BAMOS Vol 30 No. 3 2017 | Page 16

16 BAMOS Sept 2017 Article An atmospheric high-resolution regional reanalysis for Australia Dörte Jakob, Chun-Hsu Su, Nathan Eizenberg, Greg Kociuba, Peter Steinle, Paul-Fox-Hughes and Lynette Bettio Bureau of Meteorology, Australia [email protected] Abstract The Bureau of Meteorology is currently undertaking a high-resolution atmospheric reanalysis for Australia. The reanalysis will eventually cover a 25-year period, with the first six-year time slice (2010 to 2015) expected to become available to users in late 2017. The reanalysis will ultimately represent a suite of high-resolution gridded climate datasets and as such will prove valuable for a large range of applications. In this short article, we introduce the high-resolution reanalysis to the AMOS community. We provide some basic information about the development and evaluation of the reanalysis, before exploring two case studies that illustrate how the reanalysis can be used. Introduction Developing the reanalysis The Bureau of Meteorology Atmospheric high-resolution Regional Reanalysis for Australia (BARRA) is the first of its kind for the Australian region. The Bureau of Meteorology (Bureau) is making a major investment to develop this new dataset because of the important benefits it offers to Australia. This investment is supported by fire agencies in various States because of the advantages reanalysis data can offer Australia in enabling a greater understanding of past weather, including extreme events. The regional reanalysis suite is based on the UK Met Office (UKMO)’s regional reanalyses undertaken as part of the European project Uncertainties in Ensembles of Regional ReAnalyses (UERRA, Jermey, 2015), and the Australian Community Climate Earth-System Simulator (ACCESS; Bi et al. 2013, Bureau of Meteorology 2013a, b). The region covered by the reanalysis is the Australian continent, and the surrounding region including parts of southeast Asia, New Zealand, and south to the ice edge of the Antarctic continent. We are archiving about 100 parameters at hourly (and some at 10-minute) time intervals at approximately 12-km resolution and the reanalysis extends over 70 levels up to 80 km into the atmosphere. The following gives a flavour of what the reanalysis will provide: information about surface conditions (such as temperature, precipitation, wind speed and direction, humidity, evaporation and soil moisture), information at pressure and model levels, and information on solar radiation and cloud cover. Reanalysis datasets are valuable because they provide a consistent method of representing the atmosphere over multiple decades, giving greater understanding of the weather over Australia, including during extreme events. This greater understanding allows for better planning and management to reduce risks for the future. Whilst other reanalysis products cover the Australian region, such as the global reanalysis produced jointly by the National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP-NCAR) and ERA-Interim, a global atmospheric reanalysis at approximately 80 km resolution produced by the European Centre of Medium-Range Weather Forecasts, BARRA offers a higher resolution in space and time. Importantly, BARRA is being developed specifically for Australia so it makes use of local surface observations and locally produced satellite-retrieved wind vectors that are not be available to coarser global products. The evaluation of the reanalysis is also centred specifically on the Australian region. The reanalysis is being produced in two steps. The first step delivers a reanalysis over the Australian domain at an (approximately) 12-km resolution (BARRA-R). This is by far the more computationally demanding step. In the second step the 12-km reanalysis is then downscaled to a 1.5-km resolution up to 40 km into the atmosphere f