One of the objectives of the Atmospheric Composition SAF (AC SAF) is to produce satellite-derived monthly mean data records that are valuable for operational, scientific, and other applications. One of these data records is the gridded global GOME-2A/B/C ozone profile data set presented in this paper. This data record covers the period 2007-2024 and consists of ozone partial columns on a 0.25 degrees & times;0.25 degrees grid with 40 vertical layers, with the associated (averaged) averaging kernel and the a priori needed to use the data in other applications. This paper presents the GOME-2 instrument, the (level-2) ozone profile retrieval method and the subsequent gridding procedure used to generate the level-3 product. We discuss the methodology for averaging AKs in latitude bands and demonstrate that the principal structural features are preserved. We provide a description of the balloon sounding, lidar, FTIR and microwave radiometers validation data and methods, and then perform a quality assessment of the gridded ozone profile product through comparison with these independent data sources for the tropics, mid-latitude and polar latitude bands for four vertical regions: the Troposphere, the UTLS and the Lower and Upper Stratosphere. Detailed analyses of absolute and relative differences are provided for each region and height range. The results demonstrate a high level of consistency across the three GOME-2 instruments (with GOME-2A used only up to 2018). In the troposphere, all three sensors tend to slightly overestimate ozone, with absolute differences of roughly +1 to +3 Dobson Units (DU) in mid-latitudes and up to +7.5 DU in the tropics for Metop-C. In the more variable UTLS altitude region, the absolute differences range between -2.5 and 5 DU. In the lower stratosphere, all sensors show a small negative bias, typically between -3 and -7 DU (relative difference approximate to-3% to -7%), corresponding to a modest underestimation of ozone concentrations. In the upper stratosphere, biases are minimal across all sensors, with absolute difference values, close to zero (-0.1 to -0.4 DU) and low variability. These findings underscore the reliability of the GOME-2 constellation for long-term ozone analyses and the potential for merged multi-sensor time series without significant inter-calibration artifacts suitable for climate and atmospheric research.

Accurate identification of aerosol type and cloud phase is essential for understanding atmospheric processes, radiative forcing, and aerosol–cloud interactions, especially during long-range transport events such as Saharan dust intrusions and transatlantic wildfire smoke. Recent advances in automatic lidar–ceilometers (ALCs) equipped with depolarization capability, such as the Vaisala CL61, enable continuous and unattended monitoring of aerosol type and cloud phase at high temporal and vertical resolution. However, single-wavelength configurations limit the exploitation of multi-parameter aerosol classification methods developed for advanced multi-wavelength lidars. At the Royal Meteorological Institute of Belgium (RMI), we developed CONIOPOL (CONIOlogy + POLarization), an algorithm that exploits backscatter and depolarization profiles from the Vaisala CL61. By combining attenuated backscatter, linear depolarization ratio (LDR), and cloud-base height retrievals, CONIOPOL discriminates between clouds, precipitation, and aerosols, and classifies cloud phase, precipitation type, and major aerosol subtypes in near real time. Despite the spectral limitation, the algorithm demonstrates strong temporal and vertical coherence with CAMS forecasts, effectively capturing key aerosol transport events and seasonal variability over Belgium. This presentation highlights CONIOPOL’s performance through high-impact case studies, long-term statistical analyses, and direct comparisons with CAMS forecasts and surface air quality observations. We focus on the detection of distinct aerosol types—including dust and smoke—and their vertical and seasonal distributions. Beyond operational applications, CONIOPOL enables the construction of consistent aerosol and cloud climatologies from continuous ALC observations, bridging gaps between satellite, in situ, and advanced lidar measurements. These results underscore the potential of depolarization-capable ceilometers to support long-term aerosol monitoring, improve understanding of aerosol–cloud interactions, and enhance air-quality climatologies.

