The alternative of CubeSat-based advanced infrared and microwave sounders for high impact weather forecasting

近年来,小卫星技术的发展给传统气象卫星提供了经济有效的替补方案。本文针对可能出现的传统气象卫星的缺失情形,借助快速的区域观测系统模拟试验,探索了利用小卫星填补空缺的可能性。研究表明,单个小卫星,无论是近红外高光谱还是微波探测仪,都能够对局地强风暴天气的预报有所改进。然而,为了填补传统卫星缺失带来的影响,需要发射三颗甚至更多的小卫星来增加观测的覆盖面,以弥补小卫星精度略低、通道略少的缺陷。     

North Arch volcanic fields near Hawaii are evidence favouring the restite‐root hypothesis for the origin of hotspot swells

A pronounced regional bathymetric swell is a common feature of oceanic hotspot volcanism. Recently, the hypothesis of a buoyant sublithospheric swell‐root has been favoured, the root being either a ‘refracted plume’ of hot, buoyant and hence low‐viscosity plume material embedded within surrounding higher viscosity asthenosphere, or a ‘restite‐root’ composed of hot and more viscous residues to hotspot melt‐extraction from the hottest central portion of the upwelling plume. In this article, we present numerical experiments that show that these two scenarios predict different flow and melting patterns whenever the plume passes beneath an obliquely oriented fracture zone where the base of the overriding lithosphere changes in thickness. We find that the restite‐root hypothesis predicts an asymmetric spatial pattern of persistent ‘arch volcanism’ strikingly similar to that found in the Hawaiian chain surrounding the Molokai Fracture Zone. In contrast, the ‘refracted plume’ hypothesis predicts more chaotic patterns quite different from the off‐chain pattern of Hawaiian volcanism.     

Field study on influence of root characteristics on soil suction distribution in slopes vegetated with Cynodon dactylon and Schefflera heptaphylla

Vegetation evapotranspiration (ET) induced soil water suction reduces hydraulic conductivity and increases shear strength of slopes. Several field studies have been conducted to investigate suction distribution in vegetated slopes. However, these studies were conducted on natural slopes, which are prone to heterogeneity in vegetation and soil conditions. Moreover, studies quantifying the effect of different vegetation species, root characteristics (root depth and root area index) and transpiration reduction function (T_rf) on suction in slopes under natural variation are rare. This study investigated the suction distribution and root characteristics in recompacted slopes vegetated with two different species, i.e. Cynodon dactylon (Bermuda grass) and Schefflera heptaphylla (ivy tree). Bare slope served as a control. Suction distributions during different seasons and rainfall events were monitored. It is found that during the dry season, slope vegetated with young Schefflera heptaphylla seedlings have substantially higher suction within the root zone compared with bare slope and slope vegetated with Cynodon dactylon. This is because Schefflera heptaphylla has a higher root biomass, T_rf and ET than Cynodon dactylon. It was also found that suctions within root zones of vegetated slopes and bare slope were completely destroyed under rainfall events corresponding to 2 years and 20 years return period. Copyright © 2015 John Wiley & Sons, Ltd.     

Influences of Natural and Anthropogenic Factors and Tidal Restoration on Terrestrial Arthropod Assemblages in West Coast North American Estuarine Wetlands

Compared to benthic and water-column invertebrate assemblages, considerably less is known about terrestrial arthropods inhabiting estuarine wetlands despite their importance to tidal wetland biodiversity and productivity. We also need to know more about how human modification of estuaries, including efforts to restore estuarine wetlands, affects these assemblages. To address this knowledge gap, we assembled data from multiple studies on terrestrial arthropod assemblages from 87 intertidal wetland sites in 13 estuaries along the west coast of North America. Arthropods were sampled between 1998 and 2013 with fallout traps deployed in wetlands for 1 to 3 days at a time. We describe patterns in the abundance and taxonomic composition of terrestrial arthropods and evaluate the relative ability of natural and anthropogenic factors to explain variation in abundance and composition. Arthropod abundance was highly variable. Vegetation assemblage, precipitation, and temperature best explained variation in arthropod abundance, while river discharge, latitude, and developed and agricultural land cover surrounding sampling sites were less important. Arthropod abundance rapidly achieved levels of reference wetlands after the restoration of tidal influence to leveed wetlands, regardless of surrounding land cover. However, arthropod assemblage composition was affected by the amount of developed land cover as well as restoration age. These results suggest that restoration of tidal influence to leveed wetlands can rapidly restore some components of estuarine wetland ecosystems but that recovery of other components will take longer and may depend on the extent of anthropogenic modification in the surrounding landscape.     

