Ilmatieteen laitos: Recent submissions

Now showing items 1-20 of 148
  • Björkqvist, Jan-Victor (2020)
    Finnish Meteorological Institute Contributions 159
    Waves are important for both the leisure and safety of the human population. Open-sea waves have been studied since the 1940’s and their central properties are known. The wave field is described by the so called wave spectrum, which is a decomposition of the wave energy with respect to the wave frequency. In practice, the wave field is still often reduced to a few parameters, most importantly the dominant frequency (so called peak frequency) and the significant wave height. These parameters, however, does not sufficiently describe an archipelago wave field, but waves in archipelagos have still received rela - tively little attention from the scientific community. This thesis focuses on waves in archipelagos, and the study was carried out by using both numerical models and instrumental observations from the Helsinki archipelago and the Archipelago Sea in the Baltic Sea. Waves in archipelagos are heavily affected by the numerous small islands; they attenuate long waves arriving from the open sea, while also defining new fetches for local waves. As a result, the wave spectrum has a wide frequency range where the energy is practically constant. The existence of this energy carrying range is in contrast to open sea measurements where the energy is concentrated around one dominant frequency. This study proposed a characteristic frequency that quantified the centre of the energy carrying range. For a traditional open sea spectrum the characteristic frequency closely resembled the dominant frequency, thus making it suitable for a wide range of wave conditions. The height of single waves in the archipelago were lower relative to the significant wave height. As a consequence, there was a large (10-15%) discrepancy between two definitions of the significant wave height; in the open sea this discrepancy is typically only 7-8%. The three numerical models of this study simulated the archipelago wave field well. The largest discrepancy with the observations was found in an area just outside the archipelago that was sheltered by a peninsula. Inside the archipelago the models disagreed slightly on the energy distribution within the energy carrying range. These small differences strongly affected the dominant frequency in a way that was not representative of the good model performance. The differences were inconsequential for the significant wave height. During certain conditions the energy of the shortest waves were underestimated when using more advanced methods to calculate the energy transfer from the wind to the waves, most probably because a too small friction velocity. A simple older method to determine the friction velocity reproduced the shorter waves well. Coarse operational wind products were sufficient to force the high-resolution coastal wave models. Providing wind data only every third hour reduced the variability in the modelled wave field in the time scales between 2 and 10 hours. An hourly wind product captured all variations well, except for the statistical sampling variability in the measurements. Spatial properties of the wave field were inferred from high-frequency wave staff measurements taken by R/V Aranda. These measurements were used to form a new wave spectrum where the waves are decomposed according to their inverse phase-speed. The new spectrum agreed well with the spatial wavenumber spectrum for the shortest waves, while the frequency spectrum did not. The good agreement between the inverse phase-speed spectrum and the wavenumber spectrum meant that the effect of the Doppler shift was small. The reason for the disparate results of the frequency domain were attributed to wave non-linearities. Using direct measurements to determining the waves as a function of their phase speed can be useful when studying the interaction between the wind and the waves, since no additional current measurements are needed to quantify the real wave speed relative to the wind. *** Havsvågor är viktiga för människor både ur ett rekreations- och säkerhetsperspektiv. Det öppna havets vågor har studerats sedan 1940-talet och deras centrala egenskaper är kända. Vågfältet beskrivs av det så kallade vågspektrumet, i vilket vågornas energi bryts med avseende på deras frekvens. I praktiken reduceras vågfältet ofta till några beskrivande parametrar, varav de viktigaste är den dominanta vågfrekvensen och den signifikanta våghöjden. Dessa parametrar beskriver inte vågorna i skärgården tillräckligt bra, men skärgårdens vågor har ändå fått tämligen lite vetenskaplig uppmärksamhet. Denna avhandling undersökte skärgårdens vågor både med numeriska modeller och observationer från Helsingfors skärgård och Skärgårdshavet. Skärgårdens vågor påverkas i betydande grad av skärgårdens otaliga små öar; de dämpar längre vågor som anländer från det öppna havet, medan de samtidigt skapar nya svepsträckor för lokala vågor. Därför har vågspektrumet ett brett frekvensband där vågenergin är praktiskt taget konstant. Existensen av ett sådant här energibärande frekvensband står i kontrast till observationer från det öppna havet där energin är starkt koncentrerad kring en dominant frekvens. I detta arbete definierades en ny karakteristisk frekvens vilken beskriver medelpunkten av det energibärande frekvensbandet för skärgårdsvågor. För de typiska vågorna i öppna havet var denna nya karakteristiska frekvens nära den traditionella dominanta frekvensen, vilket gjorde denna nya parameter lämplig för att beskriva vågfält under vitt skilda omständigheter. I skärgården var höjden på de enskilda vågorna (i förhållande till den signifikanta våghöjden) lägre än på det öppna havet. Som en följd skilde sig de två traditionella definitionerna på den signifikanta våghöjden starkt (10-15%); på öppna havet är denna skillnad oftast bara 7-8%. De tre numeriska vågmodellerna simulerade vågfältet i skärgården väl. De största felen fanns i ett område utanför skärgården som var delvis skyddat av Porkala udden. Inom skärgården betonade modellerna energidistributionen i det energibärande frekvensbandet på olika vis. För den traditionella dominanta frekvensen införde de små skillnaderna en stark avvikelse gentemot observationerna, även om denna avvikelse inte stod i proportion till de egentliga skillnaderna mellan modellerna och observationerna. För beräknandet av den signifikanta våghöjden var skillnaderna obetydliga. Under vissa omständigheter underbetonades energin för de korta vågorna ifall energiflödet från vinden till vågorna beräknades enligt en mera avancerad metod. Detta var troligen ett resultat av en för låg friktionshastighet. En äldre metod för att beräkna energiflödet till vågorna uppvisade inte en liknande avvikelse. De grova operativa vindprodukterna var tillräckliga för att driva vågmodellerna vid kusten, men modellerna kunde inte simulera vågfältets variationer med en tidsskala på 2–10 timmar ifall vindinformationen uppdaterades bara var tredje timme. Med vinddata som gavs varje timme kunde modellen fånga alla variationer, förutom den statistiska variabiliteten i vågobservationerna. Genom att använda R/V Arandas högfrekventa vågobservationer tagna med kapacitiva trådar kunde även spatiell information deduceras. Dessa observationer användes för att definiera ett nytt vågspektrum i vilket vågorna beskrivs genom deras (inverterade) fashastighet istället för deras frekvens eller vågnummer (inversen av våglängden). Detta nya vågspektrum stämde överens med det rent spatiella vågnummerspektrumet för de kortaste vågorna, medan frekvensspektrumet gav olika resultat. Dopplereffekten bedömdes vara liten, eftersom den skulle ha påverkat fashastighetsspektrumet. Orsaken till skillnaderna var vågornas icke-linjära egenskaper, vilka påverkade den högfrekventa delen av frekvensspektrumet. Att beskriva vågorna med hjälp av den direkt observerade fashastigheten kan vara användbar då man undersöker interaktionen mellan vinden och vågorna, eftersom man då inte behöver skilda vattenströmningsmätningar för att bestämma vågornas verkliga hastighet i förhållande till vindhastigheten.
