Turbulent transport and production/destruction of ozone in a boundary layer over complex terrain

The first Intensive Observation Period (IOP) of the Swiss air pollution experiment POLLUMET took place in 1990 in the Aare River Valley between Bern and Zurich. During the IOP, fast response measurements of meteorological variables and ozone concentration were made within the boundary layer aboard a motorglider. In addition, mean values of meteorological variables and the concentrations of ozone and other trace species were measured using other aircraft, pilot balloons, tethersondes, and ground stations. Turbulent flux profiles of latent and sensible heat and ozone are calculated from the fast response data. Terms in the ozone mean concentration budget (time rate of change of mean concentration, horizontal advection, and flux divergence) are calculated for stationary time periods both before and after the passage of a cold front. The source/sink term is calculated as a residual in the budget, and its sign and magnitude are related to the measured concentrations of reactive trace species within the boundary layer. Relationships between concentration ratios of trace species and ozone concentration are determined in order to understand the influence of complex terrain on the processes that produce and destroy ozone

AEROSOL MEASUREMENTS IN THE RHINE VALLEY DURING FOEHN – ANOTHER FORM PERSPECTIVE

While the main focus of the MAP subproject FORM (Foehn in the Rhine Valley during MAP) was on atmospheric dynamics, numerous measurements of chemical constituents of the atmosphere have been performed with various instruments on different platforms. Aerosol measurements have been obtained with routinely operated conventional surface stations, in-situ airborne particle counters and a backscatter lidar. For the MAP SOP it was found that near-surface aerosol concentrations are reduced by the foehn, i.e. they are lowest at the day after the foehn event, especially in the late fall when the valley inversion becomes stronger. A case study for 2 Oct 1999 (IOP 5) reveals considerable spatial variability in aerosol concentrations and shows interactions of the aerosols with the humidity field

Atmospheric observation-based global SF6 emissions - comparison of top-down and bottom-up estimates

Emissions of sulphur hexafluoride (SF6), one of the strongest greenhouse gases on a per molecule basis, are targeted to be collectively reduced under the Kyoto Protocol. Because of its long atmospheric lifetime (≈3000 years), the accumulation of SF6 in the atmosphere is a direct measure of its global emissions. Examination of our extended data set of globally distributed high-precision SF6 observations shows an increase in SF6 abundance from near zero in the 1970s to a global mean of 6.7 ppt by the end of 2008. In-depth evaluation of our long-term data records shows that the global source of SF6 decreased after 1995, most likely due to SF6 emission reductions in industrialised countries, but increased again after 1998. By subtracting those emissions reported by Annex I countries to the United Nations Framework Convention of Climatic Change (UNFCCC) from our observation-inferred SF6 source leaves a surprisingly large gap of more than 70–80% of non-reported SF6 emissions in the last decade

Swiss Parabolic Flights: Development of a Non-Governmental Parabolic Flight Program in Switzerland Based on the Airbus A310 ZERO-G

Parabolic flights are one of the most important pillars for research, development, and applications in space. Accordingly, we developed the world’s first non-governmental parabolic flight program using Novespace’s Airbus A310 ZERO-G. Through the flexible combination of academic research with industrial experiments, as well as with the support of private persons and low administrative efforts, we achieved a highly cost-efficient small-scale campaign concept, which is located at the Air Base Dübendorf in Switzerland. The program was very successful, and it resulted in 31 experiments and tests conducted by Universities and organizations in the industry in microgravity, culminating in many scientific publications and in larger subsequent projects for all users. We describe here how we designed, developed, tested, and built up this program. We also discuss the difficulties, problems, and success factors of a project that—for the first time—was successfully built from the “bottom-up”, and which was a large-scale flight research platform by scientists for scientists on a voluntary, non-governmental, and non-commercial basis

Atmospheric methane isotopes identify inventory knowledge gaps in the Surat Basin, Australia, coal seam gas and agricultural regions

