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Work Programme VOTALP II
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 1. TITLE
Vertical ozone transports in the Alps II (Acronym VOTALP II)
 

2. WORK CONTENT

2.1 OBJECTIVES AND GOALS

The proposed project "Vertical Ozone Transports in the Alps II" (VOTALP II) is a contribution to the research tasks of areas 1.2.1.2. and 1.2.1.1. of the EU work program on Environment and Climate, edition 1996. It is a follow-up project of VOTALP (hereafter referred to as "VOTALP I"), funded by the EC under Framework Programme IV, contract Nr. ENV4-CT95-0025. It is the aim of VOTALP II to make best use of the insights gained so far, continuing the work on some topics, applying methods and models developed during VOTALP I and investigating new important questions that arose from VOTALP I.

In mountainous regions, the vertical exchange between the boundary layer and the free troposphere is enhanced, leading to a stronger venting of pollutants, such as NOx, into the free troposphere. Since the efficiency of ozone production per molecule of NOx is higher for low NOx concentrations (free troposphere) than for high NOx concentrations (polluted boundary layer), the increased vertical exchange in the Alpine area may enhance the ozone formation, averaged over both the boundary layer and the free troposphere. This motivates the fundamental question of VOTALP II:
 

What is the effect of the strong vertical exchange over the Alps on the ozone concentrations in the Alpine region and in Europe as a whole?

Before an answer to this question can be tried, different processes have to be understood:

Local ozone production in Alpine valleys

For a valley intensively studied during VOTALP I, the effect of emission reductions shall be investigated using Eulerian and Lagrangian model simulations.

Climatology of ozone influx from the stratosphere

Stratospheric ozone regularly reaches the Alps during tropopause folding events. Some intrusions are being studied in VOTALP I, but a longer time period is needed for a climatological assessment. It is intended to develop a "stratospheric intrusion index" to identify stratospheric intrusions using only routinely available data.

New aspects of vertical exchange between boundary layer and free troposphere

During VOTALP I, the vertical exchange processes due to valley winds and slope winds in an Alpine valley were studied. The exchange above Alpine foothills is completely different from that in valleys, but might be of similar magnitude. Boundary layer tops are higher above hills than above valleys in between and therefore boundary layer air and free tropospheric air might coexist at the same altitude. Two measurement campaigns are devoted to study this effect.

Advection of urban plumes into the Alps

The chemistry and dynamics of urban plumes are reasonably well understood, but their interaction with topography is not well documented, although their impact on the Alpine region could be of importance for the ozone formation in Europe. A large existing data set of aircraft measurements and Eulerian model simulations will be used to study the advection of the urban plumes of Milano, Munich and Vienna.

The Alpine effect on the European ozone concentrations

An assessment of the effect of enhanced vertical pollutant transport on the European scale will be attempted using different model studies. Eulerian model simulations with treatment of chemical reactions will be used to understand and quantify the relevant processes. A half-year Lagrangian particle dispersion model simulation with particle releases in high-emission areas close to the Alps will be performed to study whether, how often and where pollutants transported into the free troposphere above the Alps are fumigated back into the boundary layer above Europe. Combining the results from this climatological approach that only accounts for the pollutant dynamics, but not for chemical reactions, with the results from the case studies with full treatment of chemical processes will give a tentative estimate of the effect of the Alps on European ozone concentrations.

2.2 PROJECT METHODOLOGY

The project VOTALP II is divided into five work packages. Each work package is broken down into activities which are further divided into tasks. For each task, an acronym representing the responsible institution is given in italic letters in brackets.

2.2.1 Package I: Local ozone production in Alpine valleys

2.2.1.1 Activity 1: Scenario calculations for the Mesolcina Valley

In VOTALP I, simulations of the flow and the photochemistry in the Mesolcina valley, Switzerland, were performed (FhG) using a Eulerian photochemical model. These simulations are being validated with the experimental data from the VOTALP I valley campaign (summer 1996). Based on the experience gained, additional modelling studies are done.

The high resolution VOC emission inventory for the valley is checked by comparing model simulations and VOC measurements available from the campaign (FhG, FKKT). Having tested the reliability of the inventory further Eulerian model simulations are made on a grid of about 0.5 km horizontal resolution (FhG). The simulations deal with specific emission reduction scenarios. Special emphasis is given to traffic reduction scenarios for the motorway N13 which passes this valley along its main axis. Another scenario simulation is done to estimate the influence of biogenic VOC emissions on the local photooxidant production (photochemical ozone creation potentials) by switching off the biogenic sources of VOCs.

