The motivation of this website is to provide a platform for the near-realtime systematic evaluation for NSSL's experimental QPE products (Q2). Additional NWS products are available for comparisons. Q2 is a paradigm shift from the operational method used in the Multisensor Precipitation Estimator used by River Forecast Centers.
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.
TIP: Gauges can be overlayed on accumulations by selecting networks on the "Gauge" tab and returning to the "QPE" tab. The accumulated product must be then reselected. All HADS gauges are in after 2 hours.
TIP: Zooming in far enough allows the display of individual pixel/gate values. (Example)
Q2 [Radar Only] 24 hr accumulation with overlay of gauges
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 identified by the precip_flags (that are in turn identified by VPRs).
An objective analysis of all gauges from NCEP with a 3 hr delay.
Q2 with a local gauge adjustment that includes a gauge-radar bias QC application.
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 MRMS 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.
Seamless Hybrid Scan Reflectivity. Seamless means that the lowest tilt is more than 50% blocked then the resulting bin value is a weighted average of the lowest tilt and the next higher tilt. Also, an "Apparent" Vertical Profile of Reflectivity is used to provide a correction in the bright band region. See "link" for more info
Mountain Mapper (MM; Schaake et al. 2004) is used by several River Forecast Centers (RFC) in the western United States. The MM technique is based on realtime gauge observations and a background rainfall distribution map derived from Parameter-Elevation Regressions on Independent Slopes Model (PRISM; Daly et al. 1994;). PRISM is a unique analytical tool that uses point measurements of precipitation, temperature, a digital elevation model (i.e., terrain height), and expert knowledge of complex climatic features (e.g., rain shadows and coastal effects) to produce continuous, digital grid estimates of monthly, yearly, and eventbased climatic parameters.
Accumulations of model-derived precipitable water (inches).
Accumulations of model-derived precipitation efficiency (inches). PE is PW multiplied by the mean 1000-700 hPa RH expressed as a fraction less than 1. Thus, it's more like a reduced PW total reflecting the potential for evaporation by dry air.
Noel, J., and J. Dobur, 2002: A pilot study examining model-derived precipitation efficiency for use in precipitation forecasting in the eastern United States. National. Wea. Digest, 3-8.
Hydroestimator NWS operational satellite precipitation product.
Within the mosaic tools, there is the ability to select showing either one product or the difference between any two products with the same units.