ARPA-E

About: ARPA-E is a government organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Population & Climate change. The organization has 1161 authors who have published 1267 publications receiving 30049 citations. The organization is also known as: Advanced Research Projects Agency - Energy.

A simplified bi‐dimensional variational analysis of soil moisture from screen‐level observations in a mesoscale numerical weather‐prediction model

Abstract: The analysis of soil moisture for the initialization of a mesoscale numerical weather-prediction (NWP) model is considered subject to operational constraints, both in terms of computational cost and data availability. A variational technique is used to analyse the soil moisture by assimilating screen-level observations of temperature and relative humidity. We consider a simplified bi-dimensional (z and t) variational approach (simplified 2D-VAR), where the estimate of the observation operator is obtained from extra integration(s) of the numerical model. The fundamental assumptions of the method are first evaluated: linearity of the observation operator, horizontal decoupling between grid points, and truncation of the control variable space (variable decoupling), that allow the simplified 2D formalism. Thus, the variational method is applied at each grid point separately and the gain matrix is computed from finite differences given the small dimension involved. The 2D-VAR technique keeps count of the full physics of the model, so the corrections applied to the control variable are adapted to the current meteorological conditions and the grid-point characteristics (texture and vegetation), as well as to the previous soil state. The linear estimate of the observation operator is studied in detail to optimize its evaluation. The validation of the method is shown with simulated observations, and the assimilation of real observations is performed with different time-windows. A sequential assimilation cycle on a 6-hour time-window allows the comparison with the optimum interpolation technique, while a 24-hour window is considered to extend the temporal consistency of the assimilated observations in the analysis. Results from the performed analyses with the simplified 2D-VAR method show a good retrieval of soil moisture, and a comparison with other initialization methods is also provided. Copyright © 2004 Royal Meteorological Society.

A meteo-hydrological prediction system based on a multi-model approach for precipitation forecasting

Abstract: . The precipitation forecasted by a numerical weather prediction model, even at high resolution, suffers from errors which can be considerable at the scales of interest for hydrological purposes. In the present study, a fraction of the uncertainty related to meteorological prediction is taken into account by implementing a multi-model forecasting approach, aimed at providing multiple precipitation scenarios driving the same hydrological model. Therefore, the estimation of that uncertainty associated with the quantitative precipitation forecast (QPF), conveyed by the multi-model ensemble, can be exploited by the hydrological model, propagating the error into the hydrological forecast. The proposed meteo-hydrological forecasting system is implemented and tested in a real-time configuration for several episodes of intense precipitation affecting the Reno river basin, a medium-sized basin located in northern Italy (Apennines). These episodes are associated with flood events of different intensity and are representative of different meteorological configurations responsible for severe weather affecting northern Apennines. The simulation results show that the coupled system is promising in the prediction of discharge peaks (both in terms of amount and timing) for warning purposes. The ensemble hydrological forecasts provide a range of possible flood scenarios that proved to be useful for the support of civil protection authorities in their decision.

Sierra Nevada Plutonic Cycle: Part I, Origin of Composite Granitic Batholiths

Abstract: Intrusion of Mesozoic batholiths in California and the western North America Cordillera began in the Late Triassic 210 m.y. ago and ended in the Late Cretaceous 80 m.y. ago. Emplacement of granitic rocks was apparently not continuous but was accomplished during five major epochs of intrusion at approximately 30 m.y. intervals, each epoch taking 10 to 20 m.y. to complete. A progressive transgression of epicontinental seas onto the midcontinent occurred during the same interval of time as the batholithic emplacement to the west. A penecontemporaneous deformation near the loci of granitic emplacement and a temporary regression during the major progressive transgression of seas onto the midcontinent are correlated with each intrusive epoch. The locus of Mesozoic granitic rocks was a source of sediments during most of the period of time required to emplace the batholiths; the origin of the batholithic magmas cannot be related only to localized down-warping of geosynclines. The source of the major proportion of the mobile granodioritic magmas of the Sierra Nevada was within the mantle, as is indicated by Sr isotope data. All plutons now exposed in the Sierra Nevada, whether of Cretaceous age or older, were emplaced at depths of a very few kilometers, the shallowest having been emplaced at depths of 4 km or less. The spatial relationships among these synchronous geologic phenomena and the geochemical and geophysical data from the same region are accounted for by a northwestward drift of North America in the region of the western Cordillera of the United States onto and across a Mesozoic feature that had characteristics like present-day oceanic rises.

Human impact and the historical transformation of saltmarshes in the Marano and Grado Lagoon, northern Adriatic Sea

Abstract: Historical transformations of the saltmarshes in the six sub-basins of the Marano and Grado Lagoon were analyzed using aerial photographs (1954, 1990, 2006), and the support of historical maps and topographic surveys. Analysis of the 2006 set of aerial photographs enabled the definition of the present extent and distribution of the saltmarshes inside the lagoon (760 ha), with a total reduction in saltmarsh area of 16% (144 ha) compared to 1954. Direct human actions played a significant role in the budget, since total loss due to land reclamation and dredging during this period amounted to 126 ha. After excluding the total loss due to direct human interventions, different erosional and depositional marsh types were recognized and associated with different forcing factors, based on morphological and geographical evidence. Over the 52-year period marshes were lost due to: (a) drowning – the combined effects of eustatism, regional subsidence and autocompaction (102 ha); (b) edge-retreat by wind wave attack (34 ha); (c) erosion by vessel-generated waves (37 ha); and (d) coastal dynamics and inlet migration (5.7 ha). Conversely, marshes gained in area due to: (a) fluvial input (63 ha); (b) tidal input (27 ha); (c) paralagoonal deposition (45 ha); (d) the re-opening of abandoned fish farms (18 ha); and (e) the dumping of dredged material (8 ha). Our analysis demonstrates that local and short-term forcing factors can obliterate or compensate the long-term ones, especially the relative sea-level rise. A test of the integrated sediment budget carried out on one third of the total lagoon, through a bathymetric comparison between datasets from 1964 to 2009, pointed out that conservation or slight expansion of the marshes inside these basins were linked to an overall positive sediment budget of 61,000 m 3 /y. Nevertheless, significant morphological changes occurred in the submerged basin, which is affected by sustained deposition along the inner margins due to sediment supplies, by an overall erosion of tidal and sub-tidal flats far from the tributaries, and by an important infilling of the channels. The analyzed data, along with information available for the Venice Lagoon, highlights how the fate of open-water lagoons is to flatten whilst submerging because of the strong influence of wind waves, which tend to transform the lagoon into a marine embayment. This transgressive condition reduces, if not negates, the compensative effect of the sedimentation rate on wind-wave-induced shear stress excess, since supplies seem to contribute primarily to the morphological accommodation.