Quantifying the effect of SVOC condensation on cloud droplet number in different airmass types

2020 ◽  
Author(s):  
Liine Heikkinen ◽  
Samuel Lowe ◽  
Cheng Wu ◽  
Diego Aliaga ◽  
Wei Huang ◽  
...  
Keyword(s):  
Water Vapor ◽  
Size Distribution ◽  
Cloud Droplet ◽  
Ambient Air ◽  
Population Characteristics ◽  
Basis Set ◽  
Activation Process ◽  
Multiple Model ◽  
Aerosol Composition ◽  
Data Set

<p>Clouds are made of droplets that arise from the activation of suitable aerosol particles (termed cloud condensation nuclei, CCN). In the activation process, water vapor saturation ratio exceeds a critial ratio enabling CCN runaway-growth to cloud droplet sizes. The number concentration of cloud droplets (CDNC) is highly dependent on the aerosol population properties (size distribution and composition), relative humidity, and the vertical wind component. While the activation of CCN consisting of non-volatile particulate matter is fairly well understood, the same process involving semi-volatile organic vapors (SVOCs) has received less attention despite their significant presence in ambient air. A recent cloud parcel modeling study shows substanial CDNC enhancement due to SVOC condensation (Topping <em>et al</em>., 2013). Surprisingly, the topic has not been widely investigated nor the results replicated with other cloud parcel models (CPM). Thus, in the current study we seek to quantify the CDNC enhancement by SVOC condensation using a recently developed CPM framework (Lowe <em>et al.</em>, 2020, <em>in prep</em>.). Moreover, the CPM initialization is performed, for the first time, with state-of-the art measurement data including measured SVOC data for multiple airmass types.</p><p>Here, the CPM, which uses spectral microphysics for the simulation of CCN activation and hydrometeor growth, also includes a SVOC condensation equation analogous to those of water vapor. Equilibrium initialization of the SVOC volatility basis set (VBS) partitioning coefficients is performed iteratively, and constrained by the organic to inorganic ratio in the particle phase determined by ambient measurements performed at the Chacaltaya Global Atmospheric Watch (GAW) Station located at 5240 m a.s.l. in the Bolivian Andes, in spring 2018. The uniquely comprehensive data set recorded, which tracks all of the relevant aerosol population characteristics in near real-time, reveals a high degree of variability in aerosol composition, size distribution and loading depending on the air mass origin. Lagrangian backward simulations during the measurement period at Chacaltaya GAW reveal at least 18 significantly different airmass origins (Aliaga <em>et al.</em>, 2020, <em>in prep.</em>). Such variability served multiple model initialization scenarios for individual case studies. We will show a suite of CDNC enhancements by SVOC condensation under different initialization scenarios actualized in data recorded at Chacaltaya GAW Station, including airmasses originating from the Amazon (biomass burning and biogenic VOCs), Andean plateau (volcanic activity), and La Paz/El Alto metropolitan areas (anthropogenic emissions).</p><p><strong>References:</strong></p><div>Topping, D., Connolly, P. and McFiggans, G., 2013. Cloud droplet number enhanced by co-condensation of organic vapours. <em>Nature Geoscience</em>, <em>6</em>(6), p.443.</div>

scholarly journals On the competition among aerosol number, size and composition in predicting CCN variability: a multi-annual field study in an urbanized desert

2015 ◽  
Vol 15 (12) ◽  
pp. 6943-6958 ◽  
Author(s):  
E. Crosbie ◽  
J.-S. Youn ◽  
B. Balch ◽  
A. Wonaschütz ◽  
T. Shingler ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Size Distribution ◽  
North American ◽  
Monsoon Season ◽  
Aerosol Size Distribution ◽  
North American Monsoon ◽  
Aerosol Composition ◽  
Data Set ◽  
The North ◽  
Concentration Changes

