The TRMM and Other-GPI Calibration Rainfall Product algorithm (3B42) uses combined rain structure (2B31) and VIRS calibration (1B01) to adjust IR estimates from geosynchronous IR observations. Global estimates are made by adjusting the GOES Precipitation Index (GPI) to the TRMM estimates. The 3B42 algorithm provides the daily tropical precipitation estimates and also the root mean square (RMS) precipitation error estimates. The output is daily rainfall for 1x1 degree grid boxes within the tropical region from latitude 40N to 40S (Huffman et al., 2001).