Inverse modelling of atmospheric releases of radioactivity consists of reconstructing the release source by combining radiological field measurements with atmospheric transport calculations. This is typically performed with air concentration measurements, although deposition measurements or gamma dose rate measurements could also be used. In this paper, we assess the use of deposition measurements of radioactivity in this context. This is done through a case study of the undisclosed release of the radionuclide 106Ru in Eurasia during the autumn of 2017. The atmospheric transport model we utilize for this purpose is FLEXPART. Inverse modelling is performed with the inverse modelling tool FREAR (Forensic Radionuclide Event Analysis and Reconstruction), which has been modified to work with deposition measurements. The inversion consists of Bayesian and cost-function-based algorithms to reconstruct the initial source properties. Inverse modelling is applied to both real and synthetic-deposition data following the 106Ru release. We also construct synthetic air concentration data for use in inverse modelling to make a comparison with the results using deposition data. It is found that source localization is feasible with both the synthetic and real-world deposition data. Synthetic air concentration measurements lead to more precise source localization than deposition. It is demonstrated that this can be explained by the lower detection limits of air concentration measurements compared to deposition.

While the atmospheric concentrations of ozone-depleting chlorofluorocarbons (CFCs) are gradually declining following regulatory measures, the levels of other halogenated compounds, such as hydrochlorofluorocarbons (HCFCs) and sulfur hexafluoride (SF6), continue to rise or are only just starting to stabilize. These halogenated substances are potent greenhouse gases. Their radiative efficiency, which quantifies along with their lifetime their impact on the climate, has until now only been estimated indirectly by means of models. Here, we report the clear-sky instantaneous radiative efficiencies (IRE) of CFC-11, CFC-12, SF6, HCFC-22 and HFC134a estimated for the first time directly from an observational dataset. This is achieved by combining trends observed in 15 years (2008-2022) of spectrally resolved infrared radiance fluxes from the Infrared Atmospheric Sounding Interferometer (IASI) on Metop satellites, with concentrations measured from ground and space. Comparisons with literature-reported values generally confirm previous model estimates, with some notable differences. The most significant discrepancies are for CFC-11 and SF6, with our estimates being 27% lower but, nevertheless, within the bounds of the uncertainty estimates.

Atmospheric composition plays an important role in present and near-future climate change. Airborne particles exert direct and indirect radiative impacts and can serve as cloud condensation and ice nuclei, having therefore a strong influence on cloud formation and precipitation. Furthermore, a detailed understanding of present-day atmospheric transport pathways of particles from source to deposition in Antarctica remains essential.Since 2010, the aerosol total number and size distribution, aerosol absorption coefficient and mass concentration of light-absorbing aerosols and the aerosol total scattering coefficient have been monitored at the Belgian research station Princess Elisabeth Antarctica (PEA). The station is situated in Dronning Maud Land, East Antarctica (71.95° S, 23.35° E, 1390 m asl). Besides these instruments, a cloud condensation nuclei counter was operated during three austral summers. Meteorological data come from an automatic weather station. In this work, we investigate the climatology of the particle properties with respect to the air mass origin. To that end, we used the FLEXTRA trajectory model to investigate transport pathways into Antarctica. The model was driven with ECMWF ERA-5 meteorological fields. 10-days 3D backward trajectories, starting from PEA, were calculated for the period 01/01/2010 to 31/12/2020, in 3-hour-intervals. A k-means cluster analysis has been done based on latitude, longitude and altitude, resulting in four clusters of air mass origin.We will present results for the climatology of particle properties and the air mass origin. In addition, the backward trajectories have been combined with measured atmospheric particle properties and parameters like potential vorticity and exposure to sunshine duration, showing the distribution of the measured atmospheric particle properties between and within the air mass origin clusters. Some distinct features could be seen in the air mass origin clustering. Source regions from South America, Southern Africa and Australia, New Zealand were limited and the Southern Ocean was a main source region, as was the Antarctic continent itself. For each season, the dominating cluster represented mainly air masses of Antarctic continental origin with a large influence of upper tropospheric air. We will show further results of our analysis on air mass origin and atmospheric and particle properties, with respect to differentiations between seasons, clusters, continental and maritime origin and source altitude compartments.

