Examining Interior Grid Nudging Techniques Using Two-Way Nesting in the WRF Model for Regional Climate Modeling

Abstract

This study evaluates interior nudging techniques using the Weather Research and Forecasting (WRF) model for regional climate modeling over the conterminous United States (CONUS) using a two-way nested configuration. NCEP–Department of Energy Atmospheric Model Intercomparison Project (AMIP-II) Reanalysis (R-2) data are downscaled to 36 km × 36 km by nudging only at the lateral boundaries, using gridpoint (i.e., analysis) nudging and using spectral nudging. Seven annual simulations are conducted and evaluated for 1988 by comparing 2-m temperature, precipitation, 500-hPa geopotential height, and 850-hPa meridional wind to the 32-km North American Regional Reanalysis (NARR). Using interior nudging reduces the mean biases for those fields throughout the CONUS compared to the simulation without interior nudging. The predictions of 2-m temperature and fields aloft behave similarly when either analysis or spectral nudging is used. For precipitation, however, analysis nudging generates monthly precipitation totals, and intensity and frequency of precipitation that are closer to observed fields than spectral nudging. The spectrum of 250-hPa zonal winds simulated by the WRF model is also compared to that of the R-2 and NARR. The spatial variability in the WRF model is reduced by using either form of interior nudging, and analysis nudging suppresses that variability more strongly than spectral nudging. Reducing the nudging strengths on the inner domain increases the variability but generates larger biases. The results support the use of interior nudging on both domains of a two-way nest to reduce error when the inner nest is not otherwise dominated by the lateral boundary forcing. Nevertheless, additional research is required to optimize the balance between accuracy and variability in choosing a nudging strategy.

Simulation of fine organic aerosols in the western Mediterranean area during the ChArMEx 2013 summer campaign

“…The WRF configuration used for this study consists of the Single Moment-5 class microphysics scheme (Hong et al, 2004), the RRTMG radiation scheme (Mlawer et al, 1997), the Monin-Obukhov surface layer scheme (Janjic, 2003), and the NOAA Land Surface Model scheme for land surface physics (Chen et al, 2001). Sea surface temperature update, surface grid nudging (Liu et al, 2012, Bowden et al, 2012, ocean physics and topographic wind options are activated. Also, 30 the feedback option is activated, meaning that the simulation of the nested domains can influence the parent domain.…”

Adding Four Dimensional Data Assimilation by Analysis Nudging to the Model for Prediction Across Scales – Atmosphere (Version 4.0)

“…Unlike for temperature and wind, nudging water vapor concentration perturbs atmospheric mass in the simulation. Previous studies using WRF have chosen to employ smaller nudging coefficients for qv versus other variables Bowden et al, 2012;Bowden et 15 al., 2013;Bullock et al, 2014). Results discussed later in this work show some benefit from doing so.…”

The geographic distribution and economic value of climate change-related ozone health impacts in the United States in 2030

“…The RCP 6.0 scenario (Fujino et al, 2006) assumes a modest degree of mitigation of greenhouse gas emissions such that total radiative forcing will increase over the next century before stabilizing at 6.0 W m −2 in 2100. We downscaled these GCM projections using the Weather Research and Forecasting (WRF) model following techniques described by Bowden et al (2012) and Otte et al (2012). We conducted WRF simulations at 36-km horizontal grid spacing over the United States, incorporating the global climate forcing at the lateral boundaries, through the interior of the domain (following Otte et al, 2012), and in the sea-surface temperatures.…”