Aerosol profiling with the Jenoptik ceilometer CHM15kx

[摘要] Since a few years, the number of active remote sensing systems has been rapidlyincreasing as national weather services started to build up networks ofceilometers. As ceilometers can be considered as "simple" backscatterlidars, it is obvious to investigate to which extent they can provide quantitativeaerosol information. In this context, the calibration of the ceilometer is themost crucial point: whereas previous studies primarily have relied on thecomparisons with co-incident sun photometer measurements and the Rayleighcalibration, we provide an absolute calibration of the ceilometer. Theadvantage of this approach is that backscatter profiles can be derived duringdaytime and nighttime, and even in cases when the signal-to-noise ratio ofsignals from the free troposphere is very low. Moreover, the retrieval caneasily be automated. In this paper, we consider the JenoptikCHM15kx-ceilometer. We discuss the methodology and the achievable accuracyand present a set of examples to highlight the wide range of applications,and the limitations. The achievable temporal resolution is of the order of afew minutes; the relative error of the particle backscatter coefficient isless than 10%. It is emphasized that the accuracy of extinction coefficientsand – as a consequence – of the aerosol optical depth is limited due to theunknown lidar ratio. This is, however, an inherent problem of any backscatterlidar and not a special feature of the ceilometer.

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