123 research outputs found
Evolution of perturbations in 3D air quality models
The deterministic approach of sensitivity analysis is applied on the solution vector of an Air Quality Model. In
particular, the photochemical CAMx code is augmented with derivatives utilising the automatic differentiation
software ADIFOR. The enhanced with derivatives version of the model is then adopted in a study of the effect of
perturbations at the boundary conditions on the predicted ozone concentrations. The calculated derivative matrix
provides valuable information e.g., on the ordering of the infl uential factors or the localisation of highly affected
regions. Two fundamentally different domains of the Auto-Oil II programme were used as test cases for the
simulations, namely Athens and Milan. The results suggest that ozone concentration be highly affected by its own
boundary conditions and subsequently, with an order of magnitude less, by the boundary conditions of NOX and VOC
Comparison of UV-B measurements performed with a Brewer spectrophotometer and a new UVB-1 broad band detector
Measurements of the UV-B erythemal dose, based on solar spectra acquired with a Brewer spectrophotometer at Thessaloniki, Greece, are compared to measurements performed with the recently introduced, by the Yankee Environmental Systems, (Robertson type) broad band solar UV-B detector. The spectral response function of this detector, when applied to the Brewer spectral UV-B measurements, results in remarkably comparable estimates of the erythemal UV-B dose. The two instruments provide similar information on the UV-B dose when they are cross-examined under a variety of meteorological and atmospheric conditions and over the a large range of solar zenith angles and total ozone
The evolution of synoptic ozone anomalies during the European Arctic Stratospheric Ozone Experiment in winter 1991/1992
The evolution of ozone anomalies over the middle and high latitudes of the Northern Hemisphere during the winter 1991-1992 is studied in this work. The largest monthly mean negative deviations in the middle latitudes of the Northern Hemisphere were about 10 percent in November and December, and up to 20 percent in January, February, and March over Eurasian territories, and much smaller over the Canadian sector. At the end of January, on individual days, total ozone values of 190-210 D.U. were observed over Eastern Europe and European part of Russia, that is 40-45 percent below normal. On the whole, the 1991-1992 winter was one of the most anomalous over all the period of ozone observations. Finally, an attempt is made to quantify the contribution of transport in the ozone layer changes over Europe during this period
Benchmark Exercise on Major Hazard Analysis. Vol. 1. Description of the Project, Discussion of the Results and Conclusions
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