scholarly journals Aerosol characteristics and particle production in the upper troposphere over the Amazon Basin

2018 ◽  
Vol 18 (2) ◽  
pp. 921-961 ◽  
Author(s):  
Meinrat O. Andreae ◽  
Armin Afchine ◽  
Rachel Albrecht ◽  
Bruna Amorim Holanda ◽  
Paulo Artaxo ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Amazon Basin ◽  
Deep Convection ◽  
Aerosol Particles ◽  
Condensation Nuclei ◽  
Upper Troposphere ◽  
Convective Clouds ◽  
Tropospheric Aerosol ◽  
Volatile Organic ◽  
Deep Convective Clouds

Abstract. Airborne observations over the Amazon Basin showed high aerosol particle concentrations in the upper troposphere (UT) between 8 and 15 km altitude, with number densities (normalized to standard temperature and pressure) often exceeding those in the planetary boundary layer (PBL) by 1 or 2 orders of magnitude. The measurements were made during the German–Brazilian cooperative aircraft campaign ACRIDICON–CHUVA, where ACRIDICON stands for Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems and CHUVA is the acronym for Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modeling and to the GPM (global precipitation measurement), on the German High Altitude and Long Range Research Aircraft (HALO). The campaign took place in September–October 2014, with the objective of studying tropical deep convective clouds over the Amazon rainforest and their interactions with atmospheric trace gases, aerosol particles, and atmospheric radiation. Aerosol enhancements were observed consistently on all flights during which the UT was probed, using several aerosol metrics, including condensation nuclei (CN) and cloud condensation nuclei (CCN) number concentrations and chemical species mass concentrations. The UT particles differed sharply in their chemical composition and size distribution from those in the PBL, ruling out convective transport of combustion-derived particles from the boundary layer (BL) as a source. The air in the immediate outflow of deep convective clouds was depleted of aerosol particles, whereas strongly enhanced number concentrations of small particles (< 90 nm diameter) were found in UT regions that had experienced outflow from deep convection in the preceding 5–72 h. We also found elevated concentrations of larger (> 90 nm) particles in the UT, which consisted mostly of organic matter and nitrate and were very effective CCN. Our findings suggest a conceptual model, where production of new aerosol particles takes place in the continental UT from biogenic volatile organic material brought up by deep convection and converted to condensable species in the UT. Subsequently, downward mixing and transport of upper tropospheric aerosol can be a source of particles to the PBL, where they increase in size by the condensation of biogenic volatile organic compound (BVOC) oxidation products. This may be an important source of aerosol particles for the Amazonian PBL, where aerosol nucleation and new particle formation have not been observed. We propose that this may have been the dominant process supplying secondary aerosol particles in the pristine atmosphere, making clouds the dominant control of both removal and production of atmospheric particles.

scholarly journals Aerosol characteristics and particle production in the upper troposphere over the Amazon Basin

2017 ◽  
Author(s):  
Meinrat O. Andreae ◽  
Armin Afchine ◽  
Rachel Albrecht ◽  
Bruna Amorim Holanda ◽  
Paulo Artaxo ◽  
...  
Keyword(s):  
Amazon Basin ◽  
Particle Production ◽  
Aerosol Particles ◽  
Convective Transport ◽  
Oxidation Products ◽  
Condensation Nuclei ◽  
Upper Troposphere ◽  
Convective Clouds ◽  
Tropospheric Aerosol ◽  
Deep Convective Clouds

Abstract. Airborne observations over the Amazon Basin showed high aerosol particle concentrations in the upper troposphere (UT) between 8 and 15 km altitude, with number densities (normalized to standard temperature and pressure) often exceeding those in the planetary boundary layer (PBL) by one or two orders of magnitude. The measurements were made during the German-Brazilian cooperative aircraft campaign ACRIDICON-CHUVA on the German High Altitude and Long Range Research Aircraft (HALO). The campaign took place in September/October 2014, with the objective of studying tropical deep convective clouds over the Amazon rainforest and their interactions with atmospheric trace gases, aerosol particles, and atmospheric radiation. Aerosol enhancements were observed consistently on all flights during which the UT was probed, using several aerosol metrics, including condensation nuclei (CN) and cloud condensation nuclei (CCN) number concentrations and chemical species mass concentrations. The UT particles differed in their chemical composition and size distribution from those in the PBL, ruling out convective transport of combustion-derived particles from the BL as a source. The air in the immediate outflow of deep convective clouds was depleted in aerosol particles, whereas strongly enhanced number concentrations of small particles ( 90 nm) particles in the UT, which consisted mostly of organic matter and nitrate and were very effective CCN. Our findings suggest a conceptual model, where production of new aerosol particles takes place in the UT from volatile material brought up by deep convection, which is converted to condensable species in the UT. Subsequently, downward mixing and transport of upper tropospheric aerosol can be a source of particles to the PBL, where they increase in size by the condensation of biogenic volatile organic carbon (BVOC) oxidation products. This may be an important source of aerosol particles in the Amazonian PBL, where aerosol nucleation and new particle formation has not been observed. We propose that this may have been the dominant process supplying secondary aerosol particles in the pristine atmosphere, making clouds the dominant control of both removal and production of atmospheric particles.

