NMQ Verification System (QVS) Tutorial
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Tabs: RUC
The following hourly analyses are available from the RUC model:
- Surface temperature
- Wetbulb temperature (sfc)
- Dewpoint temperature (sfc)
- Height of freezing level (0C)
- Precipitable water
- Precipitation efficiency — Precipitation placement potential. A product of PW and the mean 1000–700 hPa RH. See below for details.
Precipitation Efficiency Tutorial Info for NMQ
Precipitation Efficiency (PE, also known as Precipitation Potential Placement) is a parameter derived from hourly RUC analysis fields to identify areas of heavy rainfall potential. It is the product of precipitable water and the mean 1000-700 hPa relative humidity.
In the literature PE is primarily considered to be the ratio of total rainfall and total cloud condensation. Condensation is not an easily measured parameter for real-time operational use, however, so the approximation of PE using relative humidity was developed by the Ohio River Forecast Center so that it could easily be calculated from NWP analysis data for forecasting applications (Noel and Dobur 2002). Similar combinations of precipitable water and relative humidity were first used by NESDIS as a scalar correction factor for satellite-based precipitation estimates (Scofield 1987), and modified forms of the correction are still used in the Hydroestimator and GMSRA algorithms (Scofield and Kuligowski 2003).
The relative humidity form of PE has the same units as precipitable water. The relative humidity adjustment reduces the precipitable water value in areas of dry air where evaporation of cloud water and hydrometeors may significantly impact surface rainfall estimates. The resulting field is an amplified form of precipitable water that places high emphasis on regions where heavy rainfall can be expected if storms occur. PE can also be an effective tool for delineating moist, tropical airmasses from drier, continental airmasses when assigning rainfall rates in a real-time environment such as Q2.
References:
Noel, J., and J. C. Dobur, 2002: A pilot study examining model-derived precipitation efficiency for use in precipitation forecasting in the eastern United States. Nat. Wea. Digest, 26, 3-8.
Scofield, R. A., 1987: The NESDIS operational convective precipitation estimation technique. Mon. Wea. Rev., 115, 1773-1792.
Scofield, R. A., and R. J. Kuligowski, 2003: Status and outlook of operational satellite precipitation algorithms for extreme-precipitation events. Wea. and Forecasting, 18, 1037-1051.
