| 1. |
- Bardakov, Roman, et al.
(författare)
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A Novel Framework to Study Trace Gas Transport in Deep Convective Clouds
- 2020
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Ingår i: Journal of Advances in Modeling Earth Systems. - 1942-2466. ; 12:5
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Tidskriftsartikel (refereegranskat)abstract
- Deep convective clouds reach the upper troposphere (8-15 km height). In addition to moisture and aerosol particles, they can bring aerosol precursor gases and other reactive trace gases from the planetary boundary layer to the cloud top. In this paper, we present a method to estimate trace gas transport based on the analysis of individual air parcel trajectories. Large eddy simulation of an idealized deep convective cloud was used to provide realistic environmental input to a parcel model. For a buoyant parcel, we found that the trace gas transport approximately follows one out of three scenarios, determined by a combination of the equilibrium vapor pressure (containing information about water-solubility and pure component saturation vapor pressure) and the enthalpy of vaporization. In one extreme, the trace gas will eventually be completely removed by precipitation. In the other extreme, there is almost no vapor condensation on hydrometeors and most of the gas is transported to the top of the cloud. The scenario in between these two extremes is also characterized by strong gas condensation, but a small fraction of the trace gas may still be transported aloft. This approach confirms previously suggested patterns of inert trace gas behavior in deep convective clouds, agrees with observational data, and allows estimating transport in analytically simple and computationally efficient way compared to explicit cloud-resolving model calculations.
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| 2. |
- Bardakov, Roman, 1992-, et al.
(författare)
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The Role of Convective Up- and Downdrafts in the Transport of Trace Gases in the Amazon
- 2022
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Ingår i: Journal of Geophysical Research - Atmospheres. - : American Geophysical Union (AGU). - 2169-897X .- 2169-8996. ; 127:18
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Tidskriftsartikel (refereegranskat)abstract
- Deep convective clouds can redistribute gaseous species and particulate matter among different layers of the troposphere with important implications for atmospheric chemistry and climate. The large number of atmospheric trace gases of different volatility makes it challenging to predict their partitioning between hydrometeors and gas phase inside highly dynamic deep convective clouds. In this study, we use an ensemble of 51,200 trajectories simulated with a cloud-resolving model to characterize up- and downdrafts within Amazonian deep convective clouds. We also estimate the transport of a set of hypothetical non-reactive gases of different volatility, within the up- and downdrafts. We find that convective air parcels originating from the boundary layer (i.e., originating at 0.5 km altitude), can transport up to 25% of an intermediate volatility gas species (e.g., methyl hydrogen peroxide) and up to 60% of high volatility gas species (e.g., n-butane) to the cloud outflow above 10 km through the mean convective updraft. At the same time, the same type of gases can be transported to the boundary layer from the middle troposphere (i.e., originating at 5 km) within the mean convective downdraft with an efficiency close to 100%. Low volatility gases (e.g., nitric acid) are not efficiently transported, neither by the updrafts nor downdrafts, if the gas is assumed to be fully retained in a droplet upon freezing. The derived properties of the mean up- and downdraft can be used in future studies for investigating convective transport of a larger set of reactive trace gases.
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| 3. |
- Bardakov, Roman, 1992-
(författare)
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Transport and chemical processing of trace gases in deep convective clouds
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Deep convective clouds can efficiently transport trace gases from the planetary boundary layer to the upper troposphere. Once there, some gases will contribute to new particle formation and growth, eventually producing aerosols that are large enough to influence cloud properties, the radiative budget of the Earth, and climate. The magnitude and exact pathways of the convective transport of many organic and inorganic compounds are, however, still unclear. This dissertation presents a framework to study vertical transport of gas mixtures by deep convective clouds. The method consists of a chemical box model that is driven by cloud air parcel trajectory data generated by large-eddy simulation. This combination allows us to examine detailed gas-cloud interactions as well as complex systems of gas-phase chemical reactions. A large ensemble of simulated cloud trajectories was used to identify and characterize convective up- and downdrafts in the Amazon region. The analysis showed that air parcels starting close to the surface (at 0.5 km) experienced a substantially larger probability of reaching the upper troposphere (above 10 km) than parcels starting at the top of the boundary layer. Furthermore, the framework was used to estimate the vertical transport of isoprene, isoprene oxidation products, ammonia, and several non-reactive trace gases. We found that a typical Amazonian deep convective cloud can transport around 30% of the boundary layer isoprene to the cloud outflow if the efficiency of the gas uptake on ice is high and there is no lightning within the cloud. If the efficiency of gas uptake on ice is low and lightning within the cloud is extensive, all isoprene will be oxidized. Several low-volatility isoprene oxidation products will then have relatively high concentrations in the outflow, which potentially could lead to new particle formation and growth. Another result was that up to 10% of the boundary layer ammonia can reach the cloud outflow, where it in some environments can nucleate synergistically with nitric and sulfuric acid. A key uncertainty in our estimates is the efficiency of gas uptake by ice particles.
