Temporal Changes in Ozone Concentrations and Their Impact on Vegetation

Tropospheric concentrations of phytotoxic ozone (O3) have undergone a great increase from preindustrial 10–15 ppbv to a present-day concentration of 35–40 ppbv in large parts of the industrialised world due to increased emissions of O3 precursors including NOx, CO, CH4 and volatile organic compounds. The rate of increase in O3 concentration ranges between 1 ppbv per decade in remote locations of the Southern hemisphere and 5 ppbv per decade in the Northern hemisphere, where largest sources of O3 precursors are located. Molecules of O3 penetrating into the leaves through the stomatal apertures trigger the formation of reactive oxygen species, leading thus to the damage of the photosynthetic apparatus. Accordingly, it is assumed, that O3 increase reduces the terrestrial carbon uptake relative to the preindustrial era. Here we summarise the results of previous manipulative experiments in laboratory growth cabinets, field open-top chambers and free-air systems together with O3 flux measurements under natural growth conditions. In particular, we focus on leaf-level physiological responses in trees, variability in stomatal O3 flux and changes in carbon fluxes and biomass production in forest stands. As the results reported in the literature are highly variable, ranging from negligible to severe declines in photosynthetic carbon uptake, we also discuss the possible interactions of O3 with other environmental factors including solar radiation, drought, temperature and nitrogen deposition. Those factors were found to have great potential to modulate stomata openness and O3 fluxes.

Monitorización de las concentraciones atmosféricas de metano y óxido nitroso a partir del Metop/IASI

<p>Future of the Earth-atmosphere system will depend, to a large extent, on our capability of understanding all the processes driving climate change and, in this context, of outstanding importance are the monitoring and the investigation of greenhouse gases (GHGs), as main drivers of the Earth’s climate change. With this idea the project INMENSE (IASI for Surveying Methane and Nitrous Oxide in the Troposphere) was born, which aims to improve our current understanding of the atmospheric budgets of two of the most important well-mixed greenhouse gases, methane (CH₄) and nitrous oxide (N₂O). To this end, INMENSE has generated a new global observational data set of middle/upper tropospheric concentrations of CH₄ and N₂O from the space-based remote sensor IASI (Infrared Atmospheric Sounding Interferometer), on board the meteorological satellites EUMETSAT/Metop. In this work the INMENSE IASI CH₄ and N₂O products are presented, characterized and comprehensively validated by using a multiplatform reference database (aircraft vertical profiles, ground-based in-situ and remote-sensing observations). This extensive validation exercise suggests that the IASI CH₄ and N₂O products shows a precision between 1-3% and a bias of 2% as well as they are consistent temporally and spatially. Finally, the CH₄and N₂O IASI observations over the Iberian Peninsula have been compared to MOCAGE chemical transport simulations, assessing the degree of agreement between both datasets.</p><p> </p>

OMI total bromine monoxide (OMBRO) data product: algorithm, retrieval and measurement comparisons

This paper presents the retrieval algorithm for the operational Ozone Monitoring Instrument (OMI) total bromine monoxide (BrO) data product (OMBRO) developed at the Smithsonian Astrophysical Observatory (SAO) and shows comparisons with correlative measurements and retrieval results. The algorithm is based on direct nonlinear least squares fitting of radiances from the spectral range 319.0–347.5 nm. Radiances are modeled from the solar irradiance, attenuated by contributions from BrO and interfering gases, and including rotational Raman scattering, additive and multiplicative closure polynomials, correction for Nyquist undersampling and the average fitting residual spectrum. The retrieval uses albedo- and wavelength-dependent air mass factors (AMFs), which have been pre-computed using a single mostly stratospheric BrO profile. The BrO cross sections are multiplied by the wavelength-dependent AMFs before fitting so that the vertical column densities (VCDs) are retrieved directly. The fitting uncertainties of BrO VCDs typically vary between 4 and 7×1012 molecules cm−2 (∼10 %–20 % of the measured BrO VCDs). Additional fitting uncertainties can be caused by the interferences from O2-O2 and H2CO and their correlation with BrO. AMF uncertainties are estimated to be around 10 % when the single stratospheric-only BrO profile is used. However, under conditions of high tropospheric concentrations, AMF errors due to this assumption of profile can be as high as 50 %. The retrievals agree well with GOME-2 observations at simultaneous nadir overpasses and with ground-based zenith-sky measurements at Harestua, Norway, with mean biases less than -0.22±1.13×1013 and 0.12±0.76×1013 molecules cm−2, respectively. Global distribution and seasonal variation of OMI BrO are generally consistent with previous satellite observations. Finally, we confirm the capacity of OMBRO retrievals to observe enhancements of BrO over the US Great Salt Lake despite the current retrieval setup considering a stratospheric profile in the AMF calculations. OMBRO retrievals also show significant BrO enhancements from the eruption of the Eyjafjallajökull volcano, although the BrO retrievals are affected under high SO2 loading conditions by the sub-optimum choice of SO2 cross sections.

