# First Observations of Cirrus Clouds Using the UZ Mie Lidar over uMhalthuze City, South Africa
## 4 Results and Discussion  
In general, optical as well as microphysical properties of the cirrus clouds represent important but slightly incomplete information, especially if they are characterized in averaged values without considering temporal and spatial variation. The primary reason for this is that water vapor and ice particle concentrations vary within the cloud, usually as a nonlinear process. Due to the above-mentioned reason, as well as the current optical layout of the UZ lidar, the short-term variation of mean properties of the cirrus cloud is considered in this study. Furthermore, as mentioned earlier, the present study presents the case study of two cirrus cloud events that were captured at the beginning of the operation of the UZ lidar (10 and 11 April 2019). Figure 3a,b shows the temporal evolution of the total backscatter coefficients observed for the period from 17:42:12 pm to 20:16:25 on 10 April 2019. While there seems to be a signature indicating the presence of aerosols at a height below 2 km, there is a strong total backscatter coefficient between 9.5 and 11.5 km, which indicates the presence of a cirrus cloud. This is clearer in a zoomed-in version of Figure 3a, which is presented in Figure 3b. Over the detection time period, the cirrus cloud \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{1}{c}{**CALIOP Parameters**} \\ \hline Laser & Nd: YAG, diode-pumped, Q-switched, frequency doubled \\ Wavelengths & 532 nm, 1064 nm \\ Pulse energy & 110 mJ \\ Repetition rate & 20.25 Hz \\ Receiver telescope & 1.0 m diameter \\ Polarization & 532 nm \\ Footprint/FOV & 100 m/130 urad \\ Vertical resolution & 30–60 m \\ Horizontal resolution & 333 m \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Specifications of CALIOP. is observed to propagate downwards, a characteristic that is similar to lidar observations presented by other studies. The calculation of the extinction coefficient using the successive signal returns for the 10 April 2019 also indicates a significant peak at \(\sim\)2 km presumable due to an aerosol layer and a strong peak at \(\sim\)10 km due to the presence of a cirrus cloud (see Figure 3b). COD was also estimated using Equation (6), and its time series is shown in Figure 3d. As displayed in this figure, the COD time series depicts a large variability on 10 April 2019, with increasing values up to above 1.7 during the first few minutes and in the middle of the times series, and minimum values which are less than 1.4 later in the time series. The average value of the COD is \(\sim\)1.6. A study by [PERSON] and [PERSON] [25] investigated a sub-visual-thin cirrus lidar dataset for the purpose of satellite data verification as well as climatological research. In this study, [PERSON] and [PERSON] [25] suggested that cirrus clouds can be classified as thin cirrus with 0.03 \(<\) COD \(<\) 0.3, sub-visual cirrus with COD \(<\) 0.3, and dense cirrus with COD \(>\) 0.3. In this context, with an average value of COD which is way above 0.3 on 10 April 2019, the cirrus cloud observed here is a significant dense cirrus cloud. A significant cirrus cloud was also observed over the study area on the succeeding day, 11 April 2019. It is worthy to also mention that the cirrus cloud seems to have disappeared in the days after 11 April 2019. Similar to Figure 3, Figure 4a shows the temporal evolution of the total backscatter coefficients observed for the period from 17:24:01 p.m. to 20:28:43 on 11 April 2019. Again, during this day, there seems to be a strong total backscatter coefficient peak at the height between 1 and 2 km, which is associated with the presence of aerosols in the lower troposphere over the study area. At the height between 9.5 and 11 km, a stronger total backscatter coefficient reaching a maximum value of 0.012 km\({}^{-1}\)sr\({}^{-1}\) was observed. This approximately 1.5 km thick total backscatter coefficient peak is associated with a cirrus cloud which persists throughout the experiment duration.