Radar Wind Profiler Adaptive Sampling

Description

The Atmospheric Radiation Measurement (ARM) program deploys a total of 4 Vaisala 915 MHz Radar Wind Profilers (RWP) at the Southern Great Plains (SGP) Central Facility and I8, I9, and I10 Intermediate Facilities. The RWPs provide long term, continuous measurements of backscattered signal strength and wind profiles. Currently, these systems operate sequentially in precipitation (PR) and boundary layer (BL) modes, where the PR mode alternates between low and high power that have short averaging times and large Nyquist frequencies. The single power BL mode operates with slightly larger averaging times. However, the BL mode wind product is affected by precipitation, making the wind measurements largely unusable during precipitation events. On the other hand, during non-precipitating conditions the RWP is simply measuring noise. An “adaptive” sampling strategy alternating between a pre-defined wind and PR only modes depending on weather conditions has been developed for these RWPs to improve the RWP measurements by better utilizing the sampling periods. It results in more detailed wind and SNR profiles due to longer spectral averaging during the wind mode, and increased vertical beam temporal resolution during rain events. Individual modes are identified using real-time spectral measurements of vertical velocity. The capability of the adaptive sampling strategy will be demonstrated and the potential improvements discussed.