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Jürg Joss

Bio: Jürg Joss is an academic researcher. The author has contributed to research in topics: Disdrometer & Radiosonde. The author has an hindex of 3, co-authored 3 publications receiving 469 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, a prototype optical disdrometer is presented, which is easy to handle, robust, and low cost, allowing a cluster of instruments to investigate the spatial and temporal fine-scale structure of precipitation, and it provides reliable detection of the range of small drops.
Abstract: The characteristics of a prototype optical disdrometer are presented. Particles are detectable in the diameter range from 0.3 to 30 mm having velocities of up to 20 m s−1. Advantages of the new system are (i) it is easy to handle, robust, and low cost, allowing a cluster of instruments to investigate the spatial and temporal fine-scale structure of precipitation; (ii) it provides reliable detection of the range of small drops; and (iii) it allows the possibility of snow measurements. Results of rain measurements are compared with data from a Joss–Waldvogel disdrometer and a Hellmann rain gauge. Furthermore, some snow measurements are presented and compared with results of a research spectrometer. The overall agreement is good. The repeatability of particle size estimation was checked in the diameter range between 1.4 and 8.0 mm and yielded a standard deviation of less than 5%. For drop velocities the standard deviation varies between 25% (0.3-mm drops) and 10% (5-mm drops). The optical disdromete...

521 citations

Journal ArticleDOI
TL;DR: In this paper, an intercomparison between the Vaisala, VIZ and Swiss radiosondes was conducted at an upper-air station 06610, and the results showed that the temperature sensor data from the SMI and VIZ sondes both require additional radiation compensation for daylight ascents whilst the Swiss sonde's pressure sensor has particularly large errors in the 200 −100 mb region.
Abstract: This paper describes an intercomparison between the Vaisala, VIZ and Swiss (used at upper-air station 06610) radiosondes. The field experiment was supported by a series of carefully implemented laboratory tests. The results show that the temperature sensor data from the SMI and VIZ sondes both require additional radiation compensation for daylight ascents whilst the Swiss sonde's pressure sensor has particularly large errors in the 200–100 mb region. New correction parameters have been determined for the SMI and VIZ sondes and these have now been built into the systems' software.

11 citations

Journal ArticleDOI
TL;DR: In this paper, a boiling-point barometer was developed for use on meteorological radiosondes, where water is heated electrically, and its boiling temperature is measured with a thermocouple.
Abstract: A boiling-point barometer—commonly called hypsometer—has been developed for use on meteorological radiosondes. In this hypsometer, water is heated electrically, and its boiling temperature is measured with a thermocouple. Once the boiling temperature is known, pressure is determined via the water vapor saturation pressure curve. The pressure range required is 1050–10 hPa, that is, slightly more than two orders of magnitude. In order to achieve an accuracy of 0.05% in pressure (0.5 hPa at 1000 hPa), boiling temperature must be measured to about 0.01 K. This formidable requirement calls for very accurate calibration procedures that are novel in thermocouple thermometry. However, once the thermocouple is calibrated, individual hypsometers utilizing thermocouples made of the same batch of material do not require calibration. For computing pressure from boiling temperature, the Goff-Gratch reference function is suggested; if approximations cannot be avoided, they must be specially selected. When using...

7 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, an integrative approach to monitoring, modeling, and sensing the mountain environment that will improve understanding and prediction of hydrologic fluxes and processes is proposed, which is similar to the work in this paper.
Abstract: Climate change and climate variability, population growth, and land use change drive the need for new hydrologic knowledge and understanding. In the mountainous West and other similar areas worldwide, three pressing hydrologic needs stand out: first, to better understand the processes controlling the partitioning of energy and water fluxes within and out from these systems; second, to better understand feedbacks between hydrological fluxes and biogeochemical and ecological processes; and, third, to enhance our physical and empirical understanding with integrated measurement strategies and information systems. We envision an integrative approach to monitoring, modeling, and sensing the mountain environment that will improve understanding and prediction of hydrologic fluxes and processes. Here extensive monitoring of energy fluxes and hydrologic states are needed to supplement existing measurements, which are largely limited to streamflow and snow water equivalent. Ground-based observing systems must be explicitly designed for integration with remotely sensed data and for scaling up to basins and whole ranges. Copyright 2006 by the American Geophysical Union.

