Ilmatieteen laitoksen omat julkaisut - FMI publications: Recent submissions

Now showing items 1-20 of 131
  • 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.
  • Ruuhela, Reija (2018)
    Finnish Meteorological Insitute Contributions 147
    Human beings are able to adapt to their climatic normal conditions, but weather extremes may pose a substantial health risks. The aims of this dissertation were to model the dependence of all-cause mortality on thermal conditions in Finland, and to assess changes in the relationship over the decades and regional differences in the relationships between hospital districts. Another aim was to assess impacts of weather and climate on committed and attempted suicides Finland. Various methods were applied in these studies. Time series of all-cause mortality in three age groups in Helsinki-Uusimaa hospital district were made stationary, and thus the weather impacts were comparable over the 43-year long time period regardless of changes in population and life-expectancy. The increase in relative mortality due to hot extreme was more than due to cold extreme, when compared to seasonally varying expected mortality. However, a decrease in relative mortality in extreme temperatures over the decades was found in all age-groups, even among the 75 years and older, indicating decreased sensitivity to thermal stress in the population. Regional differences in temperature‒mortality relationships between 21 hospital districts were studied using distributed lag non-linear models (DLNM), and the differences were assessed by meta-regression with selected climatic and sociodemographic covariates. Regional differences in the relationships were not statistically significant indicating that the same temperature-mortality relationship can be applied in different parts of the country. On the other hand, the meta-regression suggested that the morbidity indices and population in the hospital districts could explain part of the small heterogeneity in the temperature‒mortality relationships. The study on committed suicides on the basis of 33-year long time series showed a significant negative association between suicides and solar radiation in the period from November to March, thus, a lack of solar radiation would increase suicide risk in winter. Men appeared to be more sensitive to variation in solar radiation than women. The study on weather dependence of attempted suicides in Helsinki on the basis of two shorter periods showed another difference between genders. The risk of suicide attempts of men increased with decreasing atmospheric pressure, while the risk of suicide attempts of women increased with increasing pressure. The outcomes of this thesis can be utilized e.g. in preparedness to weather extremes in health sector and in further studies on impacts of climate change on human health.
  • Thölix, Laura (2018)
    Finnish Meteorological Insitute Contributions 146
    Ozone and water vapour are important trace gases in the atmosphere, where both play an important role in radiative and chemical processes. Ozone protects the Earth's biosphere, humans and materials from the harmful ultraviolet (UV) radiation. The distributions and changes of ozone and water vapour are thus important to understand. Restrictions on the production and use of ozone depleting substances (ODS) within the Montreal Protocol have stopped the growth of the ozone loss, even signs of recovery of the ozone layer have been seen. However, many ODSs are long lived in the atmosphere and it will take decades before they are removed. Stratospheric water vapour influences the polar ozone loss by controlling the formation of polar stratospheric clouds (PSC). The climate change will cool the stratosphere, which could favour the formation of PSCs. This could cause significant ozone depletion despite the lower chlorine loadings in the future stratosphere. Atmospheric models are needed for studying these phenomena, because the number of observations is limited. Also the prediction of future ozone loss requires models. In this study simulations of the middle atmosphere have been made using the FinROSE chemistry transport model (FinROSE-CTM). It is an off-line 3-dimensional model, covering the altitude range of ca. 10–80 km, including the stratosphere. The model can be used for short term case studies, as well as for decadal simulations. The FinROSE-CTM needs pre-calculated winds, temperature and surface pressure, and then calculates the chemistry and transport using the meteorology. In this study ECMWF reanalysis data and climate model data have been used. Model results have been compared to ground based and satellite observations, and the model has been shown to be suitable for polar stratospheric ozone and water vapour studies. When running the model with climate model data also future conditions can be predicted. Both observations and simulations show an increase in the water vapour concentration in the Arctic stratosphere after 2006, but around 2012 the concentration started to decrease. Model calculations suggest that this increase in water vapour is mostly explained by transport-related processes. The increase in water vapour in the presence of the low winter temperatures in the Arctic stratosphere led to more frequent occurrence of ICE PSCs in the Arctic vortex. In a recent study, we studied the effect of changes in the water vapour concentration in the tropical tropopause on Arctic ozone depletion. A change in the tropical tropopause water vapour concentration resulted in a corresponding change in the Arctic stratosphere. We found that the impact of water vapour changes on ozone loss in the Arctic polar vortex depends on the meteorological conditions. The strongest effect was in intermediately cold conditions, when added water vapour resulted in more ozone loss due to the additional PSCs and associated chlorine activation on their surface. The effect was less pronounced in cold winters because cold conditions persisted long enough for a nearly complete chlorine activation even with observed water vapour. The results show that the simulated water vapour concentration in the tropical tropopause has a significant impact on the Arctic ozone loss and deserves attention, and therefore needs to be well simulated in order to improve future projections of ozone layer recovery.
