Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies

Transcription

1 Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies

2 2016 State of NSW and Office of Environment and Heritage and CSIRO CSIRO advises that the information contained in this publication comprises general statements based on scientific research. The reader is advised and needs to be aware that such information may be incomplete or unable to be used in any specific situation. No reliance or actions must therefore be made on that information without seeking prior expert professional, scientific and technical advice. To the extent permitted by law, CSIRO (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this publication (in part or in whole) and any information or material contained in it. With the exception of photographs, the State of NSW and Office of Environment and Heritage are pleased to allow this material to be reproduced in whole or in part for educational and non-commercial use, provided the meaning is unchanged and its source, publisher and authorship are acknowledged. Specific permission is required for the reproduction of photographs. The Office of Environment and Heritage (OEH) has compiled this technical report in good faith, exercising all due care and attention. No representation is made about the accuracy, completeness or suitability of the information in this publication for any particular purpose. OEH shall not be liable for any damage which may occur to any person or organisation taking action or not on the basis of this publication. Readers should seek appropriate advice when applying the information to their specific needs. Every effort has been made to ensure that the information in this document is accurate at the time of publication. However, as appropriate, readers should obtain independent advice before making any decision based on this information. All content in this publication is owned by OEH and is protected by Crown Copyright. It is licensed under the Creative Commons Attribution 4.0 International (CC BY 4.0), subject to the exemptions contained in the licence. The legal code for the licence is available at Creative Commons. OEH asserts the right to be attributed as author of the original material in the following manner: State of New South Wales and Office of Environment and Heritage Citation: Ji F, Vaze J, Teng J, Wang B and Scorgie Y, 2016, Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies, Report prepared by the NSW Office of Environment and Heritage and CSIRO on behalf of NSW Department of Primary Industries Water, March Published by: Office of Environment and Heritage NSW; 59 Goulburn Street, Sydney NSW 2000 PO Box A290, Sydney South NSW 1232; Phone: (02) (switchboard) Phone: (environment information and publications requests)

3 Phone: (national parks, climate change and energy efficiency information, and publications requests); Fax: (02) ; TTY: (02) Website: ISBN: OEH2016/0237 March 2016

4 Contents 1. Summary 1 2. The purpose 1 3. Data Gridded historical climate data NARCliM Future Climate Projections 3 4. Methods Rainfall projections APET projections 5 5. Results Historical climate data Rainfall Areal potential evapotranspiration Future climate data Climate change projections for ~ Climate change projections for ~ References 23 List of figures Figure 1. NARCliM project model domains, including the CORDEX domain with about 50 km grid resolution (outer domain shown as map extent) and the NARCliM domain with about 10 km resolution (inner domain shown with red outline) 4 Figure 2. Mean annual rainfall for (mm) 6 Figure 3. Mean seasonal rainfall for (mm) 6 Figure 4. Mean annual APET for (mm) 7 Figure 5. Mean seasonal APET for (mm) 7 Figure 6. Percent change in ensemble mean annual rainfall for ~2030 relative to ~20008 Figure 7. Percent change in ensemble mean seasonal rainfall for ~2030 relative to ~ Figure 8. Percent change in mean annual rainfall across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations 9 Figure 9. Percent change in mean summer rainfall across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations 10 Figure 10. Percent change in mean autumn rainfall across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations 10 Figure 11. Percent change in mean winter rainfall across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations 11 Figure 12. Percent change in mean spring rainfall across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations 11 [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] iii

