The Atmospheric Radiation Measurement Program Cloud Profiling Radars: Second-Generation Sampling Strategies, Processing, and Cloud Data Products

Abstract

The U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Program operates millimeter-wavelength cloud radars in several climatologically distinct regions. The digital signal processors for these radars were recently upgraded and allow for enhancements in the operational parameters running on them. Recent evaluations of millimeter-wavelength cloud radar signal processing performance relative to the range of cloud dynamical and microphysical conditions encountered at the ARM Program sites have indicated that improvements are necessary, including significant improvement in temporal resolution (i.e., less than 1 s for dwell and 2 s for dwell and processing), wider Nyquist velocities, operational dealiasing of the recorded spectra, removal of pulse compression while sampling the boundary layer, and continuous recording of Doppler spectra. A new set of millimeter-wavelength cloud radar operational modes that incorporate these enhancements is presented. A significant change in radar sampling is the introduction of an uneven mode sequence with 50% of the sampling time dedicated to the lower atmosphere, allowing for detailed characterization of boundary layer clouds. The changes in the operational modes have a substantial impact on the postprocessing algorithms that are used to extract cloud information from the radar data. New methods for postprocessing of recorded Doppler spectra are presented that result in more accurate identification of radar clutter (e.g., insects) and extraction of turbulence and microphysical information. Results of recent studies on the error characteristics of derived Doppler moments are included so that uncertainty estimates are now included with the moments. The microscale data product based on the increased temporal resolution of the millimeter-wavelength cloud radars is described. It contains the number of local maxima in each Doppler spectrum, the Doppler moments of the primary peak, uncertainty estimates for the Doppler moments of the primary peak, Doppler moment shape parameters (e.g., skewness and kurtosis), and clear-air clutter flags.

Large-scale vertical velocity, diabatic heating and drying profiles associated with seasonal and diurnal variations of convective systems observed in the GoAmazon2014/5 experiment

“…3. The cloud frequency was derived from the Active Remote Sensing of Clouds (ARSCL) (Kollias et al, 2007) product, which uses a combination of the 95 GHz W-band ARM cloud radar (WACR), micropulse lidar (MPL) and ceilometer located at the ARM site pointing upward to determine a best-estimate cloud mask above the ARM site with 5 s temporal and 30 m vertical resolution. The ARSCL product leverages each instrument's strengths: the WACR penetrates non-precipitating and weakly precipitating thick clouds, the MPL is sensitive to thin clouds and the ceilometer reliably detects cloud base.…”

Improved Micro Rain Radar snow measurements using Doppler spectra post-processing

“…In the case of MRR, the integrals are reduced to a summation over all frequency bins of the identified peak. In addition to the parameters presented here, the routine also calculates the third moment (skewness), fourth moment (kurtosis), and the left and right slope of the peak as proposed by Kollias et al (2007). The peak mask, the borders of the peaks, the signal-to-noise ratio and the quality array are recorded as well.…”

Remote Sensing of Precipitation from Airborne and Spaceborne Radar

“…Doppler velocities are useful for inferring hydrometeor fall speeds and at multiple frequencies can be highly effective in discerning cloud liquid from rain (e.g., Kollias et al, 2007) as well as identification of ice particle habits (Kneifel et al, 2016), but obtaining them from rapidlymoving satellite platforms is a difficult engineering challenge that will first be attempted in the EarthCARE mission (Illingworth et al, 2015). Table 1 -Characteristics of TRMM, GPM, and CloudSat Spaceborne Weather Radars…”

“…This chapter is intended to provide an overview of the theoretical basis and some practical implementations of precipitation retrieval algorithms for nadir (or near-nadir) looking airborne and spaceborne weather radars at attenuating frequencies, without consideration of polarimetric quantities or Doppler velocity. While dualpolarimetric radars are widely used from ground-based platforms to identify preferentiallyoriented, non-spherical hydrometeors, at near-nadir incidence angles these measurements are of limited utility although the linear depolarization ratio measurements can be useful for identifying melting layers and non-spherical ice particles (Pazmany et al, 1994;Galloway et al, 1997).Doppler velocities are useful for inferring hydrometeor fall speeds and at multiple frequencies can be highly effective in discerning cloud liquid from rain (e.g., Kollias et al, 2007) as well as identification of ice particle habits (Kneifel et al, 2016), but obtaining them from rapidlymoving satellite platforms is a difficult engineering challenge that will first be attempted in the EarthCARE mission (Illingworth et al, 2015). Table 1 -Characteristics of TRMM, GPM, and CloudSat Spaceborne Weather Radars…”