  • Kontu, Anna (Finnish Meteorological Institute, 2018)
    Finnish Meteorological Insitute Contributions 144
    Remote sensing using microwave radiometry is an acknowledged method for monitoring various environmental processes in the cryosphere, atmosphere, soil, vegetation and oceans. Several decades long time series of spaceborne passive microwave observations can be used to detect trends relating to climate change, while present measurements provide information on the current state of the environment. Unlike optical wavelengths, microwaves are mostly insensitive to atmospheric and lighting conditions and are therefore suitable for monitoring seasonal snow in the Arctic. One of the major challenges in the utilization of spaceborne passive microwave observations for snow measurements is the poor spatial resolution of instruments. The interpretation of measurements over heterogeneous areas requires sophisticated microwave emission models relating the measured parameters to physical properties of snow, vegetation and the subnivean layer. Especially the high contrast in the electrical properties of soil and liquid water introduces inaccuracies in the retrieved parameters close to coastlines, lakes and wetlands, if the subnivean water bodies are not accounted for in the algorithm. The first focus point of this thesis is the modelling of brightness temperature of ice- and snow-covered water bodies and their differences from snow-covered forested and open land areas. Methods for modelling the microwave signatures of water bodies and for using that information in the retrieval of snow parameters from passive microwave measurements are presented in this thesis. The second focus point is the effect of snow microstructure on its microwave signature. Even small changes in the size of scattering particles, snow grains, modify the measured brightness temperature notably. The coupling of different modelled and measured snow microstructural parameters with a microwave snow emission model and the application of those parameters in the retrieval of snow parameters from remote sensing data are studied.
  • Gregow, Erik (2018)
    Finnish Meteorological Institute Contributions 142
    Observations have been and are an important part of today's meteorological developments. Surface observations are very useful as they are, providing weather information for a point location. ough they do not give much information, if any, on what happens between the stations across a larger area. With models one can create an analysis of the meteorological situation, i.e. calculate and estimate what happens between these fixed observation points. Remote-sensing data, such as radar and satellite, are being processed and the output is given over a domain as an analysed product of their measurements. For example, radar gives a plot of where the rain is located, i.e. an analysis of the current precipitation. With a series of radar images, a human (subjectively) or a computer objectively) can process this information to estimate where the rain will move and be located within the next few minutes (even hours), i.e. a short forecast also called "nowcast". is applies to some extent also for other observations, such as satellite data (cloud propagation). But for most quantities (such as temperature, wind, etc) it is significantly harder to make such a nowcast, since these are influenced by many other factors and there is no linear development of them. Therefore, there are forecast models that solve physical and dynamic equations, so that one can estimate the future weather for the coming hours and days. A prerequisite for generating a forecast of high quality is to capture the initial weather conditions as best as possible. This is done using observations and they are introduced into the forecast model through different techniques, where the model creates its own analysis as the initial step. There remain problems since forecast models often are affected by physical disagreements, as the dynamic conditions are not in balance. This results in the model having a spin-up effect, where the meteorological quantities are not yet in balance with each other and the resulting weather conditions are not always reliable during the first hours. Hence, a lot of research is spent on how to reduce this spin-up effect and on the use of nowcast models, in order to deliver the best model results for the first few hours of the forecast period. In this dissertation, the research work has been to improve the meteorological analysis, algorithms and functionality, using the Local Analysis and Prediction System (LAPS) model. Different kinds of observations were used and their interdependencies have been studied, in order to combine and merge information from variousinstruments. Primarily focus has been to improve the estimation of precipitation accumulation and meteorological quantities that affect wind energy. The LAPS developments have been used for several end-users and nowcasting applications, and experimentally as initial conditions for forecast modelling. The studies have been concentrated on Finland and nearby sea areas, with the available datasets for this domain. By combining surface-station measurements, radar and lightning information, one can improve the precipitation-amount estimations. The use of lightning data further improves the estimates and gives the advantage of having additional data outside radar coverage, which can potentially be very useful for example over sea areas. In addition, the improved LAPS analyses (cloud-related quantities) and a newly developed model (LOWICE), calculating the electricity production during wintertime (taking into account the icing of wind turbine rotor blades which reduces efficiency), have shown good results.
