Search Results

You are looking at 1 - 10 of 11 items for

  • Author or Editor: Elena Saltikoff x
  • Refine by Access: All Content x
Clear All Modify Search
Otto Hyvärinen
and
Elena Saltikoff

Abstract

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.

Full access
Otto Hyvärinen
,
Elena Saltikoff
, and
Harri Hohti

Abstract

In 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 network were used for determining the existence of Cb clouds. Results suggest that LCA gives reasonable estimates of verification measures and, based on these estimates, the Cb detection system at FMI gives results comparable to human observations.

Full access
Asko Huuskonen
,
Elena Saltikoff
, and
Iwan Holleman

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 volumetric data. An essential part of the OPERA work is the documentation of the members' best practices in radar operation and data production and the making of joint recommendations: for example, on the interferences caused by other microwave sources and the disturbances caused by wind turbines. Hence, the expertise of the most experienced members is made available to all members supporting the development of the network as a whole. Recent work has produced reports on best practices for production of radar data, on quality indicators, and on experiences with the use of polarimetric radars. All of these reports and recommendations are publicly available on the OPERA website, for use by the wider meteorological community.

Full access
Elena Saltikoff
,
Jari-Petteri Tuovinen
,
Janne Kotro
,
Timo Kuitunen
, and
Harri Hohti

Abstract

Two approaches to producing a hail climatology for Finland are compared. The first approach is based on 70 yr of hail reports from different sources (newspapers, storm spotters, and other volunteers). The second is derived primarily from radar data. It is shown that a selection of newspaper articles of hail damage covering a period of 70 yr provides a good overview of the typical monthly and diurnal distribution of hail occurrence over the country. Radar data covering five summers (2001–05) provide another data source, but with different potential sources of errors. The two distinct methods compared in this paper give roughly the same results in describing the hail climatology of Finland, which gives additional confidence in each of the methods. On the basis of both methods, most hailstones are observed in the afternoon, 1400–1600 local time. The hail “season” extends from May to early September with maximum occurrences in June, July, and August. This means that hail is most frequently observed when the convective energy available for storm growth is at its diurnal or seasonal peak. The length of the hail season is the same according to both radar and newspaper data. The main difference emerges in relation to July and August events: 37% of news about hail events is published in newspapers in late July but only 8% in early August, whereas for radar data the numbers are more evenly distributed, 33% and 18%, respectively. This can be partially explained by sociological factors—July is the main holiday month in Finland, when outdoor activities in more remote areas are more popular.

Full access
Elena Saltikoff
,
Mikko Kurri
,
Hidde Leijnse
,
Sergio Barbosa
, and
Kjetil Stiansen

Abstract

Weather 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 months. Failures of electricity or communications may also lead to lengthy periods of unavailability. As an example there is a story from Norway where wintertime thunderstorms severely damaged a radar at a very remote location.

Annual operative costs of a radar are typically on the order of 5%–10% of the radar purchase price. During the lifetime of a system (typically 10–20 years) the operator can hence pay as much for the running costs as for the hardware purchase. It is extremely important to take infrastructure, maintenance, and monitoring into account when purchasing a new radar.

Open access
Karoliina Hämäläinen
,
Elena Saltikoff
,
Otto Hyvärinen
,
Ville Vakkari
, and
Sami Niemelä

Abstract

Modern society is very dependent on electricity. In the energy sector, the amount of renewable energy is growing, especially wind energy. To keep the electricity network in balance we need to know how much, when, and where electricity is produced. To support this goal, the need for proper wind forecasts has grown. Compared to traditional deterministic forecasts, ensemble models can better provide the range of variability and uncertainty. However, probabilistic forecasts are often either under- or overdispersive and biased, thus not covering the true and full distribution of probabilities. Hence, statistical postprocessing is needed to increase the value of forecasts. However, traditional closer-to-surface wind observations do not support the verification of wind higher above the surface that is more relevant for wind energy production. Thus, the goal of this study was to test whether new types of observations like radar and lidar winds could be used for verification and statistical calibration of 100-m winds. According to our results, the calibration improved the forecast skill compared to a raw ensemble. The results are better for low and moderate winds, but for higher wind speeds more training data would be needed, either from a larger number of stations or using a longer training period.

Open access
Elena Saltikoff
,
Katja Friedrich
,
Joshua Soderholm
,
Katharina Lengfeld
,
Brian Nelson
,
Andreas Becker
,
Rainer Hollmann
,
Bernard Urban
,
Maik Heistermann
, and
Caterina Tassone

Abstract

Weather radars have been widely used to detect and quantify precipitation and nowcast severe weather for more than 50 years. Operational weather radars generate huge three-dimensional datasets that can accumulate to terabytes per day. So it is essential to review what can be done with existing vast amounts of data, and how we should manage the present datasets for the future climatologists. All weather radars provide the reflectivity factor, and this is the main parameter to be archived. Saving reflectivity as volumetric data in the original spherical coordinates allows for studies of the three-dimensional structure of precipitation, which can be applied to understand a number of processes, for example, analyzing hail or thunderstorm modes. Doppler velocity and polarimetric moments also have numerous applications for climate studies, for example, quality improvement of reflectivity and rain rate retrievals, and for interrogating microphysical and dynamical processes. However, observational data alone are not useful if they are not accompanied by sufficient metadata. Since the lifetime of a radar ranges between 10 and 20 years, instruments are typically replaced or upgraded during climatologically relevant time periods. As a result, present metadata often do not apply to past data. This paper outlines the work of the Radar Task Team set by the Atmospheric Observation Panel for Climate (AOPC) and summarizes results from a recent survey on the existence and availability of long time series. We also provide recommendations for archiving current and future data and examples of climatological studies in which radar data have already been used.