  • Saponaro, Giulia (2020)
    Finnish Meteorological Institute Contributions 156
    Clouds play a vital role in Earth’s energy balance by modulating atmospheric processes, thus it is crucial to have accurate information on their spatial and temporal variability. Furthermore, clouds are relevant in those processes involved in aerosol-cloud-radiation interactions. The work conducted and presented herein concentrates on the retrievals of cloud properties, as well as their application for climate studies. While remote sensing observation systems have been used to analyze the atmosphere and observe its changes for the last decades, climate models predict how climate will change in the future. Altogether, these sources of observations are needed to better understand cloud processes and their impact on climate. In this thesis aerosol and cloud properties from the three above mentioned sources are applied to evaluate their potential in representing cloud properties and applicability in climate studies on local, regional and global scales. One aim of this thesis focuses on evaluating cloud parameters from ground-based remote-sensing sensors and from climate models using the MODerate Imaging Spectroradiometer (MODIS) data as a reference dataset. It is found that ground-based measurements of liquid clouds are in good agreement with MODIS cloud droplet size while poor correlation is found in the amount of cloud liquid water due to the management of drizzle. The comparison of the cloud diagnostic from three climate models with MODIS data, enabled through the application of a satellite simulator, helped to understand discrepancies among models, as well as discover deficiencies in their simulation processes. These findings are important to further improve the parametrization of atmospheric constituents in climate models, therefore enhancing the accuracy of climate projections. In this thesis it is also assessed the impact of aerosol particles on clouds. Satellite data can be used to derive climatically crucial quantities that are otherwise not directly retrieved (such as aerosol index and cloud droplet number concentration) which can be used to infer the sensitivity of clouds to aerosols changes. Results on the local and regional scales show that contrasting aerosol backgrounds indicate a higher sensitivity of clouds to aerosol changes in cleaner ambient air and a lower sensitivity in polluted areas, further corroborating the notion that anthropogenic emission modify clouds. On the global scale, the estimates of the aerosol-cloud interaction present, overall, a good agreement between the satellite- and model-based values which are in line with the results from other models.
  • Roiha, Petra (2019)
    Finnish Meteorological Institute Contributions 157
    Managing the sea environment is a complicated interdisciplinary task. To understand changes in the sea, knowledge of the present state is essential. Many variables are monitored constantly, and long historical data sets exist. However, the spatial and temporal data coverage varies widely over the Baltic Sea. The preparation for the emerging circumstances demands the ability to forecast the future marine conditions. Thus, improved modelling and forecasting systems are needed. In this thesis, methods were developed to 1) understand the present state of the sea and 2) predict future conditions. The study areas were the Bothnian Sea and the Eastern Gotland Basin. Argo floats are a common tool in the oceans, but so far they have not been used in shallow marginal seas, such as the Baltic Sea. The autonomous measurement device brings possibilities to fill the gaps in the existing observation network (e.g. research vessels, moorings) as well as to enable new scientific experiments. To better understand the present state of the Northern Baltic Sea, methods were developed using the Argo floats. The salinity, temperature and GPS data collected with these floats from the area is analysed in this thesis for the first time and its applicability for studying the different physical phenomena, such as currents at the float diving depth and wind induced mixing, are evaluated. The usability of Argo data was compared with the ship-borne CTD data. Due to the higher frequency of the Argo data, the seasonal variations can be studied in detail with this method. However, the spatial coverage of the Argo data is not as good as the CTD data collected with a research vessel due to the fact that the floats only operate near the deep areas of the Baltic Sea. To be able to predict the future conditions of the Baltic Sea, monthly ensemble forecasting system was developed. A 3D biogeochemical model was forced with monthly ensembles of the atmospheric forcing and the results were applied to forecast upwelling events and harmful algal blooms. The monthly ensemble forecasts for upwelling events were evaluated. The result was that the upwelling events could be forecasted on a weekly scale. This enables, for example, better planning of the scientific study of upwelling events or the improvement of local-scale weather forecasts. The same probability-based ensemble prediction system was used to produce harmful algal bloom forecasts. The forecasts showed the effects of the weather scenarios on marine biogeochemistry. In the future, it will be possible to interconnect the observations and forecasts better than before. The more dense observations can be used to improve the computational methods, for example, by assimilation. The probability-based forecasts can help, for example, to mitigate the environmental risks.
  • Leppänen, Leena (2019)
    Finnish Meteorological Institute Contributions 158
    Information on snow water equivalent (SWE) of seasonal snow is used for various purposes, including longterm climate monitoring and river discharge forecasting. Global monitoring of SWE is made feasible through remote sensing. Currently, passive microwave observations are utilized for SWE retrievals. The main challenges in the interpretation of microwave observations include the spatial variability of snow characteristics and the inaccurate characterization of snow microstructure in retrieval algorithms. Even a minor variability in snow microstructure has a notable impact to microwave emission from the snowpack. This thesis work aims to improve snow microstructure modelling and measurement methods, and understanding the influence of snow microstructure to passive microwave observations, in order to enable a more accurate SWE estimation from remote sensing observations. The thesis work applies two types of models: physical snow models and radiative transfer models that simulate microwave emission. The physical snow models use meteorological driving data to simulate physical snow characteristics, such as SWE and snow microstructure. Models are used for different purposes such as hydrological simulations and avalanche forecasting. On the other hand, microwave emission models use physical snow characteristics for predicting microwave emission from a snowpack. Microwave emission models are applied for the interpretation of spaceborne passive microwave remote sensing observations, for example. In this study, physical snow model simulations and microwave emission model simulations are compared with field observations to investigate problems in characterizing snow for microwave emission models. An extensive set of manual field measurements of snow characteristics is used for the comparisons. The measurements are collected from taiga snow in Sodankylä, northern Finland. The representativeness of the measurements is defined by investigating the spatial and temporal variability of snow characteristics. The work includes studies on microwave emission modelling from natural snowpacks and from excavated snow slabs. Radiometric observations of microwave emission from natural snowpacks are compared with simulations from three microwave emission models coupled with three physical snow models. Additionally, homogenous snow samples are excavated from the natural snowpack during the Arctic Snow Microstructure Experiment, and the incident snow characteristics and microwave emission characteristics are measured with an experimental set-up developed for this study. Predictions of two microwave emission models are compared with the radiometric observations of collected snow samples. The results indicate that none of the model configurations can accurately simulate the microwave emission from natural snowpack or snow samples. The results also suggest that the characterization of microstructure in the applied microwave emission models is not adequate.
