The Forecast Model Web Map Service (NFMW) is software that runs on a web server and produces custom visualizations of atmospheric forecast data for display in a web browser. The NFMW implements the Open Geospatial Consortium (OGC) Web Map Service (WMS) specification.
The Forecast Model Web Map Service (NFMW) is able to read the output of numerical models that simulate Earth science processes and to produce visualizations of the desired output field(s) showing the geographic area, time and elevation specified by the user. Users request visualizations according to the industry-standard Web Map Service (WMS). The model outputs are in formats such as HDF, NetCDF, GRIB or raw binary. The NFMW code reads data for the desired model run time, forecast time, and field(s), subsets the data to the region of interest, interpolates the data to the specified size, generates a visualization of the data using colors, contour lines or arrows, and sends the visualization to the client. The client is typically a normal web browser. The NFMW code is a combination or Perl and Interactive Data Language (IDL).
The primary NFMW goal is to enable both expert scientists and members of the public to view the results of simulations through a normal web browser without needing to install or learn special software. A secondary goal was to demonstrate concretely the benefit of adopting open-standard interface specifications such as the OGC WMS.
The initial functional goal was to support a specific collection of weather forecasts during the 2005 hurricane season produced by the NASA Goddard Earth Observing System (GEOS) version 4 and 5 model. Following that highly successful project, the NFMW goals expanded to include other collections of NASA model outputs and to be easily reconfigurable for other organizations wishing to provide model data visualization services.
Evolvability can occur in multiple areas:
(a) New data collections: by defining a configuration file and editingan initialization routine, new model outputs can be supported. Some model outputs can also be supported without any additional configuration if they comply with certain conventions. In the future, a web-based interface for defining new configurations would be useful,
(b) Different visualization software: IDL (Interactive Data Language) is currently used to generate images of the data. However, IDL has a licensing cost. Therefore, it would be desirable to allow other packages to produce the images. To that end, a complete decoupling of the web service front-end from the image-generation back-end would be useful.
(c) Performance enhancements: to better support potential heavy loads on the service, modifications that would streamline the use of IDL, or allow the use of non-IDL packages, or distribute requests among multiple servers, would be desirable.
(d) Support for other visualization styles: currently the optional WMS styles parameter is not used--each dataset is visualize only in a style defined in a configuration file (or in a default style for unknown datasets). Support for named styles and for parameterized Styled Layer Descriptors (OGC SLD specification) is desirable.
(e) Support for other data access and visualization specifications: the WMS specification used by the NFMW supports 2-D maps (in longitude-latitude or other coordinate systems), with time, elevation and other axes being independent variables. WMS also returns images of the data rather than numeric data values. Other services that could be offered include the OGC Web Coverage Service to provide data values, the OGC Web Terrain Service to provide perspective renderings of volumetric data, and a proposed Web Data Slice Service to provide visualizations of vertical or oblique slices through multidimensional data, include plots where the vertical and/or time dimensions define one axis.
Because it implements the OGC Web Map Service specification (version 1.1.1), the NFMW is designed to be usable by software applications that implement the WMS spec. Those applications typically offer a human-operated user interface. Among the user interfaces currently supported are the NASA Web Map Viewer, Google Earth, and the multi-panel "Hyperwall" display at NASA Goddard.