16-18 October 2002, Vienna, Austria
NOAA Air Resources Laboratory (ARL)
At NOAA, the creation of CTBTO-WMO products is still considered a research issue rather than a mature product ready for operational implementation. At this time, participation by RSMC Washington in any exercises or actual events will be limited to staff from the research group rather than the 24/7 operational component of the RSMC. In the future it may be possible to arrange for the provision of products through the operational component of our RSMC.
The technical issues regarding providing customized products to the CTBTO appear to be minor. RSMC Washington uses a Lagrangian Atmospheric Transport Model (ATM) for its transport and dispersion component. The standard features of the model support both forward and backward trajectory or dispersion calculations.
The ASCII format proposed by CTBTO seems reasonable. The details of the specific format are not too critical. However our previous experience indicates that the best format is one that would be most compatible for import into the greatest number of applications. The data on each record should fully identify the information, such as start date and time of the sample, duration, location, and the value for that location. Further, only one-time period's data should be contained within one file.
It is also desirable to agree on a standard graphical format for easy exchange of images. We propose a simple method. Each center should produce an ASCII text file that contains the latitude and longitudes of the polygons that contour their data fields. This format can be directly converted to an Arc-View shapefile. A free GIS viewer, Arc Explorer, can be used to view shapefiles over a map background. This simple process would permit the overlay of any or all RSMC products on the same map projection.
The current RSMC procedure is to create a joint statement to evaluate multiple ATM products. The joint statement is difficult to produce and would not help a non-expert determine the correct solution. A more quantitative procedure is required that will automatically generate an uncertainty statement based upon various ATM results. Variations of an ensemble approach are proposed.
The framework for WMO-CTBTO cooperation should accommodate multiple ATM products in an automated manner. It may never be possible to resolve differences in the models and data such that the source-determination method using only ATM models provides a deterministic answer. The CTBTO will need to be able to apply ATM results in a stochastic manner and not expect the WMO centers to provide the answer as to which model is correct for any particular event. Further it is critically important that the initial decisions about standards and procedures be sufficiently flexible to accommodate change. Once these procedures have been implemented there will be a great reluctance for further modifications.