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Products Guide

QPE - Mountain Mapper

QPE - Mountain Mapper

Short Description

Algorithm that improves upon quantitative precipitation estimates (QPE) in the Western U.S. where complex terrain affects radar estimates and gauge density. It uses the Parameter-Elevation Regressions on Independent Slopes Model (PRISM) to create continuous grid estimates of hourly precipitation climatologies to compare against gauge observations.

Subproducts

  • 1-, 3-, 6-, 12-, 24-, 48-, and 72-hour accumulations

Primary Users

NWS: WFO, RFC

Input Sources

PRISM monthly precipitation climatology, Hydrometeorological Automated Data System (HADS) gauge data

Resolution

Spatial resolution: 1km x 1km

Temporal resolution: 1-, 3-, 6-, 12-, and 24-hourly accumulations are updated hourly at the top of the hour. 48- and 72-hour accumulations are updated daily at 12Z. All products end at the indicated time.

Product Creation

The QPE – Mountain Mapper product is based on a comparison of the Parameter-Elevation Regressions on Independent Slopes Model (PRISM) monthly precipitation climatologies (divided into hourly grids) and the real-time hourly gauge observations, via a ratio bias at each gauge site. PRISM is a tool that uses point measurements of precipitation and temperature, a digital elevation model (DEM), and expertise of complex climatic features to create continuous gridded estimates of monthly climatic parameters. The ratio biases are interpolated onto the MRMS grid, and then multiplied by the normalized PRISM hourly rainfall field to create the Mountain Mapper hourly analysis.

Technical Details

The following steps are only conducted on the one-hour accumulation estimate, since all the other accumulations are aggregates of the one-hour field:

  1. The PRISM monthly precipitation climatology (Figure 1) is evenly divided into hourly rainfall fields by dividing the monthly grid by the total number of hours in the month.
  2. A ratio (ek) is computed between the hourly gauge observation (gk) and the normalized PRISM hourly rainfall (pk) at each gauge site that has successfully passed the Gauge Quality Control.
  3. The ratio bias is then interpolated onto the MRMS grid using a similar inverse distance weighting (IDW) scheme as the QPE – Radar w/ Gauge Bias Correction product.
    1. Unlike the QPE – Radar w/ Gauge Bias Correction, the Mountain Mapper product uses predefined IDW parameters, b = 2 and D = 200 km.
  4. Finally, the interpolated ratio field is multiplied by the normalized PRISM hourly rainfall field to create the Mountain Mapper hourly analysis.
Figure 1. The PRISM total precipitation monthly climatology for August 2014.
 
As of November 2016, the Mountain Mapper domain includes British Columbia, Canada (Figure 2).
 
Figure 2. Example of Mountain Mapper including British Columbia, Canada.

References

Zhang, J., K. Howard, S. Vasiloff, C. Langston, et al., 2011: National Mosaic and multi-sensor QPE (NMQ) system: description, results and future plans. Bull. Amer. Met. Soc., 92, 1321-1338.

Zhang, J., K. Howard, S. Vasiloff, C. Langston, B. Kaney, Y. Qi, L. Tang, H. Grams, D. Kitzmiller, J. Levit, 2014: Initial Operating Capabilities of Quantitative Precipitation Estimation in the Multi-Radar Multi-Sensor System. 28th Conf. on Hydrology, Amer. Meteor. Soc.

Daly, C., R. P. Neilson, and D. L. Phillips, 1994: A statistical-topographic model for mapping climatological precipitation for mountainous terrain. J. Appl. Meteor., 33, 140-158.

Gauge Quality Control documentation

Other MRMS product documentation: QPE – Radar Only, QPE – Radar w/ Gauge Bias Correction