scholarly journals Measurements of the relation between aerosol properties and microphysics and chemistry of low level liquid water clouds in Northern Finland

2008 ◽  
Vol 8 (23) ◽  
pp. 6925-6938 ◽  
Author(s):  
H. Lihavainen ◽  
V.-M. Kerminen ◽  
M. Komppula ◽  
A.-P. Hyvärinen ◽  
J. Laakia ◽  
...  
Keyword(s):  
Chemical Properties ◽  
Cloud Droplet ◽  
Simple Relation ◽  
Number Concentration ◽  
Cloud Droplets ◽  
Air Masses ◽  
Boundary Layer Clouds ◽  
Marine Air ◽  
Physical And Chemical ◽  
Aerosol Properties

Abstract. Physical and chemical properties of boundary layer clouds, together with relevant aerosol properties, were investigated during the first Pallas Cloud Experiment (First Pace) conducted in northern Finland between 20 October and 9 November 2004. Two stations located 6 km apart from each other at different altitudes were employed in measurements. The low-altitude station was always below the cloud layer, whereas the high-altitude station was inside clouds about 75% of the time during the campaign. Direct measurements of cloud droplet populations showed that our earlier approach of determining cloud droplet residual particle size distributions and corresponding activated fractions using continuous aerosol number size distribution measurements at the two stations is valid, as long as the cloud events are carefully screened to exclude precipitating clouds and to make sure the same air mass has been measured at both stations. We observed that a non-negligible fraction of cloud droplets originated from Aitken mode particles even at moderately-polluted air masses. We found clear evidence on first indirect aerosol effect on clouds but demonstrated also that no simple relation between the cloud droplet number concentration and aerosol particle number concentration exists for this type of clouds. The chemical composition of aerosol particles was dominated by particulate organic matter (POM) and sulphate in continental air masses and POM, sodium and chlorine in marine air masses. The inorganic composition of cloud water behaved similarly to that of the aerosol phase and was not influenced by inorganic trace gases.

scholarly journals Measurements of the relation between aerosol properties and microphysics and chemistry of low clouds in northern Finland

2008 ◽  
Vol 8 (4) ◽  
pp. 14105-14143
Author(s):  
H. Lihavainen ◽  
V.-M. Kerminen ◽  
M. Komppula ◽  
A.-P. Hyvärinen ◽  
J. Laakia ◽  
...  
Keyword(s):  
Chemical Properties ◽  
Cloud Droplet ◽  
Simple Relation ◽  
Number Concentration ◽  
Cloud Droplets ◽  
Air Masses ◽  
Boundary Layer Clouds ◽  
Marine Air ◽  
Physical And Chemical ◽  
Aerosol Properties

Abstract. Physical and chemical properties of boundary layer clouds, together with relevant aerosol properties, were investigated during the first Pallas Cloud Experiment (First PaCE) conducted in northern Finland between 20 October and 9 November, 2004. Two stations located 6 km apart from each other at different altitudes were employed in measurements. The low-altitude station was always below the cloud layer, whereas the high-altitude station was inside clouds about 75% of the time during the campaign. Direct measurements of cloud droplet populations showed that our earlier approach of determining cloud droplet residual particle size distributions and corresponding activated fractions using continuous aerosol number size distribution measurements at the two stations is valid, as long as the cloud events are carefully screened to exclude precipitating clouds and to make sure the same air mass has been measured at both stations. We observed that a non-negligible fraction of cloud droplets originated from Aitken mode particles even at moderately-polluted air masses. We found clear evidence on first indirect aerosol effect on clouds but demonstrated also that no simple relation between the cloud droplet number concentration and aerosol particle number concentration exists for this type of clouds. The chemical composition of aerosol particles was dominated by organic matter (POM) and sulphate in continental air masses and POM, sodium and chlorine in marine air masses. The inorganic composition of cloud water behaved similarly to that of the aerosol phase and was not influenced by inorganic trace gases.

scholarly journals Influence of aerosols on the formation and development of radiation fog

2009 ◽  
Vol 9 (5) ◽  
pp. 17963-18019 ◽  
Author(s):  
J. Rangognio ◽  
P. Tulet ◽  
T. Bergot ◽  
L. Gomes ◽  
O. Thouron ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Chemical Properties ◽  
Cloud Droplet ◽  
Critical Value ◽  
Number Concentration ◽  
Cloud Droplets ◽  
Radiation Fog ◽  
Cloud Water Content ◽  
Aerosol Number Concentration ◽  
The Impact

