Terrestrial Water Storage Across Scales
Author | : John Thomas Reager |
Publisher | : |
Total Pages | : 110 |
Release | : 2012 |
ISBN-10 | : 1267646330 |
ISBN-13 | : 9781267646330 |
Rating | : 4/5 (30 Downloads) |
Book excerpt: Terrestrial water storage is difficult to observe over large areas, and as a result, studies of the global water cycle under changing climate tend to focus on a few key methodologies: monitoring of the large-scale fluxes of precipitation, evaporation and discharge; modeling the relationship between runoff response and precipitation forcing; or applying limited in-situ data sets to generalize and scale behavior. With NASA's Gravity Recovery And Climate Experiment (GRACE) mission, hydrologists are finally able to study terrestrial water storage for large river basins (>200,000 km2) with monthly time resolution, opening what was previously an unobservable 'black box' in land-surface water dynamics. GRACE data are ideally suited for monitoring global water storage variability and classifying differences in basin water storage behavior that are relevant for global climate studies. In this research we explore global to regional scale applications of GRACE data that highlight the novelty, functionality and importance of these groundbreaking observations. First, we present a new metric for the monitoring of global water cycle health and energy expenditure - the time-series of Total Global Ocean Mass Anomaly and Total Global Land Mass Anomaly from NASA's Gravity Recovery and Climate Experiment - and show that this metric is heavily influenced by highly variable regional water cycle dynamics in a few global "wet spots". Second, we provide results of a statistical model of basin-averaged GRACE terrestrial water storage anomaly and Global Precipitation Climatology Project (GPCP) precipitation for the world's largest basins. Third, we combine new 1-degree GRACE storage observations with state-of-the-art global land-surface model representations of surface, canopy and snow water, to derive a 1-degree spatially variable sub-surface water storage anomaly time series with error estimates. We convolve this result with global estimates of porosity from FAO Harmonized Soil Database to estimate an effective global active soil depth range and changes during the GRACE record. Finally, terrestrial water storage anomaly from the Gravity Recovery and Climate Experiment (GRACE) and precipitation observations from the Global Precipitation Climatology Project (GPCP) are applied at the regional scale to show the usefulness of a remotely sensed, storage-based flood potential method.