Observation of Stable Marine Boundary Layer by Shipborne Coherent Doppler Lidar and Radiosonde over Yellow Sea

Abstract

Shipborne observations obtained with the coherent Doppler lidar (CDL) and radiosonde during 2014 campaign were used to study the structure of marine boundary layer in the Yellow Sea. Vertical wind profiles corrected for ship motion was used to derive higher-order statistics, showing that motion correction is required and significant for turbulence analysis. During a day with weak mesoscale activity, a complexed three-layer structure system was observed. The lowest layer showed a typical stable boundary layer structure feature. An aerosol layer with abrupt variation in wind speed and relative humidity always appeared at the middle layer, the formation of which may be due to Kelvin-Helmholz instability. The top layer encountered a dramatic change in wind direction, which may result from the warm advection from the Eurasian continent on the basis of backward trajectory analysis. Furthermore, the MABL height in stable regime was derived from potential temperature, CDL signal-to-noise ratio (SNR) and CDL vertical velocity variance, respectively. The stable boundary layer (SBL) height in SBL can be derived from the inversion layer of potential temperature profile, and the mixing height in SBL can be retrieved from the vertical velocity variance gradient method. Neither the SBL height nor the mixing height is in agreement with the height retrieved from CDL SNR gradient method because of different definition and criterion. One of the limitations of SNR gradient method for MABL retrieval is that it is easier to be affected by the lofted decoupled aerosol layer, where the retrieved result is less suitable. Finally, the higher-order vertical velocity statistics within the marine stable boundary layer were investigated and compared with the previous studies, and different turbulence mechanisms have an important effect on the statistics deviation.

Keywords

• |coherent doppler lidar|stable marine boundary layer|radiosonde|turbulence characteristics