GRL

Accurate assessment of drought recovery probability is crucial for proactive strategies in cost-effective water resource allocation, resilient agriculture management, and sustainable energy planning. However, there has been a notable gap in assessing drought recovery from a probabilistic and multi-variate perspective. Here, we develop a Vine Copula-based framework to quantify global drought recovery probability and explore its elasticity to precipitation changes. Compared to the historical period (1951–1983), 51% of global land has become increasingly difficult to recover from extreme droughts over 1984–2016 within 8–14 days during growing seasons. Furthermore, the response of global drought recovery to precipitation changes depends on the background climate and varies asymmetrically between wet and dry conditions. Under an extremely wet climate, a 1% historical precipitation increase yields a mere 0.5% increase in global median drought recovery probability during June-July-August, but can lead to a pronounced 6.6% increase if climate gets extremely drier.

Proton auroras, when viewed from space, are subjected to Doppler red shifts. Reports on space-based observations of Doppler shift of H Lyman-alpha (Ly-α) spectral line associated with proton precipitation are still scarce. This study, as a first attempt, extracts Doppler shifted H Ly-α spectral profiles resulting from proton precipitation from data acquired with the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) on board the Defense Meteorological Satellite Program (DMSP)/F16 spacecraft. SSUSI consists of a scanning imaging spectrograph, which covers the far ultraviolet spectrum from ∼1,120 to 1,850 Å, with 160 spectral bins and a spectral resolution of ∼20 Å. We show redshift Ly-α spectra observed by SSUSI when its field of view traverses the auroral ovals. The inferred proton energy and energy flux are in close agreement with the DMSP SSJ in situ particle measurements. This study demonstrates the potential capability of SSUSI in monitoring the energetics of proton precipitation.

Moving down a hillslope from ridge to valley, soil develops and becomes increasingly weathered. Downslope variation in clay content, organic matter, and porosity should produce concomitant changes in soil strength that influence slope stability and erosion. This has yet to be demonstrated, however, because in situ measurements of soil rheology are challenging and rare. Here we employ a robotic leg as a mechanically sensitive and time-efficient penetrometer to map soil strength along a canonical temperate hillslope profile. We observe a systematic downslope weakening, and increasing heterogeneity, of soil strength associated with a transition from sand-rich ridge materials to cohesive valley bottom soil aggregates. Weathering-induced changes in soil composition lead to physically distinct mechanical behaviors in cohesive soils that depart from the behavior observed for sand. We also demonstrate the promise that legged robots may use their limbs to sense and improve mobility in complex environments, with implications for planetary exploration.

High-latitude winter warming was observed following strong tropical volcanism, which has long been believed to be due to the volcanic-induced positive North Atlantic Oscillation (NAO) phase. However, recent works argue that this warming is caused by El Niño–Southern Oscillation (ENSO) variability instead of volcanoes. Moreover, some studies further argue that El Niño and volcanoes work together to produce this post-volcanic NAO winter warming. To better understand these arguments on post-volcanic high-latitude winter warming, we conducted ENSO-preconditioned volcanic experiments. Our simulations strongly suggest that the post-eruption Eurasian winter warming is caused by a post-eruption positive NAO phase and not by coexisting ENSO-preconditioned variability. Additionally, we find that the El Niño-preconditioned volcanic eruption enhances the El Niño phase; however, the neutral and La Niña-preconditioned eruptions do not lead to an ENSO–like response. These findings are helpful to better understand volcanic-induced circulation impacts and have important implications for the interpretation of model results and post-volcanic prediction.