**6. Conclusions**

To elucidate the strengths and weaknesses of recently released gridded precipitation datasets, we conducted a comprehensive evaluation of the performance of IMERG-FR-V05B, -V06A, IMERG-V05B-RT, ERA5, SM2RAIN-ASCAT, and MSWEP-V2.2 at daily and monthly time-scales for Austria using a dense network of gauges (882 stations) as a reference. The evaluation was carried out based on continuous and categorical statistical metrics for the period June 2014–December 2015. Apart from standard evaluations, we also assessed their performance with respect to the elevation of the stations and extreme events. In agreement with earlier studies, skills vary with respect to elevation, land surface characteristics and snow-rain phase of precipitation. In summary, our study shows that:


As expected, all products are able to reproduce the main characteristics of the precipitation in Austria. However, MSWEP performed significantly better than other products, followed by IMERG-V05B and -V06A. Except for MSWEP, the other products indicated difficulty capturing the effects of relief on precipitation over the complex terrain. This research is to our knowledge the first study to evaluate IMERG-V06A, ERA5, MSWEP-V02.2, and SM2RAIN-ASCAT over Austria. Since MSWEP-V2.2 is more robust, statistically, and has long-recorded data (from 1979–2017), we suggest using this product for further studies in climate applications over this region. Moreover, the IMERG data are also available from 2000 to the near present. The inclusion of elevation effects seems to be crucial for a realistic estimation of the spatial distribution of precipitation in mountains areas. We suggest the developers of the examined products highly consider the actual topography, steep terrain, and deep, narrow valleys, over the mountainous area to obtain more realistic precipitation amounts. Moreover, using daily precipitation gauge data, like MSWEP, instead of monthly precipitation data, like IMERG products, can significantly improve the accuracy of the precipitation products. It is worthy to mention that the SM2RAIN-ASCAT product is available only at a daily time step (00:00 UTC), while other products are available at sub-daily time-scales. Therefore, SM2RAIN-ASCAT was evaluated against rain gauges and other products with a few hours' difference, which may contribute to increased errors in this study. Moreover, in the case of gauge measurements, there might also be some uncertainties and systematic errors due to wind effects, wetting, evaporation, and splashing, which typically amounts to 5%–10% in summer, and even higher in snow conditions [35], which should be considered in further studies. Moreover, we suggest assessing the performance of the IMERG-V06B, which was not yet available during the analysis of this study, and the near-real-time product of MSWEP and use them in hydro-meteorological models. We expect that the regional analysis of the recently released gridded precipitation products revealed in this study can give users a broader perspective and understanding of the features associated with currently precipitation products. It is worth mentioning that the

performance ranking of the products may differ across the other regions depending on the amount of gauge data utilized and the quality control applied for each dataset as well.

**Author Contributions:** Conceptualization: E.S.; J.E. and W.D.; methodology: E.S.; analysis: E.S.; writing—original draft: E.S.; writing—review and editing: E.S.; J.E. and W.D.

**Funding:** This research received no external funding.

**Acknowledgments:** We gratefully acknowledge the NASA/Goddard Space Flight Center's and PPS for IMERG data, the ERA5 datasets from the Climate Data Store (CDS) of the European Centre for Medium Range Weather Forecasts (ECMWF), Hylke Beck, the developer of the MSWEP data (https://doi.org/10.1175/BAMS-D-17-0138.1), and Luca Brocca, the developer of SM2RAIN data from https://doi.org/10.5281/zenodo.2591215, for providing the data used in this study, freely to public. The open access publishing was supported by the BOKU Vienna Open Access Publishing Fund.

**Conflicts of Interest:** The authors declare no conflict of interest.
