USERS' INTERPRETATION GUIDELINES
ATMOSPHERIC TRANSPORT MODEL OUTPUTS
Since the 1st July 1995, the National Meteorological Operations Centre (NMOC) in Melbourne has been a Regional Specialised Meteorological Centre (RSMC) for Environmental Emergency Response (EER), with responsibility for the Regional Association V area. As part of its responsibility, RSMC Melbourne is required to provide advice, in the form of a basic set of products, on the atmospheric transport of pollutants resulting from nuclear disasters, volcanic eruptions, forest fires, chemical incidents and, perhaps, other causes. (With respect to forest fires and chemical incidents, a self-contained appendix attempts to provide further guidance on procedures from a more general perspective.)
The EER system, in RSMC Melbourne, is currently based around the HYSPLIT, Version 4.0, Atmospheric Transport Model (referred to as HYSPLIT4 below) developed by Roland Draxler at NOAA=s Air Resources Laboratory (Draxler 1997) with some contribution from the Bureau of Meteorology Research Centre (Draxler and Hess 1997, 1998). HYSPLIT4 is driven by meteorological input resulting from the operational NWP systems in RSMC Melbourne. The system is maintained in a state of readiness so that the ad-hoc requests for products can be satisfied quickly.
2. NATIONAL METEOROLOGICAL OPERATIONS CENTRE (NMOC), MELBOURNE
The National Meteorological Operations Centre, Melbourne, is part of the Bureau of Meteorology, Australia's national weather service. The NMOC serves as a centralised operational centre, for the Bureau, maintaining a round-the-clock nationwide weather watch and providing guidance products to the seven Regional Forecasting Centres. In addition to its responsibility as an RSMC for Environmental Emergency Response, the NMOC also performs international functions as a World Meteorological Centre, a Regional Specialised Meteorological Centre with geographical specialization, and a Regional Telecommunications Hub on the GTS. In addition, the NMOC has aviation and oceanographic responsibilities.
The NMOC provides manual and numerical products for a wide range of national and international clients, manages the meteorological data links and their flow of information (including international exchange of data) and supports the centralised computing needs of the Bureau (for operations and other applications such as climate, research and satellite data-processing). Operational applications are implemented and supported by meteorological systems development staff. Most operational numerical weather prediction (NWP) and oceanographic systems originate from the Bureau of Meteorology Research Centre (BMRC). The NMOC's computing facility is based on the UNIX operating system. Communications, database access and general meteorological systems tasks are carried out on Hewlett-Packard UNIX servers, while the main numerical models run on a NEC SX-4. A FDDI link provides the operational connections between the Unix servers and the NEC supercomputer. Real-time data are stored in a NEONS/ORACLE relational database with a StorageTek Mass Store Automatic Cartridge System providing the archive facility. Most products are disseminated nationally via a "DIFACS" system, direct file transfer to other data servers or through the nationally connected McIDAS system. Internationally, products are issued via facsimile or as coded messages on the GTS.
Figure 1. A Schematic Representation of the EER System at the RSMC Melbourne.
3. OPERATIONAL EER SYSTEM
3.1 Integration with the Operational NWP System
A simplified schematic diagram of the operational EER system is shown in Figure 1. The EER system interfaces with all of the current operational NWP systems in NMOC, viz.GASP, TLAPS, LAPS and MESO_LAPS. The domains for each of these systems are shown in Figure 2 and a summary of their characteristics is given in Table 1. GASP (Bourke et al 1995, Seaman et al 1995) provides the necessary meteorological input to enable the EER system to be run anywhere over the globe, whereas the limited area systems are only relevant to the Australian region. The necessary pre-processing, providing the interface, is performed after each run of these NWP systems - thus minimising the time required to produce up-to-date meteorological input for HYSPLIT4. A critical facet of the system is the manual interaction whereby the operational person on duty has to define the running mode of HYSPLIT4 - ie the nature of the episode, the type of guidance required and the location, and characteristics of the source(s) or observations. Products are usually disseminated by fax or through the web. The operational system is run using NMOC=s ASMS@ scheduler, with the task-edit facilty providing the mechanism for manual interaction. Currently, most of the processing associated with the operational EER system is performed on a NEC SX-4 supercomputer.