Abstract. This paper assesses the impact of aerosol properties on the formation and the development of radiation fog. Simulations were performed using the Meso-NH meteorological model including the ORILAM aerosol scheme coupled with a two-moment microphysical cloud scheme (number concentration of cloud droplets and cloud water content). The activation scheme used was taken from the work of Abdul-Razzak and Ghan (2004). "Off-line" sensitivity analysis of CCN (Cloud Condensation Nuclei) activation was performed on number, median diameter and chemical compounds of aerosols. During this "off-line" study, the interactions with the other physical processes (e.g. radiative) were not taken into account since the cooling rate was imposed. Different regimes of CCN activation and a critical value of aerosol number concentration were found. This critical aerosol number corresponds to the maximum of activated cloud droplets for a given cooling rate and given aerosol chemical properties. As long as the aerosol number concentration is below this critical value, the cloud droplet number increases when the aerosol number increases. But when the aerosol number concentration exceeds this critical value, the cloud droplet number decreases when aerosol number increases. A sensitivity study on aerosol chemical composition showed that the CCN activation was limited in the case of hydrophilic aerosol composed of material with a solubility in the 10% range. An event observed during the ParisFOG field experiment was simulated. This case took place in the polluted sub-urban area of Paris (France) characterized by particle concentrations of 17 000 aerosols per cm3. 1D simulations successfully reproduced the observed temporal evolution of the fog layer. Beyond the initial fog formation at the surface, cloud droplet formation occurred at the top of the fog layer where the cooling rate was maximum, reaching more than −10 K h−1. These simulations confirm that the aerosol particle number concentration is a key parameter for the accurate prediction of the microphysical properties of a fog layer and also influences the vertical development of fog. The important of the interaction between microphysical and radiative processes is illustrated, showing how the life cycle of a fog layer is determined by the CCN number concentration and chemical properties.

scholarly journals The effect of physical and chemical aerosol properties on warm cloud droplet activation

2005 ◽  
Vol 5 (5) ◽  
pp. 8507-8646 ◽  
Author(s):  
G. McFiggans ◽  
P. Artaxo ◽  
U. Baltensperger ◽  
H. Coe ◽  
M. C. Facchini ◽  
...  
Keyword(s):  
Atmospheric Aerosol ◽  
Radiative Forcing ◽  
Cloud Droplet ◽  
Size Composition ◽  
Radiative Properties ◽  
Atmospheric Measurements ◽  
Derived Properties ◽  
Aerosol Effects ◽  
Physical And Chemical ◽  
Aerosol Properties

Abstract. The effects of atmospheric aerosol on climate forcing may be very substantial but are quantified poorly at present; in particular, the effects of aerosols on cloud radiative properties, or the "indirect effects" are credited with the greatest range of uncertainty amongst the known causes of radiative forcing. This manuscript explores the effects that the composition and properties of atmospheric aerosol can have on the activation of droplets in warm clouds, so potentially influencing the magnitude of the indirect effect. The effects of size, composition, mixing state and various derived properties are assessed and a range of these properties provided by atmospheric measurements in a variety of locations is briefly reviewed. The suitability of a range of process-level descriptions to capture these aerosol effects is investigated by assessment of their sensitivities to uncertainties in aerosol properties and by their performance in closure studies. The treatment of these effects within global models is reviewed and suggestions for future investigations are made.

scholarly journals Microphysical processing of aerosol particles in orographic clouds

2015 ◽  
Vol 15 (16) ◽  
pp. 9217-9236 ◽  
Author(s):  
S. Pousse-Nottelmann ◽  
E. M. Zubler ◽  
U. Lohmann
Keyword(s):  
Cloud Droplet ◽  
Number Concentration ◽  
Mixed Phase ◽  
Cloud Formation ◽  
Small Scale ◽  
Cloud Droplets ◽  
Aerosol Mass ◽  
Aerosol Processing ◽  
Orographic Clouds ◽  
Aerosol Scavenging

