[show abstract][hide abstract] ABSTRACT: In this paper, recent changes to the Meteosat thunderstorm TRacking And
Monitoring algorithm (Cb-TRAM) are presented as well as a validation of
Cb-TRAM against data from the European ground-based LIghtning NETwork
(LINET) of Nowcast GmbH and the South African Weather Service Lightning
Detection Network (SAWS LDN). Validation is conducted along the
well-known skill measures probability of detection (POD) and false alarm
ratio (FAR) on the basis of Meteosat/SEVIRI pixels as well as on the
basis of thunderstorm objects. The values obtained demonstrate specific
limitations of Cb-TRAM, as well as limitations of satellite methods in
general which are based on thermal emission and solar reflectivity
information from thunderstorm cloud tops. Although the
climatic conditions and the occurrence of thunderstorms are quite
different for Europe and South Africa, quality score values are similar.
Our conclusion is that Cb-TRAM provides robust results of well-defined
quality for very different climatic regimes. The POD for a thunderstorm
with intense lightning is about 80% during the day. The FAR for a
Cb-TRAM detection which is not even close to intense lightning is about
50%. If only proximity to any lightning activity is required, FAR is
much lower at about 15%. Pixel-based analysis shows that detected
thunderstorm object size is not indiscriminately large, but well within
physical limitations of the satellite method. Night-time POD and FAR are
somewhat worse as the detection scheme does not use the high-resolution
visible information during night-time hours. Nowcasting scores show
useful values up to approximately 30 min in advance.
[show abstract][hide abstract] ABSTRACT: Within the project Distributed Research Infrastructure for
Hydro-Meteorology (DRIHM) DLR is involved with its nowcasting tools
Cb-TRAM and Rad-TRAM. Cb-TRAM (thunderstorm Tracking And Monitoring) is
a fully automated tracking and nowcasting algorithm. Intense convective
cells are detected, tracked and discriminated with respect to onset,
rapid development, and mature phase. In addition, short range forecasts
are provided. The detection is based on Meteosat SEVIRI data by
combining four selected channels. Areas of convection initiation, of
rapid vertical development, and mature thunderstorm cells are
identified. The tracking is based on geographical overlap between
current detections and first guess patterns of cells detected in
preceding time steps. Based on a so-called pyramid matcher also nowcasts
of motion and development of detected areas are provided. In contrast
to Cb-TRAM, the tool Rad-TRAM (Radar Tracking And Monitoring) operates
with radar data (regional or composite) with the aim to detect areas of
heavy precipitation. Both trackers can be run both on observed and
model generated (synthetic) data. Examples of tracking and nowcasting of
severe convection are presented, including the Genoa flood of 4 November
[show abstract][hide abstract] ABSTRACT: In this manuscript, recent changes to the DLR METEOSAT thunderstorm
TRacking And Monitoring algorithm (Cb-TRAM) are presented as well as a
validation of Cb-TRAM against the European ground-based LIghtning
NETwork data (LINET) of Nowcast GmbH and Lightning Detection Network
(LDN) data of the South African Weather Service (SAWS). The validation
is conducted along the well known skill scores probability of detection
(POD) and false alarm ratio (FAR) on the basis of METEOSAT/SEVIRI pixels
as well as on the basis of thunderstorm objects. The values obtained
demonstrate the limits of Cb-TRAM in specific as well as the limits of
satellite methods in general which are based on thermal emission and
solar reflectivity information from thunderstorm tops.
Although the climatic conditions and the occurence of thunderstorms is
quite different for Europe and South Africa, the quality score values
are similar. Our conclusion is that Cb-TRAM provides robust results of
well-defined quality for very different climatic regimes. The POD for a
thunderstorm with intense lightning is about 80% during the day. The FAR
for a Cb-TRAM detected thunderstorm which is not at least close to
intense lightning activity is about 50%; if the proximity to any
lightning activity is evaluated the FAR is even much lower at about 15%.
Pixel-based analysis shows that the detected thunderstorm object size is
not indiscriminately large, but well within the physical limitations of
the method. Nighttime POD and FAR are somewhat worse as the detection
scheme can not use high resolution visible information. Nowcasting
scores show useful values up to approximatelly 30 min.
[show abstract][hide abstract] ABSTRACT: Near-real-time in-flight weather services for business and regional aviation are nowadays quite well developed in USA, but still very limited in Europe due to the lack of equivalent infrastructure and service offer. The operators of the business and regional aviation in Europe would strongly benefit from in-flight weather forecasting and trajectory tracking in order to fly safely and to optimise the trajectory. On the other hand, weather agencies would greatly benefit from weather observations provided by regional and business aviation (e.g. temperature and wind speed data collected by the aircraft sensors, nowadays delivered only by commercial airlines in the framework of AMDAR) as they would drastically increase geographical coverage and number of measurement thanks to different routes w.r.t. commercial airlines.
