New Cloud Radar Product Available From EPCAPE and CAPE-k Campaigns

The three images illustrate the KAZRARSCL EPCAPE product for September 10, 2023. From top to bottom are time-versus-height displays of cloud boundaries, hydrometeor best-estimate reflectivity (after clutter removal), and mean Doppler velocity (the negative sign indicates motion toward radar). Images are from Karen Johnson, Brookhaven National Laboratory.

The Atmospheric Radiation Measurement (ARM) User Facility has released a new cloud radar value-added product (VAP) from the 2023–2024 Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE) in La Jolla, California, and the ongoing Cloud And Precipitation Experiment at kennaook (CAPE-k) in northwestern Tasmania.

The Ka-Band ARM Zenith Radar Active Remote Sensing of CLouds (KAZRARSCL) VAP allows scientists to more easily use corrected observations from the vertically pointing KAZR, such as reflectivity and vertical velocities, and provides hydrometeor masks and cloud boundaries for the EPCAPE and CAPE-k field campaigns.

KAZR observations from EPCAPE were especially challenging to use because of pervasive periods of low-level clutter (mostly below 5 kilometers), which made the identification of hydrometeors unusually difficult. A more advanced clutter detection algorithm was developed and employed for use at this site.

The KAZRARSCL VAP combines KAZR, micropulse lidar, ceilometer, sounding, and microwave radiometer input observations. The Interpolated Sonde (INTERPSONDE) VAP is used in correcting KAZR reflectivities for gaseous attenuation. Reflectivity has not yet been calibrated, but it has been corrected for near-field antenna effects. 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 can be found on the KAZRARSCL web page.

KAZRARSCL data are available for the entire EPCAPE campaign from February 15, 2023, through February 14, 2024.

For CAPE-k, KAZRARSCL is currently available from the campaign’s start date of April 15, 2024, through February 28, 2025. Additional months of CAPE-k data will be produced as input data sets become available, with a lag time of approximately two months.

In summer 2025, KAZRARSCL processing with calibrated KAZR data is expected for all of EPCAPE and the first year of CAPE-k.

Scientists can use the new EPCAPE and CAPE-k KAZRARSCL data now. 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 developer Karen Johnson or ARM translator Dié Wang.

To cite the KAZRARSCL data, please use doi:10.5439/1393437 for arsclkazr1kollias and doi:10.5439/1393438 for arsclkazrbnd1kollias.