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The beneficial impact of radio occultation observations on Australian region forecasts


The Constellation Observing System for Meteorology, Ionosphere and Climate
(COSMIC) was launched in April 2006. This system provides a new observation type
for operational meteorology that has been shown to provide significant information
on the thermodynamic state of the atmosphere and to allow improvements in
atmospheric analysis and prognosis. A month of COSMIC radio occultation
observations, together with a smaller number of radio occultation observations
from the Meteorological Operational satellite (MetOp) and Gravity Recovery and
Climate Experiment (GRACE) spacecraft, have been assimilated into the global
ACCESS (Australian Community Climate Earth System Simulator) system, which
is being employed at the Australian Bureau of Meteorology to provide real-time
operational forecasts. In this study, four-dimensional variational assimilation
(4DVAR) has been used to assimilate the radio occultation and other data into the
global ACCESS system (ACCESS-G), which has been used to provide forecasts to
five days ahead. For the period studied, the accuracy of these forecasts has been
compared to forecasts generated without the use of the radio occultation data. The
forecasts using radio occultation data have been found to be improved in the lower,
middle and upper troposphere. These results, combined with the relatively unbiased
nature of the radio occultation observations indicate their use has the potential to
improve operational analysis and forecasting in the Australian Region and also to
assist in important tasks such as a regional reanalysis and climate monitoring.

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