Characterization of snowfall using ground-based passive and active remote sensors.

Snowfall is a key quantity in the global hydrological cycle and has an impact on the global energy budget as well. In sub-polar and polar latitudes, snowfall is the predominant type of precipitation and rainfall is often initiated via the ice phase. Currently, the spatial distribution of snowfall is poorly captured by numerical weather prediction and climate models. In order to evaluate the models and to improve our understanding of snowfall microphysics, global observations of snowfall are needed. This can only be obtained by space-borne active and passive remote sensors. In order to be able to penetrate even thick snow clouds, sensors operating in the microwave frequency region are favoured. The challenge for snowfall retrieval development lies first in the complexity of snowfall microphysics and its interactions with liquid cloud water. Secondly, comprehensive knowledge is needed about the interaction of electromagnetic radiation with snowfall in order to finally relate the radiative signatures to physical quantities. A general advantage of ground-based observations is that simultaneous measurements of in-situ and remote sensing instruments can be obtained. Such a six-month dataset was collected within this thesis at an alpine site. The instrumentation included passive microwave radiometers that covered the frequency range from 22 up to \unit[150]{GHz} as well as two radar systems operating at 24.1 and 35.5 GHz. These data were complemented by optical disdrometer, ceilometer and various standard meteorological measurements. State-of-the-art single scattering databases for pristine ice crystals and complex snow aggregates were used within this thesis to investigate the sensitivity of ground--based passive and active remote sensors to various snowfall parameters such as vertical snow and liquid water distribution, snow particle habit, snow size distribution and ground surface properties. The comparison of simulations with measurements within a distinct case study revealed that snow particle scattering can be measured with ground--based passive microwave sensors at frequencies higher than 90 GHz. Sensitivity experiments further revealed that ground-based sensors have clear advantages over nadir measuring instruments due to a stronger snow scattering signal and lower sensitivity to variable ground surface emissivity. However, passive sensors were also found to be highly sensitive to liquid cloud water that was frequently observed during the entire campaign. The simulations indicate that the uncertainties of sizes distribution and snow particle habit are not distinguishable with a passive-only approach. In addition to passive microwave observations, data from a low-end radar system that is commonly used for rainfall were investigated for its capabilities to observe snowfall. For this, a snowfall specific data processing algorithm was developed and the re-processed data were compared to collocated measurements of a high-end cloud radar. If the focus can be narrowed down to medium and strong snowfall within the lowest 2-3 km height, the reflectivity and fall velocity measurements of the low-end system agree well with the cloud radar. The cloud radar dataset was used to estimate the uncertainty of retrieved snowfall rate and snow accumulation of the low-end system. Besides the intrinsic uncertainties of single-frequency radar retrievals the estimates of total snow accumulation by the low-end system lay within 7% compared to the cloud radar estimates. In a more general approach, the potential of multi-frequency radar systems for derivation of snow size distribution parameters and particle habit were investigated within a theoretical simulation study. Various single-scattering databases were combined to test the validity of dual-frequency approaches when applied to non-spheroid particle habits. It was found that the dual-frequency technique is dependent on particle habit. It could be shown that a rough distinction of snow particle habits can be achieved by a combination of three frequencies. The method was additionally tested with respect to signal attenuation and maximum particle size. The results obtained by observations and simulations within this thesis strongly suggest the further development of simultaneous ground-based in-situ and remote sensing observations of snowfall. Extending the sensitivity studies of this study will help to define the most suitable set of sensors for future studies. A combination of these measurements with a further development of single-scattering databases will potentially help to improve our understanding of snowfall microphysics

Radiant Heat Effects on Ceramic Artifacts from the American Southwest: From Experimental Results to Site Treatment Guidelines

Archaeological assemblages in the American Southwest are currently subjected to periodic wildfires and prescribed burns, and have been exposed to fires in the past. Ceramics are a key constituent of these assemblages, leading to questions regarding the effects of post-depositional heat exposure on pottery. Alterations of ceramic surface appearance and other attributes have been observed following wildfires, and such changes are significant because intact ceramics provide important temporal context and social information. Over the past 150 years, southwestern wildfires have shifted away from the historical high-frequency, low-severity regime; thus, cultural resources can be exposed to fires that are potentially more damaging than have occurred in the past. The range of fire environments and the duration and intensity of heating that result in damages to ceramic artifacts have not been previously systematically assessed. Results from laboratory tests conducted as part of the Joint Fire Science Program-funded ArcBurn project demonstrate that radiant heat fire environments, sustained dose, and ceramic category are important determinates for predicting the patterns of alteration. Results can be used to identify fire environments that cause loss of cultural information from artifact assemblages in order to develop management treatments and procedures to guide archaeological preservation in fire-prone landscapes

Water-holding Properties of Milk Protein Products - A Review

Water-holding properties have been well recognized by food technologists among !he diversity of functional properties attributed to milk protein products. In general , water-holding is accomplished by a complexity of interactions between water and milk proteins. Besides the term water-holding, synonyms such as water retention, imbibing and hydration have been used to describe this phenomenon. This paper provides a clearer understanding of this parameter by considering some fundamentals of both the molecular structure of milk proteins and the physical in terrelationships between water and milk protein powder particles. Differences in water-holding properties of milk protein products are frequently observed and may be due to the nature of the protein and to technological influences. Methods measuring water absorption and methods that measure water retention are applied for the examination of water-holding. By following this distinction, the principles of various methods (e.g., the Baumann method, the absorption capacity test, Farinographic procedures, net tests, filtration tests, modem instrumental techniques) are reviewed

How to estimate total differential attenuation due to hydrometeors with ground-based multi-frequency radars?

