Shipborne Wind Measurement and Motion-induced Error Correction of a Coherent Doppler Lidar over the Yellow Sea in 2014

Abstract

Abstract. Shipborne wind observations by a coherent Doppler lidar (CDL) have been conducted to study the structure of the marine atmospheric boundary layer (MABL) during the 2014 Yellow Sea campaign. This paper evaluates uncertainties associated with the ship motion and presents the correction methodology regarding lidar velocity measurement based on modified 4-Doppler beam swing (DBS) solution. The errors of calibrated measurement, both for the anchored and the cruising shipborne observations, are comparable to those of ground-based measurements. The comparison between the lidar and radiosonde results in a bias of −0.23 ms −1 and a standard deviation of 0.87 ms −1 for the wind speed measurement, and 2. 48, 8.84 • for the wind direction. The biases of horizontal wind speed and random errors of vertical velocity are also estimated using the error propagation theory and frequency spectrum analysis, respectively. The results show that the biases are mainly related to the measuring error of the ship velocity and lidar pointing error, and the random errors are mainly determined by the signal-to-noise ratio (SNR) of the lidar backscattering spectrum signal. It allows for the retrieval of vertical wind, based on one measurement, with random error below 0.15 ms −1 for an appropriate SNR threshold and bias below 0.02 ms −1 . The combination of the CDL attitude correction system and the accurate motion correction process has the potential of continuous long-term high temporal and spatial resolution measurement for the MABL thermodynamic and turbulence process.

Taking the Motion out of Floating Lidar: Turbulence Intensity Estimates with a Continuous-Wave Wind Lidar

“…Thus, it shifts the detected Doppler frequency, which is proportional to the measured line-of-sight velocity. Stationary motion in the three translational degrees of freedom leads to a one-to-one change in measured wind velocity; e.g., a lidar being transported on a ship with velocity v along the ocean's surface would measure a wind velocity error of the same magnitude ∆ u = v. With the exception of a lidar being mounted on a ship [18,19], all three velocity components of a floating lidar typically average zero during a ten-minute interval, so that V = v = 0. This leads to zero error in mean wind speed U, but the measurements of the instantaneous wind speed u and the derived turbulence parameters like TI are affected.…”

Vehicular Motion Experiment and Data Retrieval of a Compact Floating Lidar System

“…The recorded velocity corresponds to the relative velocity along the laser beam direction between the lidar and the atmospheric target. Considering the mobility of lidar system, the motion will add to the recorded radial velocity [2]. Therefore, a necessary step in data retrieval is the calibration of the radial velocity caused by the motion of lidar [3].…”

Performance validation on an all-fiber 1.54-μm pulsed coherent Doppler lidar for wind-profile measurement

“…[20][21][22] In 2011, Leosphere displayed a long-range lidar (Windcube 200S), which could measure three-dimensional (3-D) *Address all correspondence to Xiaopeng Zhu, E-mail: xp_zhu@siom.ac.cn; Xiaolei Zhu, E-mail: xlzhu@siom.ac.cn wind profiles up to 7 km in distance with 70-m range resolution, and the radial velocity with 0.5-m∕s velocity resolution was validated by another lidar (Windcube 70). 23 In 2016, Zhai et al 24 developed a 1.5-μm pulsed CDL with variable spatial resolution from 15 to 60 m; its discrepancies with radiosonde observation results were within acceptable limits. In 2017, Wang et al 3 presented a versatile CDL with 0.5-m∕s measurement precision and 6-km detection ability, and its stability was demonstrated by continuous wind detection of the atmospheric boundary layer.…”