scholarly journals A better understanding of hydroxyl radical photochemical sources in cloud waters collected at the puy de Dôme station: experimental vs. modeled formation rates

2015 ◽  
Vol 15 (10) ◽  
pp. 13923-13955 ◽  
Author(s):  
A. Bianco ◽  
M. Passananti ◽  
H. Perroux ◽  
G. Voyard ◽  
C. Mouchel-Vallon ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Solar Spectrum ◽  
Oxidative Capacity ◽  
Xenon Lamp ◽  
Air Masses ◽  
Naturally Occurring ◽  
Field Campaigns ◽  
Experimental Values ◽  
Nitrite Nitrate ◽  
Yield Formation

Abstract. The oxidative capacity of the cloud aqueous phase is investigated during three field campaigns from 2013 to 2014 at the top of the puy de Dôme station (PUY) in France. Forty-one cloud samples are collected, and the corresponding air masses are classified as highly marine, marine and continental. Hydroxyl radical (HO·) formation rates (RHO·f) are determined using a photochemical setup (Xenon lamp that can reproduce the solar spectrum) and a chemical probe coupled with spectroscopic analysis that can trap all of the generated radicals for each sample. Using this method, the obtained values correspond to the total formation of HO· without its chemical sinks. These formation rates are correlated with the concentrations of the naturally occurring sources of HO·, including hydrogen peroxide, nitrite, nitrate and iron. The total hydroxyl radical formation rates are measured as ranging from approximately 2 × 10−11 to 4 × 10−10 M s−1, and the hydroxyl radical quantum yield formation (ΦHO·) is estimated between 10−4 and 10−2. Experimental values are compared with modeled formation rates calculated by the model of multiphase cloud chemistry (M2C2), considering only the chemical sources of the hydroxyl radicals. The comparison between the experimental and the modeled results suggests that the photoreactivity of the iron species as a source of HO· is overestimated by the model, and H2O2 photolysis represents the most important source of this radical (between 70 and 99%) for the cloud water sampled at the PUY station (primarily marine and continental).

scholarly journals A better understanding of hydroxyl radical photochemical sources in cloud waters collected at the puy de Dôme station – experimental versus modelled formation rates

2015 ◽  
Vol 15 (16) ◽  
pp. 9191-9202 ◽  
Author(s):  
A. Bianco ◽  
M. Passananti ◽  
H. Perroux ◽  
G. Voyard ◽  
C. Mouchel-Vallon ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Solar Spectrum ◽  
Oxidative Capacity ◽  
Xenon Lamp ◽  
Air Masses ◽  
Naturally Occurring ◽  
Field Campaigns ◽  
Experimental Values ◽  
Nitrite Nitrate ◽  
Yield Formation

Abstract. The oxidative capacity of the cloud aqueous phase is investigated during three field campaigns from 2013 to 2014 at the top of the puy de Dôme station (PUY) in France. A total of 41 cloud samples are collected and the corresponding air masses are classified as highly marine, marine and continental. Hydroxyl radical (HO•) formation rates (RHO•f) are determined using a photochemical setup (xenon lamp that can reproduce the solar spectrum) and a chemical probe coupled with spectroscopic analysis that can trap all of the generated radicals for each sample. Using this method, the obtained values correspond to the total formation of HO• without its chemical sinks. These formation rates are correlated with the concentrations of the naturally occurring sources of HO•, including hydrogen peroxide, nitrite, nitrate and iron. The total hydroxyl radical formation rates are measured as ranging from approximately 2 × 10−11 to 4 × 10−10 M s−1, and the hydroxyl radical quantum yield formation (ΦHO•) is estimated between 10−4 and 10−2. Experimental values are compared with modelled formation rates calculated by the model of multiphase cloud chemistry (M2C2), considering only the chemical sources of the hydroxyl radicals. The comparison between the experimental and the modelled results suggests that the photoreactivity of the iron species as a source of HO• is overestimated by the model, and H2O2 photolysis represents the most important source of this radical (between 70 and 99 %) for the cloud water sampled at the PUY station (primarily marine and continental).

scholarly journals Measurement report: Ice nucleating abilities of biomass burning, African dust, and sea spray aerosol particles over the Yucatan Peninsula

