Multidecadal Evaluation of WRF Downscaling Capabilities over Western Australia in Simulating Rainfall and Temperature Extremes

Abstract

The authors evaluate a 30-yr (1981-2010) Weather Research and Forecast (WRF) Model regional climate simulation over the southwest of Western Australia (SWWA), a region with a Mediterranean climate, using ERA-Interim boundary conditions. The analysis assesses the spatial and temporal characteristics of climate extremes, using a selection of climate indices, with an emphasis on metrics that are relevant for forestry and agricultural applications. Two nested domains at 10-and 5-km resolution are examined, with the higherresolution simulation resolving convection explicitly. Simulation results are compared with a high-resolution, gridded observational dataset that provides daily rainfall, minimum temperatures, and maximum temperatures. Results show that, at both resolutions, the model is able to simulate the daily, seasonal, and annual variation of temperature and precipitation well, including extreme events. The higher-resolution domain displayed significant performance gains in simulating dry-season convective precipitation, rainfall around complex terrain, and the spatial distribution of frost conditions. The high-resolution domain was, however, influenced by grid-edge effects in the southwestern margin, which reduced the ability of the domain to represent frontal rainfall along the coastal region. On the basis of these results, the authors feel confident in using the WRF Model for regional climate simulations for the SWWA, including studies that focus on the spatial and temporal representation of climate extremes. This study provides a baseline climatological description at a high resolution that can be used for impact studies and will also provide a benchmark for climate simulations driven by general circulation models.

Influence of antecedent soil moisture conditions on the synoptic meteorology of the Black Saturday bushfire event in southeast Australia

“…We used the Australian Water Availability Project (AWAP; Jones et al , ) gridded temperature and precipitation observations to evaluate the control simulation 2 m maximum temperatures (TMAX) and precipitation. The AWAP dataset has a resolution of 0.05° × 0.05° and is an interpolation from a network of weather stations across Australia, and has been previously used for evaluating regional climate simulations over Australia (Evans and McCabe, ; Evans et al ; Kala et al ; Andrys et al ). The AWAP data were interpolated to the coarser model grid using simple inverse distance weighting prior to comparisons.…”

“…We used the same WRF physics setting as Evans and McCabe (2010), which produces a reasonable climatology over southeast Australia, with maximum biases in the mean seasonal temperature and precipitation of approximately ±2 • C and −50 to +10 mm month −1 respectively, which were mostly confined to regions of complex topography. The model has also been shown to simulate diurnal rainfall variability over southeast Australia reasonably well (Evans and Westra, 2012) and similar results have been reported over Western Australia using the same WRF physics settings Andrys et al, 2015). The control (CNTL) simulation was carried out by initialising the model on 1 October 2008, providing a 4-month model spin-up prior to the event on 7 February 2009.…”

Added Value of a Dynamical Downscaling Approach for Simulating Precipitation and Temperature Over Tianshan Mountains Area, Central Asia

“…On the other hand, reanalysis driving data are usually used for sensitivity test of model configuration and its performance evaluation. The ERA-Interim data set has 30 vertical pressure levels of 0.75°× 0.75°horizontal resolution (Dee et al, 2011) and has proven to be useful in driving the WRF model over many complex terrains (Andrys et al, 2015;Heikkilä et al, 2010;Qiu et al, 2017).…”

“…The state-of-art Weather Research and Forecasting (WRF) model (Skamarock et al, 2008) is an RCM that has been increasingly used for such purposes. WRF has been applied in regional climate simulations such as in southwest of Western Australia (Andrys et al, 2015), Europe (Argüeso et al, 2012;Heikkilä et al, 2010), Atlantic Island in the Northwestern Africa (Expósito et al, 2015), East Asia (Yuan et al, 2011), central Asia (Qiu et al, 2017), and the continental United States (Bukovsky & Karoly, 2011;Caldwell et al, 2009;Salathé et al, 2010) and have successfully reproduced regional and local climate features at various scales.…”

A bias corrected WRF mesoscale fire weather dataset for Victoria, Australia 1972-2012

“…This model has been well established in simulations conducted over various regions globally, as explained in Andrys et al (2015), and is used operationally by agencies such as the U.S. National Weather Service. There has been increasing use of the WRF model for purposes of forestry, fire and agricultural applications though with varying results.…”