CL61 Ceilometer
A LIDAR with depolarization measurement
Objective :
Vaisala Lidar Ceilometer CL61 is a light detection and ranging (LiDAR)
instrument with depolarization measurement.
It enables to estimate cloud base height, and explore the stratification of the atmosphere.
The depolarization measurement capability enables clear liquid/solid or dissymmetrical/spherical
differentiation for particles and clouds.
Near Real Time observation (most recent image available) :
Principle :
The ceilometer sends short diode laser pulses in a near‐vertical direction. Profiles of the backscatter (reflection of this light) caused by clouds, precipitation, virga, haze, fog, and aerosols are measured, and the linear depolarization ratio is calculated. Cloud base heights are deduced from the measured profiles of backscatter.
Acquisition :
Profiles are measured initially every 5 s, but averaged every 30 s.
Radial resolution is 5 m, with an effective resolution of 48 m.
The CL61 ceilometer can measure up to 16 km. Up to 5 cloud layers may be detected, depending of the characteristics of the clouds.
In case of heavy precipitation or fog, the ceilometer software reports vertical visibility.
Examples of observations :
