Variability and Trends in the Global Water Cycle Based on Multi-Decadal Earth Science Data Record

Abstract:

Documentation of the global water cycle and its evolution over time has been a primary scientific goal of the Global Energy and Water Exchanges Project, and is fundamental to providing a benchmark for the present climate, to document inter-annual variability and global change impacts, and to validate models.

In developed countries, observation systems that include in-situ, remote sensing and modeled data can provide long-term, consistent and generally high quality datasets of water cycle variables. In less developed, data sparse regions, in situ data alone are insufficient to develop a comprehensive picture of how the water cycle is changing, and strategies that merge in-situ, model and satellite observations within a framework that results in consistent water cycle records is essential.

This presentation will utilize newly developed, multi-decadal water and energy cycles data sets to analyze and advance our understanding of the role of the terrestrial hydrosphere in Earth’s climate system. The data sets include a 60-year global water cycle dataset developed through a NASA-sponsored multi-institutional effort under the NASA MEaSUREs program, multi-model terrestrial evapotranspiration data sets coordinated under the GEWEX Data and Assessments Panel (GDAP) as part of the LandFlux initiative, and ocean evaporation under SeaFlux. The foundations of the datasets are a variety of independent large-scale datasets of the hydrologic variables that are used to bridge the gap between sparse in-situ observations, including remote-sensing based retrievals, observation-forced hydrologic modeling, and weather model reanalyses.

Analyses are carried out across a range of temporal and spatial scales from monthly to annual and decadal, and from ~250 river basins to continental and global scales, and will address long-standing GEWEX science questions that include (i) quantifying the nature and extent of changes (trends and variability) to the terrestrial hydrosphere over the last 60 years, and (ii) understanding the exchanges among the terrestrial, oceanic and atmospheric branches of the hydrosphere. The multi-decadal terrestrial water and energy budgets datasets permits putting recent studies done for shorter periods, and for specific variables, into a larger consistent framework.