Parameterising Cloud Condensation Nuclei concentrations during HOPE

Abstract. An aerosol model was used to simulate the generation and transportation of aerosols over Germany during the HD(CP)2 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.

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Parameterizing cloud condensation nuclei concentrations during HOPE

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-12059-2016 ◽

2016 ◽

Vol 16 (18) ◽

pp. 12059-12079 ◽

Cited By ~ 15

Author(s):

Luke B. Hande ◽

Christa Engler ◽

Corinna Hoose ◽

Ina Tegen

Keyword(s):

Physical Properties ◽

Vertical Velocity ◽

Temporal Variability ◽

Cloud Condensation Nuclei ◽

Size Distributions ◽

Condensation Nuclei ◽

Aerosol Model ◽

Thermodynamic Conditions ◽

Aerosol Activation ◽

Best Fit

Abstract. An aerosol model was used to simulate the generation and transport of aerosols over Germany during the HD(CP)2 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 parameterization 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 parameterization. A comparison between the parameterization and the CCN estimates from the model data shows excellent agreement. This parameterization may be used in other regions and time periods with a similar aerosol load; furthermore, the technique demonstrated here may be employed in regions dominated by different aerosol species.

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Estimating cloud condensation nuclei concentrations from CALIPSO lidar measurements

10.5194/amt-2021-358 ◽

2021 ◽

Author(s):

Goutam Choudhury ◽

Matthias Tesche

Keyword(s):

Size Distribution ◽

Extinction Coefficient ◽

Cloud Condensation Nuclei ◽

Size Distributions ◽

Marine Aerosols ◽

Condensation Nuclei ◽

Aerosol Model ◽

Initial Application ◽

Lidar Measurements ◽

Aerosol Number Concentration

Abstract. We present a novel methodology to estimate cloud condensation nuclei (CCN) concentrations from spaceborne CALIPSO lidar measurements. The algorithm utilizes (i) the CALIPSO-derived backscatter and extinction coefficient, depolarization ratio, and aerosol subtype information, (ii) the normalized volume size distributions and refractive indices from the CALIPSO aerosol model, and (iii) the MOPSMAP optical modelling package. For each CALIPSO height bin, we first select the aerosol-type specific size distribution and then adjust it to reproduce the extinction coefficient derived from the CALIPSO retrieval. The scaled size distribution is integrated to estimate the aerosol number concentration which is then used in the CCN parameterizations to calculate CCN concentrations at different supersaturations. To account for the hygroscopicity of continental and marine aerosols, we use the kappa parameterization and correct the size distributions before the scaling step. We have studied the sensitivity of the thus derived CCN concentration to the effect of variations of the initial size distributions. It is found that the uncertainty associated with the algorithm can range between a factor of 2 and 3. We have also compared our results with the POLIPHON and found comparable results for extinction coefficients larger than 0.05 km−1. An initial application to a case with coincident airborne in-situ measurements for independent validation shows promising results and illustrates the potential of CALIPSO for constructing a global height-resolved CCN climatology.

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Sensitivity of droplet size distributions to organic cloud condensation nuclei constituents

Nucleation and Atmospheric Aerosols 1996 ◽

10.1016/b978-008042030-1/50235-3 ◽

1996 ◽

pp. 952-955

Author(s):

M.C. Jacobson ◽

M.L. Shulman ◽

R.J. Charlson ◽

G.-J. Roelofs

Keyword(s):

Droplet Size ◽

Cloud Condensation Nuclei ◽

Size Distributions ◽

Condensation Nuclei ◽

Droplet Size Distributions

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Estimating cloud condensation nuclei number concentrations using aerosol optical properties: role of particle number size distribution and parameterization

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-15483-2019 ◽

2019 ◽

Vol 19 (24) ◽

pp. 15483-15502 ◽

Cited By ~ 1

Author(s):

Yicheng Shen ◽

Aki Virkkula ◽

Aijun Ding ◽

Krista Luoma ◽

Helmi Keskinen ◽

...