Abstract. An explicit and detailed treatment of cloud-borne particles allowing for the consideration of aerosol cycling in clouds has been implemented into COSMO-Model, the regional weather forecast and climate model of the Consortium for Small-scale Modeling (COSMO). The effects of aerosol scavenging, cloud microphysical processing and regeneration upon cloud evaporation on the aerosol population and on subsequent cloud formation are investigated. For this, two-dimensional idealized simulations of moist flow over two bell-shaped mountains were carried out varying the treatment of aerosol scavenging and regeneration processes for a warm-phase and a mixed-phase orographic cloud. The results allowed us to identify different aerosol cycling mechanisms. In the simulated non-precipitating warm-phase cloud, aerosol mass is incorporated into cloud droplets by activation scavenging and released back to the atmosphere upon cloud droplet evaporation. In the mixed-phase cloud, a first cycle comprises cloud droplet activation and evaporation via the Wegener–Bergeron–Findeisen (WBF) process. A second cycle includes below-cloud scavenging by precipitating snow particles and snow sublimation and is connected to the first cycle via the riming process which transfers aerosol mass from cloud droplets to snowflakes. In the simulated mixed-phase cloud, only a negligible part of the total aerosol mass is incorporated into ice crystals. Sedimenting snowflakes reaching the surface remove aerosol mass from the atmosphere. The results show that aerosol processing and regeneration lead to a vertical redistribution of aerosol mass and number. Thereby, the processes impact the total aerosol number and mass and additionally alter the shape of the aerosol size distributions by enhancing the internally mixed/soluble Aitken and accumulation mode and generating coarse-mode particles. Concerning subsequent cloud formation at the second mountain, accounting for aerosol processing and regeneration increases the cloud droplet number concentration with possible implications for the ice crystal number concentration.

scholarly journals Aerosol concentration and size distribution measured below, in, and above cloud from the DOE G-1 during VOCALS-REx

2011 ◽  
Vol 11 (6) ◽  
pp. 17289-17336 ◽  
Author(s):  
L. I. Kleinman ◽  
P. H. Daum ◽  
Y.-N. Lee ◽  
E. R. Lewis ◽  
A. J. Sedlacek ◽  
...  
Keyword(s):  
Power Plants ◽  
Marine Boundary Layer ◽  
Cloud Droplet ◽  
Pollution Source ◽  
Number Concentration ◽  
Dew Point ◽  
Cloud Droplets ◽  
The North ◽  
Stratocumulus Clouds ◽  
The Difference

Abstract. During the VOCALS Regional Experiment, the DOE G-1 aircraft was used to sample a varying aerosol environment pertinent to properties of stratocumulus clouds over a longitude band extending 800 km west from the Chilean coast at Arica. Trace gas and aerosol measurements are presented as a function of longitude, altitude, and dew point in this study. Spatial distributions are consistent with an upper atmospheric source for O3 and South American coastal sources for marine boundary layer (MBL) CO and aerosol, most of which is acidic sulfate in agreement with the dominant pollution source being SO2 from Cu smelters and power plants. Pollutant layers in the free troposphere (FT) can be a result of emissions to the north in Peru or long range transport from the west. At a given altitude in the FT (up to 3 km), dew point varies by 40 °C with dry air descending from the upper atmospheric and moist air having a BL contribution. Ascent of BL air to a cold high altitude results in the condensation and precipitation removal of all but a few percent of BL water along with aerosol that served as CCN. Thus, aerosol volume decreases with dew point in the FT. Aerosol size spectra have a bimodal structure in the MBL and an intermediate diameter unimodal distribution in the FT. Comparing cloud droplet number concentration (CDNC) and pre-cloud aerosol (Dp > 100 nm) gives a linear relation up to a number concentration of ~150 cm−3, followed by a less than proportional increase in CDNC at higher aerosol number concentration. A number balance between below cloud aerosol and cloud droplets indicates that ~25 % of aerosol in the PCASP size range are interstitial (not activated). One hundred and two constant altitude cloud transects were identified and used to determine properties of interstitial aerosol. One transect is examined in detail as a case study. Approximately 25 to 50 % of aerosol with Dp > 110 nm were not activated, the difference between the two approaches possibly representing shattered cloud droplets or unknown artifact. CDNC and interstitial aerosol were anti-correlated in all cloud transects, consistent with the occurrence of dry in-cloud areas due to entrainment or circulation mixing.

Inputs of trace gases, particles and cloud droplets to terrestrial surfaces

1990 ◽  
Vol 97 ◽  
pp. 35-59 ◽  
Author(s):  
D. Fowler ◽  
J. H. Duyzer ◽  
D. D. Baldocchi
Keyword(s):  
Major Ions ◽  
Chemical Properties ◽  
Cloud Droplet ◽  
Droplet Deposition ◽  
Cloud Droplets ◽  
Plant Canopies ◽  
Deposition Velocities ◽  
Reactive Gases ◽  
Controlling Processes ◽  
Atmospheric Concentrations