scholarly journals Ozone mixing ratios inside tropical deep convective clouds from OMI satellite measurements

2009 ◽  
Vol 9 (2) ◽  
pp. 573-583 ◽  
Author(s):  
J. R. Ziemke ◽  
J. Joiner ◽  
S. Chandra ◽  
P. K. Bhartia ◽  
A. Vasilkov ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Radar Data ◽  
Mixing Ratio ◽  
Ozone Monitoring Instrument ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Convective Clouds ◽  
Deep Convective Clouds ◽  
Oceanic Boundary Layer ◽  
Column Ozone

Abstract. We have developed a new technique for estimating ozone mixing ratio inside deep convective clouds. The technique uses the concept of an optical centroid cloud pressure that is indicative of the photon path inside clouds. Radiative transfer calculations based on realistic cloud vertical structure as provided by CloudSat radar data show that because deep convective clouds are optically thin near the top, photons can penetrate significantly inside the cloud. This photon penetration coupled with in-cloud scattering produces optical centroid pressures that are hundreds of hPa inside the cloud. We combine measured column ozone and the optical centroid cloud pressure derived using the effects of rotational-Raman scattering to estimate O3 mixing ratio in the upper regions of deep convective clouds. The data are obtained from the Ozone Monitoring Instrument (OMI) onboard NASA's Aura satellite. Our results show that low O3 concentrations in these clouds are a common occurrence throughout much of the tropical Pacific. Ozonesonde measurements in the tropics following convective activity also show very low concentrations of O3 in the upper troposphere. These low amounts are attributed to vertical injection of ozone poor oceanic boundary layer air during convection into the upper troposphere followed by convective outflow. Over South America and Africa, O3 mixing ratios inside deep convective clouds often exceed 50 ppbv which are comparable to mean background (cloud-free) amounts and are consistent with higher concentrations of injected boundary layer/lower tropospheric O3 relative to the remote Pacific. The Atlantic region in general also consists of higher amounts of O3 precursors due to both biomass burning and lightning. Assuming that O3 is well mixed (i.e., constant mixing ratio with height) up to the tropopause, we can estimate the stratospheric column O3 over clouds. Stratospheric column ozone derived in this manner agrees well with that retrieved independently with the Aura Microwave Limb Sounder (MLS) instrument and thus provides a consistency check of our method.

scholarly journals Ozone mixing ratios inside tropical deep convective clouds from OMI satellite measurements

2008 ◽  
Vol 8 (4) ◽  
pp. 16381-16407
Author(s):  
J. R. Ziemke ◽  
J. Joiner ◽  
S. Chandra ◽  
P. K. Bhartia ◽  
A. Vasilkov ◽  
...  
Keyword(s):  
Radar Data ◽  
Mixing Ratio ◽  
Ozone Monitoring Instrument ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Convective Clouds ◽  
Deep Convective Clouds ◽  
A New Technique ◽  
Oceanic Boundary Layer ◽  
Column Ozone

Abstract. We have developed a new technique for estimating ozone mixing ratio inside deep convective clouds. The technique uses the concept of an optical centroid cloud pressure that is indicative of the photon path inside clouds. Radiative transfer calculations based on realistic cloud vertical structure as provided by CloudSat radar data show that because deep convective clouds are optically thin near the top, photons can penetrate significantly inside the cloud. This photon penetration coupled with in-cloud scattering produces optical centroid pressures that are hundreds of hPa inside the cloud. We use the measured column ozone and the optical centroid cloud pressure derived using the effects of rotational-Raman scattering to estimate O3 mixing ratio in the upper regions of deep convective clouds. The data are obtained from the Ozone Monitoring Instrument (OMI) aboard NASA's Aura satellite. Our results show that low O3 concentrations in these clouds are a common occurrence throughout much of the tropical Pacific. Ozonesonde measurements in the tropics following convective activity also show very low concentrations of O3 in the upper troposphere. These low amounts are attributed to vertical injection of ozone poor oceanic boundary layer air during convection into the upper troposphere followed by convective outflow. Over South America and Africa, O3 mixing ratio inside deep convective clouds often exceeds 50 ppbv which is comparable to mean background (cloud-free) concentrations. These areas contain higher amounts of ozone precursors due to biomass burning and lightning. Assuming that O3 is well mixed (i.e. constant mixing ratio with height) up to the tropopause, we can estimate the stratospheric column O3 over clouds. Stratospheric column ozone derived in this manner agrees well with that retrieved independently with the Aura Microwave Limb Sounder (MLS) instrument and thus provides a consistency check of our method.