Keyword(s):

Optical Properties ◽

Size Distribution ◽

Cloud Condensation Nuclei ◽

Size Distributions ◽

Condensation Nuclei ◽

Aerosol Optical Properties ◽

Average Bias ◽

Angstrom Exponent ◽

Ångström Exponent ◽

Ångstrom Exponent

Abstract. The concentration of cloud condensation nuclei (CCN) is an essential parameter affecting aerosol–cloud interactions within warm clouds. Long-term CCN number concentration (NCCN) data are scarce; there are a lot more data on aerosol optical properties (AOPs). It is therefore valuable to derive parameterizations for estimating NCCN from AOP measurements. Such parameterizations have already been made, and in the present work a new parameterization is presented. The relationships between NCCN, AOPs, and size distributions were investigated based on in situ measurement data from six stations in very different environments around the world. The relationships were used for deriving a parameterization that depends on the scattering Ångström exponent (SAE), backscatter fraction (BSF), and total scattering coefficient (σsp) of PM10 particles. The analysis first showed that the dependence of NCCN on supersaturation (SS) can be described by a logarithmic fit in the range SS <1.1 %, without any theoretical reasoning. The relationship between NCCN and AOPs was parameterized as NCCN≈((286±46)SAE ln(SS/(0.093±0.006))(BSF − BSFmin) + (5.2±3.3))σsp, where BSFmin is the minimum BSF, in practice the 1st percentile of BSF data at a site to be analyzed. At the lowest supersaturations of each site (SS ≈0.1 %), the average bias, defined as the ratio of the AOP-derived and measured NCCN, varied from ∼0.7 to ∼1.9 at most sites except at a Himalayan site where the bias was >4. At SS >0.4 % the average bias ranged from ∼0.7 to ∼1.3 at most sites. For the marine-aerosol-dominated site Ascension Island the bias was higher, ∼1.4–1.9. In other words, at SS >0.4 % NCCN was estimated with an average uncertainty of approximately 30 % by using nephelometer data. The biases were mainly due to the biases in the parameterization related to the scattering Ångström exponent (SAE). The squared correlation coefficients between the AOP-derived and measured NCCN varied from ∼0.5 to ∼0.8. To study the physical explanation of the relationships between NCCN and AOPs, lognormal unimodal particle size distributions were generated and NCCN and AOPs were calculated. The simulation showed that the relationships of NCCN and AOPs are affected by the geometric mean diameter and width of the size distribution and the activation diameter. The relationships of NCCN and AOPs were similar to those of the observed ones.

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Classification of aerosol population type and cloud condensation nuclei properties in a coastal California littoral environment using an unsupervised cluster model

10.5194/acp-2018-1297 ◽

2019 ◽

Author(s):

Samuel A. Atwood ◽

Sonia M. Kreidenweis ◽

Paul J. DeMott ◽

Markus D. Petters ◽

Gavin C. Cornwell ◽

...

Keyword(s):

