Papers by Manfred Dorninger
The Fractions Skill Score (FSS) is a neighbourhood verification method originally designed to ver... more The Fractions Skill Score (FSS) is a neighbourhood verification method originally designed to verify deterministic forecasts of binary events. Previous studies employed different approaches to computing an ensemble-based FSS for probabilistic forecast verification. We show that the formulation of the ensemble-based FSS substantially affects verification results. Comparing four different approaches, we determine how the ensemble-based FSS depends on ensemble size, neighbourhood size, and frequency of occurrence of the forecast event. Furthermore, we derive an empirical formula for the expected dependence of the FSS on ensemble size. Our results are based on high-resolution 1000-member ensemble precipitation forecasts over Germany for a high-impact weather period. The large ensemble enables us to study the influence of ensemble size on forecast skill in terms of a probabilistic skilful spatial scale. We demonstrate that only one form of ensemble-based FSS, which we refer to as probabi...
Seismological Research Letters
We obtain a large dataset of seismic data from the temporary seismic network AlpArray in Europe a... more We obtain a large dataset of seismic data from the temporary seismic network AlpArray in Europe and a large dataset of lightning data from the lightning location system Austrian Lightning Detection and Information System and focus on the investigation of thunder signals recorded with seismic stations in a frequency range of 10–49 Hz if no other frequency band is specified. We try to establish whether important information about a lightning flash can be determined independent of optical and electrical measurements through the means of seismic analysis. Seismic data provide useful information on thunder and lightning, and we observe a correlation between lightning peak current and maximum ground displacement induced by the thunder for positive cloud-to-ground flashes of lightning.
<p>Lightning strokes create powerful wavefields of seismoacoustic nature, which we refer to... more <p>Lightning strokes create powerful wavefields of seismoacoustic nature, which we refer to as thunder. Unfortunately, even though bolts of lightning received much attention in such fields as physics of plasma and meteorology, less research was conducted to investigate the thunder itself.<br><br>A radio tower on the top of the Gaisberg mountain in Salzburg is permanently instrumented with electrical sensors able to record the current of lightning strokes hitting the tower&#8217;s top. In October 2020, observations of 5 thunder signals have been made using several one-component seismic sensors. At the same time, this tower is instrumented with a meteorological station, which allows us to model precisely the propagation of seismo-acoustic thunder signals from the above-mentioned lightnings.<br><br>These observations and modeling give insight into how thunder is created during the lightning stroke, which is an important milestone for seismo-acoustic observations of atmospheric events.</p>
Meteorological Applications, 2020
Boundary-Layer Meteorology, 2017
Semi-idealized model simulations are made of the nocturnal cold-air pool development in the appro... more Semi-idealized model simulations are made of the nocturnal cold-air pool development in the approximately 1-km wide and 100-200-m deep Grünloch basin, Austria. The simulations show qualitatively good agreement with vertical temperature and wind profiles and surface measurements collected during a meteorological field expedition. A two-layer stable atmosphere forms in the basin, with a very strong inversion in the lowest part, below the approximate height of the lowest gap in the surrounding orography. The upper part of the stable layer is less strongly stratified and extends to the approximate height of the secondlowest gap. The basin atmosphere cools most strongly during the first few hours of the night, after which temperatures decrease only slowly. An outflow of air forms through the lowest gap in the surrounding orography. The outflow connects with a weak inflow of air through a gap on the opposite sidewall, forming a vertically and horizontally confined jet over the basin. Basin cooling shows strong sensitivity to surface-layer characteristics, highlighting the large impact of variations in vegetation and soil cover on cold-air pool development, as well as the importance of surface-layer parametrization in numerical simulations of cold-air-pool development. Keywords Basin meteorology • Cold-air pools • Katabatic winds • Numerical modelling 1 Introduction Cold-air pools form frequently in basins, where the cold air cannot easily drain from the basin because of the enclosing orography, so that it stagnates and continues to cool in situ.
Ideas for a pattern-oriented approach towards a VERA analysis ensemble For many applications in m... more Ideas for a pattern-oriented approach towards a VERA analysis ensemble For many applications in meteorology and especially for verification purposes it is important to have some information about the uncertainties of observation and analysis data. A high quality of these "reference data" is an absolute necessity as the uncertainties are reflected in verification measures. The VERA (Vienna Enhanced Resolution Analysis) scheme includes a sophisticated quality control tool which accounts for the correction of observational data and provides an estimation of the observation uncertainty. It is crucial for meteorologically and physically reliable analysis fields. VERA is based on a variational principle and does not need any first guess fields. It is therefore NWP model independent and can also be used as an unbiased reference for real time model verification. For downscaling purposes VERA uses an a priori knowledge on small-scale physical processes over complex terrain, the so ...
