Dating website terminology


Using IFDs from the website to set up a local database is not recommended as any locally stored values will not necessarily remain current.The IFDs on the Bureau's website may be periodically updated as new information becomes available.If the input coordinates are not specified accurately enough, the IFDs could be provided for a grid point that is not the closest to the desired location.In some cases there may not be much difference in IFD analyses for points that are located close together, however some locations in Australia are characterised by high gradients in IFD data, particularly around mountainous regions.The quality controlled rainfall data was analysed using statistically rigorous tools and techniques, such as: the Generalised Extreme Value distribution, which has been fitted using the technique of L-moments for the rainfall frequency analysis; Bayesian Generalised Least Squares Regression for deriving sub-daily rainfall statistics from daily rainfall values; GIS-based methods for gridding data; and an 'index rainfall procedure' for regionalisation of point data. * EY = exceedences per year# AEP = annual exceedence probability As is to be expected, the differences between the data and methods adopted have resulted in differences between the new IFDs and the ARR87 IFDs.These differences vary not only across Australia but across durations and probabilities.Advice on how to take climate change into consideration when using the new design rainfalls is provided in Book 1; Chapter 6 Climate Change Consideration of ARR2016



Note: specifying coordinates at a higher precision than the grid size will not result in greater accuracy as these locations may fall near the same IFD grid point.The new IFDs are displayed in units of depth in millimetres (mm) by default.This means the new curves increase with rainfall duration rather than decreasing, so the slope of the curve is reversed.The main terms used to describe design rainfalls are: The table below lists the probability terminology used for the 2016 design rainfalls and shows in bold the standard EY and AEP values for which design rainfalls are available.