Status of S-PolKa Data Sets Bob Rilling, Mike Dixon, Scott Ellis, John Hubbert and Scot Loehrer EOL, NCAR, Boulder, CO DYNAMO radar workshop University of Washington, Seattle August 2012

QC-1 Data Set QC version 1 data set released July 7 Format is CfRadial – Times are given in UTC – Filename contains start and end times of volume: cfrad _ _to_ _ _SPOL_v9373_SUR.nc – Time variable in file is relative to the start time Available for download: – URL: – Max download per session: 16 GB – Mean data size per observed data: 7 GB Available on ~1 TB USB external disks containing: – QC version 1 data set – Image browser – Web cam images

QC-1 Data Set Web documentation is available at: This contains: – Project information – Data set description – Data quality and calibration reports – Download procedures – Links to format documents

Summary of Data Quality and Calibration Procedures Tower targets: for checking range accuracy Solar scans: for pointing, leveling and power calibration Engineering calibration for S-band and Ka-band S and Ka systems sensitivity checks S/Ka comparisons Self-consistent method for S-band calibration (PHI-cal) Vertical pointing for Zdr bias determination LDR sensitivity check Monitoring using Automated Test Equipment (ATE) Monitoring of data transfer and recording

Spol-Ka QC-1 fields

Overview of Changes/Improvements Merged data set created: – S-band data – Ka-band data – PID – Rain rates Noise power for all S-band and Ka-band power quantities has been re-estimated on a beam-by-beam basis impacting: – all noise-power corrections – censoring/thresholding at low measured powers. Advanced techniques for data censoring have been developed, resulting in a more reliable elimination of bad data. A new and improved computation of radial velocity was developed

Overview of Changes/Improvements A new and improved computation of correlation coefficient was developed Ka-band reflectivity was corrected to account for the change in magnetron – Changed by ?? dB on ????? S-band atmospheric attenuation was estimated using Doviak and Zrnic (Doppler Radar and Weather Observations, 2nd ed., 1993, pp44-45) – Applied to reflectivity data (DBZ_S) – Uncorrected data also included (DBZ_NAA_S) Test pulse removed S-band power and Zdr calibrations unchanged from the field data

Known Issues Beam blockage Ka-band sensitivity KDP estimation

Vertically Pointing Zdr Calibration Rain looks spherical at vertical incident – Intrinsic Zdr = 0 dB – Can be used to calibrate Zdr 29 vertical data collections Mean offset of removed from Zdr data throughout project Std dev = dB Max – Min = dB

Self-consistency Calibration Used as a calibration check Utilize relationship between Z, Zdr and Kdp – Kdp = aZ b Z dr c – Zdr is independently calibrated – Kdp is independent of calibration Integrate computed Kdp with range to obtain  DP Use rays with large  DP Compare computed and measured  DP DateTime (UTC)Estimated bias (dB) Oct 12, to Nov 17, to Dec 23, to

Comparison of Ka-band Z to S-band Z Used as a calibration check Compare S- and Ka-band reflectivity Rayleigh scattering only Account for atmospheric attenuation at Ka-band – Use Liebe microwave propagation model – Compare Z at close ranges – Near sounding time and site Bias < 0.5 dB Date/timeMean bias (dB)Variance (dB)Number of comparisons