There is no doubt that rain gauge-b

There is no doubt that rain gauge-based method is the most accurate way to evaluate and compare the performance of P products. It is worth noting that not only the six products selected in this article, but almost all global P products have been bias-corrected against gauge-based data, although it is difficult to guarantee the completeness of these rain gauge records in space and time. For example, the GPM IMERG product was calibrated against the Global Precipitation Climatology Project (GPCP) data. Therefore, the evaluation and comparison of P performance between different products based on rain gauge stations that may have been used for bias-correction (information overlap) are difficult to guarantee the accuracy of the results. However, the current studies no matter the point-to-pixel-based methods against rain gauge stations or cell by cell-based methods show problems of information overlap. Because the mesh-based estimates of P, which are used as reference, are produced based on rain gauge-based data using the interpolation or downscaling methods. Additionally, the values estimated using these methods as references inherently contains a lot of uncertainty.