How the capacity of bedrock to collect dust and produce soil affects phosphorus bioavailability in the northern Appalachian Mountains of Pennsylvania

More above-ground biomass (kg m⁻²) grows in the northern Appalachian Mountains (USA) in forests on shale than on sandstone at all landscape positions other than ridgetops. This has been tentatively attributed to physical (rather than chemical) attributes of the substrates, such as elevation, particle size, and water capacity. However, shales have generally similar phosphorus (P) concentrations to sandstones and, in the Valley and Ridge province, they erode more quickly. This led us to hypothesize that faster replenishment of the lithogenic nutrient P in shale soils through erosion + soil production could instead control the differences in biomass. To test this, soils and foliage from 10 sites on shales and sandstones in the northern Appalachians from roughly the same elevation and aspect were analysed. We discovered that, when controlling for location, concentrations of bioavailable P in soils and P in foliage were higher and P resorbed from senescing red oak leaves was lower on slower-eroding sandstone than on faster-eroding shale. Lower resorption generally can be attributed to lower P limitation for trees. Further investigation of weathering and erosion on one of the sandstone–shale pairs within a larger, paired watershed study revealed that the differences in P concentrations in biomass and foliage between lithologies likely developed because sandstones act as ‘collectors’ that trap nutrients from residual and exogenous sources, while shales erode quickly and thus promote production of soil from bedrock that releases P to ecosystems. We concluded that the combined effects of differential rates of dust collection and erosion results in roughly equal biomass growing on sandstone and shale ridgetops. This work emphasizes the balance between a landscape's capacity to collect dust versus produce soil in controlling bioavailability of nutrients.     

The Biscuit Brook and Neversink Reservoir watersheds: Long-term investigations of stream chemistry,soil chemistry and aquatic ecology in the Catskill Mountains,New York,USA, 1983–2020

This data note describes the Biscuit Brook and Neversink Reservoir watershed long-term monitoring data that includes: 1) stream discharge, (1983–2020 for Biscuit Brook and 1937–2020 for the Neversink Reservoir watershed), 2) stream water chemistry, 1983–2020, at 4 stations, 3) fish survey data from 16 locations in the watershed 1990–2019, 4) soil chemistry data from 2 headwater sub-watersheds, 1993–2012 and 5) periodic stream water chemistry sampling data from 364 locations throughout the watershed, 1983–2020. The Neversink Reservoir watershed in the Catskill Mountains of New York, USA drains an area of 172.5 km². The watershed feeds one of six reservoirs in New York City's West of Hudson water supply, which accounts for about 90% of the city's water supply. Biscuit Brook is a 9.63 km² tributary sub-watershed within the Neversink Reservoir watershed.     

The porosity and permeability of chondritic meteorites and interplanetary dust particles

Abstract— We have investigated the porosity of a large number of chondritic interplanetary dust particles (IDPs) and meteorites by three techniques: standard liquid/gas flow techniques, a new, noninvasive ultrasonic technique, and image processing of backscattered images. The latter technique is obviously best-suited to sub-kilogram sized samples. We have also measured the gas and liquid permeabilities of some chondrites by two techniques: standard liquid/gas flow techniques, and a new, nondestructive pressure release technique. We find that chondritic IDPs have a somewhat bimodal porosity distribution. Peaks are present at 0 and 4% porosity; a tail then extends to 53%. Type 1–3 chondrite matrix porosities range up to 30%, with a peak at 2%. The bulk porosities for type 1–3 chondrites have the same approximate range as exhibited by the matrix, which indicates that other components of the bulk meteorites (including chondrules and aggregates) have the same average porosity as the matrix. These results reveal that the porosities of primitive materials at scales ranging from nanogram to kilogram are similar, which implies that similar accretion dynamics operated through 12 orders of size magnitude. Permeabilities of the investigated chondrites vary by several orders of magnitude, and there appears to be no simple dependence of permeability with degree of aqueous alteration, chondrite type or porosity.     

Ultraviolet irradiation of naphthalene in H2O ice: Implications for meteorites and biogenesis

Abstract— The polycyclic aromatic hydrocarbon (PAH) naphthalene was exposed to ultraviolet radiation in H₂O ice under astrophysical conditions, and the products were analyzed using infrared spectroscopy and high‐performance liquid chromatography. As we found in our earlier studies on the photoprocessing of coronene in H₂O ice, aromatic alcohols and ketones (quinones) were formed. The regiochemistry of the reactions is described and leads to specific predictions of the relative abundances of various oxidized naphthalenes that should exist in meteorites if interstellar ice photochemistry influenced their aromatic inventory. Since oxidized PAHs are present in carbon‐rich meteorites and interplanetary dust particles (IDPs), and ubiquitous in and fundamental to biochemistry, the delivery of such extraterrestrial molecules to the early Earth may have played a role in the origin and evolution of life.