**4. Discussion**

Remote sensing of precipitation provides an alternative source for precipitation data beyond ground observations. To date, numerous studies have reported the performance of satellite precipitation products in many areas around the world [20,53–58]. However, most of these evaluations focused on the post-real-time products that are usually available after a few days or months [59–61]. The near-real-time satellite precipitation products are more attractive for some application scenarios, owing to their timeliness. To the best of our knowledge, our study is a first evaluation of the gauge-adjusted near-real-time GSMaP precipitation estimate. The results in this study showed that the GSMaP\_Gauge\_NRT has a more reliable performance than its original GSMaP\_NRT over China. This provides a positive feedback to the GSMaP algorithm team, as they expected. In the TRMM era, the CCA was proposed to improve the accuracy of TMPA-RT. However, this climatological calibration is not currently used in IMERG near-real-time products due to its poor performance at high latitudes and altitudes [9,31]. In the GPM era, the GSMaP and IMERG were the most popular high-resolution satellite precipitation products, and the GSMaP\_NRT and IMERG-early were their near-real-time products with latency periods of 3 h and 4 h, respectively. Therefore, when the CCA is applied in the IMERG product, it is necessary to compare these two near-real-time products of GSMaP and IMERG, and this work can be continued in the future.

As a preliminary assessment of the near-real-time GSMaP precipitation estimate, we performed the validation at daily scale considering the availability of reference data. Previous studies found that the performances of satellite precipitation products are sensitive to the spatiotemporal scale [62,63]. Such a resampling in this study may lose the potential characters of GSMaP products at their original resolutions. However, our study mainly focused on the comparing of GSMaP\_Gauge\_NRT and GSMaP\_NRT. Thus, this modification of scale should not change the conclusions of our study. In the

next work, we will investigate the performance of GSMaP\_Gauge\_NRT product in sub-daily or hourly time scales.

The evaluation showed that the calibrated GSMaP\_Gauge\_NRT has better performance than the original GSMaP\_NRT. Thus, it is reasonable to choose the GSMaP\_Gauge\_NRT precipitation product for users with their requirement of near-real-time data. Of course, more researches are needed for knowing the application potentiality of GSMaP\_Gauge\_NRT. The performance of the IMERG near-real-time products have been investigated in capturing extreme precipitation events [64,65]. The results of these studies indicated that the IMERG has a promising potential for monitoring typhoon rainfall. Considering the accuracy improvement of GSMaP\_Gauge\_NRT, further application researches, like rainstorm monitoring and hydrological simulation, are encouraged. This will provide useful feedbacks and insights about the GSMaP\_Gauge\_NRT to decision-makers and the scientific community.
