Radar data can usually detect hail; however, it is difficult for present day radar to accurately discriminate between hail and rain. Local ground-based hail sensors are much better at detecting hail against a rain background, and when incorporated with radar data, provide a much better local picture of a severe rain or hail event.

The previous disdrometer interpolation/ extrapolation algorithm described a method to interpolate horizontally between multiple ground sensors (a minimum of three) and extrapolate vertically. This work is a modification to that approach that generates a purely extrapolated 3D spatial distribution when using a single sensor.

A 3D high-resolution mapping of hail, as well as rain, is desirable in many instances. For example, hail mapping in the vicinity of a launch vehicle on the launch pad would help determine whether or not damage has occurred following a hail event. In addition to quantifying the size and quantity of hail, it is desirable to know where on the vehicle hail impacts may have occurred. A method that was previously developed, and that required multiple ground sensors, has been modified to accommodate a single sensor. The 3D extrapolation from a single (or multiple) ground sensor can then be compared to the 3D radar-generated spatial map.

The 3D hydrometeor size interpolation scheme described in previous work assumes that a minimum of three hydrometeor disdrometers (rain or hail) are required for successful interpolation/ extrapolation of the hydrometeor distribution in time and space. By simply bypassing the “gravity interpolation algorithm” for multiple sensors, it is shown that good agreement between single sites vs. multiple sites vs. radar is obtained.

The software modification allows any number of sensors, from 1 to N, to be used in the 3D-DSD algorithm. As would be expected, the more sensors that are available, the better, but the requirement for a minimum of three sensors has now been eliminated. This disclosure demonstrates that multiple sensors are not required for successful implementation of the 3D interpolation/extrapolation algorithm. This is a great benefit, since it is seldom that multiple sensors in the required spatial arrangement are available for this type of analysis. This can be used in conjunction with a single sensor or an array of hail monitors, or single or multiple rainfall disdrometers.

This work was done by John Lane of ASRC Aerospace Corporation for Kennedy Space Center. KSC-13244

NASA Tech Briefs Magazine

This article first appeared in the January, 2013 issue of NASA Tech Briefs Magazine.

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