Application of SSIM in Spatial Testing of High-Resolution Precipitation Numerical Forecasting Products

CHEN Bailian; YANG Fuyan; CHEN Zitong; PENG Fang; ZENG Liping

doi:10.16032/j.issn.1004-4965.2024.048

Abstract：This study proposes a new scheme for comparing and analyzing 0-1 formatted grid fields using the image structure similarity index method(SSIM).With the original application scenario and algorithms optimized,the SSIM index is improved to reflect the position change of rainbands in precipitation fields.The new method is applied to the spatial verification of high-resolution precipitation numerical forecast products generated by the regional modeling system of South China(CMA-GD),specifically for rainstorm cases in Guizhou during the summer of 2020.Comparative analysis with results obtained using the MODE and neighborhood methods shows that the qualitative evaluation of prediction cases is consistent,and the performance of the SSIM* index closely aligns with the MMI index of MODE.It shows the effective application of the improved SSIM method and the new SSIM index in spatial verification for high-resolution precipitation numerical prediction products,and results of the new method are even more reasonable in the assessment of prediction cases.With the whole 0-1 formatted grid fields of precipitation as the spatial objects considered,the new method can capture overall spatial structure characteristics that are not attainable through other methods,offering valuable references for assessing prediction cases based on rain area,rainband structure,and average position.Furthermore,the new method has the advantages of simple and efficient calculation,no subjective parameters setting,and well-determined results that overcome the limitations of the MODE which is the current mainstream method in spatial verification for the precipitation numerical prediction products.Therefore,this research holds good application prospects and is worthy of further study.