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Cloud Radar

Figure 1: Vertical cloud radar Mira-35

Figure 1: Vertical cloud radar Mira-35

Cloud Radar

Cloud Radar is a weather radar that displays the position and shape of clouds. They are also known as MMCR (millimeter-wave cloud radar). They are radar systems for measuring vertical profiles of reflectivity, Doppler velocity, and velocity variance. They use very high frequencies between K-Band and W-Band, whose waves are already reflected at the cloud's outer boundaries and are so strongly attenuated within the cloud that they often cannot penetrate the cloud at all. In return, however, the radar receives an echo signal even in the case of thin clouds of ice crystals (e.g.: Cirrus). A precipitation radar operating in C-band can only detect droplets with a diameter of at least 0.1 … 0.2 mm, i.e. it would not “see” the clouds at all. Therefore, a cloud radar must use higher frequencies.

Figure 2: Vertical scan during one hour

Figure 2: Vertical scan during one hour

Cloud radar can be operated both stationary on the ground and onboard satellites. Stationary on the ground there are two different types:

Stationary ground-based radars usually use a relatively low frequency in the Ka-Band which also has the possibility of penetrating the cloud. Thus also the cloud upper limits can be detected. However, rain attenuates these frequencies so strongly that this cloud radar can be used only in dry weather. The cloud radar onboard satellites use 96 GHz and thus only measures the cloud tops and regions with aerosols.


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