  • Tuononen, Minttu (2019)
    Finnish Meteorological Institute Contributions 155
    Synoptic situation and different meteorological phenomena can highly affect renewable energy production. Investigating different phenomena will give new information on the occurrence and characteristics of specific phenomena and their impacts on renewable energy applications. Different observational data sets and numerical models can be widely used in different phases of renewable energy projects; from planning of the project to help with the operation and the maintenance of the existing wind or solar field. In this thesis a meteorological phenomena, a low-level jet, is investigated. Thesis comprises analysis of the climatological occurrence of low-level jets, their characteristics and forcing mechanisms, as well as numerical model capability to capture the phenomena. In addition, solar radiation forecasts obtained from the operational numerical weather prediction model are evaluated and the role of cloud cover forecast skill in solar radiation forecast error is investigated. Long data sets of observational data: mainly Doppler wind lidar, ceilometer, and solar radiation observations, are used, in addition to reanalysis and operational numerical weather prediction model data. A low-level jet is a wind phenomenon that can affect wind energy production. Nighttime low-level jets are a commonly known boundary-layer phenomenon occurring during stably stratified conditions over flat terrain. In this thesis, new information on the occurrence, characteristics, and forcing mechanisms of a low-level jet was gained in different conditions: in Northern Hemisphere mid-latitude and polar regions based on reanalysis data and at two different sites in Finland and Germany based on long-term Doppler lidar observations. The low-level jet identification algorithms developed in these studies can be used to repeat the studies by using different models covering different areas or at any site operating a Doppler lidar. The low-level jet identification algorithm for Doppler lidar data can also be applied to operationally detect low-level jets, which is useful information for example from wind energy point-of-view. Solar radiation and cloud cover forecasts were evaluated at one site in Finland based on long time-series of solar radiation and ceilometer observations. The role of cloud cover forecast in solar radiation forecast error is investigated. The solar radiation and cloud cover forecasts were obtained from operational numerical weather prediction model that can be used to predict the expected power production at solar field day-ahead. It was found that there is a positive bias in the forecast incoming solar radiation even if the cloud cover forecast is correct. The study can guide model improvements as the bias is likely due to underestimation in the forecast cloud liquid water content or incorrect representation of cloud optical properties. The methods created in this study can be applied to hundreds of sites globally. In addition, the algorithms developed in this study can be further used in different applications in the field of renewable energy, for example to detect potential in-cloud icing conditions.
  • Karsisto, Virve (2019)
    Finnish Meteorological Institute Contributions 153
    Wintertime weather conditions can be hazardous for road traffic. Icy roads and poor visibility caused by snowfall increase the accident risk. Accurate forecasting of road conditions is important, because reliable and precise forecasts help the road maintenance personnel to plan their operations accordingly. Well timed maintenance operations increase safety and enable economical savings as unnecessary actions can be avoided. Drivers can also adjust their route plan and driving behaviour appropriately when warnings of hazardous conditions are given well beforehand. Road conditions are forecasted in the Finnish Meteorological Institute (FMI) with specialized road weather model. Before executing the actual forecast, the model is first initialized by feeding it with observation data. The quality of this data is essential for forecast accuracy, as the forecast is greatly dependent of the initial model state. Road weather stations have traditionally been one of the main sources of information, but their density is sparse especially in rural areas. Road surface temperature can vary considerably across the road network, so observations should be done in dense enough spatial scale. Nowadays it is possible to gather real time information from vehicles. Mobile sources provide observations with high spatial density and thus facilitate detecting the road stretches most prone to freezing. However, the quality of mobile observations should be assessed before implementing them to the road weather forecasting systems. This dissertation aims to answer to two research questions. Firstly, it has been studied how to best use available surface temperature observations in the road weather model initialization. Secondly , it has been studied how differences in two road weather models’ physics affect to the surface temperature forecast accuracy. A method called coupling was implemented to the FMI road weather model. The main idea of the method is to adjust the incoming radiation flux so that the modelled surface temperature fits to the last observed value. The results show that this method improves considerably the short range surface temperature forecasts. Mobile surface temperature observations done with Teconer RTS411 were compared to road weather station measurements to assess the mobile data quality. According to the results, the mobile observations were on average 0.62 °C warmer than the road weather station measurements at 0 °C and in dry conditions. It was found out that the difference between mobile observations and road weather station measurements was dependent on the road status. A calibration equation for mobile observations was developed using linear mixed models to get mobile observations more in line with road weather station measurements. The effect of the mobile observations to the road surface temperature forecast accuracy was studied. According to the results, using the mobile observations calibrated with the developed equation improved the accuracy of road surface temperature forecasts compared to a theoretical situation where there would not be other surface temperature observations available. However, for an area with a dense road weather station network the accuracy of forecasts assimilating mobile observations with correction were on par with the accuracy of forecast assimilating interpolated surface temperature values. Studying model physics and comparing behaviour of different models is beneficial for model development. In this work, the verification results of the FMI’s and the Royal Netherlands Meteorological institute’s (KNMI) road weather models were compared to each other. In addition, the model physics were studied to find out the reasons for differences in the surface temperature forecasts. The forecasts of the KNMI model were found to be slightly more accurate than the forecasts of the FMI model. Although the core physics of the models were rather similar, there were large differences in some physical parameters and the number and the thickness of the ground layers. Individual reason for the better performance of the KNMI model could not be found, as the effects of different physical properties eventually sum up to surprisingly similar modelled surface temperature values.
  • Venäläinen, Ari; Ruosteenoja, Kimmo; Lehtonen, Ilari (2019)
    Raportteja – Rapporter – Reports 2019:3
    This report deals with projected climatic changes in four areas of operation of the UPM-Kymmene company: Finland, southern Germany, Uruguay and eastern China. The implications of the projected changes for forestry, including forest growth and productivity and possible climate change induced disturbances, are discussed as well. Climate projections have been derived from the output of 28 global climate models. Analyses focus on the RCP4.5 greenhouse gas scenario that represents an alternative of moderately large emissions. Mainly, projections calculated for the period 2040–2069 (relative to 1971–2000) have been examined. All the models analyzed simulate higher temperatures for the future. However, the degree of warming varies quite a lot among the models. For many other climate variables, like precipitation and incident solar radiation, even the sign of the future change can be uncertain. Even so, in the regions examined mean precipitation is more likely to increase than decrease, except for southern Germany in summer and early autumn, Uruguay in Southern Hemisphere winter and spring and China in late autumn. Rising temperatures enhance evaporation and increase drought risks despite modest increases in precipitation. In some seasons, both the intense rainfall events and dry periods are projected to become more severe. In recent decades, forest resources have been increasing in Europe. Especially in Northern Europe, forests have benefitted from the warmer climate and increased CO2 concentration in the atmosphere. During the coming decades, this positive development may at least partly be cancelled due to potentially increasing disturbances for the forest growth. For example, drought, fire and insect pests may cause damage. The role of forests as a carbon sink is an important aspect in the context of climate change mitigation activities, and vivid discussion on the most beneficial and sustainable use of forest resources is foreseen to continue. If global climate policy proves to be successful, it is possible that future changes in climate will be weaker than those based on the RCP4.5 scenario discussed in this report. However, this requires rapid restrictions of the greenhouse gas emissions globally.
  • Susiluoto, Jouni (2019)
    Finnish Meteorological Institute Contributions 154
    Climate change is one of the most important, pressing, and furthest reaching global challenges that humanity faces in the 21st century. Already affecting daily lives of many directly and everyone indirectly, changes in climate are projected to have many catastrophic consequences. For this reason, researching climate and climate change is needed. Studying complex geoscientific phenomena such as climate change consists of a patchwork of challenging mathematical, statistical, and computational problems. To solve these problems, local and global process models and statistical models are combined with both small in situ observation data sets with only few observations, and equally well with enormous global remote sensing data products containing hundreds of millions of data points. This integration of models and data can be done in a Bayesian inverse modeling setting if the algorithms and computational methods used are chosen and implemented carefully. The methods used in the four publications on which this thesis is based range from high-dimensional Bayesian spatial statistical models and Markov chain Monte Carlo methods to time series modeling and point estimation via optimization. The particular geoscientific problems considered are: finding the spatio-temporal distribution of atmospheric carbon dioxide based on sparse remote sensing data, quantifying uncertainties in modeling methane emissions from boreal wetlands, analyzing and quantifying the effect of climate change on growing season in the boreal region, and using statistical methods to calibrate a terrestrial ecosystem model. In addition to analyzing these problems, the research and the results help to understand model performance and how modeling uncertainties in very large computational problems can be approached, also providing algorithm implementations on top of which future efforts may be built.
