Parameterising Cloud Condensation Nuclei concentrations during HOPE

Abstract

<p><strong>Abstract.</strong> An aerosol model was used to simulate the generation and transportation of aerosols over Germany during the HD(CP)<sup>2</sup> Observational Prototype Experiment (HOPE) field campaign of 2013. The aerosol number concentrations and size distributions were evaluated against observations, which shows satisfactory agreement in the magnitude and temporal variability of the main aerosol contributors to cloud condensation nuclei (CCN) concentrations. From the modelled aerosol number concentrations, number concentrations of CCN were calculated as a function of vertical velocity using a comprehensive aerosol activation scheme which takes into account the influence of aerosol chemical and physical properties on CCN formation. There is a large amount of spatial variability in aerosol concentrations, however the resulting CCN concentrations vary significantly less over the domain. Temporal variability is large in both aerosols and CCN. A parameterisation of the CCN number concentrations is developed for use in models. The technique involves defining a number of best fit functions to capture the dependence of CCN on vertical velocity at different pressure levels. In this way, aerosol chemical and physical properties as well as thermodynamic conditions are taken into account in the new CCN parameterisation. A comparison between the parameterisation and the CCN estimates from the model data shows excellent agreement. This parameterisation may be used in other regions and time periods with a similar aerosol load, and furthermore, this technique demonstrated here may be employed in regions dominated by different aerosol species.</p>

The HD(CP)2 Observational Prototype Experiment HOPE – An Overview

“…During HOPE-Jülich the availability of CCN was investigated using an aerosol model. The approach presented by Hande et al (2016) used the COSMO-MUSCAT model to simulate the generation and transportation of aerosols over Germany during 20 the campaign. From the simulation results, a parameterisation of the CCN concentration was derived which can be applied also to other climatological regions and different aerosol regimes.…”