Temporal variation and vertical structure of the marine atmospheric mixed layer over the East China Sea from Mie-scattering lidar data

Abstract

The marine atmospheric mixed layer (MAML) has an important influence on the diffusion of air pollutants over the East China Sea. We analyzed seasonal and diurnal variations and the vertical structure of the MAML by using continuous Mie-scattering lidar data recorded from March 2008 to February 2010 at Cape Hedo, Okinawa Island, Japan. The height of the MAML showed clear seasonal variation: a summer minimum and a winter maximum, and was significantly correlated with thermal stability (St ), which we defined as sea surface temperature minus the temperature at the 850 hPa level. The height of the MAML showed minor diurnal variations in summer: a nighttime minimum and a daytime maximum. We detected the entrainment layer between the MAML and the free atmosphere by analysis of the intensity of fluctuations of aerosol concentrations determined from lidar data. Both the intensity of the fluctuations and the thickness of the entrainment zone increased with increasing St . The altitude of maximum fluctuation was a little above the top of the MAML.