Variations in atmospheric perturbation potential energy associated with the South China Sea summer monsoon

Yazhou Zhang,Jianping Li,Jiaqing Xue,Qiuyun Wang

doi:10.1007/s00382-019-04845-7

Abstract

This study investigates the energy conversion processes and their relation to convection (circulation) during the South China Sea summer monsoon (SCSSM) years from the viewpoint of atmospheric perturbation potential energy (PPE). An atmospheric PPE dipole pattern associated with the SCSSM develops over the western North Pacific (WNP) and southern Maritime Continent (SMC) in the boreal summer, serving as a link between the SCSSM and diabatic heating. Actually, the conversion between the energy variations and the convection over the WNP is distinctly different with that over the SMC. The precipitation leads the PPE over the WNP, while similar situation is reversed over the SMC. During strong SCSSM years, the higher PPE over the WNP, controlled primarily by the latent heat released from condensation related to surplus precipitation, is corresponding to the negative energy conversion ( text{C}_{k} ) over there. This indicates that more PPE is converted to perturbation kinetic energy and further intensifying ascending motion over the WNP. Consequently, the descending movement reduces the PPE and is corresponding to positive text{C}_{k} over the SMC, suggesting that the less PPE converts into the perturbation kinetic energy and in turn favors the descending movement and deficit precipitation there. The enhanced southwesterly induced by this SCSSM Hadley circulation, superimposed on the mean southwesterly wind, further favors the intensification of the SCSSM, implying that the SCSSM can maintain development through the positive convection–PPE–circulation feedback.

Highlights

The South China Sea (SCS) is part of the tropical Indian–western Pacific warm pool and lies at the center of the Asian–Australian monsoon system, which plays an important role in moisture transport from the North Indian Ocean and Southern Hemisphere to China (Wu et al 2006)
The SCS summer monsoon (SCSSM) is significantly correlated with perturbation potential energy (PPE) over two key regions: the western North Pacific (WNP; 120°–170°E, 15°–25°N) and southern Maritime Continent (SMC; 100°–150°E, 15°–5°S), locating at the north and south sides of the SCS monsoon region and showing a dipole pattern (Fig. 1a)
Changes in atmospheric circulation related to the SCSSM have been investigated (Li and Zeng 2002; Wang et al 2009; Zhang et al 2018), less attention has been paid to the atmospheric energy variations associated with the SCSSM on the interannual variability

Summary

Introduction

The South China Sea (SCS) is part of the tropical Indian–western Pacific warm pool and lies at the center of the Asian–Australian monsoon system, which plays an important role in moisture transport from the North Indian Ocean and Southern Hemisphere to China (Wu et al 2006). In the atmospheric energy theory, PKE cannot be transformed directly from diabatic heating. The atmospheric available potential energy (APE) can serve as the medium that links diabatic heating and PKE (Lorenz 1955), this does not occur at the regional scale because APE is calculated as the global mean. To overcome these limitations, Li and Gao (2006) extended the APE to the local scale and proposed the concept of atmospheric perturbation potential energy (PPE), which represents the maximum amount of total potential energy that can be converted into PKE at the local scale. A detailed introduction to atmospheric PPE theory is provided in Sect. 2.1 ( see the Supporting Information)

Methods

Results

Conclusion