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