Abstract. A 2-year data set of measured CCN (cloud condensation nuclei) concentrations at 0.2 % supersaturation is combined with aerosol size distribution and aerosol composition data to probe the effects of aerosol number concentrations, size distribution and composition on CCN patterns. Data were collected over a period of 2 years (2012–2014) in central Tucson, Arizona: a significant urban area surrounded by a sparsely populated desert. Average CCN concentrations are typically lowest in spring (233 cm−3), highest in winter (430 cm−3) and have a secondary peak during the North American monsoon season (July to September; 372 cm−3). There is significant variability outside of seasonal patterns, with extreme concentrations (1 and 99 % levels) ranging from 56 to 1945 cm−3 as measured during the winter, the season with highest variability. Modeled CCN concentrations based on fixed chemical composition achieve better closure in winter, with size and number alone able to predict 82 % of the variance in CCN concentration. Changes in aerosol chemical composition are typically aligned with changes in size and aerosol number, such that hygroscopicity can be parameterized even though it is still variable. In summer, models based on fixed chemical composition explain at best only 41 % (pre-monsoon) and 36 % (monsoon) of the variance. This is attributed to the effects of secondary organic aerosol (SOA) production, the competition between new particle formation and condensational growth, the complex interaction of meteorology, regional and local emissions and multi-phase chemistry during the North American monsoon. Chemical composition is found to be an important factor for improving predictability in spring and on longer timescales in winter. Parameterized models typically exhibit improved predictive skill when there are strong relationships between CCN concentrations and the prevailing meteorology and dominant aerosol physicochemical processes, suggesting that similar findings could be possible in other locations with comparable climates and geography.

scholarly journals Life history characteristics of a cave isopod (Mesoniscus graniger Friv.)

ZooKeys ◽  
2018 ◽  
Vol 801 ◽  
pp. 359-370 ◽  
Author(s):  
Dávid Derbák ◽  
László Dányi ◽  
Elisabeth Hornung
Keyword(s):  
Life History ◽  
Sex Ratio ◽  
Size Distribution ◽  
Body Length ◽  
Reproductive Strategy ◽  
Population Characteristics ◽  
Female Dominance ◽  
Head Width ◽  
Data Set ◽  
Offspring Number

The special environmental conditions of caves provide habitat for several endemic and relict species, among them terrestrial isopods. The Baradla Cave system (north-eastern Hungary) hosts Mesoniscusgraniger (Frivaldszky, 1865) (Oniscidea, Microcheta, Mesoniscidae), a pygmy, blind, fragile troglophile woodlice species. Its stable environment can be characterised by the lack of light, high relative humidity (96%), low and constant temperature (about 10 °C). We explored the population characteristics (sex ratio, size distribution) and life history traits of the species (e.g. longevity, reproductive strategy, offspring number, and size). Sex ratio and size distribution of the individuals (head-width measurements) were estimated based on a yearly pooled pitfall-trap data set (N = 677). We studied the species’ reproductive strategy under natural conditions (Baradla Cave, Aggtelek National Park). Model populations were set up in the cave and checked monthly between March and October, 2016 (15 replicates, each with 12 randomly chosen adult individuals; ΣN = 180). Digital photos were taken of the live animals and their length was estimated based on the photos by using ImageJ software (average body length: 6.56 ± 0.79 mm). The results showed female dominance in the population [(male:female = 0.43:0.57); p < 0.001 (GLM)]. Female head width (0.87 ± 0.18 mm) was significantly greater than that of males [0.79 ± 0.08 mm; p < 0.001 (t-test)]. Based on our present data we assume that the offspring number per single female is low (3–5), and new-borns have a relatively large size (body length: 4.22 ± 0.53 mm) compared to the adults. The probability of reproduction was continuous by monthly intervals (binomial test) and longevity exceeds one year. Our results suggest that the species follows a stenodynamic life history.

scholarly journals Importance of aerosol composition and mixing state for cloud droplet activation in the high Arctic

2014 ◽  
Vol 14 (15) ◽  
pp. 21223-21283 ◽  
Author(s):  
C. Leck ◽  
E. Svensson
Keyword(s):  
Water Vapor ◽  
Cloud Droplet ◽  
Polymer Gels ◽  
High Arctic ◽  
Water Soluble ◽  
Local Source ◽  
Aerosol Composition ◽  
Pack Ice ◽  
Kohler Theory ◽  
Droplet Activation

Abstract. Concentrations of cloud condensation nuclei (CCN) were measured throughout an expedition by icebreaker around the central Arctic Ocean, including a 3 week ice drift operation at 87° N, from 3 August to 9 September 2008. In agreement with previous observations in the area and season median daily CCN concentrations at 0.2% water vapor supersaturation were typically in the range of 15 to 30 cm−3, but concentrations varied by two to three orders of magnitude over the expedition and were occasionally below 1 cm−3. The CCN concentrations were highest near the ice edge and fell by a factor of three in the first 48 h of transport from the open sea into the pack ice region. For longer transport times they increased again indicating a local source over the pack ice, suggested to be polymer gels, via drops injected into the air by bubbles bursting on open leads. By assuming Köhler theory and simulating the cloud nucleation process using a Lagrangian adiabatic air parcel model that solves the kinetic formulation for condensation of water on size resolved aerosol particles we inferred the properties of the unexplained non-water soluble aerosol fraction that is necessary for reproducing the observed concentrations of CCN. We propose that the portion of the internally/externally mixed water insoluble particles was larger in the corresponding smaller aerosol sizes ranges. These particles were physically and chemically behaving as polymer gels: the interaction of the hydrophilic and hydrophobic entities on the structures of polymer gels during cloud droplet activation would at first only show a partial wetting character and only weak hygroscopic growth. Given time, a high CCN activation efficiency is achieved, which is promoted by the hydrophilicity or surface-active properties of the gels. Thus the result in this study argues for that the behavior of the high Arctic aerosol in CCN-counters operating at water vapor supersaturations > 0.4% (high relative humidities) may not be properly explained by conventional Köhler theory.