In-flight measurements of atmospheric methane (CH4(a)) and mass balance flux quantification studies can assist with verification and improvement in the UNFCCC National Inventory reported CH4 emissions. In the Surat Basin gas fields, Queensland, Australia, coal seam gas (CSG) production and cattle farming are two of the major sources of CH4 emissions into the atmosphere. Because of the rapid mixing of adjacent plumes within the convective boundary layer, spatially attributing CH4(a) mole fraction readings to one or more emission sources is difficult. The primary aims of this study were to use the CH4(a) isotopic composition (13CCH4(a)) of in-flight atmospheric air (IFAA) samples to assess where the bottom-up (BU) inventory developed specifically for the region was well characterised and to identify gaps in the BU inventory (missing sources or over- and underestimated source categories). Secondary aims were to investigate whether IFAA samples collected downwind of predominantly similar inventory sources were useable for characterising the isotopic signature of CH4 sources (13CCH4(s)) and to identify mitigation opportunities. IFAA samples were collected between 100-350m above ground level (ma.g.l.) over a 2-week period in September 2018. For each IFAA sample the 2h back-trajectory footprint area was determined using the NOAA HYSPLIT atmospheric trajectory modelling application. IFAA samples were gathered into sets, where the 2h upwind BU inventory had >50% attributable to a single predominant CH4 source (CSG, grazing cattle, or cattle feedlots). Keeling models were globally fitted to these sets using multiple regression with shared parameters (background-air CH4(b) and 13CCH4(b)). For IFAA samples collected from 250-350ma.g.l. altitude, the best-fit 13CCH4(s) signatures compare well with the ground observation: CSG 13CCH4(s) of -55.4‰ (confidence interval (CI) 95%±13.7‰) versus 13CCH4(s) of -56.7‰ to -45.6‰; grazing cattle 13CCH4(s) of -60.5‰ (CI 95%±15.6‰) versus -61.7‰ to -57.5‰. For cattle feedlots, the derived 13CCH4(s) (-69.6‰, CI 95%±22.6‰), was isotopically lighter than the ground-based study (13CCH4(s) from -65.2‰ to -60.3‰) but within agreement given the large uncertainty for this source. For IFAA samples collected between 100-200ma.g.l. the 13CCH4(s) signature for the CSG set (-65.4‰, CI 95%±13.3‰) was isotopically lighter than expected, suggesting a BU inventory knowledge gap or the need to extend the population statistics for CSG 13CCH4(s) signatures. For the 100-200ma.g.l. set collected over grazing cattle districts the 13CCH4(s) signature (-53.8‰, CI 95%±17.4‰) was heavier than expected from the BU inventory. An isotopically light set had a low 13CCH4(s) signature of -80.2‰ (CI 95%±4.7‰). A CH4 source with this low 13CCH4(s) signature has not been incorporated into existing BU inventories for the region. Possible sources include termites and CSG brine ponds. If the excess emissions are from the brine ponds, they can potentially be mitigated. It is concluded that in-flight atmospheric 13CCH4(a) measurements used in conjunction with endmember mixing modelling of CH4 sources are powerful tools for BU inventory verification

UMARS : unmanned modular airborne research system

UMARS (Unmanned Modular Airborne Research System) is a fixed wing aircraft (span 5.0 m) with exceptional aerodynamic performance and stability, an MTOW of 25 kg, and a payload of 10 kg. With the electrical engine of 3.5 kW maximum power it can be operated slow (15 m/s) or fast (30 m/s) for one hour, with low levels of vibration. For longer endurance (up to 5h), a piston engine can be used. The UAV can operate from small, unprepared fields using bungee start, and can land on its skid. The first sensor package was developed for the observation of the atmospheric boundary layer, i.e. to measure three-dimensional wind, temperature and humidity in a temporal resolution of at least 10 Hz. The next steps will be to add an aerosol counter, and known sensors for NO2 and CO2

Air Pollution Transport in an Alpine Valley: Results From Airborne and Ground-Based Observations

An observational dataset from a wintertime field campaign in the Inn Valley, Austria, is analysed in order to study mechanisms of air pollution transport in an Alpine valley. The results illustrate three types of mechanisms: transport by a density current, back-and-forth transport by valley winds, and transport by slope winds. The first type is associated with an air mass difference along the valley. Cooler air located in the lower part of the valley behaves like a density current and produces the advection of pollutants by upvalley winds. In the second type, strong horizontal gradients in pollution concentrations exist close to ground. Multiple wind reversals result in a back-and-forth transport of pollutants by weak valley winds. In the third type, upslope winds during daytime decrease low-level pollution concentrations and cause the formation of elevated pollution layers

Carbon dioxide uptake of a forested region in southwest France derived from airborne CO2 and CO measurements in a quasi-Lagrangian experiment

International audienceThis paper presents a Lagrangian budgeting approach to quantify the uptake of CO2 by vegetation at horizontal scales of several tens of kilometers. For this purpose, CO2 and meteorological parameters were measured from a small aircraft during four flights in June 2001 over a flat homogeneous and productive temperate forest in the Landes region ( southwestern France). Additional CO measurements were made in order to identify and quantify the potential influence of anthropogenic emissions on the net CO2 flux derived from the measurements. For one of four flights, Lagrangian conditions were nearly perfectly fulfilled. On average, the CO2 mixing ratio in the boundary layer decreased at a rate of 0.11 ppm km(-1), yielding an average CO2 uptake by the forest of 16 +/- 2.5 mumol m(-2) s(-1) between 1230 and 1430 UT. Our result is about 15% smaller than the local net ecosystem exchange measured by eddy covariance at a tower north of the flight domain and about 12% higher than a regional estimate based on remote sensing data for the whole experimental area. The contribution of anthropogenic emissions to the regional CO2 budget was estimated from the CO measurements to be to <0.5 mu mol m(-2) s(-1)