Thermodynamic structure and evolution of the atmospheric mixed layer over the western North Pacific during the summer monsoon onset
Article first published online: 13 JUN 2013
©2013. American Geophysical Union. All Rights Reserved.
Journal of Geophysical Research: Atmospheres
Volume 118, Issue 11, pages 5655–5666, 16 June 2013
How to Cite
2013), Thermodynamic structure and evolution of the atmospheric mixed layer over the western North Pacific during the summer monsoon onset, J. Geophys. Res. Atmos., 118, 5655–5666, doi:10.1002/jgrd.50242., , and (
- Issue published online: 10 JUL 2013
- Article first published online: 13 JUN 2013
- Accepted manuscript online: 12 FEB 2013 10:38AM EST
- Manuscript Accepted: 31 JAN 2013
- Manuscript Revised: 29 JAN 2013
- Manuscript Received: 16 MAY 2012
- atmospheric mixed layer;
- monsoon onset
 This study examined the thermodynamic structure of the atmospheric mixed layer and its evolution in different periods during the onset of the western North Pacific summer monsoon by using data observed on board the research vessel Mirai at 12°N and 135°E during 6–24 June 2008. The overall mean depth of the mixed layer was 482 m, and the mixed layer tended to shrink after the monsoon onset. The mixed layer was relatively warm and moist during the early onset period. However, the mixed layer became very cool and dry during the latter onset period, when intense and sustained rainfall was observed. The surface buoyancy flux, environmental subsidence over the mixed layer, and upward motion at cloud base intensified after the monsoon onset. All of these factors were negatively correlated with the depth of the mixed layer, which implies that the upward motion at cloud base and compensating environmental subsidence act to suppress the growth of the mixed layer driven by buoyancy forcing and to shrink the mixed layer after the monsoon onset. A significant positive correlation existed between the surface buoyancy flux and the upward motion at cloud base after the monsoon onset. Such positive feedback between the sea surface and cumulus clouds facilitates the formation of the warmer and moister mixed layer during the early onset period, thereby benefiting the further development of the monsoon onset.