H. Kromp-Kolb

Interpolation Errors in Wind Fields as a Function of Spatial and Temporal Resolution and Their Impact on Different Types of Kinematic Trajectories

Abstract This paper discusses some of the uncertainties that influence kinematic trajectory calculations. The interpolation errors due to different interpolation schemes are examined by degrading high-resolution wind fields from a numerical weather prediction model with respect to space and time. Under typical circumstances, the greatest errors are due to temporal interpolation, followed by horizontal and vertical interpolation. Relative errors in the vertical wind are higher than those in the horizontal wind components. These errors are quite substantial and severely affect the accuracy of trajectories. For instance, a decrease of the temporal resolution from 3 to 6 h leads to average relative interpolation errors of 16% in the horizontal wind components and 40% in the vertical wind component. These errors cause mean transport deviations of 280 km for two-dimensional model-level trajectories and 600 km for three-dimensional trajectories after 96-h travel time. The substantial deviations for three-dimensi...

A European inventory of soil nitric oxide emissions and the effect of these emissions on the photochemical formation of ozone

Abstract An inventory of soil nitric oxide (NO) emissions for Europe was developed. The emission of NO was parameterized using empirical relationships with type of landuse, fertilization rate of agricultural areas and soil temperature. For the year 1994, it was estimated that annual soil NO emissions in the inventoried area amounted to 535 kt NON yr−1, i.e. 8% of the emissions from combustion processes. On a hot summer day, this fraction increased to 27%. The uncertainty of these emission estimates, however, is high. They are accurate only within a factor of three to four. As the major fraction (in summer 81 %) of the emissions came from arable land, soil NO emissions have to be considered as largely anthropogenic. Large regional differences existed in the soil NO emission rates with the highest emission rates found in southern and western Europe, intermediate rates in eastern Europe and the lowest rates in Scandinavia and northern Russia. The effect of the soil NO emissions on the photochemical formation of ozone (03) was investigated with a one-dimensional photochemical model. When soil NO emissions were considered in the model simulations, computed mean daily maximum 03 concentrations over Europe from June to August 1994 were 4 ppb (uncertainty range: 1.4–9.6 ppb) higher than without these emissions. Reductions of pyrogenic NOx, emissions were less efficient in reducing O3 concentrations when soil NO emissions were taken into account.

Trajectory Analysis of High-Alpine Air Pollution Data

The EUROTRAC subproject ALPTRAC (High Alpine Aerosol and Snow Chemistry Study) is devoted to the investigation of air and snow pollution at high Alpine sites. The aerosol surface concentration is continuously recorded at Jungfraujoch (3450 m a.s.1., 7° 59’E, 46° 32’N) in the Swiss Alps and Sonnblick (3106 m a.s.1, 12° 57’E,47° 03’N) in the Austrian Alps with a time resolution of 30 min with an epiphaniometer (Gaggeler et al., 1989; Baltensperger, et al. 1991). The measurements showed a pronounced seasonal cycle with mean summer concentrations more than one order of magnitude higher than mean winter concentrations, and the occurrence of episodes with especially high or low concentrations (Seibert et al., 1993). While the seasonal cycle is mainly to be explained by the atmospheric stability, the short-term variations are caused by synoptic-scale transports. These have been investigated using isobaric back trajectories at 700 hPa with a length of 72 h, computed twice daily for a period of three years (July 1990 - June 1993). Due to technical problems at Sonnblick, only 925 trajectories were available for the analysis; most of the missing data fall on winter.

Origin of ozone in Vienna and surroundings, Austria

Abstract A statistical analysis of local scale ground-level trajectories during three summer half years was made to determine the influence of Vienna on the ozone concentrations in the surroundings. It was possible to show that on average, Vienna does not act as an ozone source for sites in the surroundings. Only on the hottest days of each year around noon is it a strong source of ozone. Therefore, long-range transport of ozone must be important for the average ozone concentrations. This was investigated by a statistical analysis of isobaric backward trajectories. In summer, high ozone concentrations in Vienna and surroundings are often associated with trajectories arriving from areas in Europe which agree reasonably well with those having high anthropogenic emissions of precursors. In winter, an important source of ozone in eastern Austria is transport from the Atlantic Ocean. Tropospheric background ozone concentrations in Vienna and surroundings were estimated from surface measurements during periods of high wind speed. A mean summertime tropospheric background concentration of 30–40 ppb ozone was found for air masses of maritime origin, while it was 70–75 ppb for continental air masses.