Figure 2. Domains of the operational NWP systems in RSMC Melbourne.
HYSPLIT4 (ie Hybrid Single-Particle Lagrangian Integrated Trajectories, Version 4.0) system models the atmospheric transport and dispersion of pollutant plumes originating from a variety of sources (eg nuclear, volcanic, fire and, eventually, chemical). The Ahybrid@ part of the acronym refers to the use of both movable >Lagrangian= (for the advection and diffusion calculations) and fixed =Eulerian= (for the concentration calculations) modelling frames of reference within the system.
The current operational configuration of the system makes use of another Ahybrid@ feature of HYSPLIT4, viz. a mixed algorithm which considers puff dispersion in the horizontal and particle dispersion in the vertical. On the release of a single puff of pollutant from a source, the puff will be advected by the mean wind and will expand as a result of diffusion processes in the turbulent atmosphere. In the system, the puff is allowed to grow laterally to a certain size, after which it splits into several new puffs, each with their respective fraction of the
Table 1: Characteristics of operational NWP systems in RSMC Melbourne.
|FULL NAME||Limited Area Prediction System||MESOscale Limited Area Prediction System||Tropical Limited Area Prediction System||Global Assimilation and Prognosis|
|TYPE OF MODEL||Grid P.E.,Assimilation and Prognosis||Grid P.E. Prognosis||Grid P.E.,Dynamical nudging and Prognosis||Spectral Assimilation and Prognosis|
|NESTING||In GASP||In LAPS||In GASP||Stand Alone|
|HORIZONTAL RESOLUTION||0.3750||0.1250||0.3750||Triangular 239
|GRID||220x320 Lat./Long.||480x600 Lat./Long.||240x320 Lat./Long.||240x480 Lat./Long.(Transform)|
|NUMBER OF LEVELS||29||29||29||29|
|SIGMA (=P/P*) VALUES||0.9988 0.5000
|ANALYSIS TYPE||MVSI+Univariate OI for moisture||Not applicable||MVSI+Univariate OI for moisture||MVSI+Univariate OI for moisture|
|MAX DATA AFFECTING EACH POINT||1000||1000||1000|
|DATA INSERTIONS||6 hourly||6 hourly||6 hourly|
|DATA CUT-OFF TIMES||(H+2) hour||(H+4) hour||(H+6) hour|
|INITIALISATION||Digital Filtering||Digital Filtering||Digital Filtering,
|Incremental Non-linear Normal Mode|
|RADIATION||Diurnal Cycle,Diagnostic Clouds,Interactive Optical Properties||Diurnal Cycle,Diagnostic Clouds, Interactive Optical Properties||Diurnal Cycle, Diagnostic Clouds,Interactive Optical Properties||Diurnal Cycle, Diagnostic Clouds, Interactive Optical Properties|
|TIME STEP||40 sec||10 sec||40 sec||600 sec|
|FORECAST PERIODS||+48 hour from 00 and 12 UTC||+36 hour from 00 and 12 UTC||+48 hour from 00 and 12 UTC||+192 hour from 00 and 12 UTC|
|July 1999||November 1999||September 1999||December 1998|
pollutant mass. These new puffs will, in turn, be subject to advection and diffusion. The splitting of puffs could also occur vertically. However, in the operational configuration, particle - rather than puff - dispersion has been chosen for the vertical calculations. (In cases of strong atmospheric mixing, puff splitting in the vertical can result in too many puffs being generated.)
