Regional modelling of aerosol interaction with deep convection and the effect on new particle formation over Amazonia

2020 ◽  
Author(s):  
Xuemei Wang ◽  
Daniel Grosvenor ◽  
Hamish Gordon ◽  
Meinrat O. Andreae ◽  
Ken Carslaw
Keyword(s):  
Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Deep Convection ◽  
Particle Formation ◽  
Nucleation Mechanism ◽  
Transport Processes ◽  
Radiative Properties ◽  
Free Troposphere ◽  
New Particle Formation ◽  
New Particles

<p>It has been estimated that over 50% of the present-day global low-level cloud condensation nuclei (CCN) are formed from new particle formation (NPF), and that this process has a substantial effect on the radiative properties of shallow clouds (Gordon et al. 2017). In contrast, we have a very limited understanding of how NPF affects deep convective clouds. Deep clouds could interact strongly with NPF because they extend into the high free troposphere where most new particles are formed, and they are responsible for most of the vertical transport of the nucleating vapours. Andreae et al. (2018) hypothesised from ACRIDICON-CHUVA campaign that organic gas molecules are transported by deep convection to the upper troposphere where they are oxidised and produce new particles, which are then be entrained into the boundary layer and grow to CCN-relevent sizes.</p><p>Here we study the interaction of deep convection and NPF using the United Kingdom Chemistry and Aerosols (UKCA) model coupled with the Cloud-AeroSol Interacting Microphyics (CASIM) embedded in the regional configuration of UK Met Office Hadley Centre Global Environment Model (HadGEM3). We simulate several days over a 1000 km region of the Amazon at 4 km resolution. We then compare the regional model, which resolves cloud up- and downdrafts, with the global model with parameterised convection and low resolution.</p><p>Our simulations highlight three findings. Firstly, solely using a binary H<sub>2</sub>SO<sub>4</sub>-H<sub>2</sub>O nucleation mechanism strongly underestimates total aerosol concentrations compared to observations by a factor of 1.5-8 below 3 km over the Amazon. This points to the potential role of an additional nucleation mechanism, most likely involving biogenic compounds that occurs throughout more of the free troposphere. Secondly, deep convection transports insoluble gases such as DMS and monoterpenes vertically but not SO<sub>2</sub> or H<sub>2</sub>SO<sub>4</sub>. The time scale for DMS oxidation (~ 1 day) is much longer than for monoterpene (1-2 hours), which points to the importance of simulating biogenic nucleation over the Amazon in a cloud-resolving model, while lower-resolution global models may adequately capture DMS effects on H<sub>2</sub>SO<sub>4</sub> nucleation. Finally, we also examine the Andreae et al (2018) hypothesis of aerosol supply to the boundary layer by quantifying cloud-free and cloudy up- and downdraft transport. The transport of newly formed aerosols into the boundary layer is 8 times greater in cloud-free regions than in the clouds, but these transport processes are of similar magnitude for large aerosols.</p>

scholarly journals New Particle Formation and impact on CCN concentrations in the boundary layer and free troposphere at the high altitude station of Chacaltaya (5240 m a.s.l.), Bolivia

2016 ◽  
Author(s):  
C. Rose ◽  
K. Sellegri ◽  
I. Moreno ◽  
F. Velarde ◽  
M. Ramonet ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Particle Number ◽  
Particle Growth ◽  
Particle Formation ◽  
Number Concentration ◽  
Particle Number Concentration ◽  
Free Troposphere ◽  
New Particle Formation ◽  
Radiative Processes ◽  
The Impact