Ozone and aerosols tropospheric concentrations variability analyzed using the ADRIMED measurements and the WRF-CHIMERE models

The ozone and aerosols concentrations variability is studied over the Euro-Mediterranean area during the months of June and July 2013 and in the framework of the ADRIMED project. A first analysis is performed using meteorological variables, ozone and aerosols concentrations using routine stations network, satellite and specific ADRIMED project airborne measurements. This analysis is complemented by modelling using the WRF and CHIMERE regional models. It is shown that this period was not highly polluted, with a moderate ozone production and several precipitation periods, scavenging the aerosols. In addition, no significant vegetation fires events were observed. The CHIMERE model simulating all kind of sources (anthropogenic, biogenic, mineral dust, vegetation fires) for numerous aerosols species, the aerosol speciation was quantified: during the whole period, the aerosols were mainly constituted by mineral dust, sea salt and sulphates close to the surface, and mainly mineral dust in the troposphere. Compared to AERONET size distribution, it is shown that the model underestimates the coarse mode near mineral dust sources and overestimates the fine mode in the Mediterranean area, even if the total mass of aerosols and the optical depth are correctly reproduced.

Ethane, ethyne and carbon monoxide concentrations in the upper troposphere and lower stratosphere from ACE and GEOS-Chem: a comparison study

Near global upper tropospheric concentrations of carbon monoxide (CO), ethane (C2H6) and ethyne (C2H2) from ACE (Atmospheric Chemistry Experiment) Fourier transform spectrometer on board the Canadian satellite SCISAT-1 are presented and compared with the output from the Chemical Transport Model (CTM) GEOS-Chem. The retrievals of ethane and ethyne from ACE have been improved for this paper by using new sets of microwindows compared with those for previous versions of ACE data. With the improved ethyne retrieval we have been able to produce a near global upper tropospheric distribution of C2H2 from space. Carbon monoxide, ethane and ethyne concentrations retrieved using ACE spectra show the expected seasonality linked to variations in the anthropogenic emissions and destruction rates as well as seasonal biomass burning activity. The GEOS-Chem model was run using the dicarbonyl chemistry suite, an extended chemical mechanism in which ethyne is treated explicitly. Seasonal cycles observed from satellite data are well reproduced by the model output, however the simulated CO concentrations are found to be systematically biased low over the Northern Hemisphere. An average negative global mean bias of 12% and 7% of the model relative to the satellite observations has been found for CO and C2H6 respectively and a positive global mean bias of 1% has been found for C2H2. ACE data are compared for validation purposes with MkIV spectrometer data and Global Tropospheric Experiment (GTE) TRACE-A campaign data showing good agreement with all of them.

Ethane, ethyne and carbon monoxide concentrations in the upper troposphere and lower stratosphere from ACE and GEOS-Chem: a comparison study

Near global upper tropospheric concentrations of carbon monoxide (CO), ethane (C2H6) and ethyne (C2H2) from ACE (Atmospheric Chemistry Experiment) Fourier transform spectrometer on board the Canadian satellite SCISAT-1 are presented and compared with the output from the Chemical Transport Model (CTM) GEOS-Chem. The retrievals of ethane and ethyne from ACE have been improved for this paper by using new sets of microwindows compared with those for previous versions of ACE data. With the improved ethyne retrieval we have been able to produce a near global upper tropospheric distribution of C2H2 from space. Carbon monoxide, ethane and ethyne concentrations retrieved using ACE spectra show the expected seasonality linked to variations in the anthropogenic emissions and destruction rates as well as seasonal biomass burning activity. The GEOS-Chem model was run using the dicarbonyl chemistry suite, an extended chemical mechanism in which ethyne is treated explicitly. Seasonal cycles observed from satellite data are well reproduced by the model output, however the simulated CO concentrations are found to be systematically biased low over the Northern Hemisphere. An average negative global mean bias of 12% and 7% of the model relative to the satellite observations has been found for CO and C2H6 respectively and a positive global mean bias of 1% has been found for C2H2. ACE data are compared for validation purposes with MkIV spectrometer data and Global Tropospheric Experiment (GTE) TRACE-A campaign data showing good agreement with all of them.

The relationship between some meteorological parameters and the tropospheric concentrations of ozone in the urban area of Belgrade

During the period between June and December 2002, the concentrations of ozone in the air at 4 measuring sites in Belgrade were measured. The measuring periods varied from 10 days to several weeks. The maximal measured daily concentrations of ozone ranged from 19ppbv (23 December 2002) to 118ppbv (23 June 2002).Ozone concentrations higher than, or equal to 90ppbv were registered at three measuring sites. It was shown that at measuring sites characterized as urban, maximal O3 concentrations equal to, or higher than 90ppbv occurred at high temperatures (higher than 30?C) and low wind speeds (mostly from the north). The measured ozone concentrations mostly showed characteristics usual for a daily photochemical ozone cycle, excluding the specificities influenced by the measuring site itself. Ozone transport was recorded at increased wind speeds, primarily from south-easterly directions. On the basis of he correlations between ozone concentration and the corresponding meteorological parameters, a validation of the measuring sites was performed from the aspect of their representativeness for the measurements.