  • Nurmi, Väinö (2019)
    Finnish Meteorological Institute Contributions 152
    This thesis applies cost-benefit analysis (CBA) to certain environmental questions and through its results contributes to both the theoretical literature on CBA in environmental economics and practical issues in the application of CBA to environmental problems. The work comprises an introduction and four articles, which address three common thematic areas: 1) distributional issues, 2) climate change adaptation, and 3) urban ecosystem services. Article I contributes to the literature through analyses that i) provide a connection between the income effect and distributional issues; ii) compare weighting schemes both theoretically and empirically; iii) show how weights could be incorporated into a CBA in practice; and iv) demonstrate that results are sensitive not only to whether weights are applied, but also to the choice of the inequality parameter and spatial resolution. Article II analyzes whether over-investment in disaster risk reduction and climate change adaptation is a legitimate economic concern and examines how the public reacts to major infrastructure investments. The results constitute a contribution to both the theoretical and empirical literature on the economics of climate change adaptation. Article III evaluates how potential innovations in weather services can reduce weather sensitivity and, consequently, decrease the negative effects of climate change on transport, particularly in the road transport sector. The article illustrates how innovations in the provision and use of weather and climate information can be beneficial for adapting to the changing climate and contributes to the empirical literature on the economics of climate change adaptation. Article IV presents a CBA of a relatively novel feature in the urban green portfolio: green roofs. The specific objectives of the research are i) to facilitate benefit-transfer of ecosystem services from one urban area to another by providing detailed information on valuation methods and the role of different assumptions and parameter values and ii) to include scenic values as a benefit item based on a formal and trackable analysis rather than on a guess. The article contributes to the empirical literature related to both the cost-benefit analysis of urban ecosystem services and the economics of climate change adaptation. *** Tässä tutkielmassa sovelletaan kustannushyötyanalyysiä (KHA) ympäristöön liittyviin kysymyksiin. Tulokset vievät eteenpäin sekä KHA-analyysin teoreettista kirjallisuutta että käytännön sovellettavuutta ympäristökysymyksiin. Työ koostuu neljästä artikkelista, joissa on kolme poikkileikkaavaa teemaa: 1) tulojakauma-kysymykset, 2) ilmastonmuutokseen sopeutuminen ja 3) urbaanit ekosysteemipalvelut. Artikkeli I pääkontribuutio kirjallisuuteen on i) luoda yhteys tulovaikutuksen ja tulojakauma-kysymyksen välille, ii) vertailla eri painotustapoja teoreettisesti ja empiirisesti, iii) osoittaa, miten painotukset voidaan käytännössä sisällyttää KHA:n, iv) näyttää tulosten herkkyys paitsi siihen, painotetaanko hyötyjä vai ei, myös siihen, mikä painotustapa valitaan ja mitä maantieteellistä tarkkuutta käytetään. Artikkeli II analysoi esimerkin avulla, onko liiallinen panostaminen ilmastonmuutokseen sopeutumiseen ja onnettomuusriskien vähentämiseen todellinen huolenaihe. Liiallinen panostus määritellään taloudellisen tehokkuuden avulla. Tulokset myötävaikuttavat ilmastonmuutokseen liittyvän taloustieteen teoreettiseen ja käytännön kirjallisuuteen. Artikkelissa III arvioimme, miten sääpalveluihin liittyvät innovaatiot voivat vähentää yhteiskunnan sääherkkyyttä ja vähentää ilmastonmuutoksen tuomia negatiivisia vaikutuksia tieliikenteelle. Artikkelissa näytetään, miten sääpalveluiden jakeluun ja käytettävyyteen liittyvät innovaatiot ovat hyödyllisiä ilmastonmuutokseen sopeutumiselle. Tulokset myötävaikuttavat ilmastonmuutokseen liittyvän taloustieteen käytännön kirjallisuuteen. Artikkeli IV käsittelee viherkattojen kustannushyötyanalyysiä. Tämän tutkimuksen päätavoitteet ovat: i) mahdollistaa tulosten siirtäminen toiselta urbaanilta alueelta toiselle antamalla mahdollisimman tarkat tiedot tutkimuksessa käytetyistä menetelmistä ja parametreista, ii) sisällyttää viherkattojen maisemahyödyt yhtenä hyötylajina mukaan. Tulokset myötävaikuttavat sekä ekosysteemipalveluihin liittyvän KHA:n käytännön kirjallisuuteen että ilmastonmuutokseen liittyvän taloustieteen käytännön kirjallisuuteen.
  • Lehtonen, Ilari; Ruosteenoja, Kimmo; Mäkelä, Antti (2019)
    Raportteja – Rapporter – Reports 2019:2
    Meneillään olevan ihmiskunnan aiheuttaman ilmastonmuutoksen vaikutukset ovat havaittavissa jo nyt: esimerkiksi Suomen keskilämpötila on noussut 1800-luvun puolivälistä yli kaksi astetta. Lämpeneminen on ollut Suomessa noin kaksi kertaa nopeampaa kuin maapallolla keskimäärin. Tulevaisuuden muutokset erilaisten sääilmiöiden esiintymisessä riippuvat vahvasti kasvihuonekaasupäästöjen määrästä: mitä tehokkaammin kasvihuonekaasujen päästöjä onnistutaan rajoittamaan, sitä vähäisemmiksi ilmastonmuutoksen vaikutukset jäävät. Ilmakehään jo päässeen hiilidioksidin suhteellisen pitkästä viipymäajasta johtuu, että ilmasto joka tapauksessa vielä lämpenee seuraavina vuosikymmeninä, vaikka fossiilisten polttoaineiden käytöstä aiheutuvia kasvihuonekaasupäästöjä onnistuttaisiin leikkaamaan nopeastikin. Tässä tutkimuksessa käsitellään ilmastonmuutoksen vaikutusta sähköverkkoliiketoiminnan kannalta oleellisiin sääilmiöihin. Keskeisimmät tähän mennessä havaitut ja kuluvan vuosisadan puoliväliin mennessä odotettavissa olevat muutokset on koottu sääilmiöittäin sisällysluettelon edellä olevaan taulukkoon. Selvimmin havaittavat muutokset liittyvät lämpötilan nousuun. Esimerkiksi kasvukaudet pidentyvät kesällä ja lumipeite vähenee talvella. Sen sijaan esimerkiksi myrskyisyydessä ei välttämättä tapahdu merkittäviä muutoksia, mutta lämpenemisestä johtuva roudan väheneminen todennäköisesti lisää talviaikaisia tuulituhoja. Vastaavasti esimerkiksi jokien talvitulvien odotetaan selvästi yleistyvän, vaikka sademäärä ei talvella kasvaisikaan enempää kuin noin 10–20 %. Tämä johtuu siitä, että lämpötilan noustessa entistä suurempi osa sateesta tulee vetenä. Muutokset eivät myöskään ole yleensä kovin suuria, jos tarkastelu ulotetaan vain noin 30–40 vuoden päähän. Kuluvan vuosisadan puoliväliin mennessä ilmasto lämpenee todennäköisesti suunnilleen yhtä paljon kuin se on tähän mennessä lämmennyt 1970–1980-lukuihin verrattuna. Tällöin 2050-luvun ilmasto olisi jo selkeästi erilainen kuin 1970–1980-lukujen ilmasto, vaikka muutos nykyhetken ilmastoon verrattuna olisi melko maltillinen. Lämpenemisestä huolimatta samat sääilmiöt tuottavat meillä harmia tulevaisuudessa kuin nykyisinkin. Myrskyt säilyvät merkittävimpänä laajoja ja äkillisiä metsätuhoja aiheuttavana sääilmiönä. Kesäisin esiintyy tuhoisia ukkosmyräköitä, eivätkä lumeen ja pakkaseen liittyvät ongelmat katoa talvella. Suomen ilmastolle tyypillinen suuri vuosienvälinen vaihtelu jatkuu yhä myös tulevaisuudessa.
