Many merged multi-source global analyses of precipitation exist, including the Global Precipitation Climatology Project (GPCP) analysis and the CPC Merged Analysis of Precipitation (CMAP). The multi-source nature of these datasets allows them to use the best data available to produce the most accurate estimate of precipitation for any given place and time. However, this strength can lead to weaknesses in the form of discontinuities, artifacts and inhomogeneities in the longer record, which can impact their suitability for investigation of long-term changes in global precipitation. Additionally, high latitude precipitation is poorly determined in these datasets since the available estimates originate from either gauges (which suffer from problems related to under-catch of solid precipitation) or satellite data (which exhibit large errors at high latitudes due to ice-contamination issues).

We aim to produce a new global analysis of precipitation using Optimum Interpolation (OI) that will overcome both of these issues by using the relatively long consistent precipitation record (~20 years) from the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I) and forecast precipitation from the ERA-40 reanalysis. An additional advantage of the OI methodology is its facility in the calculation of errors associated with the analysis, which are needed for many applications. I will discuss some of the issues associated with this work and show some initial results.