Citation:

Jalowska, A. AND T. Spero. Evaluation of Dynamically Downscaled, 36- and 12-km Simulations of the WRF Model to Develop Intensity-Duration-Frequency (IDF) Curves for U.S. Urban Areas. 2018 CMAS Conference, Chapel Hill, NC, October 22 - 24, 2018.

Impact/Purpose:

Storm water management is of great importance, particularly in urban areas where there are large areas of pavement that cannot absorb rainfall. Decisionmakers need to understand the variations in the intensities, durations, and frequencies of rainfall events within these urban areas to quantify the effects on urban flooding, water quality, and water availability. This research explores using meteorologically modeled data in place of long observational records to analyze rainfall events for designated cities within the U.S.

Description:

Extreme precipitation events influence watershed, agriculture and urban management decisions. Intensity-Duration-Frequency (IDF) curves are a common tool used to project extreme precipitation events in urban and environmental planning. This study evaluates development of IDF curves using dynamically downscaled 36- and 12-km simulations of the Weather Research and Forecasting (WRF) model. The evaluation is performed on three data sets: 1) dynamically downscaled 36-km WRF model forced with 2.5-degree (~200-km) NCEP–DOE AMIP-II Reanalysis (R-2) data; 2) dynamically downscaled 36-km WRF model forced with 0.75-degree (~79-km) ERA‐Interim data; and 3) dynamically downscaled 12-km WRF model forced with ERA‐Interim data. The modeled data are verified with historical observational data for 3 cities in the U.S. using a 23- year historical period (1988–2010). IDF curves developed from the two 36-km simulations provide good representation of 6-18-hour duration events. However, both 36-km simulations fail to predict short-duration precipitation events (1- 3-hour). Increasing the resolution of the model’s driving data by changing from R-2 to ERA-Interim did not improve the model’s representation of short-duration precipitation events. Using the WRF model to downscale to a 12-km horizontal grid enhances the model’s ability to reproduce precipitation and IDF curves. Finer resolution allows better reproducibility of the frequency and intensity of 1- 3-hour rain events and improves representation of 6- 24- hour rain events. However, better performance of 12- km WRF data did not apply equally to all study sites, suggesting further modifications to the model and/or methodology are necessary.

URLs/Downloads:

Record Details: