Global Change Abstracts The Swiss Contribution - SCNAT

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60 08.1-61 The impact of NOx, CO and VOC emissions on the air quality of Zürich airport Schürmann G, Schäfer K, Jahn C, Hoffman H, Bauerfeind M, Fleuti E, Rappenglück B Germany, Switzerland, USA Meteorology & Atmospheric Sciences Atmospheric Environment, 2007, V41, N26, AUG, pp 5553-5554. 08.1-62 Dewpoint and humidity measurements and trends at the summit of Mount Washington, New Hampshire, 1935-2004 Seidel T M, Grant A N, Pszenny A A P, Allman D J USA, Switzerland Meteorology & Atmospheric Sciences Meteorological conditions have been recorded at the summit of Mount Washington, New Hampshire, (44 degrees 16 ‘ N, 71 degrees 18 ‘ W, 1914 m ASL) since November 1932. Use of consistent instrumentation allows analysis of humidity measurements as calculated from error- checked dry bulb temperature, wet bulb temperature, and pressure during the period 1935-2004. This paper presents seasonally and annually averaged dewpoint temperature, mixing ratio, and relative humidity means and trends, including clear-air and fog subsets and, beginning in 1939, day and night subsets. The majority of linear trends are negative over the full study period, although these decreases are not constant, with relatively large (small) values in the mid-1950s (late 1970s). Annual mean dewpoint (water vapor mixing ratio) over the 70-yr period has decreased by 0.06 degrees C decade(-1) (0.01 g kg(-1) decade(-1)). During this period the annual frequency of fog increased by 0.5% decade(-1). Dewpoint and mixing ratio trends, both generally decreasing, differ by season; they are smallest in spring and greatest in fall. Relative humidity has decreased most in winter. The clear-air subset shows significant decreases in both dewpoint and mixing ratio for all seasons except spring. Journal of Climate, 2007, V20, N22, NOV 15, pp 5629-5641. 08.1-63 Assessment of the performance of ECCozonesondes under quasi-flight conditions in the environmental simulation chamber: Insights from the Juelich Ozone Sonde Intercomparison Experiment (JOSIE) Smit H G J, Straeter W, Johnson B J, Oltmans S J, Davies J, Tarasick D W, Hoegger B, Stubi R, Schmidlin F J, Northam T, Thompson A M, Witte J C, Boyd I, Posny F Global Change Abstracts – The Swiss Contribution | Atmosphere Germany, USA, Switzerland, Reunion Meteorology & Atmospheric Sciences , Modelling (1) Since 1996, quality assurance experiments of electrochemical concentration cell (ECC) ozonesondes of two different model types (SPC-6A and ENSCI-Z) have been conducted in the environmental simulation facility at the Research Centre Juelich within the framework of the Juelich Ozone Sonde Intercomparison Experiment (JOSIE). The experiments have shown that the performance characteristics of the two ECC-sonde types can be significantly different, even when operated under the same conditions. Particularly above 20 km the ENSCI-Z sonde tends to measure 5-10% more ozone than the SPC-6A sonde. Below 20 km the differences are 5% or less, but appear to show some differences with year of manufacture. There is a significant difference in the ozone readings when sondes of the same type are operated with different cathode sensing solutions. Testing the most commonly used sensing solutions showed that for each ECC- manufacturer type the use of 1.0% KI and full buffer gives 5% larger ozone values compared with the use of 0.5% KI and half buffer, and as much as 10% larger values compared with 2.0% KI and no buffer. For ozone sounding stations performing long term measurements this means that changing the sensing solution type or ECCsonde type can easily introduce a change of +/- 5% or more in their records, affecting determination of ozone trends. Standardization of operating procedures for ECC-sondes yields a precision better than +/-(3-5)% and an accuracy of about +/-(5-10)% up to 30 km altitude. Journal of Geophysical Research Atmospheres, 2007, V112, ND19, OCT 11 ARTN: D19306. 08.1-64 Modelling heavy metal fluxes from traffic into the environment Steiner M, Boller M, Schulz T, Pronk W Switzerland Modelling , Meteorology & Atmospheric Sciences A new method is presented which allows emissions of traffic into the environment to be described as a function of road distance. The method distinguishes different types of emissions (runoff, spray and drift), which are determined by measurements and mass balances of a specified road section. The measurement of two-dimensional pollutant concentrations in the road shoulder is an important part of the method. In a case study performed at Burgdorf, Switzerland, the method was applied to the determination of the spatial distribution of heavy metal emissions. The results show that between 36 and 65% of the heavy met-
