Release Level	5.4
	Release Date	2008 10
	Revision Level	1.0

Last modified on:   Monday, 20-Jul-09 14:03 CEST

Model scenarios

An emission scenario is a dynamically instantiated OBJECT, similar to the emission inventories, but model specific, which includes a START TIME and a DURATION, as well as a choice of pollutant for the emission data sets. The elements of a model scenario include:

1. Spatial extent or model domain due to computational requirements, this implies the possible model (grid) resolutions and, indirectly, the feasible range of duration of a model run. Time step (for model output, internal time steps for dynamic models are derived from computational stability requirements of the respective numerical solvers) is closely related, but is largely determined by the temporaral variability of the processes simulated.

   The choice of location or area of interest constrains the set of applicable

   • Meteorological scenarios that requires a set of consistent parameters (timew series of fileds) the latter being pre-processed dynamically based on the applicable model grid resolution and for the model domain selected.

     Depending on the model implied by the choice of domain, this implies meteorological data either as (time series) of scalar values, or dynamic fields (time series of matrices) in one or more vertical layers.

2. Time and duration: together with the location and extent, a scenario is defined by the start date/time and duration for the simulations. This, in turn is constrained by the model chosen which will will either represent
   • a sequence of hourly stetady-state solutions (AERMOD),
   • an individual meteorological event with a one hour averaging time (Convolution/traffic)
   • a short-term (2-6 hours) dynamic and highly transient event (MULTI-PUFF)
   • a daily cycle at helf-hourly resolution (PBM)
   • a 48 hour scenario at hourly resolution (CAMx).
   The choice of model and its pollutant emission requirements as well as the implied duration and temporal resolution defines the:
   • Emission scenario: this is dynamically derived from all sources in the shared emission inventory within the spatial (domain) and temporal scope of the model scenario.

Dynamic Emission Scenarios

The emission pre-processing includes:

1. Pollutants: definition of a model specific list of pollutants for data are required;
2. Sources identification of all sources located within the model domain.
3. Temporal patterns: extraction of the emission data for the substances required and the period of interest (model start date/time and duration);
   The data used can either be:
   • Derived from a time series of emission observations if it overlaps with the model period;
   • Derived from the average emission value for each pollutant of concern and adapted to the model period by means of the temporal correction factors for month, day of the week, and hour of the day;

   the values extracted for point sources from the emission inventory are then adjusted with the multipliers and additive term optionally specified by the user for each source/pollutant combination.

Emission scenarios cover two basic formats:

1. Stack data (time series)
2. Gridded data (small stacks, area sources, traffic for CAMx), also as time series.
3. Line sources (used explicitly in the convolution model, gridded for CAMx).

Please note: to keep the models consistent and ensure reasonable operation, the emisison scenario generated will always include a COMPLETE set of source/pollutant combinations, even if there are no values for any one of the required source/pollutant combinations: thisa will be represented by a value od 0.00 that the user can correct with the additive corrcetion (and possibly a multiplier). By the same token, any given source in the set can be "switched off" with a 0 multiplier.

Scenario display

Hypothetical sources