Dual‐FOV Raman and Doppler lidar studies of aerosol‐cloud interactions: Simultaneous profiling of aerosols, warm‐cloud properties, and vertical wind

Abstract

For the first time, colocated dual‐field of view (dual‐FOV) Raman lidar and Doppler lidar observations (case studies) of aerosol and cloud optical and microphysical properties below and within thin layered liquid water clouds are presented together with an updraft and downdraft characterization at cloud base. The goal of this work is to investigate the relationship between aerosol load close to cloud base and cloud characteristics of warm (purely liquid) clouds and the study of the influence of vertical motions and turbulent mixing on this relationship. We further use this opportunity to illustrate the applicability of the novel dual‐FOV Raman lidar in this field of research. The dual‐FOV lidar combines the well‐established multiwavelength Raman lidar technique for aerosol retrievals and the multiple‐scattering Raman lidar technique for profiling of the single‐scattering extinction coefficient, effective radius, number concentration of the cloud droplets, and liquid water content. Key findings of our 3 year observations are presented in several case studies of optically thin altocumulus layers occurring in the lower free troposphere between 2.5 and 4 km height over Leipzig, Germany, during clean and polluted situations. For the clouds that we observed, the most direct link between aerosol proxy (particle extinction coefficient) and cloud proxy (cloud droplet number concentration) was found at cloud base during updraft periods. Above cloud base, additional processes resulting from turbulent mixing and entrainment of dry air make it difficult to determine the direct impact of aerosols on cloud processes.

Potential of polarization lidar to provide profiles of CCN- and INP-relevant aerosol parameters

“…The estimated n CCN values are no longer trustworthy for higher relative humidities, i.e., for example in the subcloud layer (from 500 m below cloud base to cloud base), i.e., in the humid layer right below the base of a convective cloud system (Schmidt et al, 2014). It remains to be investigated to what extent our method can be used for relative humidities > 80 % and also for humidities < 40 %.…”

“…logical conditions with high vertical and temporal resolution (Illingworth et al, 2007;Shupe, 2007;Ansmann et al, 2009;de Boer et al, 2011;Schmidt et al, 2014).…”

Remote Sensing of Droplet Number Concentration in Warm Clouds: A Review of the Current State of Knowledge and Perspectives

“…Both approaches are based on the relationship between r e and the intensity of forward scattering. Based on a forward iterative algorithm that uses the measured signals from a Raman lidar at two fields of view Schmidt et al (), Schmidt et al () demonstrated the derivation of profiles of the r e , extinction coefficient, L , and N d of liquid water clouds. The uniqueness of this dual‐field‐of‐view method is that light is detected which was scattered in the forward direction by cloud droplets but backscattered inelastically by nitrogen molecules.…”

Estimated desert-dust ice nuclei profiles from polarization lidar: methodology and case studies

“…Ground-based active remote sensing is, in general, of great importance for observational studies of aerosol-cloud interactions because of its unique potential to observe aerosol layers and clouds (from base to top) with high vertical and temporal resolution and this over long time periods (Ansmann et al, 2005(Ansmann et al, , 2009Illingworth et al, 2007;Martucci and O'Dowd, 2011;de Boer et al, 2011;Kanitz et al, 2011;Wandinger et al, 2012;Bühl et al, 2013;Schmidt et al, 2014). Continuously running stations can provide dense aerosol-cloud data sets for statistical analysis for all seasons of the year.…”