Definition of "banner clouds" based on time lapse movies

International audienceBanner clouds appear on the leeward side of a mountain and resemble a banner or a flag. This article provides a comprehensive definition of "banner clouds". It is based primarily on an extensive collection of time lapse movies, but previous attempts at an explanation of this phenomenon are also taken into account. The following ingredients are considered essential: the cloud must be attached to the mountain but not appear on the windward side; the cloud must originate from condensation of water vapour contained in the air (rather than consist of blowing snow); the cloud must be persistent; and the cloud must not be of convective nature. The definition is illustrated and discussed with the help of still images and time lapse movies taken at Mount Zugspitze in the Bavarian Alps

Defintion of "banner clouds" based on time lapse movies

International audienceBanner clouds appear on the leeward side of a mountain and resemble a banner or a flag. This article provides a comprehensive definition of "banner clouds". It is based primarily on an extensive collection of time lapse movies, but previous attempts at an explanation of this phenomenon are also taken into account. The following ingredients are considered essential: the cloud must be attached to the mountain but not appear on the windward side; the cloud must originate from condensation of water vapour contained in the air (rather than consist of blowing snow); the cloud must be persistent; and the cloud must not be of convective nature. The definition is illustrated and discussed with the help of still images and time lapse movies taken at Mount Zugspitze in the Bavarian Alps

An easterly tip jet off Cape Farewell, Greenland. I: Aircraft observations

An easterly tip jet event off Cape Farewell, Greenland, is described and analysed in considerable detail. In Part I of this study (this paper) comprehensive aircraft-based observations are described, while in Part II of this study numerical simulations and a dynamical analysis are presented. The easterly tip jet of 21 February 2007 took place during the Greenland Flow Distortion experiment. It resulted through the interaction of a barotropic synoptic-scale low pressure system in the central North Atlantic and the high topography of southern Greenland. In situ observations reveal a jet core at the coast with peak winds of almost 50 m s-1, about 600–800 m above the sea surface, and of 30 m s-1 at 10 m. The depth of the jet increased with wind speed from ~1500 m to ~2500 m as the peak winds increased from 30 to 50 m s-1. The jet accelerated and curved anticyclonically as it reached Cape Farewell and the end of the barrier. The easterly tip jet was associated with a tongue of cold and dry air along the coast of southeast Greenland, general cloud cover to the east, and cloud streets to the south of Cape Farewell. Precipitation was observed during the low-level components of the flight. The very high wind speeds generated a highly turbulent atmospheric boundary layer and resulted in some of the highest surface wind stresses ever observed over the ocean

Henri Temianka Correspondence; (lark quartet)

This collection contains material pertaining to the life, career, and activities of Henri Temianka, violin virtuoso, conductor, music teacher, and author. Materials include correspondence, concert programs and flyers, music scores, photographs, and books.https://digitalcommons.chapman.edu/temianka_correspondence/3866/thumbnail.jp

An improved algorithm for polar cloud-base detection by ceilometer over the ice sheets

Optically thin ice and mixed-phase clouds play an important role in polar regions due to their effect on cloud radiative impact and precipitation. Cloud-base heights can be detected by ceilometers, low-power backscatter lidars that run continuously and therefore have the potential to provide basic cloud statistics including cloud frequency, base height and vertical structure. The standard cloud-base detection algorithms of ceilometers are designed to detect optically thick liquid-containing clouds, while the detection of thin ice clouds requires an alternative approach. This paper presents the polar threshold (PT) algorithm that was developed to be sensitive to optically thin hydrometeor layers (minimum optical depth τ ≥ 0.01). The PT algorithm detects the first hydrometeor layer in a vertical attenuated backscatter profile exceeding a predefined threshold in combination with noise reduction and averaging procedures. The optimal backscatter threshold of 3 × 10^−4 km⁻¹ sr⁻¹ for cloud-base detection near the surface was derived based on a sensitivity analysis using data from Princess Elisabeth, Antarctica and Summit, Greenland. At higher altitudes where the average noise level is higher than the backscatter threshold, the PT algorithm becomes signal-to-noise ratio driven. The algorithm defines cloudy conditions as any atmospheric profile containing a hydrometeor layer at least 90 m thick. A comparison with relative humidity measurements from radiosondes at Summit illustrates the algorithm's ability to significantly discriminate between clear-sky and cloudy conditions. Analysis of the cloud statistics derived from the PT algorithm indicates a year-round monthly mean cloud cover fraction of 72% (±10%) at Summit without a seasonal cycle. The occurrence of optically thick layers, indicating the presence of supercooled liquid water droplets, shows a seasonal cycle at Summit with a monthly mean summer peak of 40 % (±4%). The monthly mean cloud occurrence frequency in summer at Princess Elisabeth is 46% (±5%), which reduces to 12% (±2.5%) for supercooled liquid cloud layers. Our analyses furthermore illustrate the importance of optically thin hydrometeor layers located near the surface for both sites, with 87% of all detections below 500 m for Summit and 80% below 2 km for Princess Elisabeth. These results have implications for using satellite-based remotely sensed cloud observations, like CloudSat that may be insensitive for hydrometeors near the surface. The decrease of sensitivity with height, which is an inherent limitation of the ceilometer, does not have a significant impact on our results. This study highlights the potential of the PT algorithm to extract information in polar regions from various hydrometeor layers using measurements by the robust and relatively low-cost ceilometer instrument

