The NARCliM project: model agreement and significance of climate projections

Abstract

NARCliM (New South Wales and Australian Capital Territory Regional Climate Modelling project) is a climate downscaling project for Australia and the surrounding regions. Present and future climate simulations are performed using a 1-way nested dynamical downscaling approach and span 2 domains. We focus on the inner 10 km domain that extends across southeast Australia. Three regional climate models (RCMs) based on the Weather Research and Forecasting System (WRF) version 3.3 dynamically downscale 4 global climate model (GCM) simulations to finer resolutions. This project complements and improves on already available GCM projections for the region. Our simulations cover 3 epochs: present (1990−2009), near future (2020− 2039), and far future (2060−2079). Here, we focus on the mean surface air temperature and precipitation. The RCMs are better able to capture spatial patterns of temperature and precipitation and improve the temperature root mean square error (RMSE) compared to the GCMs, at least for the inner domain. The RCMs tend to be biased cold compared to observations and are wetter than the GCMs during warm seasons. The downscaled RCM projections exhibit a weaker warming over land compared to the GCMs. The RCMs project no significant precipitation changes in the far future over most areas. However, Victoria is expected to see significant springtime drying of 15 mm mo −1 , which is considerably higher than previous GCM results. This drying is associated with a larger strengthening of the subtropical ridge than modelled previously by the GCMs. In addition, the RCMs project significant precipitation changes in contradicting directions for some inland areas during winter.

Change in Soil Organic Carbon Stocks under 12 Climate Change Projections over New South Wales, Australia

“…Although all models tend to reveal a warming climate with increasing temperatures, there is considerable variation in trends with respect to annual rainfall, with the MIROC and CCCMA models projecting more moist conditions over NSW, whereas the CSIRO and, to a lesser extent, the ECHAM models projecting drier conditions. The different model projections for maximum temperatures and precipitation over NSW and the whole NARCliM domain are presented in Olson et al (2014) and Office of Environment and Heritage (2015).…”

A simple method for Bayesian model averaging of regional climate model projections: Application to southeast Australian temperatures

“…Corresponding temperature observations are derived from the Australian Water Availability Project (AWAP) [ Jones et al ., ]. For consistency, the observations are first interpolated to the model grid before averaging over the regions [ Olson et al ., ]. Many models capture the warming trend, although some models appear to experience a slow cooling for some regions (Figure ).…”

Land surface albedo and vegetation feedbacks enhanced the millennium drought in south-east Australia

“…These data have been widely used in a number of hydrological and climate studies in south-east Australia (e.g. Cai et al, 2009;Olson et al, 2016;Teng et al, 2015). Here, the 5 km resolution products were interpolated to 10 km resolution to enable direct comparison with the RCM results.…”