In Europe a quarter of the adult population and a third of all children suffer from allergenic airborne pollen thereby decreasing the quality of life. In order to ease the pollen induced symptoms mitigation measures can be applied. This, however, requires timely information on forthcoming pollen episodes derived from early warning systems. These systems can substantially be improved when pollen observations from strategically well-chosen pollen monitoring stations are assimilated. Here we explore the network quality (i) and network coverage (ii) of the current five pollen monitoring stations in Belgium. As reference dataset we use the spatio-temporal distributions of daily surface airborne birch and grass pollen levels as produced by the operational early warning system for pollen on the website of the Royal Meteorological Institute of Belgium. This system implements the SILAM model (System for Integrated modeLling of Atmospheric coMposition) and ECMWF meteorological data. The ability of the network to reproduce the concentration field over the region of interest is quantified by the RMSE computed from the reference concentration field and the interpolated concentration field for each day of the pollen season. In the first step, time series of the current daily pollen observations in the network are interpolated over space by applying the radial-based function. This results in the daily interpolated concentration fields which we compare with the spatially distributed daily reference data. For evaluating the network coverage of the current five monitoring stations we perform a footprint-based analysis. Footprints relate directly to the fraction of air reaching the monitoring device. By applying pollen emission point sources in the five stations into SILAM that is run in the backward mode (three days back), we can investigate the travelling trajectory of the captured birch and grass pollen in the air observed at the network stations. Nine pollen seasons (2013-2021) were analyzed using ECMWF ERA5 meteorology. First results on the network quality for birch pollen show that over a period of nine pollen seasons more than 60% of the daily RMSE values derived from the interpolated daily concentrations are less than their mean value. This is an indication that the interpolated network performs well compared to the spatio-temporal reference dataset derived from SILAM. For the 2013 birch pollen season more than 80% is reached. In contrast, this is only ~40% for 2020. The applied time scale is of great importance, since at smaller time scales (days, hours) network configurations may degrade faster than on larger time steps (weeks, months, seasons). The footprint-based analysis shows that on average the coverage of the monitoring stations for birch pollen is quite good. There are, however, large differences during the 2013-2022 seasons which might be due to the typical large inter-seasonal variation in birch pollen production. For grass pollen, the average coverage is better, and the inter-seasonal variation much lower.

Antarctica, protected by its strong polar vortex and sheer distance from anthropogenic activity, was always thought of as pristine. However, as more data on the occurrence of persistent organic pollutants on Antarctica emerge, the question arises of how fast the long-range atmospheric transport takes place. Therefore, polycyclic aromatic hydrocarbons (PAHs) and oxygenated (oxy-)PAHs were sampled from the atmosphere and measured during 4 austral summers from 2017 to 2021 at the Princess Elisabeth station in East Antarctica. The location is suited for this research as it is isolated from other stations and activities, and the local pollution of the station itself is limited. A high-volume sampler was used to collect the gas and particle phase (PM10) separately. Fifteen PAHs and 12 oxy-PAHs were quantified, and concentrations ranging between 6.34 and 131 pg m(3) (Sigma(15)PAHs-excluding naphthalene) and between 18.8 and 114 pg m(3) (Sigma(13)oxy-PAHs) were found. Phenanthrene, pyrene, and fluoranthene were the most abundant PAHs. The gas-particle partitioning coefficient log(K-p) was determined for 6 compounds and was found to lie between 0.5 and -2.5. Positive matrix factorization modeling was applied to the data set to determine the contribution of different sources to the observed concentrations. A 6-factor model proved a good fit to the data set and showed strong variations in the contribution of different air masses. During the sampling campaign, a number of volcanic eruptions occurred in the southern hemisphere from which the emission plume was detected. The FLEXPART dispersion model was used to confirm that the recorded signal is indeed influenced by volcanic eruptions. The data was used to derive a transport time of between 11 and 33 days from release to arrival at the measurement site on Antarctica.

