The GERB TOA outgoing longwave radiation (OLR) Obs4MIPs product has been generated from GERB level 2 HR OLR fluxes. There are three main stages. The first ingests the Edition 1 GERB HR OLR data and generates an area weighted flux product at 1° by 1° spatial resolution for every 15 minute time interval. In the second stage these data are averaged over time to produce an hourly averaged product. Each hour interval is defined as the time-centred mean at half-past the hour, e.g. 1030 UTC comprises of the mean of data from 1000 UTC, 1015 UTC, 1030 UTC and 1045 UTC (or from those slots in this window that are available). An hourly average is produced for a 1° by 1° grid cell if there is one or more observation from the four observation times available for that grid cell. The final processing stage averages the hourly mean fluxes over the days in the month to produce a one degree monthly mean product at hourly intervals. The number of data points (days per monthly hourly mean) contributing to each monthly mean are used to estimate the uncertainties associated with the product.