The research project VOTALP – general objectives and main results

Abstract The research project “Vertical ozone transports in the Alps” (VOTALP), conducted between 1996 and 1998, investigated mechanisms that cause increased ozone concentrations in the Alps, focusing on vertical transport processes. The major aim of the project was to deepen our understanding of dynamics and chemistry of ozone in mountainous areas.

Requirements for the completeness of ambient air quality data sets with respect to derived parameters

Abstract Monitoring and sampling of air quality data is costly and labor intensive. The necessary efforts increase progressively with increasing accuracy requirements. Also loss of data because of instrument break down, data transmission failure, or service and calibrating procedures is more or less unavoidable. Calculation of characteristic parameters like means or percentiles as necessary for information compression and also for comparison with air quality standards do not require complete data sets, since successive primary data like half-hour means are not independent from each other. Emission patterns and periodically reappearing or comparably slowly changing transmission conditions are responsible for autocorrelation of these data. Using air quality data from the Austrian public monitoring networks for various air pollutants (NO 2 , SO 2 , CO, O 3 ) over the last decade various patterns of data loss are simulated and used to compute air quality parameters (fractiles, semi-annual means, daily means). The variation interval of these parameters is compared to equivalent parameters resulting from the complete data sets. Furthermore, autocorrelation functions of these data are calculated and discussed briefly. Finally, the applicability of the parameters obtained from truncated data sets for air quality management decisions is discussed and compared to the Austrian standard. The results indicate an error of a few percent — depending on the type of data loss — if these parameters are computed from incomplete data sets up to 50% data loss. Thus reduction of monitoring efforts without substantial loss of information is possible.

Estimating the uncertainty of a Lagrangian photochemical air quality simulation model caused by inexact meteorological input data

Abstract A deterministic Lagrangian photochemical air quality simulation model was developed at the Institute of Meteorology and Physics in Vienna. As the analysis of model uncertainty is an important part of the validation strategy, a local sensitivity and a global uncertainty analysis for model output was done. The effects of meteorological input and physical parameterisations on the model output were studied, whereas uncertainties arising from emissions and chemistry will be studied in a later stage of the model validation. As a result of the analysis, distribution density functions and vertical distributions of uncertainty in the model boxes for the chemical species ozone (O 3 ), nitrogen dioxide (NO 2 ), hydrogen peroxide (H 2 O 2 ) and peroxiacetylnitrate (PAN) were obtained. It turned out that ozone is one of the least sensitive and uncertain species in the model. Only as far as nighttime simulations in the lowest two model boxes are concerned were the uncertainty of simulated ozone concentrations considerable. A clear weather pattern dependence of uncertainty has been detected. Highest model output variations for ozone, nitrogen dioxides and hydrogen peroxide are observed during weather situations with strong westerly winds.

Modelling global radiation in complex terrain: comparing two statistical approaches

Two simple approaches for assessing global radiation in complex terrain are tested and compared. A parameterisation scheme for global radiation based on cloud cover observations was compared with interpolation of measured global radiation values from the Austrian climate observation network. Interpolation appears to be a useful method for a station density which has been available after 1992 in Austria (about 1000 km2/station). In that case interpolation is superior to parameterisation. The quality of interpolated data quickly drops with height and for elevations above 1500 m neither method delivers useful results.

Evaluation Of A Regional Scale Model For The Alpine Region With Data From The VOTALP Project

One of the VOTALP key questions is dedicated to the influence of stratospheric intrusions on the ozone concentrations at the Alpine peak level. Measurements of ozone, beryllium-7 and other components are made at a number of mountain peak sites. In addition LIDAR measurements are used A tropopause folding event in May/June 1996 has been selected to study the relevant processes in more detail (Feldmann et a/., 1998). Model calculations are performed to estimate the fluxes of ozone into the Alps during the episode.

Occurrence of nitric acid and related compounds in the Northern Vienna basin during summertime anticyclonic conditions

Abstract Atmospheric concentrations of ozone, nitric acid and particulate nitrites were measured during photochemically active periods in summer 1986 and 1987 near Vienna, Austria. Field data were taken on tower stations at different levels. On a summit 575 m asl and 10 km downwind of Vienna peak 4-h averages of 139 ppb ozone, 5.1 ppb nitric acid and 3.3 ppb ammonium nitrate were recorded in the urban plume at noon. Eighty-six per cent of daytime concentrations of ozone and 66% of daytime nitric acid were found to be present in the consecutive night in the mixed layer above an inversion indicating that it can act as a reservoir for reactive photochemical pollutants. In the late evening hours a slight increase in concentration of HNO 3 was observed at tower stations, which can be attributed to a nighttime formation.