EXERCISE 1:

The First European Tracer Experiment (The Advection)

Model used: Enviro-HIRLAM and SILAM
        (Enviro-HIRLAM is based on the DMI version of the HIRLAM - HIgh Resolution Limited Area Model)

Teachers: Mikhail Sofiev (FMI, Finland), Sergey Smyshlyaev (RSHU, Russia), and Allan Gross (DMI, Denmark)

Group 1.1:
Brian Sørensen (Denmark), Georgiy Gadzhiev (Bulgaria), Olga Patlina (Russia), Polina Zimenko (Russia), Ekaterina Mekruykova (Russia)    

Group 1.2:
Ayoe Buus Hansen (Denmark), Gantuya Ganbat (Russia), Konstantin Konstantinov (Russia), Maxim Motsakov (Russia), Mirjam Paales (Estonia)

Introduction Background:
The transfer of a property of the atmosphere, such as heat, cold, humidity, gasses and aerosols by the horizontal movement of an air mass is called advection. Advection is responsible for this transfer, not only on microscale and mesoscale environments, but also on the synoptic and global scale environments. A major problem in atmospheric chemical aerosol transport models is how to solve the differential equation of advection. Many different numerical solutions have been proposed over the years and different numerical advection schemes has been tested in Enviro-HIRLAM (Korsholm et., 2008) and SILAM against the First European Tracer EXperiment (ETEX-1) e.g. the semi-Lagrangian (Lauritzen, 2005), the Bott (Bott, 1989ab), Cell-Integrated Semi-Lagrangian (CISL) (Lauritzen, 2005), etc. schemes.
ETEX-1 will be the baseline for this exercise (Nodop et. al., 1998). ETEX-1 was a control passive point source release started on 23 October 1994, 16:00 UTC and ended on 24 October 1994, 03:50 UTC. The release site was located at Monterfil (2○ 00’30’’ W; 48○03’30’’ N; 90 m above sea level (asl)).

Main Goal:
The goal of the exercise is to study how different numerical advection schemes, model resolution and point source release heights affect the dispersion pattern of a tracer. During 1-ETEX measurements were conducted at 168 ground-level sampling stations in Europe (Dop et. al., 1998; Nodop et. al., 1998). Therefore, the model simulations can also be compared with measurements.

Specific Objectives:  
We consider simulations of the ETEX-1 tracer release and the subsequent transfer and dispersion. Group 1.1 will use the on-line model Enviro-HIRLAM and Group 1.2 will use the off-line model SILAM. In all the simulation a time step of 10 minutes will be used.  
1)    Test of advection schemes. First, write down the numerical advection schemes you will use in this exercise and discuss whether they are linear or nonlinear, implicit or non-implicit etc. and what does this mean from a numerical point of view. Second, run the model at 40×40 km2 using different numerical advection schemes. For Enviro-HIRLAM: the semi-Lagrangian (Lauritzen, 2005), Bott (Bott, 1989ab) and CISL (Lauritzen, 2005) schemes, for  SILAM the Lagrangian and SCD Eulerian ones. Validate the simulations results against measurements from B05, D44, CR05, DK02 and H02, see table below.
2)    Test of model grid resolution. Select the CISL for Enviro-HIRLAM and SCD Eurlerian scheme for SILAM and run the models at different grid resolutions (5×5 km2, 10×10 km2 20×20 km2 40×40 km2). Validate the simulations results against measurements from B05, D44, CR05, DK02 and H02, see table below.
3)    Test the sensitivity of point source release height. Select a grid resolution of 40×40 km2 and vary the point source release height: 90, 300, 500m, 1000m and 2000 m asl.
4)    Summaries the results form the simulations in form of an oral presentation (max. 15 min.). The validation shall include a calculation of normalized mean square error, bias, correlation etc.

CC

Station name

Latitude

Longitude

Altitude

B05

Uccle

50.48 

4.21

104

D44

Trier-Petrisberg

49.45

6.4 

273

CR03

Koksijde

51.05

2.39

4

DK02

Albuen

54.5

10.58

2

H02

Gyor

47.42

17.41

116


Literature List:
The students in both groups shall read these papers before the Summer School.

REQUIRED READINGS:

Korsholm U.S., A. Baklanov, A. Gross, A. Mahura, B.H. Sass and E. Kaas, 2008: Online coupled chemical weather forecasting based on HIRLAM – overview and prospective of Enviro-HIRLAM. HIRLAM Newsletter. 54: 1-17.
Sofiev M., Siljamo, P., Valkama, I., Ilvonen, M., Kukkonen, J. (2006) A dispersion modelling system SILAM and its evaluation against ETEX data. Atmosph.Environ. , 40, 674-685, DOI:10.1016/j.atmosenv.2005.09.069
Lauritzen P.H., 2005, An inherently mass-conservative semi-implicit semi-Lagrangian model. PhD-thesis, kap. 2: 15-40.
Bott A., 1989a: A positive definite advection scheme obtained by non-linear renormalization  of the advection fluxes. Mon. Wea. Rev. 117: 1006-1015.
Sofiev, M. (2000) A model for the evaluation of long-term airborne pollution transport at regional and continental scales. Atmospheric Environment. 34, No.15, pp. 2481-2493
Nodop K., R. Connolly and F. Girarardi, 1998: The field campaigns of the European tracer experiment (ETEX): overview and result. Atm. Env. 32(24): 4094-4108.

ADDITIONAL READINGS:

Bott A., 1989b: Reply. Mon. Wea. Rev. 117: 2633-2636.
Dop H.V., R. Addis, G. Fraser, F. Girardi, G. Graziani, Y. Inoue, N. Kelly, W. Klug, A. Kulmala, K. Nodop and J. Pretel, 1998: ETEX: A European tracer experiment; observations, dispersion modelling and emergency response. Atm. Env. 32(24): 4089-4094.