2.2.1.2 Activity 2: Long-term model simulations for Alpine valleys

To get a climatological assessment, the single case studies for the Mesolcina Valley done in activity 1 are supplemented using a Lagrangian photochemical box model (IMP). The computational efficiency of the Lagrangian box model concept permits the investigation of ozone formation and transport during one summer.

In VOTALP 1, the applicability of the Lagrangian box model concept in complex terrain is studied. A photochemical box model is combined with a boundary layer model developed especially for complex terrain. Three scales of the transport processes have to be considered, namely the transport towards the Alpine region, the transport across the foothills to the valley entrance and the transport within the valley. The model performs well for long-range simulations, is being evaluated for the valley entrance, but the concept might bring about problems within the valley. Therefore, different concepts have to be tested to overcome the problems. Using the experience gained in VOTALP I, a Lagrangian box model concept is developed, which remains valid as a reasonable approximation even within a valley (IMP). The box model is evaluated by comparing simulated ozone concentrations with measurements at the entrance of the Mesolcina Valley as well as within the valley or at the slopes for one summer season (IMP). Using the validated Lagrangian model, emission reduction scenarios are calculated for one summer, giving a climatological assessment of the impact of changing emissions during different weather patterns (IMP).

2.2.2 Package II: Climatology of ozone influx from the stratosphere

2.2.2.1 Activity 1: Continuation of measurements and data analyses

During VOTALP I, stratospheric intrusion events have been identified in the Alps and in the Apennines. They were characterised by a great complexity of the meteorological conditions. Three-dimensional back trajectories and measurements of 7Be concentrations at Alpine peak observatories confirmed the stratospheric origin of the air. Because of the relevance of stratosphere-troposphere exchange for tropospheric ozone budgets in the Alps, the following measurements and analyses are continued in VOTALP II: Stratospheric intrusion episodes are identified and analysed using measurement data and trajectories (FhG, CNR). The yearly variation of the frequency and intensity of stratospheric intrusions is investigated using satellite data of water vapor and total ozone column (CNR). An estimation of the downward flux of ozone is attempted (FhG, IGM-K). Based on four years of lidar and Zugspitze data, the fraction of stratospheric intrusions which reach Alpine summits is quantified (FhG).

2.2.2.2 Activity 2: Stratospheric intrusion index

In activity 1, stratospheric intrusion episodes are identified. To supplement this activity, measured ozone concentrations at mountain peaks and in the plains within and near the Alps are investigated during such episodes. Based on the measurements and case studies performed, an "intrusion index" is developed (IMP). This index shall serve as an indicator for stratospheric intrusions or for a strong downward transport from the upper troposphere (large index = intense vertical transport). It will be possible to compute it diagnostically as well as prognostically.

Different approaches to calculate such an index are tested for specific episodes. For this purpose, a Eulerian photochemical model version with high vertical resolution in the tropopause region and with detailed treatment of boundary layer chemistry and transport processes is set up (IGM-K). Calculations are done for two different episodes. If these simulations show that the index is a reliable indicator of stratospheric influence, it can be applied to assess the reliability of tropospheric and boundary layer chemistry models. Using this index, the seasonal variation and climatological importance of troposphere-stratosphere exchange in the Alpine region is investigated (IMP).

2.2.3 Package III: New aspects of vertical exchange between the boundary layer and the free troposphere - Enhanced vertical mixing due to Alpine foothills

The mechanism of vertical exchange above Alpine foothills is different from that in the Alps. For moderately steep hills, the mixing layer depth follows the topography. Free tropospheric air and boundary layer air coexist at the same altitude above sea level. If the wind in the free troposphere does not follow the terrain that closely, it might push into the boundary layer above the hills. In combination with turbulence, lee waves, rotors and thermally driven local circulation systems, there should be enhanced vertical mixing. The vertical exchange is much stronger than in the plains and pollutants are transported to higher altitudes. Two measurement campaigns are conducted to investigate vertical pollutant fluxes in the Alpine foothills and the advection of urban plumes into the Alps, one for the southern side of the Alps (Milano-plume), one for the northern side (Munich-plume).