Integraded Communications Navigation and Surveillance; 01/2013
[show abstract][hide abstract] ABSTRACT: Thunderstorms are top-ranked by pilots as weather situations compromising the flight safety. The information for pilots about adverse weather like thunderstorms today is, if at all, based on significant weather charts. Such services, however, do not give the required information for a particular flight in a particular circumstance because thunderstorms are relatively short-living phenomena. Information is required in the time-scale of up to about one hour with frequent updates clearly outlining the dangerous areas which should be avoided. Tools and products are descried which deliver that information tailored along the aircraft’s trajectory. The information is produced on ground by weather expert systems and delivered to and stored in a ground-based weather processor which serves as a data base and interface between the expert system and the aircraft. Concepts and first tests are described where the information on thunderstorms is up-linked from the data base to the aircraft.
[show abstract][hide abstract] ABSTRACT: The meteorological network of observation and prediction continuously delivers an enormous amount of various atmospheric parameters. In particular in the area of an aerodrome the observation density is typically higher than on average. In the project we spawned the idea to smartly concatenate the variety of available data which are relevant for aviation and develop new products which use the information contained in the data but describe the phenomenon of interest in a simple and unambiguous way for direct use for the aviation stakeholders. We developed this idea in a concept and related system named WxFUSION, meaning “weather forecast user-oriented system including object nowcasting”.
DLR Deutsches Zentrum fur Luft- und Raumfahrt e.V. - Forschungsberichte 02/2012;
[show abstract][hide abstract] ABSTRACT: The successful demonstration and assessment of the DLR thunderstorm nowcasting algorithms at Munich Airport during two campaigns in the summers of 2010 and 2011 are described. The algorithms Cb-TRAM and Rad-TRAM, that detect, monitor, and forecast up to one hour (nowcast) thunderstorm cells from satellite and radar data, run in real time and provided new thunderstorm products for users at the airport. The products were presented on displays the users were already familiar with as well as on webpages designed by DLR. On the webpages, also additional information like measurements with DLR’s polarimetric radar and model forecasts was shown. Moreover, thunderstorm warnings were is-sued and sent via email to the users whenever a thunderstorm was detected in the terminal manoeu-vring area of the airport of Munich. The nowcasting skills of Rad-TRAM and Cb-TRAM are encouraging, especially for lead times up to 30 minutes, and the user feedback on the DLR thunderstorm products was very positive. The Rad-TRAM and Cb-TRAM products provide a good overview on the situation and its future development, and the thunderstorm warnings were very helpful for the collaborative decision making at the airport. However, some suggestions for improvements were made like the demand for nowcasts beyond one hour. This will be considered within the integrated weather forecast system, WxFUSION, which has been further developed during the campaigns.
[show abstract][hide abstract] ABSTRACT: Weather has a significant impact on the safety and efficiency of air
traffic during all phases of flight. Especially information on adverse
weather must be tailored to the user's needs, easy to understand,
self-explaining and clear in its message. DLR-IPA has developed a
concept and tools to detect, track and predict hazardous weather
elements and provide this information in simple unambiguous form to
controllers and pilots. It has been demonstrated that these products
make a significant contribution to raising the safety and efficiency of
the air transport system.
[show abstract][hide abstract] ABSTRACT: This article is about present weather and its immediate development, on
the challenge of how to observe it, and how to forecast it in the short
term. It touches on the problems meteorologists have in delivering
reliable estimates of, e.g., which path a thunderstorm will take during
its track, whether it will bring hail or just rain, or when there will
be freezing conditions at an airport with subsequent problems for air
traffic on ground, arrival and departure. Some illustrative examples are
given, showing how the problems are tackled and how integrated
forecasting systems, in particular, can be successful in meeting the
[show abstract][hide abstract] ABSTRACT: Airborne lidar and in-situ measurements of aerosols and trace gases were performed in volcanic ash plumes over Europe between Southern Germany and Iceland with the Falcon aircraft during the eruption period of the Eyjafjalla volcano between 19 April and 18 May 2010. Flight planning and measurement analyses were supported by a refined Meteosat ash product and trajectory model analysis. The volcanic ash plume was observed with lidar directly over the volcano and up to a distance of 2700 km downwind, and up to 120 h plume ages. Aged ash layers were between a few 100 m to 3 km deep, occurred between 1 and 7 km altitude, and were typically 100 to 300 km wide. Particles collected by impactors had diameters up to 20 m diameter, with size and age dependent composition. Ash mass concentrations were derived from optical particle spectrometers for a particle density of 2.6 g cm-3 and various values of the refractive index (RI, real part: 1.59; 3 values for the imaginary part: 0, 0.004 and 0.008). The mass concentrations, effective diameters and related optical properties were compared with ground-based lidar observations. Theoretical considerations of particle sedimentation constrain the particle diameters to those obtained for the lower RI values. The ash mass concentration results have an uncertainty of a factor of two. The maximum ash mass concentration encountered during the 17 flights with 34 ash plume penetrations was below 1 mg m-3. The Falcon flew in ash clouds up to about 0.8 mg m-3 for a few minutes and in an ash cloud with approximately 0.2 mg m-3 mean-concentration for about one hour without engine damage. The ash plumes were rather dry and correlated with considerable CO and SO2 increases and O3 decreases. To first order, ash concentration and SO2 mixing ratio in the plumes decreased by a factor of two within less than a day. In fresh plumes, the SO2 and CO concentration increases were correlated with the ash mass concentration. The ash plumes were often visible slantwise as faint dark layers, even for concentrations below 0.1 mg m-3. The large abundance of volatile Aitken mode particles suggests previous nucleation of sulfuric acid droplets. The effective diameters range between 0.2 and 3 µm with considerable surface and volume contributions from the Aitken and coarse mode aerosol, respectively. The distal ash mass flux on 2 May was of the order of 500 (240-1600) kg s-1. The volcano induced about 10 (2.5-50) Tg of distal ash mass and about 3 (0.6-23) Tg of SO2 during the whole eruption period. The results of the Falcon flights were used to support the responsible agencies in their decisions concerning air traffic in the presence of volcanic ash.