  • Salmi, Jatta; Saari, Helena; Latikka, Jenni; Komppula, Birgitta; Vestenius, Mika; Wemberg, Antti; Laukkanen, Emmi (2019)
    Raportteja - Rapporter - Reports 2019:4
    Tässä työssä on selvitetty ilmanlaadun mittausasemien edustavuuden arvioinnin nykytilaa. Tällä hetkellä mittausasemien edustavuuden arvioinnille ei anneta ohjeita EU-lainsäädännössä eikä Suomen kansallisessa ilmanlaatulainsäädännössä. Kun ilmanlaadun mittaustuloksia raportoidaan EU:lle, tulee kiinteiltä mittausasemilta raportoida myös edustavan alueen alueellinen laajuus ja edustavuuden arviointi. Näiden tietojen raportointi on pakollista, mutta määritellyn referenssimenetelmän puuttuessa on toistaiseksi ollut sallittua jättää tieto raportoimatta. Eri EU-mailla on olemassa laaja kirjo erilaisia menetelmiä, joilla ne arvioivat mittausasemiensa edustavuutta. FAIRMODE järjesti vuonna 2016 mittausasemien edustavuuden arvioinnista käytännön harjoituksen, johon Suomikin osallistui. Harjoituksen tarkoituksena oli vertailla käytössä olevien erilaisten lähestymistapojen vahvuuksia ja heikkouksia. Harjoituksessa ei saatu aikaan yhtenäistä linjausta mittausaseman edustavuuden arvioimiseksi johtuen eri maiden menetelmien suurista eroavaisuuksista. Harjoituksen loppuraportissa suositeltiin jatkotoimenpiteiksi mittausaseman edustavuuden määritelmän ja kriteerien tarkentamista ja vasta tämän jälkeen yhtenäisen menetelmän kehittämistä keskipitkällä aikavälillä. Edustavuuden arviointia tullaan käsittelemään edelleen AQUILA:n ja FAIRMODE:n yhteistyön puitteissa. Tässä työssä esitetyllä menetelmällä pyritään kannustamaan mittausverkkoja arvioimaan mittausasemien edustavuusalueita. Menetelmässä on kuvattu täsmällisemmin Suomen FAIRMODE:n harjoituksessa käyttämää asiantuntija-arviota, joka perustuu olemassa olevaan monipuoliseen tietoaineistoon. Edustavuuden arviointimenetelmä jakaantuu kahteen vaiheeseen: ensimmäisessä vaiheessa arvioidaan pitoisuuksia ja toisessa vaiheessa pitoisuuksia aiheuttavia samankaltaisia syitä. Edustavuutta voivat arvioida ilmanlaadun arviointeihin hyvin perehtyneet henkilöt, joilla on ymmärtämystä ilman epäpuhtauksien päästöistä ja niihin vaikuttavista seikoista, eri päästölähteiden aiheuttamista pitoisuuksista sekä paikallisista olosuhteista. Mieluiten edustavuuden arviointi tehdään useamman asiantuntijan ryhmätyönä, mikä vähentää yksittäisen asiantuntijan näkemyksen liiallista korostumista.
  • Pajunpää, Kari; Häkkinen, Lasse; Laitinen, Tiera (2019)
    Raportteja – Rapporter – Reports 2019:1
    The magnetic yearbook of the magnetic recordings at the Nurmij¨arvi observatory contains tables, figures of hourly, monthly, and yearly means of the magnetic field components X, Y and Z as well as magnetic activity indices (K, Ak) in 2016. Magnetic isolines describing the distribution of geomagnetic field components in Finland 2017.0 are shown by a series of maps.
  • Anttila, Kati (2019)
    Finnish Meteorological Institute Contributions 149
    The topic of this dissertation is the seasonal snow surface roughness and albedo. These are studied using optical satellite data and terrestrial laser scanning. The use of remote sensing data requires knowledge on the optical properties of the measured surface. For snow, these properties are affected by surface roughness. In this dissertation, two different methods for measuring snow surface roughness were validated and used in the field. One of them is based on plate photography. It is easy to use in the field and able to study surface features in sub-millimeter scale. The other method is based on mobile laser scanning and is able to produce 3D surface descriptions of large areas. The plate-photography-based method was used in the field to gather 669 profiles of the snow surface. The profiles were analyzed using multiscale parameters. The validation of satellite data requires observations at the surface. This validation data typically consists of pointwise measurements, whereas the satellite data observations cover larger areas. Laser scanning provides data that cover larger areas, thus more in line with the satellite data. This could in the future be used for satellite data validation. The usability of laser scanning data on snow surfaces was improved by studying the incidence angle dependency of the laser scanning intensity data on different snow types. A function for correcting the incidence angle effect on all measured snow types was developed. The backscattering of laser beam on snow surface was found to take place at the very surface for dry snow, and within 1cm depth for wet snow. The final part of this dissertation studies the changes in surface albedo prior to melting and the timing of the melt season in Northern Hemisphere land areas between 40°N and 80°N. The albedo prior to melt had changed significantly in the boreal forest area, but not in the tundra. The direction of change is different in different areas. The melt season takes place at the same time of year for most of the study area, but for Central Siberian Plane the melt season takes place earlier. In Northern Canadian Rocky Mountains and in the area around the borders of Russia, China and Mongolia the melt starts earlier and ends later, thus resulting in longer melt seasons. The changes observed in the pre-melt albedo are related to vegetation, whereas the melt season timing is more related to the climatic parameters. The results of this dissertation can be used in developing remote sensing data and climate models through improved understanding of seasonal snow surface roughness and albedo. *** Tämä väitöskirja käsittelee kausittaisen lumipeitteen pinnan karkeutta ja kirkkautta hyödyntäen optista satelliittiaineistoa ja laserkeilausta. Maan pinnan kaukokartoitus tarvitsee tietoa maan pinnan säteilyominaisuuksista. Lumipinnat heijastavat suurimman osan auringosta tulevasta säteilystä takaisin ilmakehään ja avaruuteen. Kausittainen lumipeite kattaa laajan alueen pohjoisen pallonpuoliskon maaalasta. Alueellisen kattavuutensa ja kirkkautensa vuoksi sillä on merkittävä vaikutus maapallon energiataseeseen ja siten ilmastoon. Lumipinnan heijastusominaisuudet, kuten esimerkiksi pinnan karkeus, vaikuttavat suoraan lumipinnan kirkkauteen. Tässä väitöskirjassa on tarkasteltu kahta lumen pinnan karkeuden mittausmenetelmää. Ensimmäinen näistä tekniikoista perustuu lumeen asetetun mustan levyn valokuvaamiseen. Levystä ja lumipinnasta otetusta kuvasta etsitään automaattisesti lumipinnan profiili. Tämä tekniikka on helppokäyttöinen ja luotettava myös kenttäolosuhteissa. Sillä saadaan kerättyä tietoa lumen pinnan karkeudesta alle millimetrin tarkkuudella. Toisessa mittausmenetelmässä laserkeilainta liikutetaan moottorikelkalla. Näin saadaan katettua laaja alue, josta syntyy 3D havaintoja. Pinnan karkeutta kuvaavien suureiden arvoihin vaikuttaa