The influence of reference data on NWP-model verification results is evaluated in the framework o... more The influence of reference data on NWP-model verification results is evaluated in the framework of a multi-level verification experiment. A set of six limited area NWP-models is evaluated by three model-independent analysis methods, based on the operational GTS network and the JDC (Joint D-PHASE COPS) data set. Verification is performed on four regular grids with horizontal resolutions ranging from 4-32km. In doing so traditional verification measures are combined with scale separation techniques using a 2-dimensional wavelet-transform. Verification uncertainties are estimated by four different applications: A poor man's ensemble derived from the sample of analysis variations, a re-sampling approach, and two different ensemble analysis tools based on random perturbations. The outcomes provide new insights in the interaction of grid resolution, observation density and spatial scale dependence of verification measures. Variability of verification outcomes increases with larger gri...
Sinkholes represent an excellent natural laboratory to study formation, the maintenance, fluctuat... more Sinkholes represent an excellent natural laboratory to study formation, the maintenance, fluctuations and dissipation of temperature inversions during fair weather episodes with undisturbed radiative conditions. One of the first sinkhole meteorological observations in history were made at a place in the Northeastern Austrian limestone Alps, called Gstettner Alm or Gruenloch. It was known from that early observations, that the air temperature at the bottom of the sinkhole may decrease to values some 30 degrees (Centigrade) or more below the ambient temperature at the same level, leading to the lowest temperatures in Central Europe known so far (around –52 deg C). Such extreme events can only occur when a snow cover is existing, which minimizes the surface heat flux. Many aspects of cold pool life cycle have been investigated in the recent decades. Meteorological events affecting the evolution of temperature inversions or cold-air pools in the 1-km-diameter, high-altitude (1300 m MSL)...
A deep snow pack, remote locations, no external power supply and very low temperatures are often ... more A deep snow pack, remote locations, no external power supply and very low temperatures are often the main ingredients when it comes to the deployment of meteorological stations in mountainous terrain. The accurate position of the sensor related to the snow surface is normally not known. A new device called METLIFT overcomes the problems. WMO recommends a height between 1.2 m and 2 m above ground level for the measurement of air temperature and humidity. The height above ground level is specified to take care of the possible strong vertical temperature and humidity gradients at the lowest layers in the atmosphere. Especially in snow rich and remote locations it may be hardly possible to follow this advice. Therefore most of the meteorological stations in mountainous terrain are situated at mountain tops where strong winds will blow off the snow or in valleys where a daily inspection of the sensors is possible. In other unpopulated mountainous areas, e.g. basins, plateaus, the distanc...
The Convective and Orographically-driven Precipitation Study carried out in summer 2007 over nort... more The Convective and Orographically-driven Precipitation Study carried out in summer 2007 over northeastern France and southwestern Germany provided a fairly comprehensive description of the low-troposphere water vapour field thanks, in particular, to the deployment of two airborne differential absorption lidar systems. These lidar observations were assimilated using the 3D VAR assimilation system of the Application of Research to Operations at MEsoscale (AROME) numerical weather prediction mesoscale model. The assimilation was carried out for the period of 4 July-3 August by running a 3-hour forward intermittent assimilation cycle. First, the impact of the lidar observations was assessed by comparing the analyses with a set of more than 200 independent soundings. The lidar observations were found to have a positive impact on the analyses by reducing the dry bias in the first 500 m above ground level and by diminishing the root mean square error by roughly 15% in the first km. Then, t...
The influence of reference data on NWP-model verification results is evaluated in the framework o... more The influence of reference data on NWP-model verification results is evaluated in the framework of a multi-level verification experiment. A set of six limited area NWP-models is evaluated by three model-independent analysis methods, based on the operational GTS network and the JDC (Joint D-PHASE COPS) data set. Verification is performed on four regular grids with horizontal resolutions ranging from 4-32km. In doing so traditional verification measures are combined with scale separation techniques using a 2-dimensional wavelet-transform. Verification uncertainties are estimated by four different applications: A poor man’s ensemble derived from the sample of analysis variations, a re-sampling approach, and two different ensemble analysis tools based on random perturbations. The outcomes provide new insights in the interaction of grid resolution, observation density and spatial scale dependence of verification measures. Variability of verification outcomes increases with larger grid po...
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Papers by Manfred Dorninger