MISKAM advanced - Version 6 - Microscale Wind Field Modeling & Microscale Dispersion Modeling Software
MISKAM is a highly recommended prognostic microscale wind field and dispersion model to calculate single meteorological steady state conditions. To make it also available for a larger time scale, e.g. for planning purposes, SoundPLAN adds a powerful interface to automat all the input/output work and statistical aggregation needed to create maps of annual statistics.
- The SoundPLAN Meteorological Station Library helps to analyze meteorological data visually and adjust them to your task. As MISKAM is mostly used in dense building structures, where atmospheric stability has few influence, you can easily transform meteorological measurement data to classified data for neutral stability.
- Emission time histograms can be used to calculate average emissions separately for each wind direction sector. That increases the accuracy of annual mean concentrations without loss of time. This advantage has to be seen in view of the fact that a PC is not capable to calculate 8760 separate hours using such a detailed model. A post processing to regard additional emission variation cycles is in preparation.
- SoundPLAN Geodatabase allows importing, digitizing and editing model data via several interfaces or just to use models prepared for SoundPLAN noise calculations. Background bitmaps can be used, e.g. geo-referenced aerial photos.
- The SoundPLAN calculation kernel guides you with a user friendly interface to define the calculation settings and to control the runs. When the calculation is made for neutral stability and without source impulse, SoundPLAN needs only one standard wind field per wind direction calculated by MISKAM. All further wind and concentration fields, for variant wind speeds, are derived by SoundPLAN. MISKAM calculations can be distributed to several kernels on your computer, if enough work space is available. MISKAM optionally runs as 64 bit software. With our module 'Distributed Computing' you can also distribute wind field calculations parallel to several computers.
- The SoundPLAN Graphics module assists preparing outstanding presentation graphics. For MISKAMadvanced a 3D graphic is offered for wind field and concentration map display. You can choose if you want to see the SoundPLAN objects or the grid shaped MISKAM objects. The grid shaped objects show also if underflow is defined.
- Even more, the graphics module also allows to modify data in a post processing by user defined formulas or to combine results of several calculation runs, whatever model was used, and to add additional site map information.
The MISKAM model (microscale climatic and dispersion model) is one of the more sophisticated models with respect to its physical content within a wide range of available models in the world meanwhile. It has been developed at the Institute for Atmospheric Physics at the University of Mainz, Germany. This institute had been working on the development of regional and local climate and dispersion models since many years. The model was vastly verified and validated. The test calculations mainly oriented at the guidelines of the VDI-Code 3783/9 'Environmental meteorology - Prognostic microscale wind field models - Evaluation for flow around buildings and obstacles.'
Model type and field of application
MISKAM is a three-dimensional non-hydrostatic numeric flow and dispersion model for smallest-scale forecasts of wind behavior and pollutant concentrations, for street canyons as well as up to urban quarters. It was originally planned to treat microclimatic problems (Eichhorn, 1989).
MISKAM is suited for dealing with small-scale dispersion processes (typical model dimensions of several 100 m). Therefore, MISKAM is especially useful for tasks in road and urban planning, because it considers mainly the physical processes influencing the transport of pollutants within the direct environment of buildings.
MISKAM is used for more than air pollution calculations. The demand for climate studies on settlement development increases. MISKAM can be used to optimize the ventilation capacity between the buildings. Wind fields for each defined flow situation are calculated and displayed in a map.
Temporal and Spatial Resolution
Typical grid resolutions are 1-2 meters in horizontal direction. In vertical direction the layer thickness also must start very thin and increase steadily. Coarse increasing can be accepted above the buildings. Depending on the building height and the size of the investigation area the typical number of layers is between 20 and 40.
MISKAMadvanced comes along with a 64 bit MISKAM version. This allows, to define bigger, higher or better resolved calculation areas. However, increasing the number of grid cells increases the calculation time. Even if the storage problem of the 32 bit version is solved, the project size will be limited by the borders of acceptable calculation time.
Depending on the domain size, MISKAM wind field calculations need several hours for one wind field. Compromises to speed up a calculation can be made carefully by a coarser meteo classification, but they should never be made by a too coarse calculation grid. There is a 'Best Practice Guideline of the COST Action 732' where recommendations of several authors were collected together in an appendix (see link below).
The SoundPLAN Interface offers point- line- and area sources, roads. Line and area sources can be freely shaped polygons. Road sources are offered as separate object type for graphics etc. and to define the road surface width. Time variant emissions can be entered, but they are only used to calculate the average emission for each wind direction sector. A calculation hour by hour with different emissions costs too much time.
Effective source height can be entered as impulse for the whole source cell volume, but requires much more MISKAM wind field calculations than passive sources.
The pollutant list is completely user defined. It can contain neutral gases or dust defined by sedimentation speed and deposition speed.
For MISKAM calculations the NOx-NO2 conversion is always done concentration dependent in a post processing. Therefore, we recommend deriving extreme values like maximum or high percentiles using statistical derivations based on the annual mean concentrations. In this respect the Graphics module offers formulas for hourly average assessment and daily average assessment according to the current European guideline 2008/50/EC. You also can enter user defined formulas according to your national formula evaluations.
Topography can be entered (to be able to use data from a noise project), but it is not regarded! All SoundPLAN objects are set to a flat except of sources: The difference between terrain and source height is regarded as height above ground.
Calculating a flat area surrounded by slopes is possible, if the wind flow over the area is homogeneous and this flow can be represented by one measurement station. This station then must include already all terrain effects.
Buildings, Obstacles, Landuse
For common use of MISKAM as microscale model for planning purposes obstacles are required! That can be buildings and 'roughness areas' with user defined roughness length.
The soon released Upgrade to MISKAM advanced allows regarding underflow of buildings (Portals, parking lots, bridges) and the flow through of vegetation (m² leave surface / m³ air).
Results are available for each layer of the calculation area.
Single wind fields: Maps of several wind flow parameters like wind speed, wind direction, vertical inclination of wind direction.
Wind field statistics for the calculated time period: mean, min, max of wind speed, cases above or below a certain wind speed, counted as hours or as percent.
Single concentration fields: Maps of concentration and deposition
Concentration field statistics for the calculated time period: Mean concentration, max concentration, concentration percentile, hours/percent above/below a concentration threshold.
Grid operations are available for concentration maps, e.g to derive daily and hourly statistics from annual means by predefined functions or user defined formulas (both using empirical derivations).They are not available for wind field maps.
MISKAMadvanced objects can be displayed optionally as real-shaped SoundPLAN-Objects or as grid-shaped MISKAM objects. Also profile cross sections are then offered.