Simultaneous Observations of Surface Layer Profiles of Humidity, Temperature, and Wind Using Scanning Lidar Instruments

Abstract

We demonstrate the combination of three Doppler lidars, a water vapor differential absorption lidar and a temperature rotational Raman lidar for the investigation of the interactions between the land-surface and the atmospheric boundary layer. This combination of scanning lidars was operated for the first time during the Land-Atmosphere Feedback Experiment (LAFE) at the Atmospheric Radiation Measurement program’s Southern Great Plain site, Oklahoma, USA, in August 2017, and provided simultaneous surface layer profiles of horizontal wind, humidity and temperature. The horizontal wind profiles were determined using the dual-Doppler method with two Doppler lidars. The scans were performed above four towers providing atmospheric variables and fluxes. These combined lidar data allowed for the estimation of the friction velocity as well as the surface latent and sensible heat fluxes. For this purpose, profiles calculated with Monin-Obukhov similarity theory (MOST) were fitted with the Levenberg-Marquardt nonlinear least square curve-fitting method to the measured surface-layer lidar profiles. We present case studies of three 50-minute periods to illustrate the new method. The measurements resulted in friction velocities of 0.31, 0.29, and 0.38 ms-1, sensible surface heat fluxes of 312.1, 234.1, and 183.3 Wm-2 and latent surface heat fluxes of 251.8, 227.3, and 274.4 Wm-2. These values were compared with the in-situ measurements of the towers. Considering the sampling differences and the error analyses, the results agree within 25.1 %, 42.5 %, and 28.8 %, respectively, demonstrating that this synergy of scanning active remote sensing systems can be used to derive surface fluxes with reasonable accuracy.