Assessment of GPM and SM2RAIN-ASCAT rainfall products over complex terrain in southern Italy

Results show that IMERG has good performance at time resolutions higher than 6 h. At daily time scale, IMERG and SM2RASC show similar results with median correlations, R, ~0.60, and root mean square error, RMSE, ~7.6 mm/day (BIAS is −0.85 and +0.51 mm/day, respectively). The combined product outperforms the parent products (median R > 0.70, RMSE<6.5 mm/day, BIAS -0.07 mm/day). Among the different factors affecting products quality, topographic complexity seems to play the more relevant role, particularly for SM2RASC but also for IMERG. Overall, this study shows that the investigated satellite-based products agree reasonably well with observations notwithstanding the challenging features of the region, and the combination of IMERG and SM2RASC provides a way to overcome their limitations and to produce a higher quality satellite rainfall product.