The diurnal cycle and temporal trends of surface winds

Winds play an essential role in the climate system. In this study, we analyze the global pattern of the diurnal cycle of surface (10 m) winds from the ERA5 reanalysis data. We find that over the land and especially over sand dune regions, the maximal wind speed and wind drift potential (DP) occur during the hours around midday. However, over the ocean, the wind also peaks at night. Using the sensible heat flux, we show that the weaker winds over land at night are due to a nocturnal cooling that decouples upper atmospheric levels and their associated stronger winds from the surface -- nocturnal cooling is much smaller over the ocean. We also analyze wind data from more than 400 meteorological stations in the USA and find a similar diurnal trend as in the reanalysis data. The timing (during the day) of the maximum wind speed has not varied much over the past 70 years. Yet, the wind speed, wind power, and wind drift potential exhibit significant increases with time over the ocean and, to a much lesser degree, over the land and sand dune regions. We compare the USA and Europe DP and wind speed of the ERA5 to that of meteorological stations and find that the ERA5 significantly underestimates real winds; however, the temporal patterns of the two are similar

Editorial: Physics and Geomorphology of Sand Ripples on Earth and in the Solar System

Editorial on the Research Topic. Physics and Geomorphology of Sand Ripples on Earth and in the Solar System

Banded vegetation: Biological Productivity and Resilience

Abstract Vegetation band patterns on hill slopes are studied using a mathematical model. The model applies to drylands, where the limiting resource is water, and takes into account positive feedback effects between biomass and water. Multiple band patterns coexisting in wide precipitation ranges are found. For given precipitation and slope conditions band patterns with higher wavenumbers are more biologically productive. High-wavenumber patterns, however, are less resilient to environmental changes. r 2005 Published by Elsevier B.V

Characterization of blocks within a near seafloor Neogene MTC, Orange Basin: Constraints from a high-resolution 3D seismic data

Submarine mass wasting processes in deepwater settings can incorporate large blocks, which may play a key role in deepwater geological processes and geohazard assessment. However, there is a limited understanding of the deformation style arising from the interaction between submarine blocks and structural/bathymetric barriers such as ramps. The deformation and kinematic history of several submarine blocks (with a thickness of up to 150 m) within a near seafloor mass transport complex in the Orange Basin are documented using seismic geo- morphic methods. The interpreted blocks are preserved in three discrete fault-bounded morphological terrains within a Neogene mass-transport complex. These terrains vary in lengths from 2 km to 6 km; they have heights of 60 m to 150 m and are characterized by discrete and localized structural highs on the present-day seafloor. Block sizes vary across terrains suggesting differences in the block evolution process. Blocks near the ramp appear in seismic profiles comprising (a) Chaotic and transparent seismic reflections and (b) parallel to sub-parallel, continuous, low to moderate amplitude reflections. This variability in seismic facies of the blocks reflects the de- gree of their interaction and translation over a ramp at the basal shear zone of the mass transport complex, ev- idenced by the difference in the block features on the upslope portion of the ramp versus the downslope part. Notably, the deformation styles recorded in the blocks show the impact of the ramp during mass flow, which has broader implications for understanding the internal mechanisms of blocky mass transport complexes in many continental margins

Dune-like dynamic of Martian Aeolian large ripples

Martian dunes are sculpted by meter-scale bed forms, which have been interpreted as wind ripples based on orbital data. Because aeolian ripples tend to orient and migrate transversely to the last sand-moving wind, they have been widely used as wind vanes on Earth and Mars. In this report we show that Martian large ripples are dynamically different from Earth's ripples. By remotely monitoring their evolution within the Mars Science Laboratory landing site, we show that these bed forms evolve longitudinally with minimal lateral migration in a time-span of ~ six terrestrial years. Our observations suggest that the large Martian ripples can record more than one wind direction and that in certain cases they are more similar to linear dunes from a dynamic point of view. Consequently, the assumption of the transverse nature of the large Martian ripples must be used with caution when using these features to derive wind directions

Biogenic crust dynamics on sand dunes

Sand dunes are often covered by vegetation and biogenic crusts. Despite their significant role in dune stabilization, biogenic crusts have rarely been considered in studies of dune dynamics. Using a simple model, we study the existence and stability ranges of different dune-cover states along gradients of rainfall and wind power. Two ranges of alternative stable states are identified: fixed crusted dunes and fixed vegetated dunes at low wind power, and fixed vegetated dunes and active dunes at high wind power. These results suggest a cross-over between two different forms of desertification

Virtual Sea-Drifting Experiments between the Island of Cyprus and the Surrounding Mainland in the Early Prehistoric Eastern Mediterranean

Seaborne movement underpins frontier research in prehistoric archaeology, including water-crossings in the context of human dispersals, and island colonisation. Yet, it also controls the degree of interaction between locations, which in turn is essential for investigating the properties of maritime networks. The onset of the Holocene (circa 12,000 years ago) is a critical period for understanding the origins of early visitors/inhabitants to the island of Cyprus in the Eastern Mediterranean in connection with the spread of Neolithic cultures in the region. The research undertaken in this work exemplifies the synergies between archaeology, physical sciences and geomatics, towards providing novel insights on the feasibility of drift-induced seaborne movement and the corresponding trip duration between Cyprus and coastal regions on the surrounding mainland. The overarching objective is to support archaeological inquiry regarding the possible origins of these visitors/inhabitants—Anatolia and/or the Levant being two suggested origins