By now it is a trueism: the cloud base height can be best measured with lidar and the cloud top height by radar.
More generally, a human operator will understand his measurements much better if he has both lidar and radar measurements,
and not just one of them.
In principle lidar is the best instrument to measure cloud boundaries as we are most interested in the cloud
properties in the visible and infrared region. However, lidar measurements are strongly attenuated by most clouds,
therefore, the signal often does not reach the cloud top.
Radar hardly has any problems with attenuation, however it has a preference for the larger particles. Thus even in case
of very light precipitation, the radar will see the precipitation and not the cloud that produced it. Such light
precipitation, that does not even have to reach the ground, occurs very often in The Netherlands. Furthermore, radar
is often not sensitive enough to measure small cloud droplets near the cloud base. These facts make
radar unsuited to measure cloud base height. However, on theoretical grounds one would expect radar to be able to
estimate the height of the cloud top. Unfortunately, this latter expectation has not been validated yet.
The most difficult are atmospheric conditions with multiple cloud layers, especially wenn one or more of these
layers are precipitating. In this case one will have to estimate the height of all boundaries except the lowest
cloud base by radar.
In chapter 7 of my PhD the above ideas are furhter detailed and I offer
a possible solution for measuring cloud boundaries by radar during light rain. An easier reference would be my
article on cloud boundary measurements in Physics and Chemistry of the Earth.
The article "The effect of the orientation of ice crystals in the melting layer and ice clouds on measurements using radar and lidar"
is included as it advises one to use a slightly tilted lidar for cloud boundary measurements. It shows an example where
one sees two ice cloud layers in the lidar backscatter. These two layers may have been one thick ice cloud, as the radar
sees a turbulent layer in the middle of this ice cloud. The turbulence may have titled the specularly reflecting ice
crystals, thus strongly reducing their backscatter.
In the section on related work, you will find the probably very robust liquid water content profile retrieval of
Reinout Boers, which uses lidar and radar derived cloud boundaries. Furthermore, an article on the CLARA
project, which provided the framework of the above research.
Cloud measurements with radar
PhD thesis, 13 November 2000.
Chapter 7. Cloud boundary height measurements using lidar and radar
pdf (0.6 Mb)
Cloud boundary height measurements using lidar and radar (0.4 Mb)
Physics and Chemistry of the Earth, 24, no. 2, pp. 129-134, 2000.
Victor Venema, Herman Russchenberg, Arnoud Apituley, Andre van Lammeren, and Leo Ligthart
The effect of the orientation of ice crystals in the melting layer and ice clouds on measurements using radar and lidar
conference on light scattering by nonspherical particles: Theory, measurements and applications, 1998, New York
Victor Venema, Herman Russchenberg, Leo Ligthart, Andre van Lammeren and Arnoud Apituley
Observations of the vertical structure of stratocumulus with lidar and an S-band radar
4th International Symposium on Troposheric Profiling
H.W.J. Russchenberg, V.K.C Venema, A.C.A.P. van Lammeren, A.Feijt, A. Apituley
Cloud measurements with lidar and a 3 GHz radar
Final report for the European Space Agency, IRCTR report: IRCTR-S-008-98
H.W.J. Russchenberg , V.K.C Venema, A.C.A.P. van Lammeren, A. Feijt, A. Apituley
Radar-lidar observations of clouds during the CLARA-campaigns
Workshop on Synergy of Active Instruments in the Earth Radiation Mission
H.W.J. Russchenberg, V.K.C Venema, A.C.A.P. van Lammeren, A. Apituley
Ground-based remote sensing of stratocumulus properties during CLARA, 1996
Journal Applied Meteorology, 39, no. 2, pp 169-181, Feb 2000.
Reinout Boers, Herman Russchenberg, Jan Erkelens, Victor Venema, Andre van Lammeren, Arnoud Apituley, and Susanne Jongen.
Clouds and radiation: intensive experimental study of clouds and radiation in the Netherlands (CLARA)
Proc. Symposium Remote Sensing of Cloud Parameters: Retrieval and Validation, pp. 5-10, 21-22 October 1999, Delft, The Netherlands.
Andre van Lammeren, Arnout Feijt, Dave Donovan and Hannelore Bloemink, Herman Russchenberg, Victor Venema and Jan Erkelens, Arnoud Apituley, Harry ten Brink and Andrey Khlystov, Suzanne Jongen, Gert Brussaard and Matti Herben