Abstract. Global models predict that new particle formation (NPF) is, in some environments, responsible for a substantial fraction of the total atmospheric particle number concentration and subsequently contribute significantly to cloud condensation nuclei (CCN) concentrations. NPF events were frequently observed at the highest atmospheric observatory in the world, Chacaltaya (5240 m a.s.l.), Bolivia. The present study focuses on the impact of NPF on CCN population. Neutral cluster and Air Ion Spectrometer and mobility particle size spectrometer measurements were simultaneously used to follow the growth of particles from cluster sizes down to ~ 2 nm up to CCN threshold sizes set to 50, 80 and 100 nm. Using measurements performed between January 1 and December 31 2012, we found that 61% of the 94 analysed events showed a clear particle growth and significant enhancement of the CCN-relevant particle number concentration. We evaluated the contribution of NPF events relative to the transport of pre-existing particles to the site. The averaged production of 50 nm particles during those events was 5072 cm−3, and 1481 cm−3 for 100 nm particles, with a larger contribution of NPF compared to transport, especially during the wet season. The data set was further segregated into boundary layer (BL) and free troposphere (FT) conditions at the site. The NPF frequency of occurrence was higher in the BL (48 %) compared to the FT (39 %). Particle condensational growth was more frequently observed for events initiated in the FT, but on average faster for those initiated in the BL, when the amount of condensable species was most probably larger. As a result, the potential to form new CCN was higher for events initiated in the BL (67 % against 56 % in the FT). In contrast, higher CCN number concentration increases were found when the NPF process initially occurred in the FT, under less polluted conditions. This work highlights the competition between particle growth and the removal of freshly nucleated particles by coagulation processes. The results support model predictions which suggest that NPF is an effective source of CCN in some environments, and thus may influence regional climate through cloud related radiative processes.

scholarly journals Free troposphere as the dominant source of CCN in the Equatorial Pacific boundary layer: long-range transport and teleconnections

2013 ◽  
Vol 13 (1) ◽  
pp. 1279-1326 ◽  
Author(s):  
A. D. Clarke ◽  
S. Freitag ◽  
R. M. C. Simpson ◽  
J. G. Hudson ◽  
S. G. Howell ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Large Fraction ◽  
Deep Convection ◽  
Equatorial Pacific ◽  
Quasi Equilibrium ◽  
Free Troposphere ◽  
Low Carbon ◽  
Mixing Ratios

Abstract. Airborne aerosol measurements in the central equatorial Pacific during PASE (Pacific Atmospheric Sulfur Experiment) revealed that cloud condensation nuclei (CCN) activated in marine boundary layer (MBL) clouds were dominated by entrainment from the free troposphere (FT). About 65% entered at sizes effective as CCN in MBL clouds, while 25% entered the MBL too small to activate but subsequently grew via gas to particle conversion. The remaining 10% were inferred to be sea-salt aerosol; there was no discernable nucleation in the MBL. FT aerosols at low carbon monoxide (CO) mixing ratios (< 63 ppbv) were small and relatively volatile with a number mode around 30–40 nm dry diameter and tended to be associated with cloud outflow from distant deep convection (3000 km or more). Higher CO concentrations were commonly associated with trajectories from South America and the Amazon region (ca. 10 000 km away) and occurred in layers indicative of combustion sources partially scavenged by precipitation. These had number mode near 60–80 nm diameter with a large fraction already CCN.2 (those activated at 0.2% supersaturation and representative of MBL clouds) before entrainment into the MBL. Flight averaged concentrations of CCN.2 were similar for measurements near the surface, below the inversion and above the inversion, confirming that subsidence of FT aerosol dominated MBL CCN.2. Concurrent flight-to-flight variations of CCN.2 at all altitudes below 3 km imply MBL CCN.2 concentrations were in quasi-equilibrium with the FT over a 2–3 day time scale. This extended FT transport over thousands of kilometers indicates teleconnections between MBL CCN and cloud-scavenged sources of both natural and/or residual combustion origin. The low aerosol scattering and mass in such layers results in poor detection by satellite and this source of CCN is not represented in most current models. The measurements confirm nucleation in the MBL was not evident during PASE and argue against the CLAW hypothesis being effective in this region during PASE.

scholarly journals Investigating three patterns of new particles growing to cloud condensation nuclei size in Beijing's urban atmosphere

2020 ◽  
Author(s):  
Liya Ma ◽  
Yujiao Zhu ◽  
Mei Zheng ◽  
Yele Sun ◽  
Lei Huang ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Particle Formation ◽  
Urban Atmosphere ◽  
New Particle Formation ◽  
Condensation Nuclei ◽  
Median Diameter ◽  
New Particles