On at least two days aircraft measurements are done (MetAir) that follow north-south cross sections between the urban areas and the Alps. A high temporal resolution of 0.2 seconds is achieved for H2O, CO2, NO2, O3 and vertical wind measurements, allowing eddy correlation analyses. Ozonesoundings are done using a mobile sounding system instrumented with GPS (PSI). O3 and aerosol measurements with a ozone lidar/Doppler sodar system are provided (FhG) at different places between the source regions and the Alps to derive the ozone fluxes. Complementary trace gas (e.g., O3, NO2, SO2, CO, N2O) measurements are carried out with a mobile FTIR/DOAS system (FhG). For the Munich-plume data from the stationary lidar in Garmisch and the monitoring stations Garmisch/Wank/Zugspitze are provided as additional information (FhG). On-line measurements of meteorological parameters, O3, NO, NO2, J(NO2) and VOC are performed at two ground stations, one close to the urban area and one in the foothills (FKKT). Additional off-line VOC measurements are performed for better VOC characterisation (FKKT).

Using the results of the campaigns, a budget analysis is done (PSI, FhG, FKKT). Aircraft data are used to calculate vertical fluxes of water vapor, CO2, O3 and NO2. The horizontal advection of the measured species is calculated. The boundary layer budget is analysed by combining aircraft data with boundary layer heights derived from radiosoundings using a boundary layer model. The boundary layer top entrainment is calculated from the buoyancy flux (PSI). The entrainment is compared with the entrainment over the Po Valley and the Alpine region (Mesolcina Valley and surrounding).

2.2.4 Package IV: Advection of urban plumes into the Alps

2.2.4.1 Activity 1: Analysis of existing data

From 1991 onwards, several measurement campaigns have been conducted by MetAir. The urban plumes of Milano, Munich and Vienna were investigated. This data set is an important basis for studying urban plumes with respect to their impact on the Alpine region. It has never been made available or investigated as a whole. It is compiled and transformed into a single format (MetAir). Statistical investigations are done on the intensity of the plumes, their horizontal extent, on horizontal and vertical flux estimates and the relevance for the Alpine region, taking into account the climatological frequency of the occurrence of fair weather conditions during the whole summer season (IMP, PSI).

Another interesting existing data set consists of the measurements at the Garmisch (740 m) - Wank (1780 m) - Zugspitze (2962 m) sites in Bavaria. For Zugspitze, the records comprise O3, CO, CO2, CH4 NO, NO2, 7Be and natural radioactivity. For Wank they comprise O3, CO2, NO, NO2, SO2 and CO (for a few months only). For Garmisch, O3, NO, NO2 and SO2 are available. This data set and the meteorological data are made available from 1990 onwards (FhG). A data analysis is done aiming at a detailed characterisation of the individual air masses (oceanic, subtropical, stratospheric, regional influence) reaching the measurement stations and a classification of the respective O3 concentrations with respect to background levels, advection of air masses with photochemically enhanced O3 levels or O3 loss due to pollution. The frequency of occurrence of the different air masses and the differences between the respective ozone and precursor concentrations is studied climatologically (FhG). This work is supplemented by analyses of back trajectories and classifications of general weather types (IMP). Especially, a climatological estimate of the contribution of Munich to Alpine pollutant concentrations is aimed at.

2.2.4.2 Activity 2: Modeling the contribution of urban plumes to Alpine valleys

The effect of emission reductions in the Milano area and the Po Valley on the pollutant concentrations at the entrance of the Mesolcina Valley, Switzerland, is investigated using a Lagrangian photochemical model (IMP, PSI). Due to the advantages of Lagrangian modelling, these calculations are performed not only for single cases, but for one summer. The effects of abatement strategies in the major emission areas south of the Alps is compared to the effects of reductions achieved within the valley (see also Package 1, Activity 2). For one episode, emission reduction scenarios for the Milano area and their effect on the pollutant concentrations in the Mesolcina Valley are calculated using an Eulerian modelling approach. One scenario is based on the assumption "No emissions in the Po Valley" to yield the maximum possible effect (FhG).

One interesting episode of pollutant advection towards the Alps from Milano or Munich is selected for detailed budget calculations. The modelling is done using a Eulerian modelling system based on the MM5 mesoscale meteorological model (IGM-K). The chain of processes occurring during the advection from the source area to the receptor region is studied in detail. This includes emissions, chemical transformation and horizontal and vertical transport of photooxidants. A passive tracer is advected to understand the transport. Emission scenarios are calculated to estimate the effects of abatement strategies for the source regions on the concentration levels in the Alpine region.

2.2.5 Package V: The Alpine effect on the European ozone concentrations

2.2.5.1 Activity 1: Summer ozone budgets

During VOTALP I+II, many important processes affecting ozone concentrations in the Alpine region have been studied. Based on episodic studies with a Eulerian model, quantitative estimates of the effects of the various processes for the overall ozone budget (three dimensional) are made (IGM-K). In order to investigate the climatological importance of different processes for atmospheric trace gas concentrations, the budget analysis is not restricted to typical summer episodes, but extended to other weather patterns, for instance episodes with intrusions of stratospheric ozone. To allow for a sound climatological assessment, a classification of different interesting weather patterns for the selection of episodes is done (IMP).