scholarly journals Measurements of volatile organic compounds over West Africa

2010 ◽  
Vol 10 (2) ◽  
pp. 3861-3892 ◽  
Author(s):  
J. G. Murphy ◽  
D. E. Oram ◽  
C. E. Reeves
Keyword(s):  
Boundary Layer ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Marine Boundary Layer ◽  
Deep Convection ◽  
Proton Transfer Reaction ◽  
Oxidation Products ◽  
High Time Resolution ◽  
Airborne Measurements ◽  
Volatile Organic

Abstract. In this paper we describe measurements of volatile organic compounds (VOCs) made using a Proton Transfer Reaction Mass Spectrometer (PTR-MS) aboard the UK Facility for Atmospheric Airborne Measurements during the African Monsoon Multidisciplinary Analyses (AMMA) campaign. Observations were made during approximately 85 h of flying time between 17 July and 17 August 2006, above an area between 4° N and 18° N and 3° W and 4° E, encompassing ocean, mosaic forest, and the Sahel desert. High time resolution observations of counts at mass to charge (m/z) ratios of 42, 59, 69, 71, and 79 were used to calculate mixing ratios of acetonitrile, acetone, isoprene, the sum of methyl vinyl ketone and methacrolein, and benzene, respectively using laboratory-derived humidity-dependent calibration factors. Strong spatial associations between vegetation and isoprene and its oxidation products were observed in the boundary layer, consistent with biogenic emissions followed by rapid atmospheric oxidation. Acetonitrile, benzene, and acetone were all enhanced in airmasses which had been heavily influenced by biomass burning. Benzene and acetone were also elevated in airmasses with urban influence from cities such as Lagos, Cotonou, and Niamey. The observations provide evidence that both deep convection and mixing associated with fair-weather cumulus were responsible for vertical redistribution of VOCs emitted from the surface. Profiles over the ocean showed a depletion of acetone in the marine boundary layer, but no significant decrease for acetonitrile.

scholarly journals Origin of aerosol particles in the mid-latitude and subtropical upper troposphere and lowermost stratosphere from cluster analysis of CARIBIC data

2009 ◽  
Vol 9 (21) ◽  
pp. 8413-8430 ◽  
Author(s):  
M. Köppe ◽  
M. Hermann ◽  
C. A. M. Brenninkmeijer ◽  
J. Heintzenberg ◽  
H. Schlager ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Cluster Analysis ◽  
Particle Number ◽  
Aerosol Particles ◽  
Free Troposphere ◽  
Data Set ◽  
Upper Troposphere ◽  
Eurasian Continent ◽  
Aitken Mode ◽  
Seasonal Data

Abstract. The origin of aerosol particles in the upper troposphere and lowermost stratosphere over the Eurasian continent was investigated by applying cluster analysis methods to in situ measured data. Number concentrations of submicrometer aerosol particles and trace gas mixing ratios derived by the CARIBIC (Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container) measurement system on flights between Germany and South-East Asia were used for this analysis. Four cluster analysis methods were applied to a test data set and their capability of separating the data points into scientifically reasonable clusters was assessed. The best method was applied to seasonal data subsets for summer and winter resulting in five cluster or air mass types: stratosphere, tropopause, free troposphere, high clouds, and boundary layer influenced. Other source clusters, like aircraft emissions could not be resolved in the present data set with the used methods. While the cluster separation works satisfactory well for the summer data, in winter interpretation is more difficult, which is attributed to either different vertical transport pathways or different chemical lifetimes in both seasons. The geographical distribution of the clusters together with histograms for nucleation and Aitken mode particles within each cluster are presented. Aitken mode particle number concentrations show a clear vertical gradient with the lowest values in the lowermost stratosphere (750–2820 particles/cm3 STP, minimum of the two 25% – and maximum of the two 75%-percentiles of both seasons) and the highest values for the boundary-layer-influenced air (4290–22 760 particles/cm3 STP). Nucleation mode particles are also highest in the boundary-layer-influenced air (1260–29 500 particles/cm3 STP), but are lowest in the free troposphere (0–450 particles/cm3 STP). The given submicrometer particle number concentrations represent the first large-scale seasonal data sets for the upper troposphere and lowermost stratosphere over the Eurasian continent.

