KASACR Data Quality Masks Value-Added Product Now Available in Evaluation

Evaluation data for the Ka-Band Scanning ARM Cloud Radar (KASACR) Data Quality Masks are now available from the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) field campaign conducted in June and July 2017. The specific dates covered in this data set are June 18 through July 31, 2017.

Data quality masks help users remove data not suited for their work. Generally, signals from non-meteorological targets, such as ground clutter, or with weak echoes are undesirable for radar data processing.

Five data quality masks were generated for the KASACR at the Atmospheric Radiation Measurement (ARM) Climate Research Facility’s Eastern North Atlantic (ENA) atmospheric observatory: clutter, blockage, blanking, and single- and dual-polarization significant echo. The masks can and should be used by end users to identify meteorological echoes and remove unwanted or poor-quality signals.

These masks were appended to the a1 datastreams (the first data collected) to create b1 files (data that have been improved from the first collection). The file format is netCDF and matches that of the a1 files, but with the addition of five fields relating to the data masks, as follows:

mask_significant_echo: single-pol significant echo
mask_copolar_variables: dual-pol significant echo
mask_blanking_copolar_variables: transmitter blanking mask
mask_blockage_copolar_variables: beam blockage mask
mask_clutter_copolar_variables: ground clutter mask.

The example masks shown here are for plan position indicator (PPI) type images. The masks are also applied to range height indicator (RHI) and vertically pointing (VPT) type scans. The scan types are denoted by the datastream name, which is part of the file name.

Clockwise from top left, images representing blanking, blockage, significant echo, and clutter are shown for the KASACR at the ARM ENA atmospheric observatory. For each image, the yellow values indicate a “1,” which is good, or usable, data. The blue areas represent undesirable data, or “0.” Graciosa Island, the location of the ARM ENA atmospheric observatory, is outlined in black near the center of the domain. Significant blockage (top right image) to the south of the radar location can be seen due to the island terrain as well as the X-Band Scanning ARM Precipitation Radar radome directly to the south. Similarly, a significant portion of the domain is blanked (transmitter turned off) due to the proximity of the site to the airport (top left image). The clutter identification (bottom left image) algorithm is based upon Hubbert et al. (2009). A large meteorological structure is visible in the example significant echo (bottom right image) mask.

The following datastreams (scan types) are included in the evaluation data set:

b1: along-wind RHI
b1: cross-wind RHI
b1: hemispheric sky RHI
b1: PPI volume (sector-type scan)
b1: PPI volume
b1: vertically pointing scan
b1: vertically pointing scan–high resolution.

Scientists can begin using the masks now. In addition, the rest of the ACE-ENA KASACR campaign data are being processed and will be ready to use in 2018.

To share your experience or to ask questions, contact Bradley Isom or Nitin Bharadwaj, the lead developers for these evaluation data quality masks.

Access the data set in the ARM Data Center. (Go here to create an account to download the data.)

Reference:

Hubbert, JC, M Dixon, and SM Ellis. 2009. “Weather Radar Ground Clutter. Part II: Real-Time Identification and Filtering.” Journal of Atmospheric and Oceanic Technology 26: 1181–1197.