ATMOSPHERIC CHEMISTRY AND PHYSICS 02/2011; 11(2011):2245-2279. · 5.51 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this study DLR’s cloud tracker Cb-TRAM (Cumulonimbus TRAcking and Monitoring) is
adapted, applied and validated over South Africa for the first time. Cb-TRAM is a fully
automated algorithm to detect, track, and nowcast thunderstorms based on data from the
METEOSAT SEVIRI (Spinning Enhanced Visible and Infra-Red Imager) instrument. The
high resolution visible (HRV), a water vapour (WV 6.2 μm), and two infra-red (IR 10.8
μm and IR 12.0 μm) channels are combined in order to determine three different
development stages: on-set of convection, i.e. first development of growing cumulus
clouds, (2) rapid development, i.e. strong cooling at cloud top, and (3) mature stage, i.e.
thunderstorms reaching or overshooting tropopause levels. During daytime the HRV is
used to detect the most active convective updraft regions by exploring the visible texture
in the image. During nighttime or in regions where the HRV is not available the texture in
the WV 6.2 μm is used to isolate convective turbulence. The tracking is based on the
geographical overlap between detected cells and their first guess patterns derived from
preceeding time steps. Both, the first guess patterns as well as nowcasts (very short
range forecasts) up to 60 minutes are based on a pyramidal image matching algorithm
which provides fields of displacement vectors accounting for differential cloud motion.
Over South Africa, it was necessary to adapt Cb-TRAM to the HRV sector of the
Southern Hemisphere which moves with the position of the sun. In several case studies,
the Cb-TRAM detected and nowcast thunderstorm cells will be compared to radar and
lightning observations. The performance of Cb-TRAM over South Africa will be
demonstrated, and the potential of Cb-TRAM to provide early warnings of thunderstorms
and related damage in this region will be dicussed.
[show abstract][hide abstract] ABSTRACT: Today’s weather information for pilots on thunderstorm conditions on their flight path is insufficient. Weather charts provided by the World Area Forecasting Centres and taken onboard by pilots before take-off are based on forecasts of large scale weather models which are initialized only twice a day. The information of the charts is therefore outdated, at least with respect to thunderstorm occurrence, at the time of use. They can only provide a rough estimation of thunderstorm hazards for relatively large areas. In contrast, thunderstorms develop quickly within tenths of minutes up to an hour and their exact time of occurrence and location is more or less impossible to predict deterministically hours in advance.
In this paper, the value of the satellite information on thunderstorm detection over the oceans is demonstrated by applying the DLR Cb-TRAM cloud tracker (Zinner et al., 2009) to last years occurrences of aircraft accident and incident over the Atlantic. In addition, two incidents over the European area with severe turbulence and hail encounter are investigated by satellite, radar and lighting data. The aim of the study is to demonstrate the improved information pilots would gain once the thunderstorm analyses and forecasts of the satellite and ground based systems would be brought, i.e. up-linked, to the cockpit during flight.
Today, pilots have information on thunderstorm activity through onboard radar equipment which provides quite good indication on thunderstorm activity within the close range part in flight direction, about 50 miles or so, provided there is precipitation within the convective up-droughts, strong enough to give radar returns. However, the radar returns are strongly attenuated when precipitation cells are large and intense, or several cells behind one another, due to the short wave length of the radars which operate at 3 cm. In that case the pilot’s information of the situation is quite incomplete which makes it difficult for them to choose a proper path around thunderstorm cells or through a thunderstorm line. In addition there are cases where thunderstorm cells are just about to develop with weak or no returns on the radar, yet they can produce convective turbulence which can propagate to levels above the developing cells. In that case the aircraft might experience sudden turbulence without any pre-warning. Also, at high flight levels through tropical storms over the oceans, radar returns might be weak due to small droplet sizes, thereby giving a wrong indication of the severity of the storm.
