Wind profiling radars are valuable tools to measure winds as a function of altitude. Traditionally data these devices have been quality-controlled by determining a consensus of the moment values over a period of 30 minutes to an hour before using those moments to calculate horizontal winds. In the context of RAP's aviation weather projects, the need arose for more rapid update of the wind values and the concommitant need for quality control not based on long term consensus.

Human experts have long been used to perform quality control on specific cases of spectral data for detailed analysis. RAP's approach in building the NCAR Improved Moments Algorithm (NIMA) was to use a combination of mathematical analysis, image processing techniques, and fuzzy logic to try and mimic the human experts skill in analyzing these spectra. In addition, NIMA provides a confidence in its calculated moments. These confidence values can be used by subsequent algorithms in the processing chain.

Further quality control can be provided at the level of the winds calculation. The NCAR Winds and Confidence Algorithm (NWCA) utilizes the NIMA moments and confidence values to produce windspeed and direction measurements. The assumptions used by the model used to make these calculations are explicitly tested in order to estimate the confidence in the resulting winds.

The NIMA algorithm has been applied to data from a variety of wind profilers, primarily 915 MHz boundary layer radars, but also 1290 MHz (DWD Lindenberg) and 50 MHz (Ensco) radars. Experimentally it has also been used on scanning radar spectral data and lidar data. The NIMA/NWCA software has been in use operationally since 1998 as part of the Juneau Project.

Click here to view the MST10 Radar Conference poster, May 2003

History

A detailed chronology of NIMA/NWCA development.