Breakout Summary Report
ARM/ASR User and PI Meeting
2 - 6 May 2016
Radar Doppler spectra: Recent progress in retrievals and model-observation intercomparison
5 May 2016
10:45 AM - 12:45 PM
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Edward Luke
5 May 2016
10:45 AM - 12:45 PM
0
Edward Luke
Breakout Description
The breakout session included six presentations: two related to radar data quality and calibration, two on ice and mixed-phase process studies, one on drizzle retrievals, and one on spectra-based observational constraint of LES simulations of low stratiform warm clouds. The presentations were followed by a discussion of the future direction of the group regarding mixed-phase clouds and operational uses of MicroARSCL.Presentations - Mixed-phase clouds:
Mariko Oue (Stony Brook University) presented a case study demonstrating the complementary nature of information in profiles of radar polarimetric variables using the quasi-vertical profiling approach with profiles of radar Doppler spectra. The combination of KAZR and SACR observations enable a very detailed accounting of the various ice particle types and habits populating multiple fall streaks in KAZR spectra profiles.
Max Maahn (University of Colorado) provided a detailed analysis of the information content involved in using higher-order radar Doppler moments and multiple radar frequencies in ice clouds, notably showing that the information content gained from higher-order moments of a single radar frequency exceeds that from conventional moments at two radar frequencies. Max discussed the implications for retrieval of vertical air motion, turbulence, particle distribution, and mass-size relations when used in an optimal estimation framework.
Presentations - Warm clouds:
V. Chandrasekar (Colorado State University) demonstrated a parametric time domain method (PTDM) approach for the separation of cloud and drizzle radar Doppler spectra signals in warm stratiform clouds. The PTDM technique enables inference of vertical air motion, dynamical processes, and particle size distributions. Chandra suggested the action item of comparing these results with those from other existing techniques.
Jasmine Rémillard (Stony Brook University), motivated by a lack of existing approaches for constraining and evaluating LES simulations of early drizzle formation, used radar Doppler spectra forward simulation to compare two bin microphysics-based models with observations, focusing on the relationships of reflectivity to mean Doppler velocity, and reflectivity to spectrum skewness.
Presentations – Data quality and calibration:
Edward Luke (BNL) presented a new set of artifacts currently impacting KAZR2 and SACR2 spectra. The purity of KAZR spectra was contrasted with the artifacts found in comparable KAZR2 spectra. There is evidence that spectral artifacts can also bias the basic moments reported by the radars. Ed also showed evidence for a significant calibration offset of the WACR during the AMF1 deployment in the Azores (GRW).
Main Discussion
The group recognized the recent advances in the use of radar Doppler spectra applied to warm stratiform clouds and decided that a careful shift of focus toward mixed-phase clouds is desirable. The first goal is an evaluation of our radar forward operators in mixed-phase clouds followed up with a process-oriented study.The group recommended that the MicroARSCL radar Doppler spectra processing product is the best shielding layer for insulating the user community from having to deal with artifacts. The group raised no objection to running MicroARSCL operationally in real time at radar sites to gain the added advantage of a new level of data compression through merging of redundant spectra datastreams generated simultaneously by different modes. At any given time and range, spectra from the mode producing the highest-quality data would be selected. Since this ultimately means discarding some data at the collection site, adoption of such a methodology should be phased, with full data retention continuing during a trial phase in which issues can be identified.
Regarding the possible WACR calibration bias during the AMF1 GRW deployment, the group decided that a renewed effort of comparison with spaceborne data is needed. There was recognition that this suffers from drawbacks as applied to low warm clouds.
Key Findings
Forward radar Doppler spectra simulation driven by LES bin microphysics can provide great insights into microphysical parameterizations. The combination of radar polarimetry and radar Doppler spectra shows promising results for improving our ability to identify non-spherical particle types.Future Plans
Coordination of an intercomparison of radar forward simulations of mixed-phase clouds.Action Items
Revisit the validation of GRW/ENA radar calibration using spaceborne observations.Run MicroARSCL operationally at radar sites with spectra mode merging.