5 Figure 13. Percent change in ensemble mean annual APET for ~2030 relative to ~ Figure 14. Percent change in ensemble mean seasonal APET for ~2030 relative to ~ Figure 15. Percent change in mean annual APET across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations 13 Figure 16. Percent change in mean summer APET across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations 13 Figure 17. Percent change in mean autumn APET across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations 14 Figure 18. Percent change in mean winter APET across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations 14 Figure 19. Percent change in mean spring APET across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations 15 Figure 20. Percent change in ensemble mean of annual rainfall for ~2070 relative to ~ Figure 21. Percent change in ensemble mean of seasonal rainfall for ~2070 relative to ~ Figure 22. Percent change in mean annual rainfall across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations 17 Figure 23. Percent change in mean summer rainfall across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations 17 Figure 24. Percent change in mean autumn rainfall across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations 18 Figure 25. Percent change in mean winter rainfall across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations 18 Figure 26. Percent change in mean spring rainfall across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations 19 Figure 27. Percent change in ensemble mean of annual APET for ~2070 relative to ~ Figure 28. Percent change in ensemble mean of seasonal APET for ~2070 relative to ~ Figure 29. Percent change in mean annual APET across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations 20 Figure 30. Percent change in mean summer APET across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations 21 Figure 31. Percent change in mean autumn APET across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations 21 Figure 32. Percent change in mean winter APET across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations 22 Figure 33. Percent change in mean spring APET across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations 22 [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] iv

6 List of tables Table 1 Model configuration for the three RCMs in NARCliM 3 [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] v

7 1. Summary This report describes the methods and results from a study undertaken to generate future daily rainfall and areal potential evapotranspiration (APET) across New South Wales (NSW) and the Australian Capital Territory (ACT) based on the outputs from the NSW/ACT Regional Climate Modelling (NARCliM) project (Evans et al. 2014). Daily rainfall and APET were projected across this region at a spatial resolution of 0.05 o (~ 5 km x 5 km), with projected changes in rainfall and APET given for (referred to as ~2030) and (referred to as ~2070) relative to the baseline period of (referred to as ~2000). To span the range of plausible climate futures, the NARCliM project used an ensemble of twelve model members, comprising combinations of three global climate models (GCMs) and four regional climate models (RCMs). Daily rainfall and APET were projected based on each of the twelve ensemble members. The methods applied in the study are comparable to the NSW Office of Water s Future Climate and Runoff Projections (Vaze et al. 2008, 2011), the CSIRO Murray-Darling Basin Sustainable Yields (MDBSY) Project (Chiew et al. 2008) and the South Eastern Australian Climate Initiative (SEACI) (Post et al. 2008). However, unlike these earlier projects, this study uses the higher resolution NARCliM regional climate projections and reports on changes in rainfall and APET under the IPCC SRES A2 global warming scenario (IPCC, 2000). There are two main outputs from this study. The first output is the presentation of estimates of likely changes in average rainfall and APET at ~2030 and ~2070 (this report). The second output is a data set comprising 120 years ( ) of daily rainfall and APET projections for each of the 0.05 (~5km by 5km) grid cells across NSW and the ACT. This dataset can be used in hydrological, ecological and agricultural modelling to investigate the impacts of climate change. The results indicate that there is a clear east-west and north-south gradient across NSW in the magnitude of historical rainfall and APET respectively. Future projections of rainfall and APET varied considerably between the twelve GCM/RCM members of the NARCliM ensemble, and across the four seasons. The largest differences are associated with the driving GCMs. The magnitudes of changes in rainfall and changes in APET for ~2070 relative to ~2000 are larger than those for ~2030 relative to ~2000. A 10 to 15% increase in annual rainfall is projected for northern NSW, with not much change (-5 to 5%) projected for southern NSW, and more than a 10% decrease for the Snowy Mountains for ~2070. There is a clear seasonal difference in changes with larger increases in rainfall in summer and autumn, and the greatest decreases in rainfall projected in spring, especially for the Snowy Mountains. A 5 to 6% increase in annual APET is projected for northern NSW and a 4 to 5% increase for southern NSW for ~2070. The largest increase in APET is in spring and smallest increase is in winter. 2. The purpose Projections of climate variables under a changing climate are essential for sustainable natural resources planning and management. These are typically obtained from global climate models (GCMs), with hypothesized scenarios (e.g., assumptions regarding future changes in carbon dioxide concentrations). GCMs are widely used and arguably still remain the best available tools for assessing the response of the climate system to changes in atmospheric forcing. However, GCMs provide information at a spatial resolution that is too [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 1