In contrast to this onboard radar information, remote sensing by satellite, ground based radar and lightning can provide a more complete picture of the thunderstorm situation. Ground based systems have been developed which use this data to inspect cells from above, below and multiple viewing angles thereby providing a more complete picture of the thunderstorm situation (e.g.; Tafferner et al., 2009; Sénési et al., 2009). Thunderstorms can well be detected from satellite due to their cold cloud tops and characteristic cloud shape at already early development stage, the precipitation they produce can well be detected by radar and lightning discharges by lightning detectors.
Sénési, S., Y. Guillou, A. Tafferner, and C. Forster, 2009: Cb nowcasting in FLYSAFE: Improving flight safety regarding thunderstorm hazards. WMO Symposium on Nowcasting , 30 August - 4 September 2009 , Whistler, B.C., Canada
Tafferner, A. , C. Forster, S. Sénési, Y. Guillou, P. Tabary, P. Laroche, A. Delannoy, B. Lunnon, D. Turp, T. Hauf, and D. Markovic, 2009: Nowcasting thunderstorm hazards for flight operations: the CB WIMS approach in FLYSAFE. European Air and Space Conference (CEAS) , 26 - 29 Oct. 2009, Manchester, UK
Zinner, T., Mannstein, H., Tafferner, A. , 2008: Cb-TRAM: Tracking and monitoring severe convection from onset over rapid development to mature phase using multi-channel Meteosat-8 SEVIRI data. Meteorol. Atmos. Phys. 101, 191–210
[show abstract][hide abstract] ABSTRACT: Today’s weather information for pilots on thunderstorm conditions on their flight is insufficient. Weather charts provided by the World Area Forecasting Centres and taken onboard by pilots before take-off are based on forecasts of large scale weather models which are initialized only four times a day. These models have high predictive skill in forecasting the large scale weather situation, i.e., the distribution of high and low pressure areas together with synoptic scale fronts for the next days and precipitation for about one day in advance. Thunderstorms however, whose time and space scales typically range from tens of minutes up to an hour and from hundreds of meters to some kilometres in diameter, cannot be deterministically forecast by these models.
For the instantaneous picture in flight, pilots have information on thunderstorm activity through onboard radar equipment. The radar provides a good indication on thunderstorm activity within the close range ahead of the aircraft, about 50 miles or so, provided there is precipitation within the convective up-droughts, strong enough to give radar returns. However, when precipitation cells are large and intense, or several cells lie behind one another, the radar pulses are strongly attenuated. In such cases information about the situation is incomplete which makes it difficult for pilots to choose a proper path around thunderstorm cells or through a thunderstorm line. In addition there are cases where thunderstorm cells are just about to develop with weak or no returns on the radar, yet they can produce convective turbulence which can propagate to levels above the developing cells. In that case the aircraft might experience sudden turbulence without any forewarning.
In contrast to onboard radar, remote sensing by ground based radar, satellite and lightning detectors can provide a more complete picture of the thunderstorm situation. Ground based systems have been developed which use this data to inspect cells from above, below and multiple viewing angles thereby being able to provide a more complete picture of the thunderstorm situation. Thunderstorms can be detected from satellite observations due to their cold cloud tops and characteristic cloud properties; the precipitation they produce can be detected by radar and lightning discharges by lightning detectors. For the middle European area data retrieved by the Meteosat Second Generation satellites operated by EUMETSAT, radar data from the European radar network organized by the national weather services and lightning data from networks operated by EUCLID and LINET can be used in expert systems to deduce and nowcast hazards brought about by thunderstorms. Utilising these sources of data a thunderstorm weather information and management system - Cb WIMS - was set up within the course of the FLYSAFE project, which was part funded by the European Commission. CB-WIMS has successfully been employed and demonstrated during flight trials carried out in summer 2008 over Central Europe.
The aim of the paper is to demonstrate that the information provided by such a system could help pilots in gaining a better overview of the weather situation as compared to what can be provided by nowadays onboard systems. This in turn could help pilots in decision making, e.g. which route to take when passing through a thunderstorm line. For the study a number of aircraft accidents and incidents related to thunderstorm activity has been selected for demonstrating the usefulness of such a ground based weather information system. In each case, thunderstorm positions as detected by the ground based system are compared with actual aircraft positions and tracks where known. Finally, the possible up-link of the ground-based weather information to the cockpit is addressed by referring to ongoing and future activities in this direction.
International Air Safety and Climate Change Conference (IASCC); 09/2010