Estimation of Uncertainty Propagation through Terrestrial Hydrologic Simulations and Objective Evaluation Strategy for In-situ and Satellite Observations of Precipitation

Precipitation, one of the most important flux components in hydrologic circulations, has been estimated exploiting ground-based observations over global and/or regional gauge station networks which has uneven spatiotemporal distributions. In general, they are available from up to the early period of 20th Century, but their temporal resolutions only extends to monthly scale. Since Tropical Rainfall Measuring Mission (TRMM) has been launched in 1997, spatiotemporal resolutions of precipitation observation have been drastically enhanced. Follow-on multi-satellite mission, Global Precipitation Measurement (GPM), with higher resolutions and larger global coverage is ongoing, and its core observatory is scheduled to be launched on 2014. However, satellite precipitation sensor also has been struggling with observation uncertainty such as drift due to orbit change, changes of land cover states, and so on, in particular, for determination of surface rainfall. In this study, uncertainty as relative differences between existing precipitation observations including ground- and satellite-based products is quantified and evaluated over global land area and various climatic regions using a dimensionless ';similarity' index. It is also investigated how the uncertainty in precipitation propagates into evapotranspiration and runoff partitioning using global terrestrial hydrologic modeling framework. It is found uncertainty in precipitation tends to translate relatively amplified and reduced way to runoff and evapotranspiration, respectively. Also, present study suggests a validation strategy based on ';objective classification' by such as types of precipitation and intensity of background atmospheric mechanism determined by atmospheric reanalysis and digitized weather chart, which will provide additional information to evaluate the characteristics of different measurements in various atmospheric conditions.