Full access
Elena Saltikoff
,
John Y. N. Cho
,
Philippe Tristant
,
Asko Huuskonen
,
Lynn Allmon
,
Russell Cook
,
Erik Becker
, and
Paul Joe

Abstract

Wireless 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 in close contact with their national radio authorities to ensure that meteorological interests be duly taken into account in any decision-making process toward the future usage of wireless devices.

Full access
Jarkko T. Koskinen
,
Jani Poutiainen
,
David M. Schultz
,
Sylvain Joffre
,
Jarmo Koistinen
,
Elena Saltikoff
,
Erik Gregow
,
Heikki Turtiainen
,
Walter F. Dabberdt
,
Juhani Damski
,
Noora Eresmaa
,
Sabine Göke
,
Otto Hyvärinen
,
Leena Järvi
,
Ari Karppinen
,
Janne Kotro
,
Timo Kuitunen
,
Jaakko Kukkonen
,
Markku Kulmala
,
Dmitri Moisseev
,
Pertti Nurmi
,
Heikki Pohjola
,
Pirkko Pylkkö
,
Timo Vesala
, and
Yrjö Viisanen

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. Other instrumentation includes one operational radio sounding (and occasional supplemental ones), ceilometers, aerosol-particle and trace-gas instrumentation on an urban flux-measurement tower, a wind profiler, and four Doppler weather radars, three of which have dual-polarimetric capability. The Helsinki Testbed supports the development and testing of new observational instruments, systems, and methods during coordinated field experiments, such as the NASA Global Precipitation Measurement (GPM). Currently, the Helsinki Testbed Web site typically receives more than 450,000 weekly visits, and more than 600 users have registered to use historical data records. This article discusses the three different phases of development and associated activities of the Helsinki Testbed from network development and observational campaigns, development of the local analysis and prediction system, and testing of applications for commercial services. Finally, the Helsinki Testbed is evaluated based on previously published criteria, indicating both successes and shortcomings of this approach.

Full access
Jouni Heiskanen
,
Christian Brümmer
,
Nina Buchmann
,
Carlo Calfapietra
,
Huilin Chen
,
Bert Gielen
,
Thanos Gkritzalis
,
Samuel Hammer
,
Susan Hartman
,
Mathias Herbst
,
Ivan A. Janssens
,
Armin Jordan
,
Eija Juurola
,
Ute Karstens
,
Ville Kasurinen
,
Bart Kruijt
,
Harry Lankreijer
,
Ingeborg Levin
,
Maj-Lena Linderson
,
Denis Loustau
,
Lutz Merbold
,
Cathrine Lund Myhre
,
Dario Papale
,
Marian Pavelka
,
Kim Pilegaard
,
Michel Ramonet
,
Corinna Rebmann
,
Janne Rinne
,
Léonard Rivier
,
Elena Saltikoff
,
Richard Sanders
,
Martin Steinbacher
,
Tobias Steinhoff
,
Andrew Watson
,
Alex T. Vermeulen
,
Timo Vesala
,
Gabriela Vítková
, and
Werner Kutsch

Abstract

Since 1750, land-use change and fossil fuel combustion has led to a 46% increase in the atmospheric carbon dioxide (CO2) concentrations, causing global warming with substantial societal consequences. The Paris Agreement aims to limit global temperature increases to well below 2°C above preindustrial levels. Increasing levels of CO2 and other greenhouse gases (GHGs), such as methane (CH4) and nitrous oxide (N2O), in the atmosphere are the primary cause of climate change. Approximately half of the carbon emissions to the atmosphere are sequestered by ocean and land sinks, leading to ocean acidification but also slowing the rate of global warming. However, there are significant uncertainties in the future global warming scenarios due to uncertainties in the size, nature, and stability of these sinks. Quantifying and monitoring the size and timing of natural sinks and the impact of climate change on ecosystems are important information to guide policy-makers’ decisions and strategies on reductions in emissions. Continuous, long-term observations are required to quantify GHG emissions, sinks, and their impacts on Earth systems. The Integrated Carbon Observation System (ICOS) was designed as the European in situ observation and information system to support science and society in their efforts to mitigate climate change. It provides standardized and open data currently from over 140 measurement stations across 12 European countries. The stations observe GHG concentrations in the atmosphere and carbon and GHG fluxes between the atmosphere, land surface, and the oceans. This article describes how ICOS fulfills its mission to harmonize these observations, ensure the related long-term financial commitments, provide easy access to well-documented and reproducible high-quality data and related protocols and tools for scientific studies, and deliver information and GHG-related products to stakeholders in society and policy.

Open access