In Europe, more than one quarter of the adult population and one third of the children suffer from pollinosis, but the geographical variability is large. In Belgium, at least 10

Natural mineral dust are composed of reactive species affecting directly or indirectly the global climate through aerosol-radiation-cloud-chemistry interactions. They are also efficient suppliers of organic or inorganic components that can influence the primary productivity in oceans, such as the Austral Ocean.The present study attempts to solve the puzzle of the origin (the potential source areas - PSA) of dust deposition in East Antarctica (EA). We combine analyses of size, shape, mineralogy, geochemistry (trace element, and especially REE data), as well as strontium (Sr), neodymium (Nd) and lead (Pb) isotopes, performed on modern snow dust samples collected along a ~200km transect in the Dronning Maud Land area (from the Belgian Station Princess Elisabeth Antarctica to the coast). A statistical mixing model was specifically developed to fit the Rare Earth Elements (REE) patterns of Antarctic dust samples (Vanderstraeten et al., 2023) by combining REE profiles from PSA in Southern South America (Patagonia, Puna-Altiplano plateau), Southern Africa (Namibia, SAF), Australia and New-Zealand. In addition to REE, PSA isotopic compositions of Sr, Nd and Pb were analysed (Gili et al., 2022), specifically in 30 samples from the Namibian coast where an evident lack of analyzed samples was detected in the literature data collection.The atmospheric particles mainly show a submicronic size (> 98% of particles < 5μm, n=2500) and angular shape. SEM-EDS observations suggest spatial variations in mineralogy, reflecting the influence of input from the local Sør Rondanes mountains for the inland sites (Fe-Mg silicate > 50 %) and distal source’ input at the coast (predominance of aluminosilicates and quartz, with <20% of Fe-Mg silicates). The REE profiles and the Sr, Nd and Pb isotopic variability observed in present-day dust depositions at the EA coast, as it was demonstrated for the Holocene interglacial depositions (at Vostok and EDC; Gili et al., 2022) in East Antarctica and the South Atlantic Ocean, can be related to the contributions of two main PSAs: Southern South America, dominated by the major contribution of Patagonia and important percentage of the Puna–Altiplano Plateau, in combination with Southern Africa in response to the plausible transport by the strong Berg Winds. This work presents an innovative and multi-proxy approach for the identification of potential dust source contributions in the Southern Hemisphere, and East Antarctica in particular, which provides major implications for the reconstruction of atmospheric circulation and implications on climate evolution. Vanderstraeten et al., (2023), Science of the Total Environment, 881, 163450; http://dx.doi.org/10.1016/j.scitotenv.2023.163450Gili et al., (2022), Nature Communications earth & environment, 3 :129 ; https://doi.org/10.1038/s43247-022-00464

Introduction: Previous studies on prenatal green space exposure and early respiratory health show inconsistent results. This may reflect stage-specific in utero effects and pollen influence. We examine associations of surrounding greenness and pollen exposure during pregnancy (overall and by trimester) with preschool wheezing, and assess potential mediation by pollen. Methods: We used data from the PIPO birth cohort (n = 860). Wheezing was reported biannually between 18 and 48 months of age. Residential greenness was measured with Normalized Difference Vegetation Index (NDVI) in 100 and 250 m buffer. Cumulative grass and birch pollen was estimated using modelled airborne pollen counts and categorized per trimester into no, low and high. All exposures were assessed for the overall pregnancy and per trimester. We used Generalized Estimated Equations to obtain odds ratios (OR) and 95% confidence intervals (CI). To assess mediation by pollen we used a data duplication algorithm with a generalized estimation approach. Results: Approximately 10% of participants wheezed. During pregnancy, greenness (OR = 1.07, CI: 1.05-1.08) and grass pollen exposure (OR = 1.09, CI: 1.03-1.15) increased the odds of wheezing, while birch pollen decreased it (OR = 0.86, CI:0.87-1.00). Per trimester, more greenness during the 2nd trimester increased the odds (OR = 1.21, CI: 1.16-1.26), whereas third-trimester greenness decreased it (OR = 0.87, CI: 0.84-0.91). Grass pollen exposure in the 1st and 3rd trimesters increased the odds of wheezing (OR = 1.23, CI: 1.12-1.34 and OR = 1.13, CI: 1.00-1.27, respectively), while birch pollen exposure in the 1st and 2nd trimesters decreased the odds (OR = 0.88, CI: 0.77-1.00 and OR = 0.83, CI: 0.73-0.95, respectively). No significant associations were found for greenness in the 1st trimester, grass pollen in the 2nd trimester, and birch pollen in the 1st and 3rd trimester. Mediation analysis showed large uncertainty. Discussion: Surrounding greenness and pollen exposure during pregnancy may impact the likelihood of preschool wheezing differently depending on the timing of exposure and the pollen type.

