Governing Equations of Atmospheric Layer Perturbation Potential Energy and Its Applications—Energy Budget of the South China Sea Summer Monsoon Activity
大气分层扰动位能控制方程及其应用——南海夏季风活动的能量收支

On the issue of energy transform in local circulation, the governing equations of layer perturbation potential energy order 1 (denoted as LPPE1) and kinetic energy (KE) are derived and the spatial distribution and seasonal variation of the related terms are investigated, the energy budgets of South China Sea summer monsoon (SCSSM) activity in different phases are studied. At 850 hPa level, the sources of LPPE1locate in the Intertropical Convergence Zone, most monsoon regions, and storm track regions, while the sinks of LPPE1locate in the subtropical eastern oceans and high latitudes. In general, the strong sources (sinks) of LPPE1coincide with the ridges (troughs) in its zonal departure distribution. The conversion term (CK), which links LPPE1and KE, is determined by the vertical velocity and atmospheric stability. Corresponding to warm air ascending or cold air descending, the conversion term is positive, indicating that LPPE1transforms to KE, and vice verse. At 850 hPa, the conversion term is featured by the maxima over the Intertropical Convergence Zone and most monsoon regions, and CKis also positive over the storm track region in the Northern Hemisphere and in the westerly belt in the Southern Hemisphere. This is applied to the energy budget of SCSSM activity; the conversion term grows rapidly in the phase of SCSSM revival and subsequently dominates in the active phase of SCSSM. In the active phase of SCSSM, the conversion term is about 2-3 times as much as the energy flux transported through the boundary, indicating that the conversion term plays a crucial role in SCSSM revival and active SCSSM. In addition, the condition of active SCSSM is explored, the results show that when LPPE1equals its summer climatological normals, SCSSM tends to be active if the ascending velocity exceeds the threshold velocity.