Validating a 1-D SVAT model in a range of USA and Australian ecosystems: evidence towards its use as a tool to study Earth's system interactions

George Petropoulos, Matthew North, Gareth Ireland, Prashant K. Srivastava, Daisy Veronica Rendall

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Abstract

This paper describes the validation of the SimSphere SVAT model conducted at different ecosystem types in the USA and Australia. Specific focus was given to examining the models’ ability in predicting Shortwave Incoming Solar Radiation (Rg), Net Radiation (Rnet), Latent Heat (LE), Sensible Heat (H), Air Temperature at 1.3 m (T 5 air 1.3 m) and Air Temperature at 50 m (Tair 50 m). Model predictions were compared against corresponding in situ measurements acquired for a total of 72 selected days of the year 2011 obtained from 8 sites belonging to the AmeriFlux (USA) and OzFlux (Australia) monitoring networks. Selected sites were representative of a variety of environmental, 10 biome and climatic conditions, to allow for the inclusion of contrasting conditions in the
model evaluation.

The application of the model confirmed its high capability in representing the multifarious and complex interactions of the Earth system. Comparisons showed a good agreement between modelled and measured fluxes, especially for the days with smoothed 15 daily flux trends. A good to excellent agreement between the model predictions and the in situ measurements was reported, particularly so for the LE, H, Tair 1.3 m and Tair 50 m parameters (RMSD = 39.47, 55.06 Wm−2, 3.23, 3.77 ◦C respectively). A systematic underestimation of Rg and Rnet (RMSD = 67.83, 58.69 W m−2, MBE = 67.83, 58.69 W m−2respectively) was also found. Highest simulation accuracies were obtained for the open 20 woodland savannah and mulga woodland sites for most of the compared parameters.Very high values of the Nash–Sutcliffe efficiency index were also reported for all parameters
ranging from 0.720 to 0.998, suggesting a very good model representation of the observations.

To our knowledge, this study presents the first comprehensive validation of SimSphere, particularly so in USA and Australian ecosystem types. Findings are important and timely, given the rapidly expanding use of this model worldwide both as an educational and research tool. This includes ongoing research by different Space Agencies examining its synergistic use with Earth Observation data towards the development of global operational products.The application of the model confirmed its high capability in representing the multifarious and complex interactions of the Earth system. Comparisons showed a good agreement between modelled and measured fluxes, especially for the days with smoothed daily flux trends. A good to excellent agreement of the model predictions with the in-situ was reported, particularly so for LE, H, Tair 1.3m and Tair 50m (RMSD = 39.47 Wm-2, 55.06 Wm-2, 3.23°C, 3.77°C respectively). A systematic underestimation of Rg and Rnet (RMSD = 67.83 Wm-2, 58.69 Wm-2 respectively) was also found. Highest simulation accuracies were obtained for the open woodland savannah and mulga woodland sites for most of the compared parameters. Very high values of the Nash-Sutcliffe efficiency index were also reported for all parameters ranging from 0.720 to 0.998, suggesting a very good model representation of the observations.
Original languageEnglish
Pages (from-to)2437–2495
JournalGeoscientific Model Development
Volume8
DOIs
Publication statusPublished - 05 Mar 2015

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