A global network of monitoring stations is set up that can measure tiny concentrations of airborne radioactivity as part of the verification regime of the Comprehensive Nuclear-Test-Ban Treaty. If Treaty-relevant detections are made, inverse atmospheric transport modelling is one of the methods that can be used to determine the source of the radioactivity. In order to facilitate the testing of novel developments in inverse modelling, two sets of test cases are constructed using real-world 133Xe detections associated with routine releases from a medical isotope production facility. One set consists of 24 cases with 5 days of observations in each case, and another set consists of 8 cases with 15 days of observations in each case. A series of inverse modelling techniques and several sensitivity experiments are applied to determine the (known) location of the medical isotope production facility. Metrics are proposed to quantify the quality of the source localisation. Finally, it is illustrated how the sets of test cases can be used to test novel developments in inverse modelling algorithms.

The high economic impact and zoonotic potential of avian influenza call for detailed investigations of dispersal dynamics of epidemics. We integrated phylogeographic and epidemiologic analyses to investigate the dynamics of a low pathogenicity avian influenza (H3N1) epidemic that occurred in Belgium during 2019. Virus genomes from 104 clinical samples originating from 85% of affected farms were sequenced. A spatially explicit phylogeographic analysis confirmed a dominating northeast to southwest dispersal direction and a long-distance dispersal event linked to direct live animal transportation between farms. Spatiotemporal clustering, transport, and social contacts strongly correlated with the phylogeographic pattern of the epidemic. We detected only a limited association between wind direction and direction of viral lineage dispersal. Our results highlight the multifactorial nature of avian influenza epidemics and illustrate the use of genomic analyses of virus dispersal to complement epidemiologic and environmental data, improve knowledge of avian influenza epidemiologic dynamics, and enhance control strategies.

Wet deposition plays a crucial role in the removal of aerosols from the atmosphere. Yet, large uncertainties remain in its implementation in atmospheric transport models, specifically in the parameterisation schemes that are often used. Recently, a new wet deposition scheme was introduced in FLEXPART. The input parameters for its wet deposition scheme can be altered by the user and may be case-specific. In this paper, a new method is presented to optimise the wet scavenging rates in atmospheric transport models such as FLEXPART. The optimisation scheme is tested in a case study of aerosol-attached 137Cs following the Fukushima Daiichi nuclear power plant accident. From this, improved values for the wet scavenging input parameters in FLEXPART are suggested.

