Turbulent Higher-Order Moments of Humidity, Temperature and Vertical Wind in the Convective Boundary Layer during LAFE

Turbulent higher-order moments of the humidity, temperature and vertical wind in the convective boundary layer (CBL) were derived using simultaneous high-resolution measurements from water vapor differential absorption lidar, temperature rotational Raman lidar. and Doppler lidar. With lidars, profiles of these key variables can be observed from the surface or mixed layer to the including the interfacial layer (IL) in the CBL. The case study discussed here focuses on a well developed convective boundary layer during the Land-Atmosphere Feedback Experiment (LAFE) over the Southern Great Plains site in Oklahoma, USA. This study was performed on a special observation period on 30 August 2017 to study the vertical structure of the temperature, humidity and flux profiles in the CBL. Mean thermodynamic profiles, variances and third-order moments of temperature, humidity and vertical wind, as well as surface energy fluxes were investigated. Significant differences were found in the sensible and latent heat fluxes between the EC stations due to the land use and surface heterogeneity. The integral length scales of temperature and humidity show several differences at various heights in the CBL. The variance profiles of temperature and humidity show a distinct peak at the CBL top due to the entrainment of the troposphere air. A non-skewed Gaussian distribution of turbulent fluctuations was found in the lower CBL. However, a clearly non-zero values of the third-order moments (TOMs) of specific humidity and potential temperature were found in the interfacial layer. It is demonstrated how these observations can be used for studying and improving turbulence parameterizations as well as for the verification of large eddy simulations.