18 research outputs found
Aerosol characteristics and particle production in the upper troposphere over the Amazon Basin
Airborne observations over the Amazon Basin showed high aerosol particle concentrations in the upper troposphere (UT) between 8 and 15âŻkm 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 GermanâBrazilian cooperative aircraft campaign ACRIDICONâCHUVA, 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 SeptemberâOctober 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 (â90âŻnm) 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
Cold atoms in space: community workshop summary and proposed road-map
We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies
Cold atoms in space: community workshop summary and proposed road-map
We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies.publishedVersio
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Cold atoms in space: community workshop summary and proposed road-map
We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies
Gap-filling strategies for annual VOC flux data sets
Up to now the limited knowledge about the ex-change of volatile organic compounds (VOCs) between thebiosphere and the atmosphere is one of the factors whichhinders more accurate climate predictions. Complete long-term flux data sets of several VOCs to quantify the annualexchange and validate recent VOC models are basically notavailable. In combination with long-term VOC flux mea-surements the application of gap-filling routines is inevitablein order to replace missing data and make an importantstep towards a better understanding of the VOC ecosystemâatmosphere exchange on longer timescales.We performed VOC flux measurements above a mountainmeadow in Austria during two complete growing seasons(from snowmelt in spring to snow reestablishment in late au-tumn) and used this data set to test the performance of fourdifferent gap-filling routines, mean diurnal variation (MDV),mean gliding window (MGW), look-up tables (LUT) and lin-ear interpolation (LIP), in terms of their ability to replacemissing flux data in order to obtain reliable VOC sums. Ac-cording to our findings the MDV routine was outstandingwith regard to the minimization of the gap-filling error forboth years and all quantified VOCs. The other gap-fillingroutines, which performed gap-filling on 24 h average val-ues, introduced considerably larger uncertainties. The errorwhich was introduced by the application of the different fill-ing routines increased linearly with the number of data gaps.Although average VOC fluxes measured during the winterperiod (complete snow coverage) were close to zero, thesewere highly variable and the filling of the winter period re-sulted in considerably higher uncertainties compared to theapplication of gap-filling during the measurement period.The annual patterns of the overall cumulative fluxes forthe quantified VOCs showed a completely different behaviour in 2009, which was an exceptional year due tothe occurrence of a severe hailstorm, compared to 2011.Methanol was the compound which, at 381.5 mg C mâ2and449.9 mg C mâ2, contributed most to the cumulative VOCcarbon emissions in 2009 and 2011, respectively. In contrastto methanol emissions, however, considerable amounts ofmonoterpenes (â327.3 mg C mâ2)were deposited onto themountain meadow during 2009 caused by a hailstorm. Otherquantified VOCs had considerably lower influences on the annual patterns.ISSN:1810-6277ISSN:1810-628
Acetaldehyde exchange above a managed temperate mountain grassland
An overview of acetaldehyde exchange above a
managed temperate mountain grassland in Austria over four
growing seasons is presented. The meadow acted as a net
source of acetaldehyde in all 4 years, emitting between 7 and
28 mgCmâ2 over the whole growing period. The cutting of
the meadow resulted in huge acetaldehyde emission bursts
of up to 16.5 nmolmâ2 sâ1 on the day of harvesting or 1 day
later. During undisturbed conditions both periods with net
uptake and net emissions of acetaldehyde were observed. The
bidirectional nature of acetaldehyde fluxes was also reflected
by clear diurnal cycles during certain time periods, indicating
strong deposition processes before the first cut and emission
towards the end of the growing season.
The analysis of acetaldehyde compensation points revealed
a complex relationship between ambient acetaldehyde
mixing ratios and respective fluxes, significantly influenced
by multiple environmental parameters and variable throughout
the year. As a major finding of this study, we identified
both a positive and negative correlation between concentration
and flux on a daily scale, where soil temperature and soil
water content were the most significant factors in determining
the direction of the slope. In turn, this bidirectional relationship
on a daily scale resulted in compensation points between
0.40 and 0.54 ppbv, which could be well explained by
collected ancillary data. We conclude that in order to model
acetaldehyde fluxes at the site in Neustift on a daily scale
over longer time periods, it is crucial to know the type of
relationship, i.e., the direction of the slope, between mixing
ratios and fluxes on a given day.ISSN:1680-7375ISSN:1680-736
Acetaldehyde exchange above a managed temperate mountain grassland
ISSN:1680-7375ISSN:1680-736