Changes in climate and land-use may elicit an increased emission of allergenic pollen amounts in the air, causing a rise in respiratory allergies and affecting public health more than previously thought. Here we have used a well-established pollen transport model SILAM (System for Integrated modeLling of Atmospheric coMposition) for attributing the long-term changes in airborne pollen concentrations of birches and grasses to climate change and vegetation dynamics. The pollen transport model is applied for Belgium and is driven by ECMWF ERA5 meteorological data (European Centre for Medium-Range Weather Forecasts, fifth generation of ECMWF atmospheric reanalysis of the global climate). The dynamic vegetation components of the model are based on multi-decadal datasets for 1982–2019 on spatially distributed birch and grass pollen emission sources. For each model gridcell we have computed the change rate of the seasonal birch and grass pollen cycles based on daily pollen concentrations, and of the daily meteorological model input. Finally, the gridcell based association between trends in pollen and climate change are derived. Our findings show that during the period 1982–2019 a strong increase in birch pollen concentrations is associated with increasing radiation, decreasing precipitation and decreasing horizontal wind speed near the surface. A strong decrease of grass pollen concentrations over time is driven by a decreasing trend in grass pollen sources, and it is also associated with decreasing precipitation. The magnitude of the associations between meteorology and airborne birch pollen concentrations are almost twice the association between meteorology and grass pollen, and the spatial variations are substantial even on the scales of small countries. The specific contribution of birch tree and pollen production dynamics to the concentrations of birch pollen in the air over time is highly associated with wind speed and precipitation. Introducing the inter-seasonal variation in birch pollen production during the period 1982–2019 intensifies the climate induced increase of airborne birch pollen concentrations with ∼6%. In contrast, the grass pollen production dynamics resulted into ∼10 times less grass pollen over the studied period compared to climate change effects.

Antarctica is considered the most pristine environment on Earth but is also characterized by its unique conditions such as the strong polar vortex and extreme cold. A detailed understanding of volatile organic compounds (VOCs) and the atmospheric oxidation reactions they undergo is essential to document biogeochemical cycles and to better understand their impact on radiative forcing. This research aims to provide a unique dataset of oxygenated (O)VOCs occurring in the Antarctic troposphere and provide insights into their temporal behavior. A home-made sequential sorbent tube auto sampler was deployed at the atmospheric observatory of the Princess Elisabeth station (71.95 degrees S, 23.35 degrees E, 1390 m asl) to collect 20 samples during the period from December 2019 to October 2020. The samples were analyzed consecutively by TD-GC-MS followed by direct thermal desorption of samples in a high-resolution PTR-Qi-TOFMS.Concentrations of 70 VOCs allocated to 4 different chemical groups (halogenated compounds, non-aromatic hydrocarbons, sulfur-containing compounds, and oxygenated aromatic and non-aromatic compounds) were determined. The results show temporal patterns for compounds such as bromoform (14 +/- 6 ng/m3) and OVOCs such as furaldehyde (24 +/- 9 ng/m3), amongst others, which are attributed to the seasonality of atmospheric conditions. Products of the atmospheric oxidation process show linear correlation indicating their mutual relationship and association with a common parent compound.The usage of an autonomous autosampler in the extreme conditions of Antarctica was demonstrated and proved to be a powerful tool in the sampling of air in such a remote location. The novel approach of using two analytical techniques boasts increased sensitivity and a broad range of compounds that can be detected, yielding the first dataset of its kind for Antarctica.

Estimating the impact of climate change and emission scenarios on air pollution can be done using regional climate models (RCMs). Climate uncertainties are commonly estimated using RCM ensembles such as provided by EURO-CORDEX. Despite the strong relations between the weather and air pollutants, interactions are usually complex and require meteorological parameters that are not commonly available for the RCM ensembles. Pollution peaks, however, often coincide with stagnant atmospheric conditions that can be captured with widely-available RCM data. We first show that a commonly-used atmospheric stability index that uses rainfall, near-surface and 500 hPa wind speed, relates well to average and extreme air pollutant concentrations over Europe using Copernicus Atmosphere Monitoring Service (CAMS) data. We then provide an in-depth validation of 25 RCMs to reproduce the spatio-temporal features of air stagnation by comparison with ERA5. Overall the models were found to reproduce stagnant episodes fairly well, especially after bias correction. The systematic underestimation of stagnation frequency and duration is traced back to overestimated near-surface wind speed for a large group of models at high-elevation regions where the temporal correlations are also low. Regardless of the reference dataset, two model groups are identified that, independent on their resolution, give strongly different results in terms of orographic dependence of surface wind speed. These strong discrepancies underscore the need for bias correction when using RCM data for analysis of stagnation episodes.

