The impact of new water vapor spectroscopy on satellite retrievals

Water vapor, arguably the most important trace gas constituent of Earth atmospheric physics, is also both a retrieval goal and a hindrance in the retrievals of other trace gases from nadir-measuring satellite spectrometers. This is because the atmospherically-attenuated solar spectrum in the visible and shortwave infrared is littered with water vapor bands. The recent plethora of water vapor spectroscopy databases in this spectral region has prompted us to study their utility in satellite retrievals. We consider water vapor spectroscopy compiled from four sources including new spectroscopy due to University College London and Imperial College London. Radiative transfer models of satellite measurements, in combination with accurate retrieval techniques, are quite sensitive to the accuracy and completeness of the water vapor spectroscopy. Notwithstanding the high degree of variability of a number of different factors in satellite measurements we show that retrievals are sensitive to database differences which suggests that our knowledge of water vapor spectroscopy is not as yet complete. In addition, new laboratory measurements indicate that the role of both the far-line wings of water vapor and the cumulative effect of many weak lines each have an important role to play in forming the so-called continuum

Twenty years of satellite and in situ observations of surface chlorophyll-a from the northern Bay of Biscay to the eastern English Channel. Is the water quality improving?

Thevariabilityofthephytoplanktonbiomassderivedfromdailychlorophyll-a(Chl-a)satelliteimageswasinvestigated over the period 1998–2017 in the surface waters of the English Channel and the northern Bay of Biscay. Merged satellite (SeaWiFS-MODIS/Aqua-MERIS-VIIRS) Chl-a wascalculated using the OC5 Ifremeralgorithm which is optimized for moderately-turbid waters. The seasonal cycle in satellite-derived Chl-a was comparedwithinsitumeasurementsmadeatsevencoastalstationslocatedinthesouthernsideoftheEnglish ChannelandinthenorthernBayofBiscay.TheresultsfirstlyshowedthatthesatelliteChl-aproduct,derived from a suite of space-borne marine reflectance data, is in agreement with the coastal observations. For compliancewiththedirectivesoftheEuropeanUniononwaterquality,time-seriesof6-yearmovingaverageofChlawereassessedovertheregion.Acleardeclinewasobservedinthemeanand90thpercentileofChl-aatstations locatedinthemixedwatersoftheEnglishChannel.Thetime-seriesatthestationslocatedintheBayofBiscay showedyearlyfluctuationswhichcorrelatedwellwithriverdischarge,butnooverallChl-atrendwasobserved. IntheEnglishChannel,theshapeoftheseasonalcycleinChl-achangedovertime.Narrowerpeakswereobservedinspringattheendofthestudiedperiod,indicatinganearlierlimitationbynutrients.Monthlyaverages of satellite Chl-a, over theperiods 1998–2003and2012–2017,exhibitedspatial andtemporalpatternsin the evolutionofthephytoplanktonbiomasssimilartotheseobservedatthesevencoastalstations.Boththeinsitu andsatelliteChl-atimes-seriesshowedadecreaseinChl-aintheEnglishChannelinMay,JuneandJuly.This trendinphytoplanktonbiomassiscorrelatedwithlowerriverdischargesattheendoftheperiodandaconstant reduction in the riverine input of phosphorus through improvements in the water quality of the surrounding rivercatchments

Distal chromatin structure influences local nucleosome positions and gene expression

The positions of nucleosomes across the genome influence several cellular processes, including gene transcription. However, our understanding of the factors dictating where nucleosomes are located and how this affects gene regulation is still limited. Here, we perform an extensive in vivo study to investigate the influence of the neighboring chromatin structure on local nucleosome positioning and gene expression. Using truncated versions of the Saccharomyces cerevisiae URA3 gene, we show that nucleosome positions in the URA3 promoter are at least partly determined by the local DNA sequence, with so-called ‘antinucleosomal elements’ like poly(dA:dT) tracts being key determinants of nucleosome positions. In addition, we show that changes in the nucleosome positions in the URA3 promoter strongly affect the promoter activity. Most interestingly, in addition to demonstrating the effect of the local DNA sequence, our study provides novel in vivo evidence that nucleosome positions are also affected by the position of neighboring nucleosomes. Nucleosome structure may therefore be an important selective force for conservation of gene order on a chromosome, because relocating a gene to another genomic position (where the positions of neighboring nucleosomes are different from the original locus) can have dramatic consequences for the gene's nucleosome structure and thus its expression