scholarly journals Cloud-droplet growth due to supersaturation fluctuations in stratiform clouds

2019 ◽  
Vol 19 (1) ◽  
pp. 639-648 ◽  
Author(s):  
Xiang-Yu Li ◽  
Gunilla Svensson ◽  
Axel Brandenburg ◽  
Nils E. L. Haugen
Keyword(s):  
Reynolds Number ◽  
Water Vapor ◽  
Size Distribution ◽  
Cloud Droplet ◽  
Passive Scalar ◽  
Droplet Growth ◽  
Size Distributions ◽  
Stratiform Clouds ◽  
The Mean ◽  
Condensational Growth

Abstract. Condensational growth of cloud droplets due to supersaturation fluctuations is investigated by solving the hydrodynamic and thermodynamic equations using direct numerical simulations (DNS) with droplets being modeled as Lagrangian particles. The supersaturation field is calculated directly by simulating the temperature and water vapor fields instead of being treated as a passive scalar. Thermodynamic feedbacks to the fields due to condensation are also included for completeness. We find that the width of droplet size distributions increases with time, which is contrary to the classical theory without supersaturation fluctuations, where condensational growth leads to progressively narrower size distributions. Nevertheless, in agreement with earlier Lagrangian stochastic models of the condensational growth, the standard deviation of the surface area of droplets increases as t1∕2. Also, for the first time, we explicitly demonstrate that the time evolution of the size distribution is sensitive to the Reynolds number, but insensitive to the mean energy dissipation rate. This is shown to be due to the fact that temperature fluctuations and water vapor mixing ratio fluctuations increase with increasing Reynolds number; therefore the resulting supersaturation fluctuations are enhanced with increasing Reynolds number. Our simulations may explain the broadening of the size distribution in stratiform clouds qualitatively, where the mean updraft velocity is almost zero.

scholarly journals Technical Note: Formal blind intercomparison of HO<sub>2</sub> measurements in the atmosphere simulation chamber SAPHIR during the HOxComp campaign

2010 ◽  
Vol 10 (24) ◽  
pp. 12233-12250 ◽  
Author(s):  
H. Fuchs ◽  
T. Brauers ◽  
H.-P. Dorn ◽  
H. Harder ◽  
R. Häseler ◽  
...  
Keyword(s):  
Water Vapor ◽  
Correlation Coefficients ◽  
Chemical Conversion ◽  
Ambient Air ◽  
Technical Note ◽  
Data Set ◽  
Air Masses ◽  
Regression Parameters ◽  
Atmosphere Simulation Chamber ◽  
Simulation Chamber

Abstract. Hydroperoxy radical (HO2) concentrations were measured during the formal blind intercomparison campaign HOxComp carried out in Jülich, Germany, in 2005. Three instruments detected HO2 via chemical conversion to hydroxyl radicals (OH) and subsequent detection of the sum of OH and HO2 by laser induced fluorescence (LIF). All instruments were based on the same detection and calibration scheme. Because measurements by a MIESR instrument failed during the campaign, no absolute reference measurement was available, so that the accuracy of individual instruments could not be addressed. Instruments sampled ambient air for three days and were attached to the atmosphere simulation chamber SAPHIR during the second part of the campaign. Six experiments of one day each were conducted in SAPHIR, where air masses are homogeneously mixed, in order to investigate the performance of instruments and to determine potential interferences of measurements under well-controlled conditions. Linear correlation coefficients (R2) between measurements of the LIF instruments are generally high and range from 0.82 to 0.98. However, the agreement between measurements is variable. The regression analysis of the entire data set of measurements in SAPHIR yields slopes between 0.69 to 1.26 and intercepts are smaller than typical atmospheric daytime concentrations (less than 1 pptv). The quality of fit parameters improves significantly, when data are grouped into data subsets of similar water vapor concentrations. Because measurements of LIF instruments were corrected for a well-characterized water dependence of their sensitivities, this indicates that an unknown factor related to water vapor affected measurements in SAPHIR. Measurements in ambient air are also well-correlated, but regression parameters differ from results obtained from SAPHIR experiments. This could have been caused by differences in HO2 concentrations in the sampled air at the slightly different locations of instruments.

