Data / Science Data Products / VAPs

KAZRARSCL

Active Remote Sensing of CLouds (ARSCL) product using Ka-band ARM Zenith Radars

Baseline VAP, Evaluation VAP

KAZRARSCL is a core ARM VAP which provides time vs. height information on lowest cloud base and cloud boundaries for up to 10 cloud layers. In addition, it includes best-estimate cloud radar reflectivities corrected for gaseous attenuation, dealiased mean Doppler velocities, and a cloud (hydrometeor) mask, after flagging and removing vegetative and insect clutter returns. The VAP merges cloud radar moments with collocated laser ceilometer, micropulse lidar, microwave radiometer, radiosonde and surface precipitation measurements to mitigate known deficiencies in single-instrument cloud sampling. KAZRARSCL cloud properties are available at high temporal (4 s) and vertical (30 m) resolution at fixed and ARM Mobile Facility deployments, within approximately 2 months of data collection.

KAZRARSCL is released in two stages, an early ‘.c0’ data level version (noncalibrated radar reflectivity factor Z) followed by a calibrated ‘.c1’ version, which replaces the ‘.c0’ version. The ‘.c1’ files undergo radar mentor calibration to align radar Z measurements to operating conditions. Note that neither data level guarantees absolute calibration for quantitative uses of Z and both formats are suitable for relative ARSCL cloud property applications.

KAZRARSCL is a frequent selection among ARM users to inform on column (time-height) cloud properties (e.g. cloud base, thickness) or cloud frequency of occurrence. The VAP also provides a convenient way to access consistently-gridded best-estimate cloud radar moments.

At fixed ARM sites, it provides an extended time record of observations, with data available since 2011. KAZRARSCL cloud base is determined using a combination of ceilometer and micropulse lidar, and is unaffected by subcloud attenuation in rain/drizzle. KAZRARSCL sensitivity to high altitude clouds and estimates of the cloud (echo) top or thickness may be suboptimal in multi-layer cloud or rainy conditions. For shallow cloud KAZRARSCL applications, there are ambiguities when identifying mixed cloud and insect echoes. KAZRARSCL includes meteorological (cloud) and non-meteorological (e.g., biological/insect) flags to focus user attention on this potential issue. For additional information on KAZRARSCL, radar reflectivity factor Z measurement uncertainty and comparisons against standard references, please contact ARM Engineering or the ARM Translators.