How uncertain are precipitation and peak flow estimates for the July 2021 flooding event?

The disastrous July 2021 flooding event made us question the ability of current hydrometeorological tools in providing timely and reliable flood forecasts for unprecedented events. This is an urgent concern since extreme events are increasing due to global warming, and existing methods are usually limited to more frequently observed events with the usual flood generation processes. For the July 2021 event, we simulated the hourly streamflows of seven catchments located in western Germany by combining seven partly polarimetric, radar-based quantitative precipitation estimates (QPEs) with two hydrological models: a conceptual lumped model (GR4H) and a physically based, 3D distributed model (ParFlowCLM). GR4H parameters were calibrated with an emphasis on high flows using historical discharge observations, whereas ParFlowCLM parameters were estimated based on landscape and soil properties. The key results are as follows. (1) With no correction of the vertical profiles of radar variables, radar-based QPE products underestimated the total precipitation depth relative to rain gauges due to intense collision–coalescence processes near the surface, i.e., below the height levels monitored by the radars. (2) Correcting the vertical profiles of radar variables led to substantial improvements. (3) The probability of exceeding the highest measured peak flow before July 2021 was highly impacted by the QPE product, and this impact depended on the catchment for both models. (4) The estimation of model parameters had a larger impact than the choice of QPE product, but simulated peak flows of ParFlowCLM agreed with those of GR4H for five of the seven catchments. This study highlights the need for the correction of vertical profiles of reflectivity and other polarimetric variables near the surface to improve radar-based QPEs for extreme flooding events. It also underlines the large uncertainty in peak flow estimates due to model parameter estimation.</p

Direct observation of domains in model stratum corneum lipid mixtures by Raman microspectroscopy.

Several studies on intact and model stratum corneum (SC), the top layer of the epidermis, have suggested the presence of crystalline domains. In the present work, we used micro-Raman mapping to detect lipid domains in model lipid mixtures formed by an equimolar mixture of ceramides, cholesterol, and palmitic acid, the three main lipid species of SC. We were able to determine the spatial distribution of the three compounds individually based on the systematic analysis of band areas. As a control, we studied freeze-dried lipid mixtures, and the Raman microspectroscopy reported faithfully the homogeneous distribution of the three compounds. Spectral mapping was then performed on hydrated equimolar mixtures carefully annealed. In this case, clear phase separations were observed. Domains enriched in cholesterol, ceramides, or palmitic acid with a size of a few tens of square microns were detected. These findings constitute the first direct evidence of the formation of heterogeneous domains in the SC lipid models in a bulk phase. Raman microspectroscopy is an innovative approach to characterize the conditions leading to the formation of domains and provides new insights into the understanding of the skin barrier

Hordenine in the marine alga, Gelidium crinale (Hare ex Turner) Gaillon

The alkaloid hordenine was firstly isolated from marine algae Phyllophora nervosa in 1969. In this work hordenine occurrence in Gelidium crinale collected from Şile is reported. The content of hordenine was 9.54 µg/g. This amount is lower than in the other hordenine containing algae. It is the first record of hordenine in Gelidium crinale

ß-Phenylethylamine content in marine algae around Turkish coasts

ß-Phenylethylamine content was investigated in two green, five brown, and ten red marine algae by gas chromatography/mass spectrometry. ß-Phenylethylamine was found in six red algae but was not detected in the brown and green algae studied. The highest amount of ß-phenylethylamine was determined in Gelidium crinale (30.42 µg g-1). This is the first report of ß-phenylethylamine in the algae tested and also the first to quantify ß-phenylethylamine in marine algae. © 2009 by Walter de Gruyter

Small angle neutron scattering on an absolute intensity scale and the internal surface of diatom frustules from three species of differing morphologies

The internal nanostructure of the diatoms Cyclotella meneghiniana, Seminavis robusta and Achnanthes subsessilis was investigated using small angle neutron scattering (SANS) to examine thin biosilica samples, consisting of isotropic (powder) from their isolated cell walls. The interpretation of SANS data was assisted by several other measurements. The N-2 adsorption, interpreted within the Branuer-Emmet-Teller isotherm, yielded the specific surface area of the material. Fourier transform infrared (FTIR) and Raman spectroscopy indicates that the isolated material is amorphous silica with small amounts of organic cell wall materials acting as a filling material between the silica particles. A two-phase (air and amorphous silica) model was used to interpret small angle neutron scattering data. After correction for instrumental resolution, the measurements on two SANS instruments covered an extended range of scattering vectors 0.0011 nm(-1) < q < 5.6 nm(-1), giving an almost continuous SANS curve over a range of scattering vectors, q, on an absolute scale of intensity for each sample. Each of the samples gave a characteristic scattering curve where log (intensity) versus log (q) has a -4 dependence, with other features superimposed. In the high-q regime, departure from this behaviour was observed at a length-scales equivalent to the proposed unitary silica particle. The limiting Porod scattering law was used to determine the specific area per unit of volume of each sample illuminated by the neutron beam. The Porod behaviour, and divergence from this behaviour, is discussed in terms of various structural features and the proposed mechanisms for the bio-assembly of unitary silica particles in frustules. © 2013, Springer