TY - GEN
T1 - Application of ANUSPLIN to produce new intensity-frequency-duration (IFD) index rainfalls across Australia
AU - The, Cynthia
AU - Hutchinson, Michael
AU - Johnson, Fiona
AU - Beesley, Catherine
AU - Green, Janice
PY - 2014
Y1 - 2014
N2 - The Bureau of Meteorology has recently released new Intensity-Frequency-Duration (IFD) design rainfall information as a component of the broader revision of Australian Rainfall and Runoff. This information depends in part on the index rainfalls, the mean annual maximum rainfalls over 1 to 7 day periods. Interpolating these index rainfalls across Australia enables the provision of IFD design rainfall information for any location in Australia. However, because of the sparseness of the rain gauge network in some regions an integral part of deriving the new IFDs was to optimise the gridding of the observed index rainfalls. This was undertaken using the software package ANUSPLIN which applies thin plate smoothing splines to interpolate and smooth multivariate data. The splines were fitted using three independent variables; latitude, longitude and elevation. The elevation scale was exaggerated by a factor of 100 to reflect the relative importance that elevation has on precipitation patterns. A considerable number of iterations was required to achieve an optimum outcome that represented the observed index rainfalls well but which did not place too much significance on shorter rainfall records and was robustly defined in data sparse areas with high topographic relief. The appropriate degree of smoothing of the fitted functions was determined by minimising the generalised cross validation and the number of knots and the dependent data transformation were varied to achieve optimal results. In addition to regional and continent-wide statistical tests, qualitative assessments were also conducted by preparing maps that showed how well the observed 1 day index rainfalls were represented in relation to the length of record available at each station, and the spatial density of the rain gauge network. The final index rainfall grids were produced by the application of ANUSPLIN using 3570 knots with no transformation applied to the data.
AB - The Bureau of Meteorology has recently released new Intensity-Frequency-Duration (IFD) design rainfall information as a component of the broader revision of Australian Rainfall and Runoff. This information depends in part on the index rainfalls, the mean annual maximum rainfalls over 1 to 7 day periods. Interpolating these index rainfalls across Australia enables the provision of IFD design rainfall information for any location in Australia. However, because of the sparseness of the rain gauge network in some regions an integral part of deriving the new IFDs was to optimise the gridding of the observed index rainfalls. This was undertaken using the software package ANUSPLIN which applies thin plate smoothing splines to interpolate and smooth multivariate data. The splines were fitted using three independent variables; latitude, longitude and elevation. The elevation scale was exaggerated by a factor of 100 to reflect the relative importance that elevation has on precipitation patterns. A considerable number of iterations was required to achieve an optimum outcome that represented the observed index rainfalls well but which did not place too much significance on shorter rainfall records and was robustly defined in data sparse areas with high topographic relief. The appropriate degree of smoothing of the fitted functions was determined by minimising the generalised cross validation and the number of knots and the dependent data transformation were varied to achieve optimal results. In addition to regional and continent-wide statistical tests, qualitative assessments were also conducted by preparing maps that showed how well the observed 1 day index rainfalls were represented in relation to the length of record available at each station, and the spatial density of the rain gauge network. The final index rainfall grids were produced by the application of ANUSPLIN using 3570 knots with no transformation applied to the data.
UR - http://www.scopus.com/inward/record.url?scp=84925047453&partnerID=8YFLogxK
M3 - Conference contribution
T3 - Hydrology and Water Resources Symposium 2014, HWRS 2014 - Conference Proceedings
SP - 557
EP - 564
BT - Hydrology and Water Resources Symposium 2014, HWRS 2014 - Conference Proceedings
PB - Engineers Australia
T2 - 35th Hydrology and Water Resources Symposium, HWRS 2014
Y2 - 24 February 2014 through 27 February 2014
ER -