Showing papers by "André S. H. Prévôt published in 2001"
TL;DR: In this paper, the Mesoscale Alpine Programme (MAP) special observation period (SOP) between 7 September and 15 November 1999, ground-based and airborne measurements have been conducted in the Rhine valley south of the Lake of Constance to investigate the unstationary aspects of Foehn and related phenomena.
26 citations
TL;DR: In this paper, the horizontal and vertical wind component by a crosswind scintillometer during foehn, the chinook-like downslope windstorm in the Alps, is presented.
Abstract: Measurements of the horizontal and vertical wind component by a crosswind scintillometer during foehn, the chinooklike downslope windstorm in the Alps, are presented. Because of the sparsity of vertical velocity measurements in the immediate vicinity, the scintillometer calibration is checked mainly with horizontal wind measurements. Then it is assumed that the calibration is the same for both components. The concept was tested during the Mesoscale Alpine Programme field campaign in the autumn of 1999, during which two scintillometers were deployed. Strong, long-lasting, quasi-stationary downward motions on the order of 5 m s−1 and horizontal wind speeds of over 30 m s−1 were detected during strong foehn phases within the valley. Aircraft measurements of various transects near the light paths are compared with two crosswind evaluation techniques. One of them, the slope method, tends to overestimate the actual wind speed by about 20%, whereas the peak technique gives values that are about 10% too ...
18 citations
TL;DR: Ozone isopleths plotted with measured values of ozone, hydrocarbons and total reactive nitrogen (NOy) are proposed to visualize ozone production regimes at distinct locations as mentioned in this paper.
Abstract: Ozone isopleths plotted with measured values of ozone, hydrocarbons and total reactive nitrogen (NOy) are proposed to visualize ozone production regimes at distinct locations The applicability of the concept is confirmed with measurements at two distinct sites in the Italian Po Basin Empirical ozone isopleths at the urban site clearly show ROG-sensitive ozone production, with ozone increasing with increasing ROG concentrations and decreasing with increasing ambient levels of NOx At the rural site NOx-sensitive ozone production prevails, in accordance with previous results
15 citations
TL;DR: In this paper, threshold values derived from various model simulations at two different locations (the area of Switzerland by UAM Model and San Joaquin Valley of Central California by SAQM Model) are examined using a new approach for defining NOx and VOC sensitive regimes.
15 citations
TL;DR: In this article, airborne measurements of non-methane hydrocarbons have been performed with an on-line gas chromatograph over large cities such as Vienna and Milano, the polluted Lombardy region and moderately polluted regions such as the Swiss Plateau and alpine areas.
Abstract: Traffic is one of the main emission sources of non-methane hydrocarbons (NMHC), which play a key role in the formation of ozone. Over the last years, airborne measurements of non-methane hydrocarbons have been performed with an on-line gas chromatograph over large cities such as Vienna and Milano, the polluted Lombardy region and moderately polluted regions such as the Swiss Plateau and alpine areas. This set of data has been analysed with respect to pollution level, composition, reactivity and contribution of emission sources in the different areas. The measured hydrocarbon concentrations coincide with the emission strengths given by the emission inventories of the respective regions. The alpine Mesolcina valley south of the Alps is strongly influenced by advected air polluted with hydrocarbons. The relative concentration of individual species to the sum of the measured hydrocarbons is similar in all regions, but show a few peculiarities specific to some regions.
4 citations