8 coarse to be directly used in hydrological modelling and other impact studies requiring finer resolution information. Through the NSW and ACT Regional Climate Model (NARCliM) project, the NSW and ACT governments collaborated with the Climate Change Research Centre at the University of NSW to produce an ensemble of fine scale regional climate projections for south-eastern Australia that can be used to assess and plan for the range of likely future changes in climate (Evans et al. 2014). Dynamical downscaling was used to generate fine scale climate projections, with three configurations of the Weather Research and Forecasting (WRF) regional climate model (RCM) used to downscale projections from four global climate models (GCMs) providing a total of 12 models. The 12 models were run for three time periods: 1990 to 2009 (base), 2020 to 2039 (near future), and 2060 to 2079 (far future) with regional climate projections produced on a ~10km spatial resolution across south-eastern Australia. Differences between the near future and base period projections are taken to be indicative of near future changes in climate, with differences between the far future and base period projections indicative of far future changes. This study derives future projections of daily rainfall and areal potential evapotranspiration (APET) for a 0.05 o (~5km) spatial resolution across NSW based on an empirical scaling method which perturbs observed climate time series based on the near and far future changes projected by NARCliM (Evans et al. 2014). This data set is derived for subsequent use in water security studies by the NSW Department of Primary Industries Water. 3. Data Two datasets are used in the study: (1) Historical climate ( ) data, including daily time series of rainfall and Morton s APET, is the baseline against which the future climate is compared. The source of the historical climate data is the SILO Data Drill of the Queensland Department of Natural Resources and Water ( and Jeffrey et al., 2001). The SILO Data Drill provides daily rainfall, temperature and other climate variables for 0.05 o grids across Australia, interpolated from point measurements made by the Australian Bureau of Meteorology. There are 30,985 grid cells within NSW and ACT. (2) NARCliM outputs (non-bias corrected daily rainfall, maximum and minimum temperature, relative humidity and radiation) for three time slices ( , and ) from each of the 12 ensemble members (four GCMs x three RCM parameterisations). Further description of these data sets are given in the following sub-sections. 3.1 Gridded historical climate data Historical daily climate data from 1895 to 2014 for 0.05 o x 0.05 o (~ 5 km x 5 km) grid cells across NSW and ACT are used from the SILO Data Drill of the Queensland Department of Natural Resources and Water. The SILO Data Drill provides surfaces of daily rainfall and other climate data interpolated from point measurements made by the Australian Bureau of Meteorology. The rainfall surfaces are interpolated using a trivariate thin plate smoothing spline with latitude, longitude and elevation as independent variables (Chiew et al 2008). The other climate surfaces after 1957 are also interpolated using the same method, but a different interpolation algorithm (anomaly-interpolation spline algorithm) is used prior to 1957 (see The gridded climate data is derived from observations that have been quality checked by the Australian Bureau of Meteorology and have been subject to error checking by the [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 2

9 Queensland Department of Natural Resources and Water. Nevertheless, it is inevitable that there will still be errors in the data and the interpolation routines can also introduce errors. In general, the data accuracy is expected to be lower in areas where the observation density is low relative to the climate gradients. In this context, it should be noted that rainfall varies spatially more than the other climate variables, but this is compensated by the generally denser rainfall observation network. 3.2 NARCliM Future Climate Projections In the NARCliM project, simulations from four GCMs are used to drive three RCMs to form a 12 member GCM/RCM ensemble (Evans et. al. 2014). The four selected GCMs are MIROC3.2, ECHAM5, CCCMA3.1, and CSIRO-MK3.0 (Evans and Ji, 2012a). For the future projections, the SRES A2 emission scenario (IPCC, 2000) is used. The three selected RCMs (detailed in Table 1) are three physics scheme combinations of the WRF model (Evans and Ji, 2012b). Each simulation consists of three 20-year runs ( , , and ). There are two model domains, one model domain covers the Coordinated Regional Climate Downscaling Experiment (CORDEX) (Giorgi et al., 2009) AustralAsia region with 50 km spatial resolutions, and the second is the NARCliM domain which covers south-eastern Australia with 10km resolution (Figure 1). The results from the NARCliM domain are used in this study. Table 1 Model configuration for the three RCMs in NARCliM NARCliM Ensemble member Planetary Boundary layer physics / Surface layer physics cumulus physics Microphysics Shortwave / Longwave radiation physics R1 MYJ / Eta similarity KF WDM 5 class Dudhia / RRTM R2 MYJ / Eta similarity BMJ WDM 5 class Dudhia / RRTM R3 YSU / MM5 similarity KF WDM 5 class CAM / CAM Some initial evaluation of NARCliM simulations shows that RCMs have strong skills in simulating the climate of Australia with a small cold bias and overestimation of precipitation on the Great Dividing Range (Evans et al. 2013b, Ji et al. 2015). The differing responses of the three RCMs confirm the importance of considering model independence when choosing the RCMs. The RCM response to large scale modes of variability also reflect the observations well (Evans et al. 2013b). The evaluations indicate that while there is a spread in model predictions, all models perform adequately with no single model performing the best overall for all variables and metrics. The use of the full ensemble provides a measure of robustness such that any result that is common through all models in the ensemble is considered to have higher confidence. [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 3