2.2.5.2 Activity 2: Effects of the Alps on the European ozone concentrations

Mountains act as barriers to the flow and produce enhanced vertical transport. In the Alps, pollutants are diluted over a larger volume and chemical processes differ from those in the flatlands. Increased vertical mixing, leading to a redistribution of ozone precursors, may cause an increase in the production rate of ozone averaged through the troposphere. Therefore, higher ozone levels should occur in the free troposphere above Europe than what would be the case without the Alps.

Using the knowledge from VOTALP, the importance of vertical transports in the Alps for the chemistry of the lower troposphere above Europe is estimated. A model experiment is done (IGM-K) during a period with strong vertical transports. A hypothetical scenario is calculated for which topographical effects are disregarded by flattening the model topography. A comparison of ozone concentrations for this scenario with concentrations for the base case indicates the topographical influence on the ozone formation. Regional differences are investigated as well as the overall effect.

To investigate the dynamics and climatology of air parcels heaved into the free troposphere above the Alps, a half-year Lagrangian model simulation with a continuous particle release in urban areas close to the Alps is done (IMP in close co-operation with IMP-subcontractor LMUM, see section 3). The vertical particle transports in the Alps is parameterized based on the results of VOTALP I+II. Their subsequent fate will be simulated using three-hourly meteorological fields of a numerical weather prediction model (ECMWF). This allows to investigate how frequently pollutant reservoir layers formed above the Alps are entrained into the boundary layer above Europe and thus influence surface concentrations. The areas most affected by this process are identified.

2.2.5.3 Activity 3: Synthesis and open questions

The results obtained during VOTALP I+II are used to summarise the state of knowledge of pollutant dynamics in the Alps. The progress achieved by the VOTALP project group are outlined and questions that deserve further research are identified (all partners).
 

2.3 MILESTONES

Work to achieve the following milestones will be done during the time period indicated by the black bars.
 
Milestone
Year 1
Year 2
Scenario calculations for an Alpine valley
X
X
X
X
X
 
 
 
 
 
 
 
Lagrangian modeling for Alpine valleys
X
X
X
X
X
X
 
 
 
 
 
 
Measurements at mountain tops
X
X
X
X
X
X
X
X
X
X
X
X
Stationary lidar measurements
X
X
X
X
X
X
X
X
X
X
X
X
Stratospheric intrusion index
 
 
 
 
X
X
X
X
X
X
 
 
Alpine foothills: Milano campaign
 
X
X
 
 
 
 
 
 
 
 
 
Alpine foothills: Munich campaign
 
 
 
X
X
 
 
 
 
 
 
 
Urban plumes: analysis of existing data
X
X
X
X
X
X
X
X
 
 
 
 
Urban plume modeling
 
 
 
 
 
 
X
X
X
X
 
 
Calculation of summertime ozone budgets
 
 
 
X
X
X
X
X
X
X
X
 
Effects of the mountains: Eulerian model experiment 
 
 
 
 
 
 
 
 
 
X
X
X
Effects of the mountains: Lagrangian model simulation 
 
 
 
X
X
X
X
X
X
X
X
X
VOTALP II database
X
X
X
X
X
X
X
X
X
X
X
X
VOTALP II synthesis
 
 
 
 
 
 
 
 
 
 
X
X
 

3. ROLE OF PARTICIPANTS

The VOTALP project will be carried out by the following institutions:
 
Acronym
Status
Institutiontitution
IMP Coordinator  Institut fuer Meteorologie und Physik der Universitaet fuer Bodenkultur, Vienna, Austria 
IGM-K Contractor  Institut fuer Geophysik und Meteorologie der Universitaet zu Koeln, Cologne, Germany 
FhG  Contractor Fraunhofer-Institut fuer Atmosphaerische Umweltforschung, Garmisch-Partenkirchen, Germany 
PSI Contractor  Paul Scherrer Institut, Villigen, Switzerland 
FKKT Associated Contractor  Fakulteta za kemijo in kemijsko tehnologijo, Univerza v Ljubljani, Ljubljana, Slovenia 
CNR Contractor  Istituto FISBAT - C.N.R., Bologna, Italy
MetAir Subcontractor of PSI  MetAir AG, Illnau, Switzerland
LRU Associated Contractor  Labor für Radio- und Umweltchemie, Universität Bern, Bern, Switzerland
 
The responsibility of the institutions for the individual research tasks have already been indicated in chapter 2 and will be summarized in this section. All partners are required to deliver a report on their activities to the coordinator 12 months after the start of the project and their contribution to the final report at the end of the project. The final report will be completed and submitted by the project coordinator. All partners have to deliver their measurement data to the coordinator in time and well-documented for use in the VOTALP II database. All partners contribute to the VOTALP II synthesis (work package V, activity 3).