Global Change Abstracts – The Swiss Contribution | Atmosphere 61 als Cd, Cr, Cu, Ph and Zn are present in runoff and spray and between 35 and 64% are dispersed diffusely in the environment (defined as drift). The runoff infiltrates into the vegetated road shoulder up to a distance of approx. 1 m from the road. The distribution of spray shows a maximum at 1 m and decreases steadily up to a distance of 5 m. This information can serve as a basis for the quantitative evaluation of road-runoff treatment scenarios. Although the results of the Burgdorf study are case- specific, several general guidelines for the reduction of traffic- related emissions can be derived from it. Journal of Environmental Monitoring, 2007, V9, N8, AUG, pp 847-854. 08.1-65 Ultrafine (aerosol) particles and their agglomerate and aggregate - revised international measuring convention Steinle P Switzerland Meteorology & Atmospheric Sciences , International Relations Gefahrstoffe Reinhaltung der Luft, 2007, V67, N6, JUN, pp 243-245. 08.1-66 Light induced conversion of nitrogen dioxide into nitrous acid on submicron humic acid aerosol Stemmler K, Ndour M, Elshorbany Y, Kleffmann J, Danna B, George C, Bohn B, Ammann M Switzerland, France, Germany, Egypt Urban Studies , Meteorology & Atmospheric Sciences The interactions of aerosols consisting of humic acids with gaseous nitrogen dioxide (NO 2) were investigated under different light conditions in aerosol flow tube experiments at ambient pressure and temperature. The results show that NO 2 is converted on the humic acid aerosol into nitrous acid (HONO), which is released from the aerosol and can be detected in the gas phase at the reactor exit. The formation of HONO on the humic acid aerosol is strongly activated by light: In the dark, the HONO-formation was below the detection limit, but it was increasing with the intensity of the irradiation with visible light. Under simulated atmospheric conditions with respect to the actinic flux, relative humidity and NO 2-concentration, reactive uptake coefficients gamma(rxn) for the NO 2 -> HONO conversion on the aerosol between gamma(rxn) < 10(-7) (in the dark) and gamma(rxn)=6x 10(-6) were observed. The observed uptake coefficients decreased with increasing NO 2-concentration in the range from 2.7 to 280 ppb and were dependent on the relative humidity (RH) with slightly reduced values at low humidity (< 20% RH) and high humidity (> 60% RH). The measured uptake coefficients for the NO 2 -> HONO conversion are too low to explain the HONO-formation rates observed near the ground in rural and urban environments by the conversion of NO 2 -> HONO on organic aerosol surfaces, even if one would assume that all aerosols consist of humic acid only. It is concluded that the processes leading to HONO formation on the Earth surface will have a much larger impact on the HONO-formation in the lowermost layer of the troposphere than humic materials potentially occurring in airborne particles. Atmospheric Chemistry and Physics, 2007, V7, N16, pp 4237-4248. 08.1-67 Impact of scale and aggregation on the terrestrial water exchange: Integrating land surface models and Rhone catchment observations Stöckli R, Vidale P L, Boone A, Schär C Switzerland, USA, England, France Modelling , Meteorology & Atmospheric Sciences , Hydrology Land surface models (LSMs) used in climate modeling include detailed above- ground biophysics but usually lack a good representation of runoff. Both processes are closely linked through soil moisture. Soil moisture however has a high spatial variability that is unresolved at climate model grid scales. Physically based vertical and horizontal aggregation methods exist to account for this scaling problem. Effects of scaling and aggregation have been evaluated in this study by performing catchment- scale LSM simulations for the Rh ne catchment. It is found that evapotranspiration is not sensitive to soil moisture over the Rhone but it largely controls total runoff as a residual of the terrestrial water balance. Runoff magnitude is better simulated when the vertical soil moisture fluxes are resolved at a finer vertical resolution. The use of subgrid-scale topography significantly improves both the timing of runoff on the daily time scale (response to rainfall events) and the magnitude of summer baseflow (from seasonal groundwater recharge). Explicitly accounting for soil moisture as a subgrid- scale process in LSMs allows one to better resolve the seasonal course of the terrestrial water storage and makes runoff insensitive to the used grid scale. However, scale dependency of runoff to above-ground hydrology cannot be ignored: snowmelt runoff from the Alpine part of the Rh ne is sensitive to the spatial
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