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A new backscatter lidar forward operator was developed which is based on the\uddistinct calculation of the aerosols' backscatter and extinction properties.\udThe forward operator was adapted to the COSMO-ART ash dispersion simulation\udof the Eyjafjallajökull eruption in 2010. While the particle number\udconcentration was provided as a model output variable, the scattering\udproperties of each individual particle type were determined by dedicated\udscattering calculations. Sensitivity studies were performed to estimate the\uduncertainties related to the assumed particle properties. Scattering\udcalculations for several types of non-spherical particles required the usage\udof T-matrix routines. Due to the distinct calculation of the backscatter and\udextinction properties of the models' volcanic ash size classes, the\udsensitivity studies could be made for each size class individually, which is not the case for forward\udmodels based on a fixed lidar ratio. Finally, the forward-modeled lidar\udprofiles have been compared to automated ceilometer lidar (ACL) measurements\udboth qualitatively and quantitatively while the attenuated backscatter\udcoefficient was chosen as a suitable physical quantity. As the ACL\udmeasurements were not calibrated automatically, their calibration had to be\udperformed using satellite lidar and ground-based Raman lidar measurements. A\udslight overestimation of the model-predicted volcanic ash number density was\udobserved. Major requirements for future data assimilation of data from ACL\udhave been identified, namely, the availability of calibrated lidar\udmeasurement data, a scattering database for atmospheric aerosols, a better\udrepresentation and coverage of aerosols by the ash dispersion model, and more\udinvestigation in backscatter lidar forward operators\udwhich calculate the backscatter coefficient directly for each\udindividual aerosol type. The introduced forward operator offers the\udflexibility to be adapted to a multitude of model systems and measurement\udsetups

atmospheric measurement techniques

Development and application of a backscatter lidar forward operator for quantitative validation of aerosol dispersion models and future data assimilation