Causmaecker, Karen De Mangold, Alexander Delcloo, Andy W.The austral summer of 2019–2020 was marked by a severe wildfire season. Continuous wildfires including many pyrocumulonimbus events were observed in Australia. On a global level climate change is expected to lead to a change in intensity, extent and location of wildfires. Intense wildfires inject a huge amount of pollutants in the air which can reach the upper troposphere and sometimes even the stratosphere. The smoke affects the nearby environment but can also indirectly affect the climate in various ways. Therefore, it is important to understand fire emissions and their atmospheric transport well. We use fire emissions from the CAMS Global Fire Assimilation System (GFAS) to run the Lagrangian particle model Flexpart and we investigate how well this model setup performs. We compare our results directly with observations from ground-based measurement stations as well as with observations from the CALIOP instrument on board of the CALIPSO satellite.

&lt;p&gt;Air pollution contributes to increased mortality and lower quality of life. It imposes additional distress on people suffering from respiratory diseases such as pollinosis. A quarter of the adult population and a third of all children in Europe are estimated to suffer from airborne allergenic pollen. In the future even more people might be subjected to pollen allergies since changes in climate and land-use tend to increase the amount of allergenic airborne pollen and prolong the pollen seasons. Good pollen mitigation measures may ease the symptoms but it requires proper knowledge on the modelling and forecasting of allergenic pollen in the air.&lt;/p&gt; &lt;p&gt;We start from the setup of the pollen transport model SILAM (System for Integrated modeLling of Atmospheric coMposition), driven by ECMWF ERA5 meteorology in a bottom-up emission approach for the period 1982-2019 for the Belgian territory. The dynamic vegetation component in the pollen transport model is determined by pollen emission source maps which have to be ingested in the model for every pollen season. The used maps are derived by merging multi-decadal datasets of spaceborne NDVI with forest inventory data in a Random Forest statistical framework.&lt;/p&gt; &lt;p&gt;Here we study the impact of spatially-varying pollen emission sources on the modelled airborne birch pollen levels compared with in-situ observations in a Monte-Carlo approach. Preliminary analysis indicates that by selecting the model scenario corresponding with median pollen levels, the correlation between the modelled and observed pollen levels increases with 16%. We show the importance of ingesting the appropriate pollen emission source map when the modelling and forecasting of airborne birch pollen levels is aimed for. Finally, we review methods to relate the pre-pollen season meteorology or vegetation state on the birch pollen loads of the up-coming season as tool for selecting the best emission source map in the forecasting framework.&lt;/p&gt;

Green space could influence adult cognition and childhood neurodevelopment , and is hypothesized to be partly driven by epigenetic modifications. However, it remains unknown whether some of these associations are already evident during foetal development. Similar biological signals shape the developmental processes in the foetal brain and placenta.Therefore, we hypothesize that green space can modify epigenetic processes of cognition-related pathways in placental tissue, such as DNA-methylation of the serotonin receptor HTR2A. HTR2A-methylation was determined within 327 placentas from the ENVIRONAGE (ENVIRonmental influence ON early AGEing) birth cohort using bisulphite-PCR-pyrosequencing. Total green space exposure was calculated using high-resolution land cover data derived from the Green Map of Flanders in seven buffers (50 m-3 km) and stratified into low (<3 m) and high (≥3 m) vegetation. Residential nature was calculated using the Land use Map of Flanders. We performed multivariate regression models adjusted for several a priori chosen covariables. For an IQR increment in total green space within a 1,000 m, 2,000 m and 3,000 m buffer the methylation of HTR2A increased with 1.47% (95%CI:0.17;2.78), 1.52% (95%CI:0.21;2.83) and 1.42% (95%CI:0.15;2.69), respectively. Additionally,, we found 3.00% (95%CI:1.09;4.91) and 1.98% (95%CI:0.28;3.68) higher HTR2A-methylation when comparing residences with and without the presence of nature in a 50 m and 100 m buffer, respectively. The methylation status of HTR2A in placental tissue is positively associated with maternal green space exposure. Future research is needed to understand better how these epigenetic changes are related to functional modifications in the placenta and the consequent implications for foetal development.