# Evaluating the Latest IMERG Products in a Subtropical Climate: The Case of Parana State, Brazil
## 1 Introduction
The authors also reported the lower accuracy of the satellite precipitation estimates in areas of high altitudes or in arid and semiarid climates. Evaluating the IMERG precipitation compared to ground-based data, [22] observed a tendency for restimating the precipitation using the sub-daily products and overestimating the maximum rainfall in monthly variations over the Indian subcontinent. In a seasonal analysis, [21; 23] found that IMERG performed better in warm and wet seasons. In a subtropical climate, [24] concluded that IMERG performed well for detecting precipitation events with a limitation in representing the amount of rainfall at sub-daily scales, while in tropical climates [25; 26] demonstrated that it is essential to calibrate the IMERG products to reduce random and systematic errors. On the other hand, studies comparing the IMERG to different satellite products, highlighted the better accuracy of IMERG in estimating precipitation. [27] found better performance of IMERG in estimating precipitation on a global scale compared to TMPA products. The better performance of IMERG's products was also observed by [28] concerning the TMPA in estimating precipitation in all regions of Brazil. Recently, [29] observed better performance of IMERG-Late version 6 products compared to IMERG-Early, GSMaP-NVK, TMPA-RT, and PERSIANN-CCS products on a global scale The better performance of IMERG in relation to other remote sensing products, reported in previous studies, supports the analysis of the performance of its products in different climates and geographic scales.The quality of IMERG products was improved over time by increasing the number of passive microwave samples [30]. The latest version of the IMERG algorithm (version 6), made available to the public in October 2019, combines the reanalysis of precipitation estimated by satellites between 2000-2014 by TMPA and in the subsequent period by GPM, resulting in 19 years of information so far. Its products have a spatial resolution of 0.1\({}^{\circ}\) and a 30-min temporal resolution [31]. In this way, trend analysis and analysis of extreme events could be carried out with greater accuracy. In addition, the performance of climatological and hydrological models could be improved with greater detail of recent precipitation information. Thus, studies evaluating the performance of IMERG version 6 products are important and promising at regional scales. Brazil is a country of continental dimensions, with different micro-climates and rainfall patterns throughout its territory. Among its states, Parana, located in the south of the country in the Parana River Basin region, is the most important socio-economically hydrologic region in Brazil [32]. This basin has the largest hydroelectric infrastructure in the country, which is responsible for approximately 44.6% of the electric energy production and transmission system in Brazil [33]. Thus, the determination of precipitation in this region is essential for forecasting with hydrological and climatological monitoring models. Also, it is important for this region to detect anomalies related to excess or deficit of precipitation, which can compromise the supply of energy and hydraulic structures. Thus, the purpose of this study is to provide a comprehensive assessment of IMERG (version 6) precipitation estimates over a subtropical region, specifically the objectives of the study are (1) to evaluate the performance of IMERG's daily and monthly products, and (2) to evaluate IMERG's performance in detecting monthly anomalies in Parana using observations from a dense network of precipitation gauges. This study is expected to provide a reference for the use of IMERG products in monthly and daily temporal resolutions and further contribute to improvements of the satellite precipitation algorithm.