Abstract. At millimeter wavelengths, attenuation by hydrometeors, such as liquid droplets or large snowflakes, is generally not negligible. When using multi-frequency ground-based radar measurements, it is common practice to use the Rayleigh targets at cloud top as a reference in order to derive attenuation-corrected reflectivities and meaningful dual-frequency ratios (DFR). By capitalizing on this idea, this study describes a new quality-controlled approach aiming at identifying regions of the cloud where particle growth is negligible. The core of the method is the identification of a Rayleigh plateau, i.e. a large enough region near cloud top where the vertical gradient of DFR remains small. By analyzing collocated Ka-W band radar and microwave radiometer (MWR) observations taken at two European sites under various meteorological conditions, it is shown how the resulting estimates of differential path-integrated attenuation (DeltaPIA) can be used to characterize hydrometeor properties. When the DeltaPIA is predominantly produced by cloud liquid droplets, this technique alone can provide accurate estimates of the liquid water path. When combined with MWR observations, this methodology paves the way towards profiling the cloud liquid water and/or quality flagging the MWR retrieval for rain/drizzle contamination and/or estimating the snow differential attenuation

Comparison of Selective Media for the Enumeration of Probiotic Enterococci from Animal Feed

The project »Methods for the Official Control of Probiotics Used as Feed Additives« has been undertaken to develop and validate methods for the selective enumeration and strain identification of six probiotic microorganism genera (enterococci, lactobacilli, bifidobacteria, pediococci, bacilli and yeast). A diversity of media has been used for the detection, isolation and enumeration of enterococci. Aiming at the selective enumeration of enterococci (mainly Enterococcus faecium) present in probiotic animal feeds, either as a single component or in combination with other microorganisms, an extensive screening of published methods for culturing and enumerating enterococci was carried out. A collection of enterococcal strains used as probiotics in animal feeds and of isolates as well as reference strains from culture collections was established. Moreover, selected strains of lactobacilli, pediococci and streptococci were included for reference purposes. Based on a multitude of publications, twelve commercially available media were selected for testing and then compared with regard to their usefulness and selectivity. Bile esculin azide (BEA) agar showed good selectivity and pronounced growth of most enterococcal strains. Good reproducibility and electivity (esculin hydrolysis) as well as no influence of the feed matrix on the colony counts and a simple preparation procedure formed the basis for the proposed enumeration protocol. This work formed the basis for the enumeration protocol that was adapted to ISO format and validated in a collaborative study involving twenty laboratories from twelve European countries

Evaluation of ARM Tethered Balloon System instrumentation for supercooled liquid water and distributed temperature sensing in mixed-phase Arctic clouds

A tethered balloon system (TBS) has been developed and is being operated by Sandia National Laboratories (SNL) on behalf of the U.S. Department of Energy’s (DOE) Atmospheric Radiation Measurement (ARM) User Facility in order to collect in situ atmospheric measurements within mixed-phase Arctic clouds. Periodic tethered balloon flights have been conducted since 2015 within restricted airspace at ARM’s Advanced Mobile Facility 3 (AMF3) in Oliktok Point, Alaska, as part of the AALCO (Aerial Assessment of Liquid in Clouds at Oliktok), ERASMUS (Evaluation of Routine Atmospheric Sounding Measurements using Unmanned Systems), and POPEYE (Profiling at Oliktok Point to Enhance YOPP Experiments) field campaigns. The tethered balloon system uses helium-filled 34 m3 helikites and 79 and 104 m3 aerostats to suspend instrumentation that is used to measure aerosol particle size distributions, temperature, horizontal wind, pressure, relative humidity, turbulence, and cloud particle properties and to calibrate ground-based remote sensing instruments. Supercooled liquid water content (SLWC) sondes using the vibrating wire principle, developed by Anasphere Inc., were operated at Oliktok Point at multiple altitudes on the TBS within mixed-phase clouds for over 200 hours Sonde-collected SLWC data were compared with liquid water content derived from a microwave radiometer, Ka-band ARM Zenith radar, and ceilometer at the AMF3, as well as liquid water content derived from AMF3 radiosonde flights. The in situ data collected by the Anasphere sensors were also compared with data collected simultaneously by an alternative SLWC sensor developed at the University of Reading, UK; both vibrating wire instruments were typically observed to shed their ice quickly upon exiting the cloud or reaching maximum ice loading. Tethered balloon fiber optic distributed temperature sensing measurements were also compared with AMF3 radiosonde temperature measurements. Combined, the results indicate that TBS distributed temperature sensing and supercooled liquid water measurements are in reasonably good agreement with remote-sensing and radiosonde-based measurements of both properties. From these measurements and sensor evaluations, tethered balloon flights are shown to offer an effective method of collecting data to inform and constrain numerical models, calibrate and validate remote sensing instruments, and characterize the flight environment of unmanned aircraft, circumventing the difficulties of in-cloud unmanned aircraft flights such as limited flight time and in-flight icing

Raw milk and allergy prevention – a possible feature for organic milk?

This review aims to give some update on the role of raw milk and/or its constituents in allergy prevention, also considering possible advantages of organic milk in such a context. In addition, challenges and strategies will be discussed to control and maintain safety of a raw milk-based formula product