Elena Saltikoff

The Helsinki Testbed: A Mesoscale Measurement, Research, and Service Platform

Abstract The Finnish Meteorological Institute and Vaisala have established a mesoscale weather observational network in southern Finland. The Helsinki Testbed is an open research and quasi-operational program designed to provide new information on observing systems and strategies, mesoscale weather phenomena, urban and regional modeling, and end-user applications in a high-latitude (~60°N) coastal environment. The Helsinki Testbed and related programs feature several components: observing system design and implementation, small-scale data assimilation, nowcasting and short-range numerical weather prediction, public service, and commercial development of applications. Specifically, the observing instrumentation focuses on meteorological observations of meso-gamma-scale phenomena that are often too small to be detected adequately by traditional observing networks. In particular, more than 40 telecommunication masts (40 that are 120 m high and one that is 300 m high) are instrumented at multiple heights. Oth...

Social Media as a Source of Meteorological Observations

An increasing number of people leave their mark on the Internet by publishing personal notes (e.g., text, photos, videos) on Web-based services such as Facebook and Flickr. This creates a vast source of information that could be utilized in meteorology, for example, as a complement to traditional weather observations. Photo-sharing services offer an increasing amount of useful data, as modern mobile devices can automatically include coordinates and time stamps on photos, and users can easily tag them for content. In this study, different weather-related photos and their metadata were accessed from the photo-sharing service Flickr, and their reliability was assessed. Case studies of hail detection were then performed. The position of hail detected in the atmosphere by radar was compared with positions of Flickr photos depicting hail on the ground. As a result of this preliminary study, the authors think that further exploration of the use of Flickr photographs is warranted, and the consideration of other social media as data sources can be recommended.

The Operational Weather Radar Network in Europe

The operational weather radar network in Europe covers more than 30 countries and contains more than 200 weather radars. The radar network is heterogeneous in hardware, signal processing, transmit/receive frequency, and scanning strategy, thus making it fundamentally different than the Next Generation Weather Radar (NEXRAD) network. Another difference is that the density of the European weather radar network is roughly twice that of the NEXRAD network. Within the European National Meteorological Services (EUMETNET), a grouping of services, the Operational Program for Exchange of Weather Radar Information (OPERA) has been working since 1999 on improving the harmonization of radars and their measurements. In addition, OPERA has facilitated and stimulated the exchange of radar data between its members, among others, by the development of a radar data information model and jointly agreed data formats. Since 2011, a radar data center (“Odyssey”) has been in operation, producing network-wide radar mosaics from ...

Cold-Season Thunderstorms in Finland and Their Effect on Aviation Safety

A total of 13 commercial airplanes were struck by lightning in October (10 in 1 day) and December (3 on 3 separate days) 2011 in the main Finnish Helsinki–Vantaa airport. The number of lightning-struck airplanes is extremely large, considering the time of year and the small number of flashes by the storms. This paper indicates the characteristics of these cases regarding the synoptic situation as well as their forecasting. There were remarkable differences in the operational models; the high-resolution nonhydrostatic model was superior in predicting the convective nature of the event compared to the coarser-resolution hydrostatic model. The interview of the pilots of the struck airplanes shows that the pilots did not receive detailed information to avoid the situation; also, the lightning strike affected the pilots, even causing temporary loss of sight and hearing. Luckily, no fatalities or severe damage to the airplanes occurred. The most interesting case is 19 October 2011; during this single day, a tot...

Experience of real time spatial adjustment of the Z-R relation according to water phase of hydrometeors

Abstract According to hydrometeor water phase analysis (rain, snow, sleet) an optimal relation between the radar reflectivity factor (Z) and precipitation intensity (R in rain, S in snowfall) is applied individually at each radar pixel in real time. Gauges are used to evaluate the improvement in radar accumulation. The results show that the phase dependent Z-R/S selection does not significantly improve the accuracy of radar measurements. Reflectivity profile effects and wind deflection in gauges are dominating error factors.

THE THREAT TO WEATHER RADARS BY WIRELESS TECHNOLOGY

AbstractWireless technology, such as local area telecommunication networks and surveillance cameras, causes severe interference for weather radars because they use the same operational radio frequencies. One or two disturbances can be removed from the radar image, but the number and power of the interfering wireless devices are growing all over the world, threatening that one day the radars could become useless for weather observations. Some agencies have already changed or are considering changing frequency bands, but now even other bands are under threat.Use of equipment at radio frequencies is regulated by laws and international agreements. Technologies have been developed for peaceful coexistence. If wireless devices use these technologies to protect weather radars, their data transmission capabilities become limited, so it is tempting to violate the regulations. Hence, it is an important task for the worldwide weather community to involve themselves in the radio frequency management process and work ...

Precipitation nowcasting using radar-derived atmospheric motion vectors

Abstract The method to predict precipitation for couple of hours in the future, developed at FMI, applies modified correlation-based atmospheric motion vector (AMV) system provided by EUMETSAT. PseudoCAPPI reflectivity fields with interval of 5 minutes are used as the input to the AMV system. That provides a smooth vector field from which a trajectory field is calculated. Speed and direction inaccuracies along the trajectories gives us an “error ellipse” around each starting point of a trajectory. The reflectivities within the ellipse are then applied to calculate a set of forecast products for 0.5 4 hours from the initial time. The verification results show that some conventional quantities like POD and FAR are quite sensitive to the size of the precipitating area.

Validation of Automatic Cb Observations for METAR Messages without Ground Truth

AbstractIn aviation meteorology, METAR messages are used to disseminate the existence of cumulonimbus (Cb) clouds. METAR messages are traditionally constructed manually from human observations, but there is a growing trend toward automation of this process. At the Finnish Meteorological Institute (FMI), METAR messages incorporate an operational automatic detection of Cb based solely on weather radar data, when manual observations are not available. However, the verification of this automatic Cb detection is challenging, as good ground truth data are not often available; even human observations are not perfect as Cb clouds can be obscured by other clouds, for example. Therefore, statistical estimation of the relevant verification measures from imperfect observations using latent class analysis (LCA) was explored. In addition to radar-based products and human observations, the convective rainfall rate from EUMETSAT’s Nowcasting Satellite Application Facility and lightning products from the Finnish lightning...

Maintenance Keeps Radars Running

AbstractWeather radars provide us with colorful images of storms, their development, and their movement, but from time to time the radars fail and we are left without data. To minimize these disruptions, owners of weather radars carry out preventive maintenance.The European radar project Operational Programme for the Exchange of Weather Radar Information (OPERA) conducted a survey among technicians from 21 countries on their experiences of maintenance. Regular maintenance frequency varies widely from as frequent as weekly to as infrequent as 6 months. Results show that the primary causes of missing data are not the failure of radar components and software or lack of maintenance but rather issues with the electricity supplies or telecommunications. Where issues are with the radars themselves, they are most commonly with the transmitter or the antenna controllers. Faults can be repaired quickly, but, if certain parts are required or the site is very remote, a radar can be out of service for weeks or even mo...