10 Figure 1. NARCliM project model domains, including the CORDEX domain with about 50 km grid resolution (outer domain shown as map extent) and the NARCliM domain with about 10 km resolution (inner domain shown with red outline) During the NARCliM project, the four GCMs and three RCMs were selected based on the following criteria (Evans et al. 2014): i) adequate performance when simulating historic climate; ii) most independent; iii) cover the largest range of plausible future climates for Australia (only for selection of GCMs). The results are model dependent, but this dependence has been minimised through the use of a carefully selected ensemble. This model selection process demonstrates that it is possible to create relatively small ensemble that is able to reproduce the ensemble mean and variance from the parent large ensemble as well as minimise the overall error (Evans et al. 2013a). For easier description in this report, the 12 simulations are named MIROC-R1, MIROC-R2, MIROC-R3; ECHAM-R1, ECHAM-R2, ECHAM-R3; CCCMA-R1, CCCMA-R2, CCCMA-R3; and CSIRO-R1, CSIRO-R2, CSIRO-R3. The simulations driven by the same GCM are referred to as GCM simulations, the simulations using the same RCM are referred to as RCM simulations. In total, there are 4 GCM simulations (average of 3 members) and 3 RCMs simulations (average of four members). 4. Methods NARCliM projections are limited to 20 years of daily data, however, water security studies require much longer time series to investigate long-term trends of rainfall and APET, and wet-dry cycles. This study uses the NARCliM projections to calculate scaling factors that are interpolated to 0.05 by 0.05 grid cells to scale the 120 years of historical daily rainfall and APET data from the SILO dataset. 4.1 Rainfall projections An empirical method for scaling daily data is used to obtain the future rainfall projections. The daily scaling method has been widely used in Australia for many climate change impact studies such as to the NSW Office of Water s Future Climate and Runoff Projections (Vaze et al. 2008, 2011), the CSIRO Murray-Darling Basin Sustainable Yields (MDBSY) Project (Chiew et al. 2008) and the South Eastern Australian Climate Initiative (SEACI) (Post et al. 2008). The method takes into account changes in daily distribution as well as changes in seasonal means. This is important for rainfall because NARCliM studies suggest that the extreme rainfall is likely to become more intense in the future, even in the regions where lower average rainfalls are likely. As runoff is mainly generated by high rainfall events, only [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 4

11 considering changes in seasonal means would lead to an underestimation of high runoff amounts, and consequently, an underestimation of mean annual runoff. To account for changes in the future daily rainfall distribution, the different rainfall amounts are scaled differently based on rainfall volume. Scaling factors for the different rainfall percentiles/amounts are determined by comparing daily rainfall simulations from the NARCliM twelve member ensemble for two future 20-year time slices, (referred to as ~2030) and (referred to as ~2070), to a historical time slice (referred to as ~2000). The seasonal scaling factors are derived and used to adjust the final time series to reflect the changes in seasonal means. The future climate projections are derived by scaling the observed climate data based on the analysis of 12 NARCliM ensemble members as described above to represent the climate around 2030 and APET projections The gridded areal potential evapotranspiration (APET) daily time series is calculated from observed maximum and minimum temperature, vapour pressure and incoming solar radiation using Morton s wet environment algorithms (Morton, 1983). A similar calculation is carried out on the 12 NARCliM ensemble members except here specific humidity and air pressure are used to replace vapour pressure in the calculation due to the data availability. Seasonal scaling factors are then derived in a similar way as those for rainfall from analysis of APET time series calculated for the 12 NARCliM ensemble members. The scaling factors are used to obtain a series of 120 years of daily APET data to represent the climate centred at ~2030 and ~ Results 5.1 Historical climate data Rainfall Figure 2 and 3 show the mean annual and seasonal rainfall across NSW. There is a clear east west rainfall gradient across NSW, with the highest rainfall over the north-east coast and high altitude snowy mountains (mean annual rainfall of more than 2000 mm), and lowest over western NSW (mean annual rainfall of less than 200 mm). In northern NSW, most of the rainfall occurs during the warmer half of the year, and in the southern NSW, most of the rainfall occurs in during the cooler half of the year. Ji et al. (2015) provide a discussion of rainfall seasonality across southeast Australia including NSW. [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 5

