High Frequency Radar Quality Control Site
Welcome to the radial comparison website! The over-arching goal of this website is to improve the data
quality of the high-frequency (HF) radars comprising the Surface Current Mapping Network of the NOAA Integrated
Ocean Observing System (NOAA IOOS). The approach for achieving this goal is to provide operational, real-time
comparisons of radial current velocities (hereafter radials) from all HF radars in the network with
overlapping coverage. Radars with overlapping coverage
are grouped into two categories: (1) baseline comparisons in which radials are measured over
straight lines connecting pairs of radars and, (2) synthetic radials in which two or more radars capable generate radials to
compare with directly measured radials from another site.
The fundamental assumption underlying the approach is that if radar sites can be configured such that they achieve high correlations and low RMS differences in radials among radars in baseline and synthetic radial comparisons, the result will be higher quality, more accurate total vectors that are derived from the radials. A challenge will be determining how to adjust radar hardware and software to increase correlation and decrease RMS differences among radials.
These automated real-time comparisons provide metrics for HF radar operators to efficiently and objectively monitor the quality and consistency of the data from HF radars that they maintain. We intend that these metrics may also be used by regional associations, program managers and NOAA officials to assess network status and function.
The basis for comparisons are independent measures of velocity. The simplest example occurs when two radars look at
the same patch of ocean from opposite directions. These radars make independent measurements of the radial current
component which can be compared. The statistical measures of agreement can be used to inform Quality Assurance and
Quality Control activities (QAQC).
When overwater baselines are not available, such as for radars situated along a straight coastline, we can sometimes use two of the radars to estimate (that is, synthesize) the radial component that is observed at the third site. These synthetic radials are computed from nearly orthogonal components from the two sites.
Maps show the HF radar sites involved in the comparison (yellow triangles), and the (clickable) ocean patches in between them that are available for comparison (circular dots). The color bar (right) associates the dot colors with the overall RMS difference between the time series.
Clicking on a dot will bring up the time series from that location, along with the scatterplot of the time series data.
Changing the time range generates corresponding changes in the scatterplot and the statistics that are computed from the scatterplot data.
A yellow background indicates that the data is more than 1 day old, and a red background indicates that the data is more than 1 week old.
Wei Tung Chen
Baseline Radial Comparison
Synthetic Radial Comparison