Oreste Reale | Searcharxiv

arXiv2026

The Lunar Polar Icy Regolith and Possible Moonflows

The Lunar CRater Observation and Sensing Satellite (LCROSS) experiment, which created a crater 27 meters in size, showed that up to 6 percent water appear to be present in the permanently shadowed region (PSR) of Cabeus crater. Past independent theoretical analyses have concluded that some water molecules released elsewhere on the lunar surface can migrate to permanently shadowed areas. The estimated amount of ice, ice fragments, and other volatiles located in the polar regions in and beneath the regolith at depths of several meters may be still affected by significant uncertainties. Data from the Kaguya mission provide strong evidence for active plumes of water vapor erupting from polar regions outside the PSRs to heights of several km. These plumes appear to originate from subsurface ice located beneath the regolith surface at depths of approximately 20 cm. On the other hand, the polar highlands exhibit a relative deficit of craters larger than 25 meters, which may be caused by impact-melted ice lubricating regolith that flowed into initial crater depressions. At both the north and south poles of the Moon, signs of possible short-lived flows of liquid water-bearing material "moonflows" are presented in this work. Limited hydrous alteration of regolith ultra-fines to phyllosilicates may have occurred as these moonflows cooled.

astro-ph.EP↗

arXiv2023

Assimilation of SMAP Observations Over Land Improves the Simulation and Prediction of Tropical Cyclone Idai

Soil moisture conditions can influence the evolution of a tropical cyclone (TC) that is partially or completely over land. Hence, better constraining soil moisture initial conditions in a numerical weather prediction model can potentially improve predictions of TC evolution near or over land. This study examines the impact of assimilating observations from the NASA Soil Moisture Active Passive (SMAP) mission into the NASA Goddard Earth Observing System (GEOS) global weather model on the prediction of South-West Indian Ocean TC Idai (2019). Two sets of retrospective forecasts of TC Idai are compared in an Observing System Experiment framework: (i) forecasts initialized from an analysis that is comparable to the GEOS operational analysis and (ii) forecasts initialized from an analysis that additionally assimilates SMAP brightness temperature observations over land. Results indicate that SMAP assimilation leads to pronounced improvements in the representation of TC Idai structure and prediction of its intensity and track. The wind speed radius (a measure for TC compactness) is reduced by up to 18% in the analysis with SMAP assimilation relative to the control experiment without SMAP assimilation. The forecast intensity error, measured against the observed intensity, is reduced by up to 23%. The forecast along-track error is reduced by up to 34%, indicating a more accurate propagation speed, while the impact of SMAP assimilation on the forecast cross-track error is neutral. These results provide a valuable demonstration that SMAP assimilation can have a highly beneficial impact on TC prediction in global weather forecast models.

physics.ao-ph↗