Monitoring aerosol–cloud interactions at the CESAR Observatory in the Netherlands

Abstract

Abstract. The representation of aerosol-cloud interaction (ACI) processes in climate models, although long studied, still remains the source of high uncertainty. Very often there is a mismatch between the scale of observations used for ACI quantification and the ACI process itself. This can be mitigated by using the observations from groundbased remote sensing instruments. In this paper we presented a direct application of the aerosol-cloud interaction monitoring technique (ACI monitoring). ACI monitoring is based on the standardised Cloudnet data stream, which provides measurements from ground-based remote sensing instruments working in synergy. For the data set collected at the CESAR Observatory in the Netherlands we calculate ACI metrics. We specifically use attenuated backscatter coefficient (ATB) for the characterisation of the aerosol properties and cloud droplet effective radius (r e ) and number concentration (N d ) for the characterisation of the cloud properties. We calculate two metrics: ACI r = ln(r e )/ln(ATB) and ACI N = ln(N d )/ln(ATB). The calculated values of ACI r range from 0.001 to 0.085, which correspond to the values reported in previous studies. We also evaluated the impact of the vertical Doppler velocity and liquid water path (LWP) on ACI metrics. The values of ACI r were highest for LWP values between 60 and 105 g m −2 . For higher LWP other processes, such as collision and coalescence, seem to be dominant and obscure the ACI processes. We also saw that the values of ACI r are higher when only data points located in the updraught regime are considered. The method presented in this study allow for monitoring ACI daily and further aggregating daily data into bigger data sets.

Dual-field-of-view high-spectral-resolution lidar: Simultaneous profiling of aerosol and water cloud to study aerosol–cloud interaction

“…The short lifetime, high temporal variability, and complex vertical structure of water cloud layers lead to a major difficulty for ACI studies (3,10,11). Despite the advances in the characterization of ACI by ground-based measurements (12)(13)(14)(15)(16)(17)(18)(19)(20)(21), satellite retrieved products (22)(23)(24)(25), and airborne in situ measurements (26)(27)(28), uncertainties remain in the effects of the aerosols on the water cloud properties. The reason for this gap in our knowledge is closely linked to the inadequate observations of the water cloud microphysical properties under various aerosol conditions (3).…”

“…Quintessential ground-based remote-sensing techniques for retrieving cloud properties, such as the cloud radar and the microwave radiometer, cannot provide simultaneous aerosol observations for ACI studies. Therefore, ground-based measurements commonly combine those with other remote-sensing or in situ aircraft instruments for characterizing aerosol loading beneath clouds (12)(13)(14)(15)(16)(17)(18)(19)(20). However, given the high variability of clouds, differences in perspective or mismatched sampling in space and time would raise uncertainty and bias in the characterization of ACI (15).…”

Influence of Black Carbon Aerosol on the Atmospheric Instability

“…Warming effect of light‐absorbing aerosols within and beyond the atmospheric boundary layer effectively influences the thermodynamic normality in atmospheric column and thus has its significant interactions with atmospheric stability (Ding et al, ; Li et al, ). Several researchers mentioned about the processes of aerosol‐cloud interaction in climate models that still exist as an important source of uncertainty (Fan et al, ; Sarna & Russchenberg, ). In addition to this, aerosols and their association with the stability of the lower atmosphere increases the regional uncertainties (Qiu et al, ).…”

The Large-Eddy Simulation (LES) Atmospheric Radiation Measurement (ARM) Symbiotic Simulation and Observation (LASSO) Activity for Continental Shallow Convection

“…The U.S. Department of Energy's (DOE) Atmospheric Radiation Measurement (ARM) user facility presently has long-term supersites in Oklahoma, in Alaska, and on Graciosa Island, with previous locations in the west Pacific Ocean and shorter-term, "mobile" deployments worldwide (Turner and Ellingson 2016). Examples of supersites from other organizations include the Cabauw Experimental Site for Atmospheric Research (CESAR) in the Netherlands (Leijnse et al 2010;Sarna and Russchenberg 2017) and the Barbados Cloud Observatory (Stevens et al 2016).…”