Wave-activity relation containing wave-basic flow interaction based on decomposition of general potential vorticity
Na Li(李娜)1, Ling-Kun Ran(冉令坤)1,3,†, and Bao-Feng Jiao(焦宝峰)1,2
1 Key Laboratory of Cloud-Precipitation Physics and Severe Storms (LACS), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China; 2 Nanjing University of Information Science and Technology, Nanjing 210044, China; 3 University of the Chinese Academy of Sciences, Beijing 100049, China
Abstract On the basis of the general potential vorticity theorem (GPV), a new wave-activity relation is derived in an ageostrophic and nonhydrostatic dynamic framework. When the Reynolds average is taken, the wave-activity relation shares an exchange term with the equation of the basic-state GPV. Thus, the two equations are capable of presenting the dynamic process of the wave-basic flow interaction. Unlike the E-P flux theory which can only be used in large-scale atmosphere, the corresponding derivation provides a useful tool to analyze the feedback of waves to basic states and the forcing of basic states to waves simultaneously, and it can be used in mesoscale systems, such as heavy rainfall processes. The theory was initially applied to the landfalling Typhoon Mujigae (2015) by assigning the scalar φ to the generalized potential temperature (GPT). The results showed that the newly-derived wave-activity density is able to describe the wave activities associated with strong precipitation in Typhoon Mujigae (2015), including the eyewall and spiral rainbands. However, the interaction between the basic-state vortex and mesoscale waves denoted by the exchange term between basic-state GPV and wave-activity density mainly occurs in the eyewall in Typhoon Mujigae (2015). A comparison of the exchange term with other forcing terms in the newly-derived wave-activity relation indicates that the basic state-wave interaction plays a significant role in enhancing wave activities in the high-precipitation eyewall. By a magnitude analysis of the interaction term, it is found that the strong interaction between basic-state vortex and mesoscale waves is mainly attributed to two factors: the vertical vorticity intensity of the basic-state vortex and the averaged perturbation advection of perturbation GPT which is an exchange between the basic-state GPT and perturbation GPT.
Fund: Project supported by the Strategic Pilot Science and Technology Special Program of the Chinese Academy of Sciences (Grant No. XDA17010105), the National Key Research and Development Project, China (Grant No. 2018YFC1507104), the Key Scientific and Technology Research and Development Program of Jilin Province, China (Grant No. 20180201035SF), and the National Natural Science Foundation of China (Grant Nos. 41875056, 41775140, and 41575065).
Na Li(李娜), Ling-Kun Ran(冉令坤), and Bao-Feng Jiao(焦宝峰) Wave-activity relation containing wave-basic flow interaction based on decomposition of general potential vorticity 2021 Chin. Phys. B 30 049201
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