Found 9758 publications. Showing page 173 of 391:
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Atmospheric ammonia (NH3) is a key transboundary air pollutant that contributes to the impacts of nitrogen and acidity on terrestrial ecosystems. Ammonia also contributes to the atmospheric aerosol that affects air quality. Emission inventories indicate that NH3 was predominantly emitted by agriculture over the 19th and 20th centuries but, up to now, these estimates have not been compared to long-term observations. To document past atmospheric NH3 pollution in south-eastern Europe, ammonium (NH) was analysed along an ice core extracted from Mount Elbrus in the Caucasus, Russia. The NH ice-core record indicates a 3.5-fold increase in concentrations between 1750 and 1990 CE. Remaining moderate prior to 1950 CE, the increase then accelerated to reach a maximum in 1989 CE. Comparison between ice-core trends and estimated past emissions using state-of-the-art atmospheric transport modelling of submicron-scale aerosols (FLEXPART (FLEXible PARTicle dispersion) model) indicates good agreement with the course of estimated NH3 emissions from south-eastern Europe since ∼ 1750 CE, with the main contributions from south European Russia, Türkiye, Georgia, and Ukraine. Examination of ice deposited prior to 1850 CE, when agricultural activities remained limited, suggests an NH ice concentration related to natural soil emissions representing ∼ 20 % of the 1980–2009 CE NH level, a level mainly related to current agricultural emissions that almost completely outweigh biogenic emissions from natural soil. These findings on historical NH3 emission trends represent a significant contribution to the understanding of ammonia emissions in Europe over the last 250 years.
2025
Measurement programme for heavy metals and persistent organic pollutants in air and deposition in Europe. WMO Global Atmosphere Watch, 136
2000
Measurement programme for heavy metals and persistent organic pollutants in air and deposition in Europe. WMO Global Atmosphere Watch, 136
1999
Satellite-based measurements of volcanic ash give the total amount of volcanic ash per area, typically in units of grams of volcanic ash per square meter. To convert this to concentration the vertical thickness of the ash cloud is needed. The ash cloud thickness is not available from passive remote sensors, e.g. IR-sensors, but may be obtained from ground- and space-based lidars. Dispersion models will also provide information of the ash thickness.
This report gives an overview of volcanic ash cloud thickness as observed by space, aircraft and ground-based lidars. Also, ash cloud thickness as simulated by the Flexpart particle dispersion model is analysed. The impact of varying cloud thickness on the signal measured by IR-sensor in space is investigated. Focus is on the Eyjafjallajokull 2010 eruption for which a unique wealth of data are available.
2013
For retrieval of ash mass loading from infrared satellite measurements, estimates of the ash cloud temperature and the surface temperature are required. The ash cloud temperature and surface temperature may be taken from satellite measurements, weather model forecast, or deduced by satellite retrievals.
The report describes various methods to estimate the ash cloud temperatue and surface temperature. The impact of varying cloud temperature and surface temperature on the signal measured by an IR-sensor in space is investigated.
2013
Measurement of volcanic ash in Norwegian air space. WP 1.4.2 Improved detection of ash clouds. NILU OR
Water and ice clouds and temperature conditions may often influence the detection of volcanic ash affected pixels in infrared satellite images. Several methods are available for the detection of ash clouds in SEVIRI images. Manual adjustments to the methods are often needed for a given ash situation. The report describes various methods for detection of ash affected pixels. A quantitative comparison of the methods is made based on synthetic SEVIRI images from the 2010 Eyafjallajokull eruption.
2013
Measurement techniques used for characterization of volcanic ash clouds have been evaluated specifically with regard to applicability and limitations. This report summarizes how future infrastructure investments in Norway will be able to provide additional information about volcanic ash clouds that can be used to inform operational aviation authorities. Three main recommendations are given.
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