## 5 Discussion
It also shows the time averaged uncalibrated Doppler velocity profile; (**c**) shows the lidar backscattered intensity for the time period from 11:07 a.m. to 11:42 a.m., Chilean local time. extends from 600 m to about 1600 m, therefore confirming that the top of the cloud was at about 600 to 700 m at both sites. Changes during the day also tend to increase the base height even 100 m during the morning hours (e.g., [23]) which makes for a thinner cloud. Therefore, independent observations of the cloud from satellite and radiosonde tend to confirm the cloud base height seen by the cloud radar and ceilometer (\(\sim\)360-380 m (a.g.l)) vs. \(\sim\)385-405 m (a.g.l)). Regarding the top of the cloud, this feature should be observed at higher levels than presently seen by the cloud radar which shows very few echoes above 500 m. It is therefore more likely that radar range prevents the characterization of the full structure of the cloud in this case, although some echoes near 600 m could indicate a possible detection of cloud echoes near the top of the cloud. The lower part of the cloud appears as having a positive Doppler velocity (see Figure 8 (middle-image)), which implies that part of the cloud is approaching the radar. It can be interpreted as drizzle. As expected, the height where Doppler shows a positive velocity is the height with the strongest reflectivity. The internal structure of the stratocumulus cloud as this one is such that the cloud liquid water content should increase linearly between the base and the top of the cloud (e.g., [24]). However, this behavior is not clear in the profile presented in Figure 8a, due to the variations in the higher gates,  
Figure 10: Skew-T log-P (SHARPpy) [22]. Sounding launched from Santo Domingo (120 km south of Papudo) on 20 January 2019 at 12:00 p.m. UTC. The red line is temperature in \({}^{\circ}\)C and green line is dew point temperature in \({}^{\circ}\)C. Cloud is expected when the two curves intercept. Thus, the cloud layer is estimated from 311 to 663 m (a.m.s.l) capped by a strong inversion layer. Data from Direccion Meteorologica de Chile, [[https://climatologia.metecchile.gob.cl/application/index/productos/RE5014](https://climatologia.metecchile.gob.cl/application/index/productos/RE5014)]([https://climatologia.metecchile.gob.cl/application/index/productos/RE5014](https://climatologia.metecchile.gob.cl/application/index/productos/RE5014)) (Santo Domingo station code of 330030 at 12:00). Figure 9: (a) MODIS terra cloud height on 20 Jan 2019 3:00 p.m. UTC, (b) MODIS True Color (Terra, Day) 20 January 2019 3:00 p.m. UTC, and (c) MODIS Cloud Top Temperature [K] (Terra, Day) 20 January 2019 3:00 p.m. UTC. which are not only weak echoes but too few. Nevertheless, reflectivity appears to increase from lower to higher gates within the cloud at a rate of 1 to 2 dBZ/100 m, which is consistent with values observed from Stratocumulus over the Southern Pacific (e.g., [25]). However, reflectivity profiles in the presence of light and heavy drizzle are also presented in [25]. In presence of drizzle, the reflectivity reaches its maximum below the cloud base to either decrease or remain constant inside the stratocumulus (Figure 4 in [25]). The reflectivity profile of the field campaign agrees with this description suggesting the presence of drizzle, which is consistent with the Doppler data of the field campaign (Figure 8b). The drizzle might explain the height difference between the radar and the ceilometer. The higher attenuation of drizzle might be responsible for a shorter maximum-detectable-range than expected in the radar (460 m-480 m instead of 500 m). Figure 6b shows that, if left uncalibrated, the radar would have an error in range retrievals due to a slope different from the theoretical value and an offset. Therefore, the UAV based calibration procedure is essential to guarantee the precision of the range estimation and should be repeated frequently [19].