scholarly journals Technical Note: Formal blind intercomparison of HO<sub>2</sub> measurements in the atmosphere simulation chamber SAPHIR during the HOxComp campaign

2010 ◽  
Vol 10 (9) ◽  
pp. 21189-21235 ◽  
Author(s):  
H. Fuchs ◽  
T. Brauers ◽  
H.-P. Dorn ◽  
H. Harder ◽  
R. Häseler ◽  
...  
Keyword(s):  
Water Vapor ◽  
Correlation Coefficients ◽  
Chemical Conversion ◽  
Ambient Air ◽  
Technical Note ◽  
Data Set ◽  
Air Masses ◽  
Regression Parameters ◽  
Atmosphere Simulation Chamber ◽  
Simulation Chamber

Abstract. Hydroperoxy radical (HO2) concentrations were measured during the formal blind intercomparison campaign HOxComp carried out in Jülich, Germany. Three instruments detected HO2 via chemical conversion to hydroxyl radicals (OH) and subsequent detection of the sum of OH and HO2 by laser induced fluorescence (LIF). Instruments sampled ambient air for three days and were attached to the atmosphere simulation chamber SAPHIR during the second part of the campaign. Six experiments of one day each were conducted in SAPHIR, where air masses were homogeneously mixed, in order to investigate the performance of instruments and to determine potential interferences of measurements under well-controlled conditions. Linear correlation coefficients between measurements of the LIF instruments are generally high and range from 0.82 to 0.98. However, the agreement between measurements is variable. The regression analysis of the entire data set of measurements in SAPHIR yields slopes between 0.69 to 1.26 and intercepts are smaller than typical atmospheric daytime concentrations (less than 1 pptv). The quality of fit parameters improves significantly, when data are grouped into data subsets of similar water vapor concentrations. Because measurements of LIF instruments were corrected for a well-characterized water dependence of their sensitivities, this indicates that an unknown factor related to water vapor affected measurements in SAPHIR. Measurements in ambient air are also well correlated, but regression parameters differ from results obtained from SAPHIR experiments. This is most likely caused by sampling different air masses at the slightly distant locations of instruments.

The variability of warm cloud droplet radius induced by aerosols and water vapor in Shanghai from MODIS observations

2021 ◽  
Vol 253 ◽  
pp. 105470
Author(s):  
Qiong Liu ◽  
Shengyang Duan ◽  
Qianshan He ◽  
Yonghang Chen ◽  
Hua Zhang ◽  
...  
Keyword(s):  
Water Vapor ◽  
Cloud Droplet ◽  
Droplet Radius ◽  
Warm Cloud

scholarly journals Remote sensing of water cloud droplet size distributions using the backscatter glory: a case study

2004 ◽  
Vol 4 (5) ◽  
pp. 1255-1263 ◽  
Author(s):  
B. Mayer ◽  
M. Schröder ◽  
R. Preusker ◽  
L. Schüller
Keyword(s):  
Remote Sensing ◽  
Size Distribution ◽  
Droplet Size ◽  
Cloud Droplet ◽  
Droplet Size Distribution ◽  
Single Scattering ◽  
Effective Radius ◽  
Radiative Properties ◽  
High Angular Resolution ◽  
Size Distributions

Abstract. Cloud single scattering properties are mainly determined by the effective radius of the droplet size distribution. There are only few exceptions where the shape of the size distribution affects the optical properties, in particular the rainbow and the glory directions of the scattering phase function. Using observations by the Compact Airborne Spectrographic Imager (CASI) in 180° backscatter geometry, we found that high angular resolution aircraft observations of the glory provide unique new information which is not available from traditional remote sensing techniques: Using only one single wavelength, 753nm, we were able to determine not only optical thickness and effective radius, but also the width of the size distribution at cloud top. Applying this novel technique to the ACE-2 CLOUDYCOLUMN experiment, we found that the size distributions were much narrower than usually assumed in radiation calculations which is in agreement with in-situ observations during this campaign. While the shape of the size distribution has only little relevance for the radiative properties of clouds, it is extremely important for understanding their formation and evolution.

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