution of vorticity perturbation in boundary layer increased from 0.2％during the development stage to 8.3％during the mature stage.The vorticity perturbation of dry air decreases with the enhancement of the negative geopotential heights perturbation caused by latent heat release and boundary layer air,accounting for about 26.5％during the intensity-maintaining period.During the rapid dissipation period,the positive contribution of these physical processes are redistributed due to the landfall and weakening of typhoon.In addition,the maximum relative vorticity of these physical process appeared 12 hours ahead of the intensity-maintaining stage of typhoon,which can be considered as a forecast indicator for long-term maintenance of typhoon intensity.
万方数据
维普
