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CSIRO Marine and Atmospheric Research
Past Seminars

Seminar Abstract

Tasmania’s water environment in the middle of the 21st century: results from the CSIRO Conformal-Cubic Atmospheric GCM

This study examined future climate for Tasmania with emphasis on irrigation needs and water balance impacts on the physical environment in general. The CSIRO Conformal –Cubic Atmospheric GCM (CCAM) was used in the analysis. The model is embedded in the MK3 CSIRO coupled atmosphere-ocean model, meaning that CCAM obtains sea surface temperatures, ice extent and far-wind values on a daily basis from this GCM. The model presents a grid resolution of around 60 km near the Australian region but is much coarser on the far side of the globe. A model run was started in 1960 and allowed to run continuously until 2100 with the A2 CO2 emission scenario. Two thirty – year data sets were selected from this run: a “present” set (1975-2005) and a “future” (2035-2065). Each set contained daily precipitation, net solar and net longwave radiation, maximum and minimum air temperature, and additionally wind speed and wind direction, air temperature, mixing ratios and soil moisture at 9:00 AM and 3:00 PM. These data formed the basis of the analysis.

Measured seasonal precipitation data (P) was compared with modelled seasonal precipitation for the “present”. Model results mimic well the basic features and trends of the rainfall pattern for all seasons, but overpredicts maximum rainfall in the west coast and underpredicts in the low precipitation region near the east coast. A linear regression was established between measured and modelled precipitation, and this relationship was used to correct “future” model precipitation data. The Penman – Monteith model of potential evapotranspiration (PE) was derived using measured Tasmanian data and compared with estimates using model data for the “present”. This yielded correction factors that were also used to calculate present and future (PE) for Tasmania.

Model results show lowered precipitation along the east coast and central/eastern part of the State during summer, autumn and spring. However these values are not high, with a maximum drop of around 6% in summer. By contrast potential evaporation is much higher, causing the net water storage (P-PE) to drop by a maximum of 33% along the central/east coast. Implications of this increasing deficit to the Tasmanian environment will be discussed.

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CSIRO = Marine Laboratories Auditorium, Castray Esplanade, Hobart

For further information, or to schedule a seminar, contact:
Peter Oke, (Oceanographic seminars) CSIRO Marine Research (03) 6232 5387
Keith Hayes, (Biological seminars) CSIRO Marine Research (03) 6232 5298
Katrina Nitschke, Antarctic Climate and Ecosystems CRC (03) 6226 2265 & IASOS, University of Tasmania (03) 6226 2509