scholarly journals Measurements of CH<sub>3</sub>O<sub>2</sub>NO<sub>2</sub> in the upper troposphere

2014 ◽  
Vol 7 (9) ◽  
pp. 9453-9479
Author(s):  
B. A. Nault ◽  
C. Garland ◽  
S. E. Pusede ◽  
P. J. Wooldridge ◽  
K. Ullmann ◽  
...  
Keyword(s):  
Detection Limit ◽  
Low Temperatures ◽  
Theoretical Calculations ◽  
Thermal Dissociation ◽  
Atmospheric Composition ◽  
Upper Troposphere ◽  
Convective Clouds ◽  
Peroxy Nitrates ◽  
Deep Convective Clouds ◽  
Pernitric Acid

Abstract. The non-acyl peroxy nitrates, HO2NO2 and CH3O2NO2, are predicted to be important for photochemistry at low temperatures characteristic of the upper troposphere. We report the first measurements of methyl peroxy nitrate (CH3O2NO2). During the Deep Convective Clouds and Chemistry (DC-3) and the Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS) experiments, different inlet configurations for the UC Berkeley Thermal Dissociation-Laser Induced Instrument were tested to optimize measurements of CH3O2NO2 from the NASA DC-8. In addition, the inlet modifications were optimized for measurements of NO2 without CH3O2NO2 interferences. The CH3O2NO2 measurements we report have a detection limit (S/N = 2) of 15 pptv (parts per trillion by volume) at 1 min averaging on a background of 200 pptv NO2 and an accuracy of ±40%. Both observations and theoretical calculations were used to constrain the interference of pernitric acid (HO2NO2), which partially decomposes (~ 11%) along with CH3O2NO2 in our heated CH3O2NO2 channel. Evaluation of the accuracy of the CH3O2NO2 measurements is presented.

scholarly journals What do we learn on bromoform transport and chemistry in deep convection from fine scale modelling?

2011 ◽  
Vol 11 (11) ◽  
pp. 29561-29600 ◽  
Author(s):  
V. Marécal ◽  
M. Pirre ◽  
G. Krysztofiak ◽  
B. Josse
Keyword(s):  
Boundary Layer ◽  
Transport Model ◽  
Deep Convection ◽  
Chemical Species ◽  
Convective Cloud ◽  
Initial Boundary ◽  
Mixing Ratio ◽  
Atmospheric Conditions ◽  
Upper Troposphere ◽  
Soluble Species

Abstract. Bromoform is one of the main sources of halogenated Very Short-Lived Species (VSLS) that possibly contributes when degradated to the inorganic halogen loading in the stratosphere. Because of its short lifetime of about four weeks, its pathway to the stratosphere is mainly the transport by convection up to the tropical tropopause layer (TTL) and then by radiative ascent in the low stratosphere. Some of its degradation product gases (PGs) that are soluble can be scavenged and not reach the TTL. In this paper we present a detailed modelling study of the transport and the degradation of bromoform and its PGs in convection. We use a 3-D-cloud resolving model coupled with a chemistry model including gaseous and aqueous chemistry. We run idealised simulations up to 10 days, initialised using a tropical radiosounding for atmospheric conditions and using outputs from a global chemistry-transport model for chemical species. Bromoform is initialised only in the low levels. The first simulation is run with stable atmospheric conditions. It shows that the sum of the bromoform and its PGs significantly decreases with time because of dry deposition and that PGs are mainly in the form of HBr after 2 days of simulation. The other simulation is similar to the first simulation but includes perturbations of temperature and of moisture leading to the development of a convective cloud reaching the TTL. Results of this simulation show an efficient vertical transport of the bromoform from the boundary layer in the upper troposphere and TTL (mixing ratio up to 45% of the initial boundary layer mixing ratio). The organic PGs, which are for the most abundant of them not very soluble, are also uplifted efficiently. For the inorganic PGs, which are more abundant than organic PGs, their mixing ratios in the upper troposphere and in the TTL depend on the partitioning between inorganic soluble and inorganic non soluble species in the convective cloud. Important soluble species such as HBr and HOBr are efficiently scavenged by rain. This removal is reduced by the production of Br2 (not soluble) in the gas phase from aqueous processes in the cloud droplets. This Br2 production process is therefore important for the PG budget in the upper troposphere and in the TTL. We also showed that this process is favoured by acidic conditions in the coud droplets, i.e. polluted conditions.