HYSPLIT4 also includes a number of other processes for removing, adding to, or changing the composition of the pollutant plume. Dry deposition is the transport of pollutant gaseous or particulate species onto surfaces (in the absence of precipitation). In the system, a dry deposition velocity can be defined explicitly or can be calculated using details about the nature of the surface. For particles, gravitational settling, requiring estimates of particle shape, size and density, is another option. In wet deposition, the pollutant is scavenged by the atmospheric hydrometeors and is thus delivered to the earth=s surface. HYSPLIT4 allows for both within-cloud ("washout") and below-cloud ("rainout") scavenging. If the winds are sufficiently strong, and the pollutant is not bound to the surface, then resuspension can also occur. In the case of nuclear incidents, radioactive decay is incorporated. Chemical transformations will eventually be included in the system.
HYSPLIT4 can be run in a purely trajectory, or advective, mode (see Figure 1) producing either forward or backward trajectory plots at specified levels. Alternatively, it can be run in a dispersion mode producing exposure (or concentration) and surface deposition charts integrated over various time periods and layers. The nature of a source can be defined according to its strength, height and size, and duration of emission.
3.3.1 Automatically scheduled component
After completion of the 00 or 12 UTC runs of the operational NWP systems (GASP, TLAPS, LAPS and MESO_LAPS) each day, jobs are automatically initiated, using the NMOC=s SMS scheduling system, to extract the necessary fields (viz. surface pressure, surface height, precipitation and the multi-level: temperature, specific humidity and wind components). These fields are then interpolated horizontally (to an internal grid) and temporally, before being packed into a form suitable for direct input into HYSPLIT4.
3.3.2 Manual intervention
Details of the source are entered manually using the edit facility of the SMS scheduling system The basic details required for successful running include the latitude/longitude and the height (above sea level) of the source. Other details required depend on the nature of the source and may include, for example, the starting heights of trajectories, height of ash cloud, actual time of release and release amount per hour (if known). The operational staff in the NMOC provide 24 hours/day supervision of the operational NWP and EER system.
3.4 Product Dissemination
A number of mechanisms are available, at RSMC Melbourne, for disseminating the various products from the operational EER system.
3.4.1 Scanning into fax
The traditional mechanism is to enter the relevant fax numbers for the destination and to manually scan the hardcopy printed charts into the fax machines. A FaxStream facility is available to reduce the number of scannings necessary.
3.4.2 PostScript to fax
A direct PostScript to fax facility is available for operational use. This saves the need for manual scanning. As the charts are produced, they are converted into PostScript format (which is also required for hardcopy production) and are sent directly to the HylaFAX system. The various destination fax numbers are stored in the task script and can be edited, as required.
3.4.3 External web
EER products are also made available on the Bureau=s external (and internal) web server. Again these products can be made available to various users as soon as the required trajectory and dispersion tasks have run successfully.
Email can be, and has been used in tests, as a disseminating mechanism for the various products. Charts (in, for eg, gif format) can be attached to the mail message. Email is also a useful mechanism for alerting users to the availability of products, in sections 3.4.2 and 3.4.3 above.
Currently, the system caters for point or uniform line sources. However, it could be extended to area and volume sources. Unless otherwise specified, a nuclear dispersion run will assume a release of Cs-137, and a volcanic ash dispersion run will assume the presence of 7 types of particles with a size spectrum from 0.3 to 30 Fm and densities of 2.5 g/cc (corresponding to a mixture of pumice, shards and basalt) - see Table 2.
3.5.2 Running modes
At the present time, the following running configurations are readily available under the standard setup for the operational EER system:
(i) Forecast Forward and Forecast Backward Trajectories to: +144 hrs for GASP, +48 hrs for LAPS and TLAPS, +36 hrs for MESO_LAPS;
(ii) Analysed Backward Trajectories from: -144 hrs for GASP, -96 hrs for LAPS and TLAPS;
(iii) Forecast Nuclear Dispersion to: +72 hrs for GASP, +48 hrs for LAPS and TLAPS, +36 hrs for MESO_LAPS;
(iv) Forecast Volcanic Ash Dispersion to: +48 hrs for GASP and TLAPS;
(v) Forecast Smoke Dispersion to: +72 hrs for GASP, +48 hrs for LAPS and TLAPS, +36 hrs for MESO_LAPS.