analysoidun profiilin pituus tai alueen laajuus. Kaukokartoituksen kannalta on oleellista mitata pinnankarkeutta kaikissa sovellukselle oleellisissa mittakaavoissa. Maan pinnan sirontamallit käyttävät pinnan karkeuden kuvaamiseen vain yhtä suuretta. Siten tämän suureen tulisi sisältää tietoa useista mittakaavoista. Tässä väitöskirjassa kerättiin Sodankylän alueelta 669 lumiprofiilia levymenetelmää käyttäen. Nämä profiilit analysoitiin käyttäen suureita, jotka kuvaavat profiilin korkeusvaihtelun riippuvuutta mitatusta matkasta ja sisältävät siten tietoa useista mittakaavoista. Käyttämällä näitä suureita kyettiin erottelemaan eri lumipintoja niiden iän ja lumityypin mukaan. Satelliittien instrumentit mittaavat kerralla laajoja alueita. Maan pinnalla tehtävillä pistemäisiä alueita kuvaavilla havainnoilla selvitetään, kuinka laadukkaita satelliittituotteet, kuten lumi- ja albedotuotteet, ovat. Koska pintahavaintojen ja satelliittihavaintojen kattamat alueet eivät ole samat, itse ahavainnotkaan eivät täysin vastaa toisiaan. Laserkeilausaineistot kattavat laajempia alueita kuin perinteisin menetelmin tuotetut havainnot ja ovat siten lupaavia satelliittiaineistojen arviointiin. Tämän väitöskirjan sisältämä tutkimus lasersäteen käyttäytymisestä lumipinnoilla edistää laserkeilausaineistojen käytettävyyttä lumeen liittyvässä tutkimuksessa ja satelliittiaineistojen laadun määrittämisessä. Tulosten mukaan kuivasta lumesta lasersäde heijastuu takaisin aivan lumen pinnasta, kun taas märässä lumessa se heijastuu noin 1 cm syvyydestä. Takaisin heijastuneen lasersäteen kirkkaus riippuu tulokulmasta samalla tavalla erityyppisillä lumipinnoilla. Siten tulokulman vaikutus laserhavainnon kirkkauteen voidaan korjata samalla tavalla kaikilla mitatuilla lumipinnoilla. Tämän väitöskirjan viimeisessä osassa tutkittiin kausittaisen lumipeitteen peittämien alueiden pinnan kirkkauden (albedon) ja sulamiskauden ajankohdan muutoksia vuosina 1982-2015 pohjoisen pallon puoliskon maa-alueilla leveyspiirien 40°N ja 80°N välillä. Tutkimus keskittyi sulamiskautta edeltävään pinnan kirkkauteen, joka oli muuttunut huomattavasti boreaalisen metsävyöhykkeen alueella. Muutos oli erisuuntaista eri alueilla. Tundralla sulamista edeltävä pinnan kirkkaus ei ollut muuttunut. Sulamiskausi oli aikaistunut Keski-Siperian ylängöllä ja pidentynyt Kiinan, Mongolian ja Venäjän rajaa ympäröivällä alueella sekä Kanadan Kalliovuorten pohjois-osissa. Pinnan kirkkauden muutokset olivat sidoksissa kasvillisuuden muutoksiin, kun taas sulamiskauden ajankohdan muutoksiin vaikuttivat enemmän ilmastolliset tekijät. Tämä väitöskirja parantaa kausittaisen lumipeitteen pinnan sirontaominaisuuksien ymmärtämistä ja sen tuloksia voidaan käyttää kaukokartoitusaineistojen ja ilmastomallien kehittämisessä.
  • Strahlendorff, Mikko; Veijola, Katriina; Gallo, Jason; Vitale, Vito; Hannele, Savela; Smirnov, Alexander; Tanaka, Hajime; Sueyoshi, Tetsuo; Nitu, Rodica; Larsen, Jan René (2019)
    Raportteja - Rapporter - Reports 2019:3
    This report describes the first instance to employ the international assessment framework for arctic observations developed by SAON and IDA STPI in 2017. Earth Observation (EO) inputs like SYNOP station measurements of physical atmosphere and in other stations ocean variables were linked to key products/outcomes/services like numerical weather prediction and through groups like in this case weather service connected to key objectives of the assessment framework. Representative yearly unit costs of EO inputs and modelling components were estimated by station experts or estimated based on European Union projects or Copernicus program tenders. The WMO OSCAR database for satellite and surface observation systems north of 60°N was used for numbers of the different station and mission categories in the Arctic. The total yearly value of this observation system including EO inputs and modeling is over 204 million €. Compared to the observing system estimated costs in the area 30°N to 60°N this is only about a fifth. The value tree can now follow and combine the value invested in these components as it flows towards services. The key objectives have been connected by SAON/AMAP project members in a workshop to the services to build the first full value tree for a certain kind of observations. These observations are mainly produced by national meteorological and marine institutes in an operational mode. The yearly value invested in the observation can now be distributed between the 12 Societal Benefit Areas and their sub areas identified in the assessment framework. The value tree is presented at a web page by FMI and Spatineo (2019) with a browser that can highlight single components to analyze which inputs and which SBA targets its being used for. This can help to more holistically support the whole observation system for optimal impact on societal benefit. The value tree tool will be available for further work to address the many more EO domains like atmospheric composition or biodiversity. All in all this report can hopefully start a continuous action to update and improve the value tree. EO inputs are not static, the network changes, the costs are fluctuating and as the Arctic is becoming more accessible, it would be important to extend the observation system accordingly.
  • Takala, Matias (2018)
    Finnish Meteorological Institute Contributions 151
    Hemispheric snow extent and snow mass are two important parameters affecting the water cycle, carbon cycle and the radiation balance in particular at the high latitudes. In this dissertation these topics have been investigated focusing on the mapping of snow clearance day (melt-off day) and Snow Water Equivalent (SWE) by applying spaceborne microwave radiometer instruments. New algorithms have been developed and existing ones have been further advanced. Specific attention has been paid to estimate snow in boreal forests. This work has resulted in Climate Data Records (CDRs) of snow clearance day and daily values of SWE. Data are available for the entire Northern Hemisphere covering more than three decades. The developed CDRs are relevant for climate research, for example concerning the modeling of Earth System processes. CDR on snow clearance day can be used to map the CO2 balance between the biosphere and atmosphere in the case of boreal forests, which is demonstrated in the thesis. Further, methodologies to assess snow mass in terms of SWE for hemispherical and regional scales have been developed. The developed methodologies have also resulted in the establishment of new Near-Real-Time (NRT) satellite data services for hydrological end-use. In hydrology SWE data are used to enhance the performance of river discharge forecasts, which is highly important for hydropower industry and flood prevention activities.
