Wavelet Compression Technique for High-Resolution Global Model Data on an Icosahedral Grid Journal of Atmospheric and Oceanic Technology

Modern Earth modeling systems often use high-resolution unstructured grids to discretize their horizontal domains. One of the major challenges in working with these high-resolution models is to efficiently transmit and store large volumes of model data for operational forecasts and for modeling research. A newly developed compression technique is presented that significantly reduces the size of datasets produced by high-resolution global models that are discretized on an icosahedral grid. The compression technique is based on the wavelet transform together with a grid rearrangement algorithm and precision-controlled quantization technology. The grid rearrangement algorithm converts an icosahedral grid to a set of 10 rhombus grids that retain the spatial correlation of model data so that a three-dimensional wavelet transform can be effectively applied. The precision-controlled quantization scheme guarantees specified precision of compressed datasets. The technique is applied to the output of a global weather prediction model, the Flow-Following, Finite-Volume Icosahedral Model (FIM) developed by NOAA's Earth System Research Laboratory. Experiments show that model data at 30-km resolution can be compressed up to 50:1 without noticeable visual differences; at specified precision requirements, the proposed compression technique achieves better compression compared to a state-of-the-art compression format [Gridded Binary (GRIB) with JPEG 2000 packing option]. In addition, model forecasts initialized with original and compressed initial conditions are compared and assessed. The assessment indicates that it is promising to use the technique to compress model data for those applications demanding high fidelity of compressed datasets.