CMAQv5.0 Dry Deposition MOSAIC option

Dry Deposition MOSAIC option release notes September 26th 2011

Donna Schwede and Jon Pleim

Currently, CMAQ model deposition outputs are available at the grid scale (typically 12 km). This grid estimate is calculated based on the area-weighted average surface and land use characteristics within the grid. Dry deposition velocities vary with the underlying surface and this information is not available from the typical gridded output. However, ecological applications, such as critical loads, often require knowledge of the deposition to individual land cover types within a grid rather than the grid-averaged value. This new runtime option in CMAQ allows the user to output files of land use category specific values of deposition velocity and flux. The flux for a land use category is the product of the land use category specific deposition velocity and the concentration for the grid cell. Once the MOSAIC runtime option has been selected, the user has the option of additionally outputting a file of stomatal deposition velocity and flux. Since stomatal flux is one of the primary pathways for plant damage, this flux may be useful in ecosystem studies. These land use specific values are for output only and are not used in the mass balance of the model. Therefore, invoking these options does not change the concentration or deposition values for the grid.

Run time configuration

The MOSAIC option is invoked by setting the runtime option CTM_MOSAIC=Y|T. To create the stomatal flux file, the runtime option CTM_FST must be set to Y|T in addition to having set the CTM_MOSAIC option to Y|T. The default configuration for both options is N|F.

Structure of the output files

The output files for the land use specific deposition velocity and flux as well as the stomatal flux are structured with the land use category being the 3rd dimension (i.e. equivalent to the layers in a concentration file). So, for model runs using the NLCD land use category system, the files will have 50 "layers".