569 citations

Journal ArticleDOI
TL;DR: A photometric model that describes the intensities produced by individual rain streaks and a dynamic model that captures the spatio-temporal properties of rain are developed, which describe the complete visual appearance of rain.
Abstract: The visual effects of rain are complex. Rain produces sharp intensity changes in images and videos that can severely impair the performance of outdoor vision systems. In this paper, we provide a comprehensive analysis of the visual effects of rain and the various factors that affect it. Based on this analysis, we develop efficient algorithms for handling rain in computer vision as well as for photorealistic rendering of rain in computer graphics. We first develop a photometric model that describes the intensities produced by individual rain streaks and a dynamic model that captures the spatio-temporal properties of rain. Together, these models describe the complete visual appearance of rain. Using these models, we develop a simple and effective post-processing algorithm for detection and removal of rain from videos. We show that our algorithm can distinguish rain from complex motion of scene objects and other time-varying textures. We then extend our analysis by studying how various factors such as camera parameters, rain properties and scene brightness affect the appearance of rain. We show that the unique physical properties of rain--its small size, high velocity and spatial distribution--makes its visibility depend strongly on camera parameters. This dependence is used to reduce the visibility of rain during image acquisition by judiciously selecting camera parameters. Conversely, camera parameters can also be chosen to enhance the visibility of rain. This ability can be used to develop an inexpensive and portable camera-based rain gauge that provides instantaneous rain-rate measurements. Finally, we develop a rain streak appearance model that accounts for the rapid shape distortions (i.e. oscillations) that a raindrop undergoes as it falls. We show that modeling these distortions allows us to faithfully render the complex intensity patterns that are visible in the case of raindrops that are close to the camera.

434 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a review of the many aspects of precipitation measurement that are relevant to providing an accurate global assessment of this important environmental parameter, including ground data, satellite estimates and numerical models.

403 citations

Journal ArticleDOI
TL;DR: In this paper, the authors review the state of citizen science in a hydrological context and explore the potential for citizen science to complement more traditional ways of scientific data collection and knowledge generation.
Abstract: The participation of the general public in the research design, data collection and interpretation process together with scientists is often referred to as citizen science. While citizen science itself has existed since the start of scientific practice, developments in sensing technology, data processing and visualisation, and communication of ideas and results, are creating a wide range of new opportunities for public participation in scientific research. This paper reviews the state of citizen science in a hydrological context and explores the potential of citizen science to complement more traditional ways of scientific data collection and knowledge generation for hydrological sciences and water resources management. Although hydrological data collection often involves advanced technology, the advent of robust, cheap and low-maintenance sensing equipment provides unprecedented opportunities for data collection in a citizen science context. These data have a significant potential to create new hydrological knowledge, especially in relation to the characterisation of process heterogeneity, remote regions, and human impacts on the water cycle. However, the nature and quality of data collected in citizen science experiments is potentially very different from those of traditional monitoring networks. This poses challenges in terms of their processing, interpretation, and use, especially with regard to assimilation of traditional knowledge, the quantification of uncertainties, and their role in decision support. It also requires care in designing citizen science projects such that the generated data complement optimally other available knowledge. Lastly, we reflect on the challenges and opportunities in the integration of hydrologically-oriented citizen science in water resources management, the role of scientific knowledge in the decision-making process, and the potential contestation to established community institutions posed by co-generation of new knowledge.

382 citations

Journal ArticleDOI
TL;DR: In this article, the authors describe the design and operation of a two-dimensional video disdrometer (2DVD) for in situ measurements of precipitation drop size distribution in a field setting.
Abstract: This paper describes the design and operation of a two-dimensional video disdrometer (2DVD) for in situ measurements of precipitation drop size distribution. The instrument records orthogonal image projections of raindrops as they cross its sensing area, and can provide a wealth of information, including velocity and shape, of individual raindrops. The 2DVD is a sensitive optical instrument that is exposed to rain, high humidity, and possibly high temperatures. These and other issues such as calibration procedures impact its performance. Under low-wind conditions, the instrument can provide accurate and detailed information on drop size, terminal velocity, and drop shape in a field setting, and the instrument's advantages far outweigh its disadvantages.

378 citations