2020 ◽  
Author(s):  
Fernanda Córdoba ◽  
Carolina Ramirez-Romero ◽  
Diego Cabrera ◽  
Graciela B. Raga ◽  
Javier Miranda ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Aerosol Particles ◽  
Air Masses ◽  
African Dust ◽  
Site Density ◽  
Sea Spray Aerosol ◽  
Surface Active ◽  
Field Campaigns ◽  
Aerosol Types ◽  
Aerosol Type

Abstract. Most precipitation from deep clouds over the continents and in the intertropical convergence zone is strongly influenced by the presence of ice crystals, whose formation requires the presence of ice nucleating particles (INP). Although there are a large number of INP sources, the ice nucleating abilities of aerosol particles emitted from oceans, deserts, and wildfires are poorly described at tropical latitudes. To fill this gap in knowledge, the UNAM-MicroOrifice Uniform Deposit Impactor-Droplet Freezing Technique (UNAM-MOUDI-DFT) was built. Aerosol samples were collected in Sisal and Merida, Yucatan (Mexico) under the influence of cold fronts, biomass burning (BB), and African dust (AD), during five short-term field campaigns between January 2017 and July 2018. The three different aerosol types were distinguished by characterizing their physicochemical properties. Marine aerosol (MA), BB, and AD air masses were found to contain INP; the highest concentrations were found for AD (from 0.071 L−1 to 36.07 L−1), followed by MA (from 0.068 L−1 to 18.90 L−1), and BB (from 0.063 L−1 to 10.21 L−1). However, MA had the highest surface active site density (ns) between −15 °C and −30 °C. Additionally, supermicron particles contributed more than 72 % of the total INP concentration independent of aerosol type; MA had the largest contribution from supermicron particles.

scholarly journals Evidence for heterogeneous chlorine activation in the tropical UTLS

2010 ◽  
Vol 10 (7) ◽  
pp. 18063-18099
Author(s):  
M. von Hobe ◽  
J.-U. Grooß ◽  
G. Günther ◽  
P. Konopka ◽  
I. Gensch ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Air Masses ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Gas Phase Chemistry ◽  
In Situ Observations ◽  
Field Campaigns ◽  
Phase Chemistry ◽  
The Tropics

Abstract. Airborne in-situ observations of ClO in the tropics were made during the TROCCINOX (Aracatuba, Brasil, February 2005) and SCOUT-O3 (Darwin, Australia, November/December 2005) field campaigns. While during most flights significant amounts of ClO (≈10–20 parts per trillion, ppt) were present only in aged stratospheric air, instances of enhanced ClO mixing ratios of up to 40 ppt – significantly exceeding those expected from gas phase chemistry – were observed in air masses of a more tropospheric character. Most of these observations concur with low temperatures or with the presence of cirrus clouds (often both), suggesting that cirrus ice particles and/or liquid aerosol at low temperatures may promote significant heterogeneous chlorine activation in the tropical upper troposphere lower stratosphere (UTLS). In two case studies, particularly high levels of ClO observed were reproduced by chemistry simulations only under the assumption that significant denoxification had occurred in the observed air. At least for one of these flights, a significant denoxification is in contrast to the observed NO levels suggesting that the coupling of chlorine and nitrogen compounds in the tropical UTLS may not be completely understood.

scholarly journals Soluble Iodine Speciation in Marine Aerosols Across the Indian and Pacific Ocean Basins

2021 ◽  
Vol 8 ◽  
Author(s):  
Elise S. Droste ◽  
Alex R. Baker ◽  
Chan Yodle ◽  
Andrew Smith ◽  
Laurens Ganzeveld
Keyword(s):  
Oxidative Capacity ◽  
Anthropogenic Emissions ◽  
Marine Aerosols ◽  
Climate Feedbacks ◽  
Ph Measurements ◽  
Air Masses ◽  
Aerosol Acidity ◽  
Coarse Mode ◽  
Halogen Chemistry ◽  
Iodine Speciation