  • Hooda, Rakesh (2019)
    Finnish Meteorological Institute Contributions 150
    Atmospheric aerosol particles are linked to visibility reduction and adverse health effects, and radiation balance of the Earth— directly by reflecting and absorbing solar radiation and indirectly by influencing the cloud properties and processes and, possibly, by changing the heterogeneous chemistry of reactive gaseous species. Atmospheric aerosols are the most uncertain driver of global climate change. The South‒Asian region has been increasingly recognized as one of the global hotspots of aerosols; and Indo Gangetic Plains (IGP) is one among them with complex geography, heterogeneity in sources and varying atmospheric dynamics. These factors make IGP’s aerosol and pollution very difficult to characterize. So far, long-term regional observations of aerosol properties have been scarce in this region, but argued necessary in order to bring the knowledge of regional and global distribution of aerosols further. In this context, regional studies of aerosol properties their dynamics and atmospheric processes are very important areas of investigation to better estimate the climatic importance of submicron aerosol particles. Moreover regional studies over IGP-Himalayas domain are inevitable to know how trans-Himalayan valleys are acting as conduits for aerosol and pollution transport from the plains to the Himalayas. Therefore, in this thesis we studied these issues by applying basic to state-of-the-art instrumentation in two different environments, plains—Gual Pahari, and Himalayan foothills— Mukteshwar; to obtain physical and optical properties of submicron particles. Additionally, we used meteorological parameters, emissions and process modelling to determine local and regional scale transport of atmospheric aerosols. The work carried out as part of the thesis infers four main conclusions, 1) Simultaneous long-term measurements at both the environments in Northern India region are useful to establish linkages between sub-urban environment and high altitude sites. One site represents a source region, while another characterize as a receiver site of atmospheric pollutants; 2) A distinct cycle of aerosol properties, both seasonal and diurnal, is present and provides information of driving factors of aerosol variability at both the sites; 3) The contribution of regional sources seem to dominate over the local /sub-urban sources, in the IGP region boundary layer; 4) Aerosol properties and specific humidity “passive tracer” based analysis clearly reveal that the mountainous terrain sites are under the influence of air from the plains due to convective transport processes enhanced by local and mesoscale topography. The results presented in this thesis are particularly useful, first, when examining the linkages of aerosol properties variability between two different environments. The second, in determining for instance local versus regional influences, and pollutants reaching high altitude sites which can be explained by boundary layer dynamics processes, especially in the mountain terrain where the modelled mixing layer depths have uncertainties. This work outlines future direction of multi-points measurements on vertical profile of atmospheric particles and local boundary layer over mountainous terrain where the atmospheric structure becomes much more complicated. Additionally, investigations including isotope-based analysis and modelling work over the Himalayan region are desirable to be able to describe better the transport of atmospheric aerosols from IGP to high altitudes and further up to Himalayan ice-pack and glaciers where aerosol deposition could have serious environmental impacts.
  • Waldén, Jari; Vestenius, Mika (2018)
    Raportteja - Rapporter - Reports 2018:2
    The Air Quality Directive, AQD, (2008/50/EC), set up the rules concerning the reference methods (RM) for the measurements of e.g. mass concentration of particulate matter in air. A member state (MS) can use any other method, which it can demonstrate to display a consistent relationship with the reference method. Demonstration of equivalence (DoE) for automated continuous monitoring systems (AMS) for determination of the PM2.5 and PM10 mass concentration of suspended particulate matter was conducted in Finland at the city of Kuopio during 2014-15 (Walden et al., 2017). The tested AMS were used in Finland at the local air quality networks for controlling the limit values for PM2.5 and PM10 mass concentration measurements. The purpose of the verification exercise was to demonstrate whether the AMS tested and approved during the DoE study in Kuopio are applicable elsewhere in Finland. The comparison of the AMS of the local network (site) with the RM was performed in various parts of Finland (south and north, east and west) to see if the AMS, which was approved as equivalence method still fulfills the suitability criteria elsewhere in Finland. Verification campaigns took place at eight measurement sites of different local air quality networks in Finland either for PM2.5 or PM10 measurements. AMS whose DoE was approved were: FH62-IR, Grimm model 180, MP101 CPM, Osiris, SHARP model 5030 and TEOM 1405. Additionally TEOM 1405D and APM-2 were tested for verification, though they did not participate in the DoE tests in Kuopio, but are used at some of the networks. The test strategy was modified from the relevant EN-standard for using the AMS for measurements of PM2.5 and PM10 concentrations in ambient air. This strategy enabled to include more sites and tested instruments into the study but with lack of less seasonality than would have been needed by following the guide accurately. As a result of the verification study the calibration factors achieved at DoE in Kuopio are applicable for the same model of AMS tested in Kuopio in different locations in Finland with few limitations. The FH62-IR made better performance by using the calibration factor obtained in this study in Helsinki than based on the DoE in Kuopio. Osiris passed the test for PM10 but not for PM2.5 measurements just like in Kuopio. APM-2 has been tested by Rheinland Energie und Umwelt GmbH, TÜV that is accredited testing laboratory and found to be equivalent with the reference method both for PM2.5 and for PM10 measurements. Based on the test results by TÜV and the verification results achieved in this study, the APM-2 can be used for PM2.5 and for PM10 measurements in Finland, but applying the calibration factors obtained in this study. TEOM 1405D has not been tested for DoE and cannot be claimed equivalent to reference method. Therefore calibration factors obtained in this study cannot be used for TEOM 1405D.
  • Saarnio, Karri; Kyllönen, Katriina; Laurila, Sisko; Lusa, Kaisa; Waldén, Jari (2018)
    Raportteja - Rapporter - Reports 2018:1
    Neljäs kaasumaisten yhdisteiden vertailumittauskampanja sekä mittausasemien kenttä- ja laatujärjestelmä-auditointi suoritettiin Suomen ilmanlaadun mittausverkoille vuoden 2017 aikana. Vertailumittauksessa kaasu-komponentit olivat rikkidioksidi (SO2), typpimonoksidi (NO) ja otsoni (O3). Vertailupitoisuudet eri komponenteille koostuivat kahdesta eri pitoisuudesta, joista toinen edusti alhaista pitoisuutta ja toinen korkeahkoa pitoisuutta. Lisäksi kullekin komponentille suoritettiin nollatason mittaus. Mittaustulosten raportointi vertailuun osallistuneilta tahoilta edellytti korjatut tulokset jokaisesta vertailumittauksesta sekä arvion mittaustulosten epävarmuudesta. Vertailu-mittauksiin osallistui 21 mittausverkkoa 31:stä ilmanlaadun seurantaa suorittavasta mittausverkosta. Näissä vertailu-mittauksia suoritettiin yhteensä 80 mittausta 28:lla eri mittausasemalla. Pitoisuusvertailujen ohessa suoritetussa kenttä- ja laatujärjestelmäauditoinnissa pyrittiin selvittämään mittausverkon laatujärjestelmän laajuus ja toimivuus. Pääpaino oli erityisesti mittausmenetelmää kuvaavien standardien vaatimusten toteutuminen kentällä tehtävissä laadunvarmennus-toimissa. Auditoinnissa tarkasteltiin kaasumaisten komponenttien mittausten lisäksi ulkoilman hiukkasmittauksia. Tässä raportissa esitetään vertailumittausten sekä kenttä- ja laatujärjestelmäauditoinnin tulokset sekä johtopäätökset. Raportoiduista SO2-tuloksista 22 tulosta 24:stä oli hyväksyttäviä. NO:n osalta 38 tulosta 40:stä oli hyväksyttäviä. O3:n osalta 14 tulosta 16:sta oli hyväksyttäviä. SO2:n, NO:n ja O3:n osalta yhteensä 92,5 % tuloksista oli hyväksyttäviä, mutta korjaavien toimenpiteiden jälkeen kaikki mittausverkot tuottivat hyväksyttävän vertailutuloksen. Mittausepävarmuusarvion oli laatinut noin 86% osallistuneista mittausverkoista. Laatujärjestelmä- ja kenttäauditointien tulokset olivat ylipäätään hyviä. Mittausverkot ovat laatineet menetelmäohjeita mittausaseman sijoittamisesta, mittausmenetelmistä, laadunvarmennustoimista, tulosten käsittelystä ja raportoinnista. Laatujärjestelmiä on kehitetty viime auditoinnin jälkeen. Mittausverkkojen ylläpitämistä laatu-järjestelmistä 16 oli kattavia, neljä oli rakenteilla ja kahdella mittausverkolla laatujärjestelmä oli pääasiallisesti dokumentoitu, mutta se ei ollut aktiivikäytössä. Kaikissa verkoissa oli toimivat tietojen keruu- ja käsittelyohjelmistot. Ilmanlaatumittausten tulokset oli jäljitetty kansalliseen vertailulaboratorioon joko suoraan mittausverkkojen ylläpitämillä tai välillisillä kalibroinneilla, joskin kalibrointivälit eivät aina täyttäneet EN-menetelmästandardeja (EN 14211, EN 14212, EN 14625). Välillisistä kalibroinneista suurin osa oli ulkoistettu yhdelle konsultille, jonka jäljitettävyys kansalliseen vertailulaboratorioon oli ylläpidetty säännöllisillä kalibroinneilla. Kaasumittausten laadunvarmennustoimet olivat pääasiallisesti em. EN-menetelmästandardien mukaisia, joskin poikkeuksiakin oli. Hiukkasmittausten osalta laadunvarmennustoimissa tavattiin eniten vaihtelevuutta eri verkkojen välillä ja tätä on syytä kehittää.