IMP contributes to the work packages I, II, IV and V. Tasks of IMP are the coordination of VOTALP II, modelling of ozone and precursors in Alpine valleys, acquisition of data from Sonnblick and Hohenpeissenberg, calculation of air mass trajectories including potential vorticity, development of a "stratospheric intrusion index", analysis of existing aircraft measurement data and data from Zugspitze, Wank and Garmisch, urban plume modelling using a Lagrangian photochemical model, particle model simulations of the long-range transport of pollutants and the management of the VOTALP II database. The basic concept of the Lagrangian particle model simulations will be set up in cooperation with subcontractor Ludwig-Maximilians University of Munich, Germany (LMUM).

IGM-K participates in the work packages II, IV and V. Tasks are the simulation of stratospheric intrusion episodes to check the stratospheric intrusion index, the simulation of an advection episode of an urban plume towards the Alps, the calculation of ozone budgets for different weather patterns and the set up of an Eulerian model experiment to assess the effect of the Alps on vertical pollutant fluxes. All simulations are done using the EURAD modelling system.

FhG contributes to all work packages of VOTALP II. Tasks are the scenario calculations for the Mesolcina Valley, the measurements at Zugspitze, Wank and Garmisch, the measurement campaigns in the Alpine foothills, a data analysis to investigate the urban plume of Munich and the calculation of emission reduction scenarios for the Milano area.

PSI contributes to all work packages. Tasks are the modelling of ozone and precursors in Alpine valleys, the acquisition of routine data from Jungfraujoch and Payerne, vertical and horizontal budget calculations using the data of the Alpine foothill campaigns and urban plume modelling using a Lagrangian photochemical model. PSI subcontractor MetAir is responsible for aircraft measurements during the Alpine foothill measurement campaigns and makes available existing aircraft measurement data from 1991 onwards.

FKKT participates in the work packages I, III and V. Tasks are the validation of the VOC emission inventory needed for the scenario calculations in the Mesolcina Valley and the set up of ground stations during the measurement campaigns in the Alpine foothills.

CNR participates in the work packages II and V. Tasks are measurements of O3 and CO, decay products of 222Radon, 7Be and 210Pb, UVA and UVB radiation at Mt. Cimone and single-case studies of stratospheric intrusions.

LRU contributes to work package II. Tasks are the measurements of 7Be, Radon and aerosols at Jungfraujoch.
 
 

4. DELIVERABLES AND WORK PLANNING/SCHEDULE

The VOTALP II project lasts for two years.

Contract deliverables:

After one year, a progress report will be provided, describing all activities done so far. At the end of the project, the VOTALP II final report will be supplied, covering detailed reports on the activities of every work package and a detailed synthesis of the results.

Technical deliverables:

Because of the relatively short duration of the project, all technical deliverables will be supplied at the end of VOTALP. The following technical deliverables can be expected:
 
Content of technical deliverable Type
Scenario calculations for an Alpine valley (Eulerian model, Lagrangian model)  model results
Measured data from Alpine peak observatories  data set
Lidar measurements Garmisch data set 
Trajectory data calculated for observatories  data set
Stratospheric intrusion index method 
Measurement campaigns for Alpine foothills data set
Chemical and meteorological data from 3 Bavarian sites since 1990  data set
Existing aircraft measurements data set 
Model studies - urban plumes model results 
Model study - summertime ozone budgets model results
Model experiment - effect of the Alps on European ozone concentrations  model results
Particle model simulation - effects of the Alps on European pollutant levels  model results
VOTALP database database
Access to reports/data/results:

All VOTALP II reports are public. The access to foreground information, especially measurement data and models, is restricted until one year after the ending date of VOTALP II. The publication of data and results during the project has been regulated in a consortium agreement.

5. COMPLEMENTARY PROJECTS

There are not yet any complementary projects.
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Last update: 16 February 1999 by Thomas Gerersdorfer. URL of this page: http://www.boku.ac.at/imp/votalp/wkpr2.html.