This example shows MULIS-measurements in Ouarzazate (Morocco) of May 19, 2006. The wavelength is 532 nm. It demonstrates the potential to distinguish between spherical particles (water droplets) and non-spherical particles (ice crystals) by means of the linear depolarization ratio.

Fig. 1: range corrected signal

Fig. 1 shows the range corrected signal: from 21:04 UTC till 22:40 UTC and from ground to 7 km in the vertical. Clearly visible are several cloud structures, mainly in the height-range between 4 km and 5 km. The white portions of the color plot are the most dense cloud parts. However, it is not possible to determine the type of the cloud (ice/water).

Fig. 2: linear depolarization ratio

Fig. 2 shows the (volume) linear depolarization ratio for the same height-time section, note, that the lowest 300 m have no physical meaning. Red and white colors mean high depolarization, indicating a large amount of non-spherical ice particles. However, there are some section within the cloud, where the depolarization is very low (pink color): here, supercooled water droples are existing! Clearly visible are several cloud structures, mainly in the height-range between 4 km and 5 km. The white portions of the color plot are the most dense cloud parts. However, it is not possible to determine the type of the cloud (ice/water).

Fig. 3: Combine backscatter signal and depolarization

Fig. 3 shows the range corrected signal again: the circles mark two pronounced cloud features (high backscattering). When you move the mouse over the figure, you can see the linear depolarization ratio for direct comparison. In the circles, low depolarization is obvious, indicating spherical particles. It is also visible, that the droplets tend to be in the upper part of the clouds; below ice crystals are falling out.