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SCD lead story: March 22, 2005 Comparison of the two images below shows how ERA-40 reanalysis data, converted in Dataset 124.1 to a T85 grid, closely matches the state of the atmosphere as documented by actual U.S. Weather Service observations. SCD's Data Support Section (DSS) produced Dataset 124.1, which is now available for researchers.
The above DSS-derived T85 visualization from ERA-40 reanalysis data shows 500-millibar geopotential height and winds on January 1, 1979, at noon Greenwich Mean Time. The winds have been computed from spectral coefficients of vorticity and divergence. A pressure of 500 millibars corresponds to 5.5 kilometers (3.4 miles) in a standard atmosphere. Comparing these data with actual National Weather Service observations for the same time period, below, shows the same well-defined low-pressure system moving over the central United States. Image:
Dave Stepaniak produced the above visualization using NCAR Command Language
(NCL) software.
This visualization shows a 500-millibar analysis from the U.S. National Weather Service on January 1, 1979, at 1 p.m. Greenwich Mean Time. Note that the contour encircling the "LOW" at 16,700 feet corresponds to 5,090 meters, and that the wind barb located at approximately 105 °W, 35 °N corresponds to a range of 78–83 miles per hour, or 35–37 meters per second. Image: Courtesy National Weather Service |
