The paper evaluates the PERSIANN system, an automated method for estimating tropical rainfall using geostationary satellite longwave infrared imagery (GOES-IR) and the Tropical Rainfall Measurement Mission (TRMM) microwave imager (TMI) data. The PERSIANN-GT product, which combines GOES-IR and TMI data, is assessed over a region spanning 30°S to 30°N and 90°E to 30°W, including the tropical Pacific Ocean, parts of Asia, Australia, and the Americas. The accuracy of the PERSIANN-GT product is compared with National Climatic Data Center radar-gauge composite data over Florida and Texas, showing a correlation coefficient (ρ) greater than 0.7. The product also compares well with World Meteorological Organization gauge measurements (ρ ~ 0.77–0.90) for 5° × 5° grid locations with high gauge densities. Further comparisons with various TRMM rainfall products (3A11, 3B31, 3B42, 3B43) reveal that the PERSIANN-GT product aligns well with the TRMM 3B43 1° × 1° monthly product but tends to show higher rainfall over the western Pacific Ocean compared to the TRMM 3B42 product. The study highlights the importance of combining geosynchronous and TRMM data to improve the spatial and temporal resolution of rainfall estimates, making the PERSIANN-GT product suitable for climate and hydrology studies.The paper evaluates the PERSIANN system, an automated method for estimating tropical rainfall using geostationary satellite longwave infrared imagery (GOES-IR) and the Tropical Rainfall Measurement Mission (TRMM) microwave imager (TMI) data. The PERSIANN-GT product, which combines GOES-IR and TMI data, is assessed over a region spanning 30°S to 30°N and 90°E to 30°W, including the tropical Pacific Ocean, parts of Asia, Australia, and the Americas. The accuracy of the PERSIANN-GT product is compared with National Climatic Data Center radar-gauge composite data over Florida and Texas, showing a correlation coefficient (ρ) greater than 0.7. The product also compares well with World Meteorological Organization gauge measurements (ρ ~ 0.77–0.90) for 5° × 5° grid locations with high gauge densities. Further comparisons with various TRMM rainfall products (3A11, 3B31, 3B42, 3B43) reveal that the PERSIANN-GT product aligns well with the TRMM 3B43 1° × 1° monthly product but tends to show higher rainfall over the western Pacific Ocean compared to the TRMM 3B42 product. The study highlights the importance of combining geosynchronous and TRMM data to improve the spatial and temporal resolution of rainfall estimates, making the PERSIANN-GT product suitable for climate and hydrology studies.