3.5.3 Graphical products
The basic products from the operational EER system are in chart form and are produced using NCAR graphics.
3.5.4 Request protocol
On receipt of a faxed request from delegated authorities within RA V, an acknowledgment fax is sent. After successful running of the required tasks in the scheduler, the requested products are then sent by fax. It is perhaps worth noting that, in the case of a recent request, the use of email (sent to firstname.lastname@example.org), complementing the fax request, quickly alerted the actual person with responsibility for generating the products. Requests for volcanic ash guidance are addressed to the Volcanic Ash Advisory Centre (VAAC), in Darwin. Internal Bureau requests for products are usually directed to the Shift Supervisor of NMOC. However, as mentioned above, certain details of the source (minimally, its latitude and longitude) need to be specified in the request.
Table 2. Standard settings used in the production of charts (with GASP meteorological input). (These settings can readily be changed, if requested.)
|TRAJECTORIES||Forward||Forecast Period: +72 hour
Products: 1 chart
Starting Heights: 500,1500,3000m
|DISPERSION||Nuclear||Forecast Period: +72 hour
Products: 3 (24hour ave.) exposure charts
1 (72 hour) deposition chart
Source: Uniform between 0 and 500m
Emission Duration: 6 hour
Release/hour: 0.1667 Bq
Half-life: 8760 day
Dry Deposition: Included
Wet Deposition: Included
Deposition Velocity: 0.001ms-1
In-cloud removal (by vol.): 3.2x105
Below-cloud Removal: 5.0x10-5s-1
|Volcanic||Forecast Period: +48 hour
Products: 4 (12 hourly) ash cloud charts
Emission Duration: 1 hour
Release/hour: 1 unit
No of Particle Types: 7
Shape Factor: 1.0,1.0,1.0,1.4,1.6,1.8,2.0
Dry Deposition: Included
Wet Deposition: Not Included
|Smoke||Forecast Period: +72 hour
Emission Duration: 6 hour
Release/hour: 0.1667 unit
Dry Deposition: Included
Wet Deposition: Not Included
4. COMPLETE SET OF OUTPUT MAPS FOR THE DEFAULT NUCLEAR SCENARIO
Figures 3 to 7 show a complete set of the 5 output charts for the default nuclear scenario. For this sample set, the source is located at 34.050S and 150.980E (ie Lucas Heights, Australia). The test release shown was assumed to start at 0900 UTC 10 August 1999. The basic set of 5 charts provide forecast guidance up to 72 hours ahead , depending on the release time specified.
Figure 3 shows the first 24-hour (of a 72-hour forecast) time-integrated exposure from the ground to 500 metres.
Figure 4 shows, the same as for Figure 3 but, the second 24-hour period.
Figure 5 shows, the same as for Figure 3 but, the third 24-hour period.
Figure 6 shows the total accumulated ground level deposition (up to 72 hours, depending on the release time).
Figure 7 shows forecast (up to 72 hours, depending on the release time) forward trajectories starting at heights of 500, 1500 and 3000 metres.
4.1 Description associated with itemised output charts
For the present documentation purposes only, the first exposure chart (Figure 3) has been itemised (with circled numbers) to highlight the following aspects of the chart:
1: Identifies the chart as coming from RSMC Melbourne.
2: Indicates the nature of the event - in this case a Test or Exercise.
3: Defines the integration period over which the concentrations apply.
4: Defines the date/time at which this particular chart was produced.
5: Defines the latitude and longitude of the release location in degrees (to the nearest hundredth) - where the Southern Hemisphere has a negative latitude and the Western Hemisphere has a negative longitude).
6: Indicates that the radioactive pollutant is Cesium 137.
7: Gives the half-life of the pollutant named in item 6.
8: Shows the date/time at which the release started.
9: Shows the height of the release ( in metres).