Iodine affects the radiative budget and the oxidative capacity of the atmosphere and is consequently involved in important climate feedbacks. A fraction of the iodine emitted by oceans ends up in aerosols, where complex halogen chemistry regulates the recycling of iodine to the gas-phase where it effectively destroys ozone. The iodine speciation and major ion composition of aerosol samples collected during four cruises in the East and West Pacific and Indian Oceans was studied to understand the influences on iodine’s gas-aerosol phase recycling. A significant inverse relationship exists between iodide (I–) and iodate (IO3–) proportions in both fine and coarse mode aerosols, with a relatively constant soluble organic iodine (SOI) fraction of 19.8% (median) for fine and coarse mode samples of all cruises combined. Consistent with previous work on the Atlantic Ocean, this work further provides observational support that IO3– reduction is attributed to aerosol acidity, which is associated to smaller aerosol particles and air masses that have been influenced by anthropogenic emissions. Significant correlations are found between SOI and I–, which supports hypotheses that SOI may be a source for I–. This data contributes to a growing observational dataset on aerosol iodine speciation and provides evidence for relatively constant proportions of iodine species in unpolluted marine aerosols. Future development in our understanding of iodine speciation depends on aerosol pH measurements and unravelling the complex composition of SOI in aerosols.

scholarly journals Solid particles in the tropical lowest stratosphere

2007 ◽  
Vol 7 (3) ◽  
pp. 685-695 ◽  
Author(s):  
J. K. Nielsen ◽  
N. Larsen ◽  
F. Cairo ◽  
G. Di Donfrancesco ◽  
J. M. Rosen ◽  
...  
Keyword(s):  
Point Of View ◽  
Solid Particles ◽  
Theoretical Point ◽  
Mixing Ratio ◽  
Observation Site ◽  
Air Masses ◽  
Occasional Occurrence ◽  
Field Campaigns ◽  
Water Vapor Mixing Ratio

Abstract. We report in situ and remote observations proving occasional occurrence of solid particles in the tropical lowest stratosphere, 200 km from deep convective events. The particles were found during field campaigns in Southeast Brazil (49.03 W 22.36 S). They occur in the altitude range from 17.5 to 20.8 km, at temperatures up to at least 10 K above the expected frost point temperature. While stability of ice particles at these altitudes is unexpected from a theoretical point of view, it is argued that these observations are indications of tropospheric air masses penetrating into the stratosphere during convective overshoots. It is argued that the intrusion of tropospheric air must have carried a large amount of water with it, which effectively hydrated the lowest stratosphere, and consequently suppressed sublimation. This conclusion is further supported by a separate water vapor mixing ratio profile obtained at the same observation site.

Long-Term Evolution of SCD-1 Satellite Temperatures Based on Comparative Analysis of Telemetric Data Measured in Orbit

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Andreia F. S. Genaro ◽  
Ezio C. Garcia ◽  
Issamu Muraoka ◽  
Kevin E. de Conde
Keyword(s):  
Mathematical Model ◽  
Thermal Behavior ◽  
Heat Dissipation ◽  
Solar Spectrum ◽  
Temperature Sensitive ◽  
Term Evolution ◽  
Optimization Routine ◽  
Experimental Values ◽  
The Mathematical Model

This paper presents results of the research investigation regarding the causes for temperature variation of the SCD-1 (data-collection satellite) by analyzing its thermal behavior evolution throughout 13 years in orbit. SCD-1, the first satellite designed and built in Brazil, was launched in 1993 and is still in operation. A mathematical model has been developed to simulate thermal behavior of SCD-1 in orbit, which was used as a working tool during project design phase, and is presented here. Temperatures of SCD-1 in orbit have been monitored and recorded in the Control and Tracking Center (São José dos Campos, SP, Brazil) since its launch. An analysis carried out at the mission’s beginning showed that all the temperatures were within the ranges predicted in model. Over the years, the battery, which is the most temperature-sensitive equipment in the satellite, had an increase in temperature approaching upper limit. A method has been developed to investigate the causes of this upswing in which an optimization routine linked to the mathematical model corrects a selected set of parameters in order to adjust the theoretical temperature values to the experimental values. By means of this methodology, data from SCD-1 were analyzed from 1995 to 2005 period and it was concluded that the rise in temperature was caused by an increase in internal battery heat dissipation and absorptivity in solar spectrum of some of the external satellite shielding, both consequences of a long-term degradation.

Simulating the Solar Spectrum with a Filtered High-Pressure Xenon Lamp

1963 ◽  
Vol 2 (1) ◽  
pp. 105 ◽  
Author(s):  
E. A. Boettner ◽  
L. J. Miedler
Keyword(s):  
High Pressure ◽  
Solar Spectrum ◽  
Xenon Lamp
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