Säätutkan monipuolinen käyttö pohjoisissa oloissa

Mesoscale weather phenomena, such as the sea breeze circulation or lake effect snow bands, are typically too large to be observed at one point, yet too small to be caught in a traditional network of weather stations. Hence, the weather radar is one of the best tools for observing, analyzing and understanding their behavior and development. A weather radar network is a complex system, which has many structural and technical features to be tuned, from the location of each radar to the number of pulses averaged in the signal processing. These design parameters have no universal optimal values, but their selection depends on the nature of the weather phenomena to be monitored as well as on the applications for which the data will be used. The priorities and critical values are different for forest fire forecasting, aviation weather service or the planning of snow ploughing, to name a few radar-based applications. The main objective of the work performed within this thesis has been to combine knowledge of technical properties of the radar systems and our understanding of weather conditions in order to produce better applications able to efficiently support decision making in service duties for modern society related to weather and safety in northern conditions. When a new application is developed, it must be tested against ground truth . Two new verification approaches for radar-based hail estimates are introduced in this thesis. For mesoscale applications, finding the representative reference can be challenging since these phenomena are by definition difficult to catch with surface observations. Hence, almost any valuable information, which can be distilled from unconventional data sources such as newspapers and holiday shots is welcome. However, as important as getting data is to obtain estimates of data quality, and to judge to what extent the two disparate information sources can be compared. The presented new applications do not rely on radar data alone, but ingest information from auxiliary sources such as temperature fields. The author concludes that in the future the radar will continue to be a key source of data and information especially when used together in an effective way with other meteorological data.Säätutka ei ole pelkkä sadetutka, vaan sen mittauksista saadaan monipuolista tietoa ilmakehän tilasta. Erityisen tärkeitä nämä mittaukset ovat, kun tarkastellaan keskikokoisia sääilmiöitä tyypillisesti muutamia tunteja kestäviä, alle sadan kilometrin kokoisia ilmiöitä kuten merituulikiertoliikettä ja Suomenlahden lumikuuronauhoja. Ne ovat niin suuria, ettei niistä saa yhdestä paikasta katsoen käsitystä, ja kuitenkin niin pieniä, että mahtuvat piileksimään kahden sääaseman välissä. Tällaisten ilmiöiden havaitsemisessa tutkan noin yhden kilometrin ja viiden minuutin välein sijoittuvat mittauspisteet ovat omiaan. Tämän työn alkuosassa keskitytään siihen, miten säätutkalla kannattaa mitata tällaisessa ilmastossa, jossa räntäsade on yleisempää kuin tuhoisat tornadot. Mittausten suunnittelun pohjana on sekä tekniikan että ilmakehän ymmärtäminen, ja se vaatii aina kompromisseja. Työn muodostavista artikkeleista kahdessa ensimmäisessä käydään läpi näitä kompromisseja ja kuvataan paitsi se, mitä valintoja on tehty, myös perustelut näille valinnoille. Tarkoituksena on auttaa sellaista lukijaa, joka joutuu mittaamaan samalla laitteella erilaisessa ilmastossa tai erilaisella laitteella samassa ilmastossa. Kun mittaukset on tehty, alkaa tiedon analysoiminen. Siinä nojataan jälleen ilmakehän ymmärtämiseen ja muihin samaan aikaan tehtyihin havaintoihin. Silloin, kun tutkatiedosta pyritään löytämään ilmiöitä joita ei muilla havaintolaitteilla nähdä, on vaikea tietää, kuinka hyvin tämä analysointi onnistui. Yksi tämän väitöskirjatyön tavoitteista onkin ollut löytää menetelmiä, joilla voi verrata hyvin eriluonteisia havaintoja toisiinsa. Työn kolmessa viimeisessä artikkelissa säätutkaa käytetään raekuurojen tunnistamiseen ja lumisateen heikentämän näkyvyyden arviointiin. Muina sovellusesimerkkeinä on mainittu lyhyet sade-ennusteet ja metsäpalovaaran arviointi. Kaikki nämä ovat sovelluksia, joissa hyvin käytetty säätutka tuo ainutlaatuista lisätietoa ilmakehän keskikokoisten ilmiöiden ominaisuuksista

Improving OPERA radar data for nowcasting

Póster presentado en: 3rd European Nowcasting Conference, celebrada en la sede central de AEMET en Madrid del 24 al 26 de abril de 2019

The Threat to Weather Radars by Wireless Technology

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.United States. Federal Aviation Administration (FA8721-05-C-0002

The Integrated Carbon Observation System in Europe

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 degrees C above preindustrial levels. Increasing levels of CO2 and other greenhouse gases (GH6s), 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.Peer reviewe

Nowcasting snow for airports at heterogeneous terrain

The forecast of snow events at airports is a major challenge in airport operation during winter time. In contrast to rain, snow has to be actively removed from aircraft or operation areas. Short term forecasting - or nowcasting - of snow events is required for airport operation. Airport stakeholders need to know the start and duration of snow events, but they need also an estimate of the snow accumulation during the event. Extrapolation techniques based upon weather radar observations are used to generate a probabilistic nowcast for airports. These techniques assume a linear propagation of the precipitation fields. In case of intensifying, decaying or non-linear propagation the forecast quality is considerably reduced. In this paper we show that lake effects along the coastlines or flow within the proximity of mountains degrade the forecast quality and the lead time for reliable nowcasts is shorter than for situations which are not affected by heterogeneous terrain

OPERA the Radar Project

The Operational Program on the Exchange of Weather Radar Information (OPERA) has co-ordinated radar co-operation among national weather services in Europe for more than 20 years. It has introduced its own, manufacturer-independent data model, runs its own data center, and produces Pan-European radar composites. The applications using this data vary from data assimilation to flood warnings and the monitoring of animal migration. It has used several approaches to provide a homogeneous combination of disparate raw data and to indicate the reliability of its products. In particular, if a pixel shows no precipitation, it is important to know if that pixel is dry or if the measurement was missing