12 Figure 2. Mean annual rainfall for (mm) Figure 3. Mean seasonal rainfall for (mm) Areal potential evapotranspiration Daily APET is calculated using 0.05 o x 0.05 o climate data from the SILO Data Drill (temperature; relative humidity, calculated as actual vapour pressure divided by saturation vapour pressure; and incoming solar radiation) using Morton s wet environment evapotranspiration algorithms ( and Morton, 1983; Chiew and Leahy, 2003). [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 6

13 APET is defined as the evapotranspiration that would take place, if there was unlimited water supply, from an area large enough that the effects of any upwind boundary transitions are negligible, and local variations are integrated to an areal average. APET is therefore conceptually the upper limit to actual evapotranspiration in rainfall-runoff modelling. Figures 4 and 5 show the mean annual and seasonal APET respectively across NSW. Mean annual APET varies from 1700 mm in the north-west to 1000 mm in the snowy mountains. Figure 4. Mean annual APET for (mm) Figure 5. Mean seasonal APET for (mm) [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 7

14 5.2 Future climate data As previously discussed, future climate data were derived to assess the range of possible climate conditions around the years 2030 and There are forty-eight future climate variants, comprising 12 GCM/RCM ensemble members x 2 future periods x 2 variables (rainfall and APET), each with 120 years of daily climate sequences for 0.05 o x 0.05 o grid cells across NSW and ACT. The future climate variants come from scaling the 1895 to 2014 climate data to represent the climate around 2030 and 2070, based on analyses of the 12 NARCliM ensemble members for the near and far future time periods Climate change projections for ~2030 1) Rainfall The ensemble mean change in annual rainfall for ~2030 relative to ~2000 is shown in Figure 6. It is clear that the magnitude of changes is small with 0 5% increase in northern NSW and 0 5% decrease in southern NSW. Changes in the ensemble mean seasonal rainfall are presented in Figure 7. The largest increase (15 20%) is projected for autumn and largest decrease (10 15%) for spring. Figure 6. Percent change in ensemble mean annual rainfall for ~2030 relative to ~2000 [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 8

15 Figure 7. Percent change in ensemble mean seasonal rainfall for ~2030 relative to ~2000 Figure 8 depicts the percent change in ensemble mean annual rainfall for ~2030 relative to ~2000 across the 12 NARCliM ensemble member simulations. The results indicate that the potential changes in rainfall can be very significant (-20% to 40%). The different RCM simulations driven by the same GCM generally provide similar changes in annual rainfall, however, the different GCMs using same RCM simulations can produce large differences. CCCMA driven RCMs project the largest increase in annual rainfall, with CSIRO driven RCMs projecting the largest decrease in annual rainfall. Figure 8. Percent change in mean annual rainfall across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 9

16 Changes in seasonal rainfall for each of the 12 NARCliM GCM/RCM ensemble member simulations are presented in Figures 9-12 for summer, autumn, winter and spring rainfall, respectively. For each season, different ensemble member simulations project the most diverse changes, however, most of the simulations project an increase in autumn rainfall (Figure 10) and the majority of the simulations project a decrease in spring rainfall (Figure 12). Figure 9. Percent change in mean summer rainfall across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations Figure 10. Percent change in mean autumn rainfall across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 10