10: Indicates that the air concentration, or exposure, is averaged from the ground to 500 metres, in units of Becquerel second / metre3 . Ground level deposition may also be specified here in units of Becquerel / metre2 .
Figure 3. Time-integrated exposure, from the ground to 500 metres, for the first 24-hour period. (This chart has been itemised.)
Figure 4. Time-integrated exposure, from the ground to 500 metres, for the second 24-hour period.
Figure 5. Time-integrated exposure, from the ground to 500 metres, for the third 24-hour period.
Figure 6. Total accumulated ground level deposition from time of release from source.
Figure 7. Itemised chart showing forecast forward trajectories starting at heights of 500, 1500 and 3000 metres.
11: Indicates the values of the 4 concentration contours. The units are specified in item 10.
12: Indicates the duration of the release.
13: Indicates the maximum concentration, corresponding to a filled-in square on the chart.
14: Indicates the number of Becquerel units of radioactivity associated with the release.
15: States the deposition processes and the horizontal resolution of the grid used in the run of the transport model that produced the chart.
16: Indicates the operational atmospheric NWP model providing meteorological input to the transport model.
In the trajectory chart (Figure 7) the lateral, or horizontal, depiction of trajectory paths on a map background are annotated by the times (UTC) at 6-hourly intervals with different symbols (filled-in squares, circles and triangles) for the different heights. The vertical motion is displayed at the bottom of the chart with the same 6-hourly intervals and symbols. Some of the different features have been itemised in Figure7 as follows:
1: Defines the type of trajectories (forward or backward) on the chart.
2. Shows the starting date/time of the trajectories.
3. Gives the type of vertical motion used in the calculations in the transport model.
4: Shows the vertical motion of the trajectories and defines the levels of the trajectories (depicted in the larger horizontal display above).
5: Indicates the 6-hourly intervals by symbols (filled-in squares, circles and triangles).
6: Defines the starting heights (in metres or hpa) for the forward trajectories.
5. OTHER PRODUCTS AVAILABLE FROM RSMC MELBOURNE AND CONTACT FOR ADDITIONAL INFORMATION
Many different transport and dispersion products can be produced from the various running modes (see section 3.5.2 above) of the operational EER system. Some examples are shown of guidance available for volcanic ash (Figure 8), smoke episodes associated with forest fires (Figure 9) and the back-tracking of paths taken by atmospheric aerosols (Figure 10). In addition to the EER products, standard meteorological charts (depicting, for example, wind and precipitation fields) and satellite imagery can be produced for the region of interest.
For any additional information, please contact Paul Stewart (Telephone: (613) 9669 4039; Fax: (613) 9662 1222; Email: email@example.com).
Figure 8. Panel display showing example (from an Intercomparison Test) of volcanic ash guidance available.
Figure 9. Forecast concentrations from 5 sources, during SE Asian fire episode 1997.
Figure 10. Backward (6-day) trajectories, ending at Cape Grim, using analysis data.
Bourke, W., Hart, T., Steinle, P., Seaman, R., Embery, G., Naughton, M. and Rikus L. 1995. Evolution of the Bureau of Meteorology's Global Assimilation and Prediction system. Part 2: resolution enhancements and case studies. Australian Meteorological Magazine, 44, 19-40.
Draxler, R.R. 1997. HYSPLIT_4.0 -- User's Guide. NOAA Tech. Mem. ERL ARL.
Draxler, R.R. and Hess, G.D. 1997. Description of the HYSPLIT_4 Modelling System. NOAA Tech. Mem. ERL ARL-224.
Draxler, R.R. and Hess, G.D. 1998. Overview of the HYSPLIT_4 modelling system for trajectories, dispersion and deposition. Australian Meteorological Magazine, 47, 295-308.
Seaman, R., Bourke, W., Steinle, P., Hart, T., Embery, G., Naughton, M. and Rikus, L. 1995. Evolution of the Bureau of Meteorology's Global Assimilation and Prediction system. Part 1: analysis and initialisation. Australian Meteorological Magazine, 44, 1-18.