Interpreting Results, Part 2: Scientific Visualization
The simplest way to analyze and interpret climate model output is to display it. The Analyze Output feature of EdGCM makes this step simple by putting a simulation’s geospatial data into the widely used netCDF file format, with a variety of summary tables, time series sets and latitude-altitude (vertical) data sets saved as tab-delimited text files. The common file formats used for the post-processed data ensure that the user has great flexibility in their choice of visualization options.
The EdGCM suite offers a specially designed companion program called EVA (EdGCM Visualization Application) as the first option in the display and graphical analysis of model output. The engine that drives EVA is IDL, a powerful visualization tool commonly used in the scientific community. Depending on the type of data available, EVA can be used to display and analyze data in a variety of ways (see, e.g., Figure 3-15):
- Plot longitude-latitude data as global maps
- Overlay continent outlines or masks on longitude-latitude maps (including custom overlays of continental reconstructions for the paleoclimate simulations included with EdGCM)
- Display specific latitude-longitude arrays (zonal averages) or latitude-altitude arrays (vertical profiles) as slices from larger multidimensional variables
- Produce line plots of time series data (e.g., change in average global temperature through time)
- Function as a tool for graphical data analysis by allowing the user to combine two arrays in one map plot by differencing (i.e., displaying anomalies)
EVA supports many map projections, colorbars, and overlays that may be further customized as needed. Please visit the EVA website (http://dev.edgcm.columbia.edu/wiki/EVA) for updates and complete documentation.
Earlier users of EdGCM will be familiar with Panoply, a Java-based cross-platform imaging program that can also be used to visualize data as maps or line plots. Users may continue to use that program with post-processed files generated by EdGCM if they wish. Please visit the Panoply website (http://www.giss.nasa.gov/tools/panoply/)for updates and documentation.
Since the files for time series, altitude-latitude data sets and summary tables are formatted as tab-delimited text, the data within them can be viewed and plotted with any spreadsheet program (such as Microsoft Excel) available to the user. The tables may also be viewed as an HTML file, which is perhaps easier to understand as it starts with a series of links to the tables for each variable (Figure 3-16).
Mac users have the additional option of viewing their data in SuSpect (Figure 3-17), which also allows the sync’ed viewing of multiple data files simultaneously.