17 Figure 11. Percent change in mean winter rainfall across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations Figure 12. Percent change in mean spring rainfall across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations 2) APET Ensemble mean changes in APET for ~2030 relative to ~2000 is shown in Figure 13. The magnitude of changes is small with 1.5 2% increase across NSW. The seasonal variation of changes in APET is presented in Figure 14. The largest increase (2 2.5%) is projected to occur in spring and smallest increase (0.5 1%) in the winter. [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 11

18 Figure 13. Percent change in ensemble mean annual APET for ~2030 relative to ~2000 Figure 14. Percent change in ensemble mean seasonal APET for ~2030 relative to ~2000 Figures 15 shows the percent change in mean annual APET for ~2030 relative to ~2000 for the 12 NARCliM ensemble member simulations. The results indicate that the changes in APET are small (0 3%). The different RCM simulations driven by the same GCM generally [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 12

19 provide similar changes in annual APET, however, the different GCMs using same RCM simulations can produce notable differences. Figure 15. Percent change in mean annual APET across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations Changes in seasonal APET are presented in Figures for summer, autumn, winter and spring, respectively. Different simulations project substantially different changes in APET for each season. Figure 16. Percent change in mean summer APET across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 13

20 Figure 17. Percent change in mean autumn APET across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations Figure 18. Percent change in mean winter APET across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 14

21 Figure 19. Percent change in mean spring APET across NSW (~2030 relative to ~2000) for the 12 NARCliM simulations Climate change projections for ~2070 1) Rainfall Ensemble mean changes in rainfall for ~2070 relative to ~2000 is shown in Figure 20. Larger increases in mean annual rainfall (10 15%) is projected for northern NSW and a smaller increases (0 5%) or even decrease (0 to -5%) is projected for southern NSW. The largest decrease in ensemble mean annual rainfall (>10% decrease) is projected for the Snowy Mountains. Changes in ensemble mean seasonal rainfall is presented in Figure 21. The largest increase (25 30%) is projected in summer for western NSW and in autumn for the central northern NSW, with the largest decreases (>20% decrease) projected to occur in spring for the Snowy Mountains. [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 15

22 Figure 20. Percent change in ensemble mean of annual rainfall for ~2070 relative to ~2000 Figure 21. Percent change in ensemble mean of seasonal rainfall for ~2070 relative to ~2000 Figure 22 depicts the percent change in ensemble mean annual rainfall for ~2070 relative to ~2000 for the 12 NARCliM simulations. The results indicate that the changes in rainfall can be very significant (-30% to +60%). Different RCM simulations driven by the same GCM generally provide similar changes in annual rainfall, however, the different GCMs using same RCM simulations can produce large differences. CCCMA and MIROC driven RCMs projected larger increases in annual rainfall, and CSIRO driven RCMs projected the largest decrease in annual rainfall. [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 16

23 Figure 22. Percent change in mean annual rainfall across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations Changes in seasonal rainfall are presented in Figures for summer, autumn, winter and spring rainfall, respectively. For each season, different simulations project different changes, however, most of simulations projected a larger increase in summer and autumn rainfall (Figure 23 and Figure 24) and the majority of ensemble member simulations project a decrease in spring rainfall (Figure 26). Figure 23. Percent change in mean summer rainfall across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 17

24 Figure 24. Percent change in mean autumn rainfall across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations Figure 25. Percent change in mean winter rainfall across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 18

25 Figure 26. Percent change in mean spring rainfall across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations 2) APET Ensemble mean changes in APET for ~2070 relative to ~2000 are shown in Figure 27. The magnitude of changes are much larger than that for ~2030 relative to ~2000, with 5.5 6% increase for northern NSW and 4.5 5% increase for southern NSW. Changes in ensemble mean seasonal average APET are presented in Figure 28. The largest increase is projected to occur in the spring and smallest increase in winter. Figure 27. Percent change in ensemble mean of annual APET for ~2070 relative to ~2000 [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 19