Noise Pollution Filters Bird Communities Based on Vocal Frequency

BACKGROUND: Human-generated noise pollution now permeates natural habitats worldwide, presenting evolutionarily novel acoustic conditions unprecedented to most landscapes. These acoustics not only harm humans, but threaten wildlife, and especially birds, via changes to species densities, foraging behavior, reproductive success, and predator-prey interactions. Explanations for negative effects of noise on birds include disruption of acoustic communication through energetic masking, potentially forcing species that rely upon acoustic communication to abandon otherwise suitable areas. However, this hypothesis has not been adequately tested because confounding stimuli often co-vary with noise and are difficult to separate from noise exposure. METHODOLOGY/PRINCIPAL FINDINGS: Using a natural experiment that controls for confounding stimuli, we evaluate whether species vocal features or urban-tolerance classifications explain their responses to noise measured through habitat use. Two data sets representing nesting and abundance responses reveal that noise filters bird communities nonrandomly. Signal duration and urban tolerance failed to explain species-specific responses, but birds with low-frequency signals that are more susceptible to masking from noise avoided noisy areas and birds with higher frequency vocalizations remained. Signal frequency was also negatively correlated with body mass, suggesting that larger birds may be more sensitive to noise due to the link between body size and vocal frequency. CONCLUSIONS/SIGNIFICANCE: Our findings suggest that acoustic masking by noise may be a strong selective force shaping the ecology of birds worldwide. Larger birds with lower frequency signals may be excluded from noisy areas, whereas smaller species persist via transmission of higher frequency signals. We discuss our findings as they relate to interspecific relationships among body size, vocal amplitude and frequency and suggest that they are immediately relevant to the global problem of increases in noise by providing critical insight as to which species traits influence tolerance of these novel acoustics

Matter manipulation with extreme terahertz light: Progress in the enabling THz technology

Terahertz (THz) light has proven to be a fine tool to probe and control quasi-particles and collective excitations in solids, to drive phase transitions and associated changes in material properties, and to study rotations and vibrations in molecular systems. In contrast to visible light, which usually carries excessive photon energy for collective excitations in condensed matter systems, THz light allows for direct coupling to low-energy (meV scale) excitations of interest, The development of light sources of strong-field few-cycle THz pulses in the 2000s opened the door to controlled manipulation of reactions and processes. Such THz pulses can drive new dynamic states of matter, in which materials exhibit properties entirely different from that of the equilibrium. In this review, we first systematically analyze known studies on matter manipulation with strong-field few-cycle THz light and outline some anticipated new results. We focus on how properties of materials can be manipulated by driving the dynamics of different excitations and how molecules and particles can be controlled in useful ways by extreme THz light. Around 200 studies are examined, most of which were done during the last five years. Secondly, we discuss available and proposed sources of strong-field few-cycle THz pulses and their state-of-the-art operation parameters. Finally, we review current approaches to guiding, focusing, reshaping and diagnostics of THz pulses. (C) 2019 The Author(s). Published by Elsevier B.V

The ionospheric oxygen green airglow: Electron temperature dependence and aeronomical implications.

The laboratory measurement of processes involved in terrestrial airglows is essential in developing diagnostic tools of the dynamics and photochemistry of the upper atmosphere. Dissociative electron recombination of O 2+ in the ionospheric F-region is expected to produce both O( 1D) and O( 1S) which are the sources of the 630.0 nm red airglow and the 557.7 nm green airglow lines, respectively. We present both theoretical and experimental evidence, the latter from a heavy ion storage ring technique, that the O( 1S) quantum yield from O 2+ (v = 0) is a strong function of the electron temperature due to a molecular resonance phenomenon. At present the O 2+ (v = O) theoretical and laboratory recombination data cannot explain rocket observations of the ionospheric green and red airglows [Takahashi et al. 1990; Sobral et al. 1992]

Dissociative recombination and excitation of O-2(+): Cross sections, product yields and implications for studies of ionospheric airglows

The dissociative recombination (DR) and the dissociative excitation (DE) of O2+ were experimentally studied using a heavy ion storage ring. The 300 K thermal rate coefficient was deduced. Experimental, theoretical, and observational arguments indicate that the O(1S) quantum yield equals the O(1)+O(1D) branching fraction

Wet dune slacks: decline and new opportunities

For a number of infiltrated coastal dune areas it is discussed to what extent artificial infiltration for the public water supply affects the quality of soil, groundwater and vegetation around pools and ponds, and what its effect is on the vegetation. Further, the results of investigations into the quality of vegetation, soil and water of a number of non-infiltrated, less affected dune areas are presented. The emphasis is on changes in groundwater flow pattern and on changes in the chemical composition of groundwater on the vegetation of wet dune slacks. Finally, recommendations for the management of wet dune slacks are presented. It can be concluded that the introduction of nutrients through infiltration causes an abundance of nitrophilous herbaceous vegetation along the banks of all infiltration ponds and most dune pools. Of the three investigated macro-nutrients, nitrate, potassium and phosphate, the latter shows the most significant correlation with the composition, cover and biomass of the vegetation. The moist biotopes of non-infiltrated dunes have largely disappeared because of desiccation, mainly as a consequence of water withdrawal, afforestation and coastal erosion. Relatively unaffected dune slacks can be found in the dunes on the Dutch Wadden Sea islands and a small number of dune areas on the mainland. In most areas, however, a serious decline in many rare species has been observed during the past twenty years because of eutrophic and acid precipitation, often in combination with disturbances of the groundwater regime.