Proceedings with Extended Abstracts (single PDF file) - Radio ...

The profilers of WINDAS weredesigned based on the technologies developedby the Radio Science Center for Space andAtmosphere(RASC) of the Kyoto Universityand were produced by the Mitsubishi ElectricCorporation. The following points were paidmuch attention : 1)high transmittingpower(1.8kW), 2)high antenna gain(33dB),3)up-to date pulse compression technique (8-bitcoding), 4)intense clutter fences to preventground clutter and interference with otherradars, 5)semi-globe radomes against heavysnow accumulation, 6) automated data qualitycontrol, and 7)full remote operation of theprofilers from the headquarters of JMA inTokyo. Table 1 summarizes maincharacteristics of WINDAS.4. SIGNAL/DATA PROCESSINGS ANDDATA QUALITY CONTOROLAt each profiler site, vertical profiles of10-minute averages of spectral moments on thefive beams are measured, and U, V, Wcomponents of wind are sent every hour to theControl Center via the JMA exclusivetelecommunication lines or public digital lines.The computer system of the Control Centermakes quality control, and sends the data to theJMA central computer for numerical predictionsby 20 minutes after each hour.Signal processing as well as data qualitycontrol are the keys to keep profiler data highquality. The specific processes to WINDAS arethe estimation of Doppler spectral momentsusing the Gaussian function fitting (Hashiguchiet al., 1995) and the quadratic surface check forU and V components (Sakota, 1997). Theformer has the advantage of obtaining spectralmoments under the condition of low S/N ratio.The latter has effectively eliminate erroneousdata based on continuity of U or V componentson a time-height cross. One to two percents ofthe total amount of data has been rejected onaverage at the stage of the data quality control.At the early stages of the operation ofWINDAS, ground clutter disturbed the windmeasurement at several profiler sites.Enhancement of the performances of the clutterfences and improvement of the zero-Dopplervelocity rejection in Doppler spectra in the dataprocessing have almost solved the problem.Clutters from aircrafts or side robes of theantenna radiation occasionally appear, but theycause little troubles on the wind measurements.The significant wind measurement errorresults from migrating birds. The erroneousdata appear mostly in the night of spring andautumn under the fair weather conditions aswell as in the profiler networks of U.S. and ofEurope (Wilczak et al,1995 ; Engerbart andGorsdorf 1997). The wind measurementdeviations due to migrating birds extended to 90degree in direction and 10 m/s in speed for themost pronounced case. In October 2001 whenbirds actively migrated over about half of theprofiler sites, 12% of the total amount ofWINDAS data were contaminated by birds.Echoes from migrating birds had been rejectedby monitoring spectrum width during December2001 to March 2003. The new algorithm, inwhich Doppler spectra with intense signalpower are eliminated before the incoherentintegration, has been developed and wasintroduced in the signal processor of theprofilers in March 2003. The algorithm hasrecovered atmospheric signal from nearly halfof birds-contaminated echoes.5. DATA QUALITY AND IMPACT ONNWP MODELSThe wind profilers of WINDAS havefour options in vertical resolutions: 100, 200,300 and 600m corresponding to four pulselengths. The longer pulse length has betterheight coverage, but the less vertical resolution.Data availability for each height resolutionexamined prior to the operation. Dataavailabilities of 50% in 100, 200, 300m height353