26 Figure 28. Percent change in ensemble mean of seasonal APET for ~2070 relative to ~2000 Figure 29 depicts the percent change in mean annual APET for ~2070 relative to ~2000 across the 12 NARCliM ensemble member simulations. The results indicate that the changes in APET are much larger than that for ~2030 relative to ~2000, which is about 3 8% for different simulations. The different RCM simulations driven by the same GCM generally provide similar changes in annual APET (except for MIROC-R3), however, the different GCMs using same RCM simulations can produce notable differences. Figure 29. Percent change in mean annual APET across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 20

27 Changes in seasonal APET are presented in Figures 30 to 33 for summer, autumn, winter and spring, respectively. Different simulations project different changes in APET for each season. Most of the ensemble member simulations projected smaller increase in winter and the majority of the simulations projected larger increases in spring. Figure 30. Percent change in mean summer APET across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations Figure 31. Percent change in mean autumn APET across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 21

28 Figure 32. Percent change in mean winter APET across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations Figure 33. Percent change in mean spring APET across NSW (~2070 relative to ~2000) for the 12 NARCliM simulations [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 22

29 6 References Chiew FHS, Teng J, Kirono D, Frost A, Bathols J, Vaze J, Viney N, Young W, Hennessy K and Cai W (2008) Climate data for hydrologic scenario modelling across the Murray-Darling Basin. A report to the Australian government from the CSIRO Murray-Darling Basin Sustainable Yields Project. CSIRO, Australia. Chiew FHS and Leahy C (2003) Comparison of evapotranspiration variables in Evapotranspiration Maps of Australia with commonly used evapotranspiration variables. Australian Journal of Water Resources 7, Evans JP, Ji F (2012a) Choosing GCMs. NARCliM Technical Note 1, 7pp, NARCliM Consortium, Sydney, Australia. Evans JP, Ji F (2012b) Choosing the RCMs to perform the downscaling. NARCliM Technical Note 2, 8pp, NARCliM Consortium, Sydney, Australia. Evans JP, Ji F, Abramowitz G, Ekstrom M (2013a) Optimally choosing small ensemble members to produce robust climate simulations. Environmental Research Letters, 8, , doi: / /8/4/ Evans JP, Fita L, Argüeso D, Liu Y (2013b) Initial NARCliM evaluation. In Piantadosi, J., Anderssen, R.S. and Boland J. (eds) MODSIM2013, 20th International Congress on Modelling and Simulation. Modelling and Simulation Society of Australia and New Zealand, December 2013, p ISBN: Evans JP, Ji F, Lee C, Smith P, Argüeso D, Fita L (2014) Design of a regional climate modelling projection ensemble experiment NARCliM. Geosci Model Dev 7(2): doi: /gmd Giorgi F, Jones C, Asrar GR (2009) Addressing climate information needs at the regional level: the CORDEX framework, WMO Bull. 58: IPCC (2000) Special report on emission scenarios (SRES) Special Report of the Intergovernmental Panel on Climate Change (Editors: N Nakicenovic and R Swart), Cambridge University Press. Jeffrey SJ, Carter JO, Moodie KB and Beswick AR (2001) Using spatial interpolation to construct a comprehensive archive of Australian climate data. Environmental Modelling and Software 16, Ji F, Evans JP, Teng J, Scorgie Y, Argueso D, Di Luca A (2015) Evaluation of long-term precipitation and temperature WRF simulations for southeast Australia, Climate Research, in press. Doi: /cr01366 Morton FI (1983) Operational estimates of areal evapotranspiration and their significance to the science and practice of hydrology, Journal of Hydrology, 66 (1983) Post DA, Chiew FHS, Vaze J, Teng J, Perraud J-M, and Viney NR (2008) Future Runoff Projections (~2030) for Southeast Australia: A SEACI Report. CSIRO Land and Water, Australia. Vaze J, Teng J, Post D, Chiew F, Perraud J-M, Kirono D (2008) Future climate and runoff projections (~2030) for New South Wales and Australian Capital Territory, NSW Department of Water and Energy, Sydney. Vaze J and Teng J (2011) Future climate and runoff projections across New South Wales, Australia results and practical applications. Hydrological Processes, Vol 25(1), [Future Rainfall and Areal Potential Evapotranspiration (APET) Projections to Inform Water Security Studies] 23