Adaptive Lossy Compression of Complex Environmental Indices Using Seasonal Auto-Regressive Integrated Moving Average Models

Significant increases in computational resources have enabled the development of more complex and spatially better resolved weather and climate models. As a result the amount of output generated by data assimilation systems and by weather and climate simulations is rapidly increasing e.g. due to higher spatial resolution, more realisations and higher frequency data. However, while compute performance has increased significantly because of better scaling program code and increasing number of cores the storage capacity is only increasing slowly. One way to tackle the data storage problem is data compression. Here, we build the groundwork for an environmental data compressor by improving compression for established weather and climate indices like El Ni~no Southern Oscillation (ENSO), North Atlantic Oscillation (NAO) and Quasi-Biennial Oscillation (QBO). We investigate options for compressing these indices by using a statistical method based on the Auto Regressive Integrated Moving Average (ARIMA) model. The introduced adaptive approach shows that it is possible to improve accuracy of lossily compressed data by applying an adaptive compression method which preserves selected data with higher precision. Our analysis reveals no potential for lossless compression of these indices. However, as the ARIMA model is able to capture all relevant temporal variability, lossless compression is not necessary and lossy compression is acceptable. The reconstruction based on the lossily compressed data can reproduce the chosen indices to such a high degree that statistically relevant information needed for describing climate dynamics is preserved. The performance of the (seasonal) ARIMA model was tested with daily and monthly indices.