# The NEWA Ferry Lidar Experiment: Measuring Mesoscale Winds in the Southern Baltic Sea
## 4 Processed Dataset  
The processed dataset comprises the corrected time series of horizontal wind speed and direction for the 12 measurement heights together with an availability measure for each data value. This measure represents the percentage of valid data in a 10-min interval where validity was defined on the basis of the respective carrier-to-noise ratio (CNR) value output by the lidar device and the availability of the motion data required to correct the lidar measurements. As a CNR threshold, we have used the value of \(-23\) dB, which was pre-set and recommended by the manufacturer. High-frequency data, defined by one LoS measurement, that have a CNR value below this threshold were ignored for the derivation of the 10-min average.  
Additionally, the position data of the ship--in terms of mean, minimum and maximum longitude (Ion)/latitude (lat) coordinates, plus the distance between the minimum and maximum--were saved, along with the timestamp of the data vector. Figure 6 gives an impression of the processed data; the plot covers the same time span as in Figure 5 but this time shows the whole (corrected) wind speed and direction profiles instead of only a single time series. Note that the purpose of the plots was not to show and identify the single trajectories at the individual height levels, but rather to underline the profile information provided by the data. The occurrence of different atmospheric stability cases, represented by different wind shear and veer that is defined as wind speed and direction deviations with height, is clearly visible in this presentation. The magnitude of the vertical wind shear is correlated to the atmospheric stratification (e.g., References [16; 17]). Periods with little or no wind shear (e.g., during most of February 25) indicate neutral or unstable stratification, while periods with a strong wind shear of up to 7 m/s between 65 and 275 m height (e.g., during most of February 26) indicate stable stratification. Thus, the vertical change of the wind speed with height is an indicator of the presence of different atmospheric stabilities that are mainly caused by air-sea temperature differences.  
Figure 5: Four days of wind measurements from the ship lidar system: (**left**) path of Victoria Seaways in geo-coordinates, symbols show the position after 1, 2, 3, and 4 days; (**right**) corrected [blue/black] and uncorrected [red/pink] time series of horizontal wind speed [**top**] and direction [**bottom**] for 100 m measurement height. Periods where the ferry was in the harbor and therefore not moving are shown with the gray arrows.  
Based on the derived availability measures for the individual 10-min averages, overall and monthly averages for the 12 measurement heights were evaluated (see Table 1). For this, it was additionally assumed that the 10-min availability must be equal to 80% or greater for a measured data point to be valid. This value is a typical threshold for a wind resource assessment. The so assessed availability of the corrected lidar time series was well above 90% for the seven lower measurement heights up to 150 m and only decreased for the upper heights.