New Cloud Radar Products Available for 4 ARM Sites

Published: 20 November 2025

The Atmospheric Radiation Measurement (ARM) User Facility has released the Ka-Band ARM Zenith Radar Active Remote Sensing of CLouds value-added product (KAZRARSCL VAP) for the ongoing Coast-Urban-Rural Atmospheric Gradient Experiment (CoURAGE) in the Baltimore, Maryland, area and the Bankhead National Forest (BNF) atmospheric observatory in northern Alabama. In addition, updated KAZRARSCL data are now available for the 2021–2023 Surface Atmosphere Integrated Field Laboratory (SAIL) campaign near Crested Butte, Colorado, and the 2023–2024 Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE) in La Jolla, California.

KAZRARSCL allows scientists to more easily use corrected observations from the vertically pointing KAZR, such as reflectivity and mean Doppler velocity. It also provides hydrometeor masks and cloud boundaries for each site.

The KAZRARSCL VAP combines KAZR, micropulse lidar, ceilometer, sounding, and microwave radiometer observations. KAZR reflectivities are corrected for gaseous attenuation and near-field antenna effects. The reflectivities in the BNF and CoURAGE data have not yet been calibrated, while the updated SAIL and EPCAPE products feature calibrated values. As a result, the new SAIL and EPCAPE KAZRARSCL products are considered c1-level data, while the CoURAGE and BNF data are c0-level.

For the c0- and c1-level data, KAZR operating modes are optimally merged, and non-hydrometeor clutter returns are removed to provide best-estimate reflectivity. Mean Doppler velocities are dealiased to correct periods when observed velocities exceeded the radar’s maximum (Nyquist) velocity. Cloud boundaries are determined by combining cloud detections from the KAZR and the Micropulse Lidar Cloud Mask (MPLCMASK) VAP.

KAZRARSCL produces two daily datastreams. The arsclkazr1kollias datastream provides best-estimate radar reflectivities, mean Doppler velocities, spectral widths, and a significant detection mask in time and height. Vertical profiles of these quantities are provided every four seconds from approximately 160 meters above ground level up to 18 kilometers, with 30-meter height resolution. This datastream also provides up to 10 layers of cloud boundaries (cloud base and cloud top) and best-estimate cloud base at the four-second resolution. The smaller arsclkazrbnd1kollias datastream includes only the cloud boundaries and cloud base fields.

More information about the VAP, including the technical report, can be found on the KAZRARSCL web page.

CoURAGE KAZRARSCL data are currently available from December 1, 2024, through August 31, 2025. BNF data are available from November 15, 2024, through August 31, 2025. Additional months of data from these sites will be produced once input data sets become available, with a lag time of two to three months. It is expected that c1-level KAZRARSCL data for CoURAGE and the BNF will be processed and made available in the first half of 2026 after calibrated KAZR data are released.

The updated SAIL KAZRARSCL product is available from September 14, 2021, through June 15, 2023. The updated EPCAPE data are from February 15, 2023, through February 14, 2024. Users who downloaded the previously released c0-level SAIL and EPCAPE data are encouraged to download the c1-level data.

Access the KAZRARSCL data in the ARM Data Center. (To download the data, first create an ARM account.)

To ask questions, provide feedback, or report data issues, please contact VAP developer Karen Johnson or KAZRARSCL’s interim translator, Scott Giangrande.

To cite the CoURAGE and BNF c0-level data, please use doi:10.5439/1393437 for arsclkazr1kollias and doi:10.5439/1393438 for arsclkazrbnd1kollias. For the SAIL and EPCAPE c1-level data, please use doi:10.5439/1228768 for arsclkazr1kollias and doi:10.5439/1228769 for arsclkazrbnd1kollias.