Ocean / Land Moisture Transport: Estimates from Reanalyses, Satellites and Land Surface Models

Atmospheric transport of moisture between ocean and land (-DivQV) is a fundamental component of the physical climate system linking both the hydrologic and energy cycles of the planet as well as determining fresh water availability to the biosphere. On monthly and regional time scales - DivQV P-E; thus, both direct estimates of this transport from reanalysis wind and moisture fields as well as E and P from satellite retrievals and surface observations offer relatively independent information. In concert with terrestrial and ocean water mass storage estimates from GRACE or steric-corrected ocean mass change from altimeters, -DivQV or E-P estimates have been used by various research groups — including the NASA Energy and Water Cycle Study (NEWS) Science Team — to infer estimates of continental water discharge. But the accuracy of moisture transport remains a key uncertainty.

In this work we bring together a variety of atmospheric reanalysis, satellite and observationally-constrained land surface data to narrow -DivQV and P-E uncertainties. We take advantage of a number of new data sets, among them MERRA-2 and JRA-55 reanalyses, but also the emerging ERA-5. E estimates from the SeaFlux 2, J-OFURO 3, HOAPS4 and IFREMER employ the most recent algorithms. GPCP precipitation is supplemented by TRMM /GPM data. Terrestrial E, GPCC P and discharge estimates from the WaterGAP hydrologic model and several similar observationally-constrained models are used. Our analysis addresses both climatological biases and variability over recent decades. Particular emphasis is placed on determining how weaknesses in each data type (data density and availability, weather regime bias, satellite intercalibration) propagate through estimates and determine -DivQV P-E uncertainty. Results of this analysis contribute to the overarching NASA NEWS objective of documenting and enabling improved, observationally-based, predictions of energy and water cycle consequences of Earth system variability and change.