scholarly journals The impact of the 1783–1784 AD Laki eruption on global aerosol formation processes and cloud condensation nuclei

2010 ◽  
Vol 10 (2) ◽  
pp. 3189-3228
Author(s):  
A. Schmidt ◽  
K. S. Carslaw ◽  
G. W. Mann ◽  
B. M. Wilson ◽  
T. J. Breider ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Northern Hemisphere ◽  
General Circulation ◽  
Cloud Condensation Nuclei ◽  
General Circulation Models ◽  
Aerosol Formation ◽  
Condensation Nuclei ◽  
Upper Troposphere ◽  
Microphysical Processes ◽  
The Impact

Abstract. The 1783–1784 AD Laki flood lava eruption commenced on 8 June 1783 and released 122 Tg of sulphur dioxide gas over the course of 8 months into the upper troposphere and lower stratosphere above Iceland. Previous studies have examined the impact of the Laki eruption on sulphate aerosol and climate using general circulation models. Here, we study the impact on aerosol microphysical processes, including the nucleation of new particles and their growth to cloud condensation nuclei (CCN) using a comprehensive Global Model of Aerosol Processes (GLOMAP). Total particle concentrations in the free troposphere increase by a factor ~16 over large parts of the Northern Hemisphere in the 3 months following the onset of the eruption. Particle concentrations in the boundary layer increase by a factor 2 to 5 in regions as far away as North America, the Middle East and Asia due to long-range transport of nucleated particles. CCN concentrations (at 0.22% supersaturation) increase by a factor 65 in the upper troposphere with maximum changes in 3-month zonal mean concentrations of ~1400 cm−3 at high northern latitudes. 3-month zonal mean CCN concentrations in the boundary layer at the latitude of the eruption increase by up to a factor 26, and averaged over the Northern Hemisphere, the eruption caused a factor 4 increase in CCN concentrations at low-level cloud altitude. The simulations show that the Laki eruption would have completely dominated as a source of CCN in the pre-industrial atmosphere. The model also suggests an impact of the eruption in the Southern Hemisphere, where CCN concentrations are increased by up to a factor 1.4 at 20° S. Our model simulations suggest that the impact of an equivalent wintertime eruption on upper tropospheric CCN concentrations is only about one-third of that of a summertime eruption. The simulations show that the microphysical processes leading to the growth of particles to CCN sizes are fundamentally different after an eruption when compared to the unperturbed atmosphere, underlining the importance of using a fully coupled microphysics model when studying long-lasting, high-latitude eruptions.

Comments on “Do Ultrafine Cloud Condensation Nuclei Invigorate Deep Convection?”

2021 ◽  
Vol 78 (1) ◽  
pp. 329-339
Author(s):  
Jiwen Fan ◽  
Alexander Khain
Keyword(s):  
Cloud Condensation Nuclei ◽  
Deep Convection ◽  
Diffusional Growth ◽  
Loading Effect ◽  
Convective Clouds ◽  
Nonlinear Responses ◽  
High Acceleration ◽  
Deep Convective Clouds ◽  
Physics Modeling ◽  
Aerosol Effects

AbstractHere we elaborate on the deficiencies associated with the theoretical arguments and model simulations in a paper by Grabowski and Morrison (2020, hereafter GM20) that argued convective invigoration by aerosols does not exist. We show that the invigoration can be supported by both accurate theoretical analysis and explicit physics modeling with prognostic supersaturation and aerosols. Negligible invigoration by aerosols via drop freezing in GM20 was explained by a complete compensation between the heating effect from the freezing of extra liquid water and the extra loading effect during droplet ascending. But the reality is that droplet ascending then freezing occur at different locations and time scales, producing complex nonlinear responses that depend on the duration and location of the forcing. Also, this argument neglects the effect of off-loading of precipitating ice particles, increases in condensation during ascending, and riming and deposition accompanying droplet freezing. Regarding the warm-phase invigoration, the quasi-steady assumption for supersaturation as adopted in GM20 makes condensation independent of droplet number and size, therefore an incorrect interpretation of warm-phase invigoration. We illustrate that the quasi-steady assumption is invalid for updrafts of deep convective clouds in clean conditions because of the high acceleration of vertical velocity and the fast depletion of droplets by raindrop formation and accretion. Any assumption imposed on supersaturation, such as quasi-steady approximation and saturation adjustment, leads to errors in the evaluation of aerosol effects on diffusional growth and related buoyancy. Furthermore, we demonstrate that the piggybacking approach they used cannot prove or disprove the convective invigoration.

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