This data was submitted by Chris Landreth ( landreth@ncsc.org ) The data was visualized using Volume Visualization in Caustic Sky- an entry in Siggraph '92's Electron Theater... This directory containes a tar file of ten (10) compressed RADM files of SO2 (sulfur dioxide) concentration. Each file is {x, y, z} = {63, 69, 29} in size. They're in C order (z varies fastest). RADM is an environmental model of the U.S. EPA which tracks acid deposition over the eastern U.S. This data is courtesy of the U.S. EPA, AREAL Branch, and the NCSC Visualization Group. For more information, contact Robin Dennis ( rdennis@flyer.ncsc.org ) or Chris Landreth ( landreth@ncsc.org ) Enjoy !! Terry Myerson Vol Vis 92 Dataset Chair This description of the data is from the AVS4 demo suite, and describes a slightly different data set from the same model, fyi - ----------------------------------------------------------------- RADM Description and Description of Demonstration Data Robin Dennis U.S. Environmental Protection Agency The Regional Acid Deposition Model, RADM, was developed under funding from the U.S. Environmental Protection Agency. Development was initiated as part of the federal National Acid Precipitation Assessment Program. RADM is described in detail in Chang et al., 1987; and Chang et al., 1990. RADM covers the geographic domain east of central Texas and western Manitoba, north to James Bay, Canada, east to Nova Scotia and south to the tip of Florida. RADM uses grid cells of 80x80 km and there either are 6 or 15 non-uniformly space layers in the vertical, covering the distance from the ground to approximately 16 km in altitude. The lowest 6 layers of the 15 layer are typically in the planetary boundary layer (from 1-2 kilometers in height) during the day. The lowest layer has a height of 75 m. The modeling structure of RADM incorporates the key physical and chemical processes needed for a more scientifically detailed description of acidic deposition. RADM includes modularized process descriptions for transport (horizontal and vertical, including the influence of clouds), gas-phase chemistry, cloud physics and aqueous-phase chemistry, wet deposition and dry deposition. These processes are represented by mathematical formulations that seek to capture the relevant complexity and detail. The mathematical representation of the physical and chemical processes is carried out through the conservation of mass equation. Emissions and meteorology are input from modeling systems outside the main chemical model. The meteorological inputs for RADM are obtained from a prognostic mesoscale meteorological model (MM4). MM4 employs a four-dimensional data assimilation (4DDA) technique to develop a diagnostic meteorological field that resembles the observations as closely as possible within the consistency of the dynamic equations. The species of primary importance predicted by RADM are: * Ambient Concentrations: SO2, NO, NO2, HNO3, O3, H2O2, NH3, PAN, HCHO, CO, aerosol SO4 * Wet Deposition: SO4, NO3 as HNO3, NH3, H+ * Dry Deposition: SO2, aerosol SO4, H2O2, O3, NO2 The predictions of these species are output at hourly intervals. The predictions from RADM have been extensively compared to empirical data collected during a special 2-year field study. The first 6 months of data has been used in the evaluation to date. Early errors in the model appear to have been largely corrected. The RADM has been found to reproduce the measurements of sulfur and nitrogen with reasonably good fidelity, especially for sulfur. With its large grid size, RADM still does not capture the full dynamic range of concentrations of the oxidant fields. The RADM does represent the state of the science in modeling of air quality and acidic deposition on the regional scale. RADM Demonstration Data Description The RADM data in the demonstration are from a simulation of September 1, 1988 for the 8-hour period of 9:00 a.m. to 5:00 p.m. Four species are provided: sulfur dioxide (SO2); nitrogen dioxide (NO2); a product involved in the production of ozone, hydrogen peroxide (H2O2); and an oxidant of general concern, ozone (O3). On September 1st a high pressure system was sitting over Pennsylvania, leading to elevated levels of SO2 and SO4 over the mid-west. The wind flow from the back side of the high was also pushing the pollutants towards Canada. SO2 and SO4 are main contributors to acidic deposition. Sulfur dioxide contributes most significantly to dry sulfur deposition and SO4 contributes most to wet deposition of sulfur. The key oxidizer of SO2 in clouds, through aqueous chemistry, is H2O2 and its levels were building up in this period. The highest concentrations of SO2, NO2 and O3 are in the mixed layer between the Earth's surface and roughly 2 kilometers. The high SO2 concentrations are proximate to large power plant emissions of SO2. Because ozone is a secondary product with high background levels, its concentrations are more ubiquitous throughout the domain. References Chang, J.S., Brost, R.A., Isaksen, I.S.A., Madronich, S., Middleton, P., Stockwell, W.R. and Walcek, C.J. (1987) A Three-Dimensional Eulerian Acid Deposition Model. Physical Concepts and Formulation, J. Geophys. Res. 92, 14681-14700. Chang, J.S., Middleton, P.B., Stockwell, W.R., Walcek, C.J., Pleim, J.E., Lansford, H.H., Madronich, S., Binkowski, F.S., Seaman, N.L. and Stauffer, D.R. (1990) The Regional Acid Deposition Model and Engineering Model, NAPAP SOS/T Report 4, in: National Acid Precipitation Assessment Program: State of Science and Technology, Volume 1, National Acid Precipitation Assessment Program, 722 Jackson Place, N.W., Washington, D.C. Dennis, R.L., Barchet, W.R., Clark, T.L., and Seilkop, S.K. (1990) Evaluation of Regional Acidic Deposition Models, (Part 1) NAPAP SOS/T Report 5, in: National Acid Precipitation Assessment Program: State of Science and Technology, Volume 1, National Acid Precipitation Assessment Program, 722 Jackson Place, N.W., Washington, D.C. Contact for Further Information Robin L. Dennis Modeling Division, MD-80 U.S. Environmental Protection Agency Research Triangle Park, NC 27711 Telephone (919) 541-2870