Abstract. The growth of newly formed particles with diameters from ~ 10 nm to a larger size was investigated in Beijing's urban atmosphere on 10–23 December 2011, 12–27 April 2012 and through June–August 2014. The maximum geometric median diameter (Dpgmax) of newly formed particles in 11/27 new particle formation (NPF) events through June–August exceeded 75 nm, and the grown new particles may contribute to the population of cloud condensation nuclei. In contrast, no apparent growth in new particles with Dpgmax 

scholarly journals Changes in the production rate of secondary aerosol particles in Central Europe in view of decreasing SO<sub>2</sub> emissions between 1996 and 2006

2010 ◽  
Vol 10 (3) ◽  
pp. 1071-1091 ◽  
Author(s):  
A. Hamed ◽  
W. Birmili ◽  
J. Joutsensaari ◽  
S. Mikkonen ◽  
A. Asmi ◽  
...  
Keyword(s):  
Growth Rate ◽  
Cloud Condensation Nuclei ◽  
Formation Rate ◽  
Global Radiation ◽  
Particle Diameter ◽  
Particle Formation ◽  
Research Station ◽  
Particle Nucleation ◽  
New Particle Formation ◽  
New Particles

Abstract. In anthropogenically influenced atmospheres, sulphur dioxide (SO2) is the main precursor of gaseous sulphuric acid (H2SO4), which in turn is a main precursor for atmospheric particle nucleation. As a result of socio-economic changes, East Germany has seen a dramatic decrease in anthropogenic SO2 emissions between 1989 and present, as documented by routine air quality measurements in many locations. We have attempted to evaluate the influence of changing SO2 concentrations on the frequency and intensity of new particle formation (NPF) using two different data sets (1996–1997; 2003–2006) of experimental particle number size distributions (diameter range 3–750 nm) from the atmospheric research station Melpitz near Leipzig, Germany. Between the two periods SO2 concentrations decreased by 65% on average, while the frequency of NPF events dropped by 45%. Meanwhile, the average formation rate of 3 nm particles decreased by 68% on average. The trends were statistically significant and therefore suggest a connection between the availability of anthropogenic SO2 and freshly formed new particles. In contrast to the decrease in new particle formation, we found an increase in the mean growth rate of freshly nucleated particles (+22%), suggesting that particle nucleation and subsequent growth into larger sizes are delineated with respect to their precursor species. Using three basic parameters, the condensation sink for H2SO4, the SO2 concentration, and the global radiation intensity, we were able to define the characteristic range of atmospheric conditions under which particle formation events take place at the Melpitz site. While the decrease in the concentrations and formation rates of the new particles was rather evident, no similar decrease was found with respect to the generation of cloud condensation nuclei (CCN; particle diameter >100 nm) as a result of atmospheric nucleation events. On the contrary, the production of CCN following nucleation events appears to have increased by tens of percents. Our aerosol dynamics model simulations suggest that such an increase can be caused by the increased particle growth rate.

scholarly journals New Particle Formation: A Review of Ground-Based Observations at Mountain Research Stations

Atmosphere ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 493 ◽  
Author(s):  
Karine Sellegri ◽  
Clemence Rose ◽  
Angela Marinoni ◽  
Angelo Lupi ◽  
Alfred Wiedensohler ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Particle Number ◽  
Cloud Condensation Nuclei ◽  
Particle Formation ◽  
New Particle Formation ◽  
High Altitudes ◽  
Positive Ions ◽  
Low Altitude ◽  
Term Data

New particle formation (NPF) was predicted to contribute to a major fraction of free tropospheric particle number and cloud condensation nuclei (CCN) concentrations by global models. At high altitudes, pre-existing particle concentrations are low, leading to limited condensational sinks for nucleation precursor gases, and temperatures are cooler compared to lower altitudes, whereas radiation is higher. These factors would all be in favor of nucleation to occur with an enhanced frequency at high altitudes. In the present work, long term data from six altitude stations (and four continents) at various altitudes (from 1465 to 5240 m a.s.l) were used to derive statistically relevant NPF features (frequency, formation rates, and growth rates) and seasonal variability. The combined information together with literature data showed that the frequencies of NPF events at the two Southern hemisphere (SH) stations are some of the highest reported thus far (64% and 67%, respectively). There are indications that NPF would be favored at a preferential altitude close to the interface of the free troposphere (FT) with the planetary boundary layer (PBL) and/or at the vicinity with clouds, which otherwise inhibit the occurrence of NPF. Particle formation rates are found to be lower at high altitudes than at low altitude sites, but a higher fraction of particles are formed via the charged pathway (mainly related to positive ions) compared to boundary layer (BL) sites. Low condensational sinks (CS) are not necessarily needed at high altitudes to promote the occurrence of NPF. For stations at altitudes higher than 1000 m a.s.l., higher CSs favor NPF and are thought to be associated with precursor gases needed to initiate nucleation and early growth.