Cluster Model ◽

Particle Number ◽

Cloud Condensation Nuclei ◽

Sea Breeze ◽

Northern Coast ◽

Size Distributions ◽

Condensation Nuclei ◽

Entire Study ◽

Total Particle Number ◽

Total Particle

Abstract. Aerosol particle and cloud condensation nuclei (CCN) measurements from a littoral location on the northern coast of California at Bodega Bay Marine Laboratory (BML) are presented for approximately six weeks of observations during the CalWater-2015 field campaign. A combination of aerosol microphysical and meteorological parameters was used to classify variability in the properties of the BML surface aerosol using a K-means cluster model. Eight aerosol population types were identified that were associated with a range of impacts from both marine and terrestrial sources. Average measured total particle number concentrations, size distributions, hygroscopicities, and activated fraction spectra between 0.08 % and 1.1 % supersaturation are given for each of the identified aerosol population types, along with meteorological observations and transport pathways during time periods associated with each type. Five terrestrially influenced aerosol population types represented different degrees of aging of the continental outflow from the coast and interior of California and their appearance at the BML site was often linked to changes in wind direction and transport pathway. In particular, distinct aerosol populations, associated with diurnal variations in source region induced by land/sea-breeze shifts, were classified by the clustering technique. A terrestrial type representing fresh emissions, and/or a recent new particle formation event, occurred in approximately 10 % of the observations. Over the entire study period, three marine influenced population types were identified that typically occurred when the regular diurnal land/sea-breeze cycle collapsed and BML was continuously ventilated by air masses from marine regions for multiple days. These marine types differed from each other primarily in the degree of cloud processing evident in the size distributions, and in the presence of an additional large-particle mode for the type associated with the highest wind speeds. One of the marine types was associated with a multi-day period during which an atmospheric river made landfall at BML. The generally higher total particle number concentrations but lower activated fractions of four of the terrestrial types yielded similar CCN number concentrations to two of the marine types for supersaturations below about 0.4 %. Despite quite different activated fraction spectra, the two remaining marine and terrestrial types had CCN spectral number concentrations very similar to each other, due in part to higher number concentrations associated with the terrestrial type.

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Simultaneous measurements of aerosol size distributions at three sites in the European high Arctic

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-7377-2019 ◽

2019 ◽

Vol 19 (11) ◽

pp. 7377-7395 ◽

Cited By ~ 6

Author(s):

Manuel Dall'Osto ◽

David C. S. Beddows ◽

Peter Tunved ◽

Roy M. Harrison ◽

Angelo Lupi ◽

...

Keyword(s):

Cluster Analysis ◽

Cloud Condensation Nuclei ◽

High Arctic ◽

The Arctic ◽

Research Station ◽

Size Distributions ◽

Aerosol Formation ◽

Condensation Nuclei ◽

Main Mode ◽

Accumulation Mode

Abstract. Aerosols are an integral part of the Arctic climate system due to their direct interaction with radiation and indirect interaction through cloud formation. Understanding aerosol size distributions and their dynamics is crucial for the ability to predict these climate relevant effects. When of favourable size and composition, both long-range-transported – and locally formed particles – may serve as cloud condensation nuclei (CCN). Small changes of composition or size may have a large impact on the low CCN concentrations currently characteristic of the Arctic environment. We present a cluster analysis of particle size distributions (PSDs; size range 8–500 nm) simultaneously collected from three high Arctic sites during a 3-year period (2013–2015). Two sites are located in the Svalbard archipelago: Zeppelin research station (ZEP; 474 m above ground) and the nearby Gruvebadet Observatory (GRU; about 2 km distance from Zeppelin, 67 m above ground). The third site (Villum Research Station at Station Nord, VRS; 30 m above ground) is 600 km west-northwest of Zeppelin, at the tip of north-eastern Greenland. The GRU site is included in an inter-site comparison for the first time. K-means cluster analysis provided eight specific aerosol categories, further combined into broad PSD classes with similar characteristics, namely pristine low concentrations (12 %–14 % occurrence), new particle formation (16 %–32 %), Aitken (21 %–35 %) and accumulation (20 %–50 %). Confined for longer time periods by consolidated pack sea ice regions, the Greenland site GRU shows PSDs with lower ultrafine-mode aerosol concentrations during summer but higher accumulation-mode aerosol concentrations during winter, relative to the Svalbard sites. By association with chemical composition and cloud condensation nuclei properties, further conclusions can be derived. Three distinct types of accumulation-mode aerosol are observed during winter months. These are associated with sea spray (largest detectable sizes, >400 nm), Arctic haze (main mode at 150 nm) and aged accumulation-mode (main mode at 220 nm) aerosols. In contrast, locally produced particles, most likely of marine biogenic origin, exhibit size distributions dominated by the nucleation and Aitken mode during summer months. The obtained data and analysis point towards future studies, including apportioning the relative contribution of primary and secondary aerosol formation processes and elucidating anthropogenic aerosol dynamics and transport and removal processes across the Greenland Sea. In order to address important research questions in the Arctic on scales beyond a singular station or measurement events, it is imperative to continue strengthening international scientific cooperation.

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