There is a decision to be made when deciding between these 2 forms of instrument when considering a monitoring program.

Firstly both Ceilometers and MPL ( Micro pulsed Lidar)  are  instruments based on the LIDAR principle.     MPL uses photon counting detectors,  while Ceilometers use avalanche photodiodes in analog mode.   Beyond that all sampling and data conversion are digital.

• Cost

Ceilometers are significantly lower in cost than MPL  This is mainly due to the laser technology used.    The lasers in Ceilometers can last up to 6-8 years and the laser replacement cost is  relatively low.

• Laser Pulse Source.

Most Ceilometers use  a low cost solid-state pulsed laser diode,  while the MPL  uses a frequency doubled NdYag laser.

• Wavelength

Most Ceilometers emit in the range 905 to 920 nm,  which is not  visible and the launch pulses are reduced in energy so that the sensor is eye safe.   The MPL emits at 532 nm and is able to launch higher energy pulses meaning the range is greater,  or conversely the ability to detect low levels of scattering ( eg MIE )  at low levels is enhanced.   Potential users need to look at the differences between scattering properties of the target at the 2 wavelengths.

• Polarisation

Ceilometers do not have dual polarisation channels and the discrimination capabilities of MPL may make them more suitable for the planned studies

• Deployment Costs

Ceilometers are designed to be operated long term in a wide range of environments and are more suited to remote deployment where there is less maintenance available.

Ceilometers are widely used for PBL studies.   Because of increased range/sensitivity MPL is favoured in high cloud studies,  but high range ceilometers are available and might be selected if a multi sensor long term study is being undertaken.