scholarly journals Rapid sulfuric acid–dimethylamine nucleation enhanced by nitric acid in polluted regions

2021 ◽  
Vol 118 (35) ◽  
pp. e2108384118
Author(s):  
Ling Liu ◽  
Fangqun Yu ◽  
Lin Du ◽  
Zhi Yang ◽  
Joseph S. Francisco ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Sulfuric Acid ◽  
Nitric Acid ◽  
Atmospheric Boundary Layer ◽  
High Temperatures ◽  
Cluster Formation ◽  
Particle Formation ◽  
Nucleation Mechanism ◽  
Free Troposphere ◽  
Particulate Pollution

Recent research [Wang et al., Nature 581, 184–189 (2020)] indicates nitric acid (NA) can participate in sulfuric acid (SA)–ammonia (NH3) nucleation in the clean and cold upper free troposphere, whereas NA exhibits no obvious effects at the boundary layer with relatively high temperatures. Herein, considering that an SA–dimethylamine (DMA) nucleation mechanism was detected in megacities [Yao et al., Science 361, 278–281 (2018)], the roles of NA in SA-DMA nucleation are investigated. Different from SA-NH3 nucleation, we found that NA can enhance SA-DMA–based particle formation rates in the polluted atmospheric boundary layer, such as Beijing in winter, with the enhancement up to 80-fold. Moreover, we found that NA can promote the number concentrations of nucleation clusters (up to 27-fold) and contribute 76% of cluster formation pathways at 280 K. The enhancements on particle formation by NA are critical for particulate pollution in the polluted boundary layer with relatively high NA and DMA concentrations.

scholarly journals High concentration of ultrafine particles in the Amazon free troposphere produced by organic new particle formation

2020 ◽  
Vol 117 (41) ◽  
pp. 25344-25351 ◽  
Author(s):  
Bin Zhao ◽  
Manish Shrivastava ◽  
Neil M. Donahue ◽  
Hamish Gordon ◽  
Meredith Schervish ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Ultrafine Particles ◽  
Cloud Condensation Nuclei ◽  
Formation Rate ◽  
Particle Formation ◽  
Free Troposphere ◽  
New Particle Formation ◽  
High Altitudes ◽  
High Concentration ◽  
Anthropogenic Aerosol

The large concentrations of ultrafine particles consistently observed at high altitudes over the tropics represent one of the world’s largest aerosol reservoirs, which may be providing a globally important source of cloud condensation nuclei. However, the sources and chemical processes contributing to the formation of these particles remain unclear. Here we investigate new particle formation (NPF) mechanisms in the Amazon free troposphere by integrating insights from laboratory measurements, chemical transport modeling, and field measurements. To account for organic NPF, we develop a comprehensive model representation of the temperature-dependent formation chemistry and thermodynamics of extremely low volatility organic compounds as well as their roles in NPF processes. We find that pure-organic NPF driven by natural biogenic emissions dominates in the uppermost troposphere above 13 km and accounts for 65 to 83% of the column total NPF rate under relatively pristine conditions, while ternary NPF involving organics and sulfuric acid dominates between 8 and 13 km. The large organic NPF rates at high altitudes mainly result from decreased volatility of organics and increased NPF efficiency at low temperatures, somewhat counterbalanced by a reduced chemical formation rate of extremely low volatility organic compounds. These findings imply a key role of naturally occurring organic NPF in high-altitude preindustrial environments and will help better quantify anthropogenic aerosol forcing from preindustrial times to the present day.

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