JOYCE: Jülich Observatory for cloud evolution

The Jülich Observatory for Cloud Evolution (JOYCE), located at Forschungszentrum Jülich in the most western part of Germany, is a recently established platform for cloud research. The main objective of JOYCE is to provide observations, which improve our understanding of the cloudy boundary layer in a midlatitude environment. Continuous and temporally highly resolved measurements that are specifically suited to characterize the diurnal cycle of water vapor, stability, and turbulence in the lower troposphere are performed with a special focus on atmosphere–surface interaction. In addition, instruments are set up to measure the micro- and macrophysical properties of clouds in detail and how they interact with different boundary layer processes and the large-scale synoptic situation. For this, JOYCE is equipped with an array of state-of-the-art active and passive remote sensing and in situ instruments, which are briefly described in this scientific overview. As an example, a 24-h time series of the evolution of a typical cumulus cloud-topped boundary layer is analyzed with respect to stability, turbulence, and cloud properties. Additionally, we present longer-term statistics, which can be used to elucidate the diurnal cycle of water vapor, drizzle formation through autoconversion, and warm versus cold rain precipitation formation. Both case studies and long-term observations are important for improving the representation of clouds in climate and numerical weather prediction models

A speech-based empathy training system - initial design insights

Empathy is an essential component of human communication since it increases our understanding and perception of others. However, studies show that students\u27 empathy skills have declined rapidly in the last decades. Against this background, practitioner reports predict that the importance of empathy will increase as a skill for successful agile teamwork in the future. Therefore, researchers have designed information systems to train empathy abilities of learners in different domains. Nevertheless, research on automated speech-based training is rather scarce. Hence, we aim to investigate how to design a speech-based empathy training system that helps students react emotionally adequately in communication. This research in progress paper presents five initial requirements that guide future research and development of a speech-based empathy training system intended to support students\u27 self-regulated learning. With this, we hope to provide guidance for the design and embedding of speech-based empathy training systems at scale

Erweiterung der `Localized Near Field' Theorie zur Bestimmung von Quellstärken bei beliebiger thermischer Schichtung in einem Waldbestand

The energy and mass budget of the atmosphere is mainly determined by the exchange at the earths surface. Here plant canopies play a major role. The 'Localized Near Field Theorie' (LNF) of Raupach (1989) describes the relation between concentration profiles and source/sink profiles inside the plant canopy. This work describes a general method based on the LNF to calculate source distributions from measured concentration profiles inside a plant canopy. The LNF is used for the first time to examine the effects of the so called roughness sublayer. To apply the LNF during arbitrary thermal stratification it is necessary to find parametrisations for the input parameters standard deviation of vertical velocity and Lagrangian integral time scale. These are derived from values measured inside a pine forest. Using these parametrisations the distribution of heat sources inside the forest canopy is calculated from measured temperature profiles.Energie- und Stoffumsätze an der Erdoberfläche bestimmen den Energie- und Stoffhaushalt der Atmosphäre. Dabei spielen Pflanzenbestände eine wichtige Rolle. Die 'Localized Near Field Theorie' (LNF) nach Raupach (1989) beschreibt wie Konzentrationsprofile im Pflanzenbestand und die Verteilung der Quellen dort in Beziehung zueinander stehen. In der vorliegenden Arbeit wird ein allgemeines Verfahren auf Basis der LNF zur Berechnung von Quellprofilen aus gemessenen Konzentrationsprofilen vorgestellt. Erstmals werden die Effekte in der sogenannten Rauhigkeitsschicht Mithilfe der LNF untersucht. Um die LNF auf beliebige thermische Schichtung anwenden zu können müssen Parametrisierungen für die Eingangsparameter Standardabweichung der Vertikalgeschwindigkeit und die integrale Lagrangesche Zeitskala gefunden werden. Dies geschieht anhand von in einem Waldbestand gemessenen Werten. Mit dieser Parametrisierung läßt sich schließlich die Verteilung der Wärmequellen im Wald aus gemessenen Temperaturprofilen bestimmen

Erweiterung der `Localized Near Field' Theorie zur Bestimmung von Quellstärken bei beliebiger thermischer Schichtung in einem Waldbestand

The energy and mass budget of the atmosphere is mainly determined by the exchange at the earths surface. Here plant canopies play a major role. The 'Localized Near Field Theorie' (LNF) of Raupach (1989) describes the relation between concentration profiles and source/sink profiles inside the plant canopy. This work describes a general method based on the LNF to calculate source distributions from measured concentration profiles inside a plant canopy. The LNF is used for the first time to examine the effects of the so called roughness sublayer. To apply the LNF during arbitrary thermal stratification it is necessary to find parametrisations for the input parameters standard deviation of vertical velocity and Lagrangian integral time scale. These are derived from values measured inside a pine forest. Using these parametrisations the distribution of heat sources inside the forest canopy is calculated from measured temperature profiles.Energie- und Stoffumsätze an der Erdoberfläche bestimmen den Energie- und Stoffhaushalt der Atmosphäre. Dabei spielen Pflanzenbestände eine wichtige Rolle. Die 'Localized Near Field Theorie' (LNF) nach Raupach (1989) beschreibt wie Konzentrationsprofile im Pflanzenbestand und die Verteilung der Quellen dort in Beziehung zueinander stehen. In der vorliegenden Arbeit wird ein allgemeines Verfahren auf Basis der LNF zur Berechnung von Quellprofilen aus gemessenen Konzentrationsprofilen vorgestellt. Erstmals werden die Effekte in der sogenannten Rauhigkeitsschicht Mithilfe der LNF untersucht. Um die LNF auf beliebige thermische Schichtung anwenden zu können müssen Parametrisierungen für die Eingangsparameter Standardabweichung der Vertikalgeschwindigkeit und die integrale Lagrangesche Zeitskala gefunden werden. Dies geschieht anhand von in einem Waldbestand gemessenen Werten. Mit dieser Parametrisierung läßt sich schließlich die Verteilung der Wärmequellen im Wald aus gemessenen Temperaturprofilen bestimmen