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| 4. |
- Bardakov, Roman, et al.
(författare)
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Transport and chemistry of isoprene and its oxidation products in deep convective clouds
- 2021
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Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 73:1, s. 1-21
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Tidskriftsartikel (refereegranskat)abstract
- Deep convective clouds can transport trace gases from the planetary boundary layer into the upper troposphere where subsequent chemistry may impact aerosol particle formation and growth. In this modelling study, we investigate processes that affect isoprene and its oxidation products injected into the upper troposphere by an isolated deep convective cloud in the Amazon. We run a photochemical box model with coupled cloud microphysics along hundreds of individual air parcel trajectories sampled from a cloud-resolving model simulation of a convective event. The box model simulates gas-phase chemical reactions, gas scavenging by liquid and ice hydrometeors, and turbulent dilution inside a deep convective cloud. The results illustrate the potential importance of gas uptake to anvil ice in regulating the intensity of the isoprene oxidation and associated low volatility organic vapour concentrations in the outflow. Isoprene transport and fate also depends on the abundance of lightning-generated nitrogen oxide radicals (NOx = NO + NO2). If gas uptake on ice is efficient and lightning activity is low, around 30% of the boundary layer isoprene will survive to the cloud outflow after approximately one hour of transport, while all the low volatile oxidation products will be scavenged by the cloud hydrometeors. If lightning NOx is abundant and gas uptake by ice is inefficient, then all isoprene will be oxidised during transport or in the immediate outflow region, while several low volatility isoprene oxidation products will have elevated concentrations in the cloud outflow. Reducing uncertainties associated with the uptake of vapours on ice hydrometeors, especially HO2 and oxygenated organics, is essential to improve predictions of isoprene and its oxidation products in deep convective outflows and their potential contribution to new particle formation and growth.
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| 5. |
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| 6. |
- Wang, Mingyi, et al.
(författare)
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Synergistic HNO3–H2SO4–NH3 upper tropospheric particle formation
- 2022
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 605:7910, s. 483-489
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Tidskriftsartikel (refereegranskat)abstract
- New particle formation in the upper free troposphere is a major global source of cloud condensation nuclei (CCN). However, the precursor vapours that drive the process are not well understood. With experiments performed under upper tropospheric conditions in the CERN CLOUD chamber, we show that nitric acid, sulfuric acid and ammonia form particles synergistically, at rates that are orders of magnitude faster than those from any two of the three components. The importance of this mechanism depends on the availability of ammonia, which was previously thought to be efficiently scavenged by cloud droplets during convection. However, surprisingly high concentrations of ammonia and ammonium nitrate have recently been observed in the upper troposphere over the Asian monsoon region. Once particles have formed, co-condensation of ammonia and abundant nitric acid alone is sufficient to drive rapid growth to CCN sizes with only trace sulfate. Moreover, our measurements show that these CCN are also highly efficient ice nucleating particles—comparable to desert dust. Our model simulations confirm that ammonia is efficiently convected aloft during the Asian monsoon, driving rapid, multi-acid HNO3–H2SO4–NH3 nucleation in the upper troposphere and producing ice nucleating particles that spread across the mid-latitude Northern Hemisphere.
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| 7. |
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