  • Westerlund, Antti (2018)
    Finnish Meteorological Institute Contributions 145
    Circulation and surface layer dynamics are of significant importance, for example, when considering how hazardous substances or nutrients are transported in the sea. The earliest studies mapping circulation patterns in the northern Baltic Sea were done before the Second World War and were based on lightship observations. Although the number of available observation points was low, these studies showed that there is a cyclonic long-term surface circulation pattern in the northern subbasins. Even today, there are considerable research gaps and uncertainties in knowledge. For example, observational data still has insufficient coverage, descriptions of processes in numerical models need tuning to the conditions of the Baltic Sea and model forcing data can have large uncertainties. With modern analysis methods and new observational datasets, gaps in the current understanding of Baltic Sea circulation patterns can be identified and analyzed. In this thesis, circulation dynamics were investigated in the northern Baltic Sea with numerical hydrodynamic modelling. The complex dynamics of the brackish Baltic Sea put hydrodynamic models to the test. Several different model configurations were applied and developed further, including a high-resolution configuration of the NEMO (Nucleus for European Modelling of the Ocean) model for the Gulf of Finland (GoF). Methods such as machine learning algorithms, new data from automated observational platforms and ensemble forecasting were applied. Circulation patterns in the GoF were investigated with the self-organizing map (SOM) algorithm. The cyclonic circulation pattern visible in earlier studies was not seen in the GoF in the overall means calculated from the model results for the studied periods 2007–2013 and 2012–2014. SOM analysis of currents in the GoF revealed that they are highly variable and complex. There was significant inter-annual and intra-annual variability in the circulation patterns. A connection between wind forcing and the characteristic patterns from the SOM analysis was found. Analysis emphasized the estuary-like nature of the GoF. The results showed that circulation in the GoF changes rapidly between normal estuarine circulation and reverse estuarine circulation. The fact that the dominant wind direction is from the southwest supports this reversal. The cyclonic mean circulation pattern seems to appear only if the normal estuarine circulation is common enough for it to emerge during the averaging period. Small changes to wind direction distribution can have a significant effect on the longterm circulation patterns. Upwelling events on a timescale of days to weeks can also affect long-term circulation patterns. The NEMO model proved to be a suitable tool for the studies of circulation in the northern sub-basins of the Baltic Sea. It quality seems comparable to other models commonly used in the GoF and Bothnian Sea. The GoF is still a challenging environment for circulation modelling. Salinity gradients in the GoF are still not reproduced in a satisfactory manner by the models. More information is required on how well the models reproduce true circulation patterns and, for example, upwelling frequency and intensity. The need for accurate model inputs, especially wind forcing, was demonstrated. The value of observations (especially the better spatial coverage of current measurements) was once again emphasized. Furthermore, the results highlighted that care must be taken to make sure that models and observations represent the same thing when they are compared.
  • Välisuo, Ilona (2018)
    Finnish Meteorological Institute Contributions 148
    Polar ice sheets, glaciers, and ice shelves, referred to as land ice in this document, are under transition in the changing climate. Observations show that glaciers have retreated and melt water discharge from land ice has increased together with the warming climate. Decreasing volume of land ice is reflected to the whole Earth system via changes in surface radiation balance, sea level rise, and water balance in inland watersheds. Warming and melting land ice creates positive feedback loops that further increase melting. The study of polar land ice in changing climate is challenging due to lack of observations from the remote areas. Large interannual variability of climate, rapid changes in temperature and ice conditions, and short observational timeseries further complicate the research. This Ph.D. thesis concentrates on the aspects of melting land ice in the polar regions. The focus is on the interannual variability of surface melt and weather conditions on two of the Antarctic Peninsula Ice Shelves (Larsen C and Wilkins) and the Greenland Ice Sheet. Surface melt is addressed through the surface energy balance and other direct measures of melt. Furthermore, the changes in surface accumulation and ablation patterns have been modelled on a small Arctic valley glacier, Midtre Lovénbreen. This modelling study presents for the first time a method that allows to produce high resolution maps of accumulation and ablation, using only a glacier flow model and the digital elevation models of the glacier surface. Surface energy balance controls the melt of snow and ice. The effect of atmospheric moisture or clouds on the surface energy balance was important in the Antarctica Peninsula region and on the Greenland Ice Sheet. Cloud cover fraction was related to the wintertime surface net heat flux on Larsen C Ice Shelf. A multi-regression model, including the cloud cover fraction as one of the explanatory variables, explained up to 80% of the interannual variation of the surface net heat flux in June-August. On the Greenland Ice Sheet the vertically integrated total column water was positively correlated with the summertime surface melt. Local near surface winds (at 10 m height above ground level) were important in explaining the surface net heat flux on Larsen C Ice Shelf in summer, autumn, and winter. In Greenland, the wind components correlated locally with the number of melt days. The positive correlation was likely related to the adiabatic heating of descending air on the lee side of the ice sheet and, in other locations, to the advection of warm air from lower latitudes. The number of melt days on the Greenland Ice Sheet were also correlated with positive North Atlantic Oscillation Index and Greenland Blocking Index, indicating that these large scale patterns contribute in creating conditions that favour melt. The large scale atmospheric conditions that increase humidity or advect warm air to the polar regions are likely to increase surface melt in Greenland or Antarctic Peninsula region. Nevertheless, explaining the high resolution melt patterns requires understanding of the local conditions and topographic features. This Ph.D. thesis contributes in understanding local surface melt as part of the large scale climate system.