Historical reconstruction of monthly oceanic precipitation (1900-2006)

An oceanic precipitation reconstruction is developed and evaluated for periods extending back to as early as 1900. Large-scale monthly oceanic precipitation is reconstructed using the available network of historical gauge data fit to a set of large-scale covariance spatial modes based on modern analysis. The modern analysis is based on satellite microwave estimates merged with atmospheric reanalysis estimates. For 1900-2006, a monthly and 5 degrees spatial product is developed for reconstructing climate-scale (large-scale spatial and inter-seasonal and longer timescales) variation in pre-satellite periods. Advantages of this study include the use of a homogeneous satellite analysis for computing reconstruction statistics and improved tuning of the reconstruction methods. Cross-validation testing is used to show how much historical variance can be reconstructed with the available sampling. In addition, reconstructions are performed using several different gauge data sets to evaluate differences due to the choice of gauge data. Testing shows that that these improved methods produce reconstructions with useful skill in the tropics and Northern Hemisphere midlatitudes. In the Southern Hemisphere midlatitudes and in polar latitudes in both hemispheres, sampling is too sparse to yield much skill. The reconstruction is able to resolve large-scale modes of variation useful for some diagnostic studies of the 20th century. Reconstruction efforts will continue as improved satellite and atmospheric reanalyses become available.