R. L. Buckley and C. H. Hunter Atmospheric Technologies Group Savannah River National Laboratory Recent Improvements to an Advanced Atmospheric Transport Modeling System 1

2 Savannah River Site (SRS): DOE facility containing waste- processing, chemical hazards, etc. covering ~800 km 2 BACKGROUND

3 BACKGROUND (cont) Weather INformation and Display (WIND) System designed for emergency response (1) Network of computers and instruments to collect meteorological data (2) Graphical/tabular display (updated every 15 minutes) (3) Supplies data to Gaussian dispersion models This work utilizes these data in an advanced atmospheric transport model

4 PURPOSE/IMPORTANCE This work utilizes the WINDS tower data in an advanced atmospheric (Lagrangian) transport model. SRS tower observations are blended with mesoscale simulated wind fields. This results in improved transport prediction capabilities.

5 RAMS LOCAL GRID SYSTEM 3-D finite-difference numerical model, originally developed at Colorado State University Initial/lateral boundary conditions obtained from Rapid Update Cycle (RUC) Typical configuration: Nested horizontal grid spacing 6 hour forecast window Updated every 3 hours

6 TIMING ASPECTS Time window for emergency response needs. Hindcast ~12 to 24 hrs Persist 6 hours into the future (steady-state) after final forecast hour Blend SRS tower horizontal winds into local 3-D forecast fields as they become available (Archived).

7 BLENDING Use horizontal wind fields from SRS towers. Barnes objective analysis: computationally simple, Gaussian weighted- average technique For a station, i, assign a weight, W, which is a function of distance from the station to a gridpoint, d, and the radius of influence, R Give strong relative weighting to SRS winds (within 50 km of towers) Technique not valid for locations far from SRS

8 METHODOLOGY Scripts/shell commands provide automation of RAMS forecasts on UNIX Workstations Transport calculations performed using batch scripts and graphical user interface (GUI) on a PC Software component functions: 1. Input conditions for transport calculation (GUI) 2. Execute LPDM 3. Generate graphical output 4. Provide user choices to examine/archive graphical output (GUI)

9 LAGRANGIAN PARTICLE DISPERSION MODEL (LPDM) Particles released in three-dimensions and time Advect, disperse using winds and turbulence from RAMS Track particle position in space (Lagrangian) Depletion mechanisms: radioactive decay, wet and dry deposition (dry deposition incorporated as partially reflecting surface boundary condition)

10 WET/DRY DEPOSITION REMOVAL MECHANISMS Types WET: Precipitation involved (rainout, washout). Use first-order DECAY process: scavenging coefficient DRY: No precipitation, near surface. Use concept of dry DEPOSITION VELOCITY (v D ): F D surface FLUX Calculate in two ways: Simple: v D, CONSTANT (v D ~ 0.1 to 1.0 cm s -1, ~ s -1 ) Complex: v D, VARY with conditions o v D based on RESISTANCE METHOD o based on PRECIPITATION INTENSITY

11 OUTPUT PRODUCTS Instantaneous surface concentration [pCi/m 3 ] (animated) Integrated surface deposition [pCi/m 2 ] (animated) Dose quantities [rem]: Initial exposure dose:(inhalation + cloud shine) 4-day total dose: (inhalation + cloud shine + ground shine) Dose rate: (ground shine only) 1-year total dose: (ground shine only) 2-year total dose: (ground shine only) Results shown for each isotope, or for sum over all isotopes

12 Surface Concentration: 06-January UTC (0800 LST) APPLICATION #1: Graniteville Train Collision

13 APPLICATION #2: Emergency Response Exercise 22-June-2005 Use Meteorology from 2-grid local simulation (6-hr duration: 12 UTC (08 EDT), 22-Jun to 18 UTC, 22-Jun, Run LPDM assuming the following: 15-min surface release starting at 12:06 UTC, 22-Jun from H-area (Pu 238 ) Plot integrated surface deposition at 18 UTC for 2 cases: Blending of SRS tower information at 13:45 UTC Blending of SRS tower information at 17:00 UTC

14 Plume Comparisons (22-June-2005 Emergency Response Exercise) Blending at 13:45 UTC Blending at 17:00 UTC

15 Simulation –vs- Observations: Example #2

16 APPLICATION #3: Emergency Response Exercise 30-March-2004 Use Meteorology from 2-grid local simulation (6-hr duration: 18 UTC (14 EDT), 30-Mar to 23 UTC, 30-Mar, 2004). Run LPDM assuming the following: 15-min surface release starting at 18:03 UTC, 30-Mar from H-area ( Ci of tritium oxide, HTO) Plot integrated surface deposition at 30-min intervals for two cases: No blending of SRS tower information (forecast only) Blending of SRS tower information up to 21 UTC

17 Simulation –vs- Observations: Example #3

18 CONCLUSIONS Emergency response tool previously developed using 3-D winds and turbulence at fine-scale resolution Horizontal wind fields are blended with local tower observations to improve predictive transport capabilities. Technique demonstrated in various onsite exercises, as well as during the Graniteville train collision.