SynopsisThe deposition of reactive gases on terrestrial surfaces is one of the primary mechanisms by which pollutant gases are removed from the atmosphere. The chemical properties of the gases (SO2, NO2, HNO3, HCl) and of the absorbing surfaces lead to differing rates of exchange and controlling processes. The most reactive gases, HNO3, HCl (and for many surfaces NH3) exhibit negligible surface resistances; deposition velocities (Vg) appropriate for short vegetation ranging from 2 to 5 cm s−1, for forests Vg may approach 10 cm s−1. The large rates of deposition for NH3 on moorland and forests lead to annual inputs, in areas with large atmospheric concentrations of NH3 (≥ 5 μg NH3 m−3), ranging from 20 to 60 kg N ha−1. The net exchange of NH3 over cropland, attributable to deposition during vegetative growth and emission of NH3 during senescence, is less well known but believed to be small.The co-deposition of NH3 and SO2 on external surfaces of plant canopies is believed to enhance SO2deposition with reported deposition velocities over short vegetation of 2.0 cm s−1.Rates of cloud droplet deposition to vegetation have been shown to be very similar to rates of momentum deposition (i.e. Vt ≈ ram−1). These findings provide the basis for estimates of cloud deposition inputs of major ions to upland Britain where they may contribute up to 30% of the wet deposited sulphur and nitrogen.

scholarly journals Secondary new particle formation in Northern Finland Pallas site between the years 2000 and 2010

2011 ◽  
Vol 11 (24) ◽  
pp. 12959-12972 ◽  
Author(s):  
E. Asmi ◽  
N. Kivekäs ◽  
V.-M. Kerminen ◽  
M. Komppula ◽  
A.-P. Hyvärinen ◽  
...  
Keyword(s):  
Growth Rates ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Detailed Examination ◽  
Particle Formation ◽  
New Particle Formation ◽  
Air Masses ◽  
Event Frequency ◽  
Marine Air

Abstract. Secondary new particle formation affects atmospheric aerosol and cloud droplet numbers and thereby, the aerosol effects on climate. In this paper, the frequency of nucleation events and the associated particle formation and growth rates, along with their seasonal variation, was analysed based on over ten years of aerosol measurements conducted at the Pallas GAW station in northern Finland. The long-term measurements also allowed a detailed examination of factors possibly favouring or suppressing particle formation. Effects of meteorological parameters and air mass properties as well as vapour sources and sinks for particle formation frequency and event parameters were inspected. In addition, the potential of secondary particle formation to increase the concentration of cloud condensation nuclei (CCN) sized particles was examined. Findings from these long-term measurements confirmed previous observations: event frequency peaked in spring and the highest growth rates were observed in summer, affiliated with increased biogenic activity. Events were almost exclusively observed in marine air masses on sunny cloud-free days. A low vapour sink by the background particle population as well as an elevated sulphuric acid concentration were found to favour particle formation. These were also conditions taking place most likely in marine air masses. Inter-annual trend showed a minimum in event frequency in 2003, when also the smallest annual median of growth rate was observed. This gives further evidence of the importance and sensitivity of particle formation for the condensing vapour concentrations at Pallas site. The particle formation was observed to increase CCN80 (>80 nm particle number) concentrations especially in summer and autumn seasons when the growth rates were the highest. When the growing mode exceeded the selected 80 nm limit, on average in those cases, 211 ± 114% increase of CCN80 concentrations was observed.

scholarly journals The influence of nitric acid on the cloud processing of aerosol particles

2006 ◽  
Vol 6 (6) ◽  
pp. 1627-1634 ◽  
Author(s):  
S. Romakkaniemi ◽  
H. Kokkola ◽  
K. E. J. Lehtinen ◽  
A. Laaksonen
Keyword(s):  
Sulfuric Acid ◽  
Nitric Acid ◽  
Aerosol Particles ◽  
Cloud Droplet ◽  
Number Concentration ◽  
Radiative Properties ◽  
Aerosol Size Distribution ◽  
Cloud Droplets ◽  
Cloud Processing ◽  
Cloud Droplet Number Concentration

Abstract. In this paper we present simulations of the effect of nitric acid (HNO3) on cloud processing of aerosol particles. Sulfuric acid (H2SO4) production and incloud coagulation are both affected by condensed nitric acid as nitric acid increases the number of cloud droplets, which will lead to smaller mean size and higher total surface area of droplets. As a result of increased cloud droplet number concentration (CDNC), the incloud coagulation rate is enhanced by a factor of 1–1.3, so that the number of interstitial particles reduces faster. In addition, sulfuric acid production occurs in smaller particles and so the cloud processed aerosol size distribution is dependent on the HNO3 concentration. This affects both radiative properties of aerosol particles and the formation of cloud droplets during a sequence of cloud formation-evaporation events. It is shown that although the condensation of HNO3 increases the number of cloud droplets during the single updraft, it is possible that presence of HNO3 can actually decrease the cloud droplet number concentration after several cloud cycles when also H2SO4 production is taken into account.

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