NMQ Verification System (QVS) Tutorial
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Figure 17. Default Q2 tab image showing Q2RAD_HSR.
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Figure 18. Different Z-R
relations. Only the convective, stratiform and tropical are used in Q2 at this time.
Additional Z-Rs used by the NWS will be incorporated in algorithm updates.
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Figure 19. Gauge-only analysis.
Tabs: Q2
Next-generation QPE (Q2) products are experimental in nature. Q2 products can be derived from single or multiple sensors and can be combined in various ways. Figure 17 (at right) shows the default Q2RAD_HSR 24h image.
Hourly gauge data are FTPed from NCEP every 10 min. Just after the top of the hour, the number of gauges is small. All gauges are in after 6 hours.
The following products are available for testing and comparison:
- RadarCov
- Indicates the percentage of time a grid point was covered by any radar.
- Q2RAD_HSR
- "Radar-based precipitation rate and accumulations over various time periods (1- to 72-hour). The rate is derived from the hybrid scan reflectivity using convective, stratiform and tropical Z-R relations (see Figure 18 at right) identified by the precip_flags (that are in turn identified by VPRs). Note the additional optional Z-Rs used by the NWS.
- Q2RAD_HSR_GC
- Local gauge corrected radar QPE fields. The local gauge correction is applied onto the 1-h Q2RAD_HSR precipitation field. It runs hourly and uses hourly rain gauge observations from the HADS (Hydrometeorological Automated Data System) data sets at NCEP. In the local gauge correction scheme, radar-gauge biases are calculated at each gauge site and then interpolated onto the NMQ grid using an inverse distance weighted (IDW) mean scheme. The two parameters in the IDW scheme, exponent and radius of influence, are determined through a cross-validation procedure. The interpolated radar-gauge bias field is applied back to the Q2RAD_HSR 1-h precipitation field and a local gauge bias corrected 1-h precipitation field is obtained. Longer-term accumulations are computed by aggregating the 1-h local gauge corrected precipitation fields.
- STAGE4
- NWS operational 24 h precipitation product.
- HYDRO_EST
- Hydroestimator NWS operational satellite precipitation product.
- Q2GAUGE
- Gauge-only analysis (Figure 19) using the same IDW scheme as determined in the Q2RAD_HSR_GC process.
Analysis Tools allows product comparisons (see Mosaic 3D Derived).
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