  • Mäkelä, Antti; Laurila, Terhi K.; Haapalainen, Jussi; Halabi, Tuomas (Finnish Meteorological Institute, 2017)
    Raportteja - Rapporter - Reports 2017:8
    Ilmatieteen laitos on koonnut ja julkaissut salamanlaskijoiden havainnot vuosilta 1960–1997. Vuodesta 1998 lähtien kaikki järjestelmälliset maasalamahavainnot perustuvat salamanpaikantimeen, jonka nykyinen malli aloitti toimintansa elokuussa 1997. Se käsitti 2016 kahdeksan anturia, pohjoisin Lokassa. Vuodesta 2002 mukana ovat olleet lisäksi Norjan ja Ruotsin anturit, joiden ansiosta koko Lappi on katettu ja suorituskyky on parantunut myös muualla Suomessa, sekä yksi anturi Virossa (mukaan vuonna 2005) ja kolme anturia Liettuassa (mukaan 2014). Laitteisto paikantaa maasalamoista erikseen jokaisen osaiskun ja ryhmittelee ne kokonaisiksi salamoiksi. Paikannettu salama voi sisältää 1-15 iskua; keskiarvo Suomessa on vajaa kaksi iskua/salama. Tilastoinnin pohjana käytetään salama- eikä iskumääriä, koska salama on ilmastollisesti edustavampi suure. Kesän 2016 aikana paikannettiin Suomen noin 115 000 maasalamaa, joka on hieman alle keskimääräisen (138 000). Suurin osa salamoista esiintyi heinäkuussa (80 000), ja touko-, kesä- ja elokuussa määrät olivat noin puolet keskimääräisestä.
  • von Lerber, Annakaisa (Finnish Meteorological Institute, 2018)
    Finnish Meteorological Institute Contributions 143
    Globally, snow influences Earth and its ecosystems in several ways by having a significant impact on, e.g., climate and weather, Earth radiation balance, hydrology, and societal infrastructures. In mountainous regions and at high latitudes snowfall is vital in providing freshwater resources by accumulating water within the snowpack and releasing the water during the warm summer season. Snowfall also has an impact on transportation services, both in aviation and road maintenance. Remote sensing instrumentation, such as radars and radiometers, provide the needed temporal and spatial coverage for monitoring precipitation globally and on regional scales. In microwave remote sensing, the quantitative precipitation estimation is based on the assumed relations between the electromagnetic and physical properties of hydrometeors. To determine these relations for solid winter precipitation is challenging. Snow particles have an irregular structure, and their properties evolve continuously due to microphysical processes that take place aloft. Hence also the scattering properties, which are dependent on the size, shape, and dielectric permittivity of the hydrometeors, are changing. In this thesis, the microphysical properties of snowfall are studied with ground-based measurements, and the changes in prevailing snow particle characteristics are linked to remote sensing observations. Detailed ground observations from heavily rimed snow particles to openstructured low-density snowflakes are shown to be connected to collocated triple-frequency signatures. As a part of this work, two methods are implemented to retrieve mass estimates for an ensemble of snow particles combining observations of a video-disdrometer and a precipitation gauge. The changes in the retrieved mass-dimensional relations are shown to correspond to microphysical growth processes. The dependence of the C-band weather radar observations on the microphysical properties of snow is investigated and parametrized. The results apply to improve the accuracy of the radar-based snowfall estimation, and the developed methodology also provides uncertainties of the estimates. Furthermore, the created data set is utilized to validate space-borne snowfall measurements. This work demonstrates that the C-band weather radar signal propagating through a low melting layer can significantly be attenuated by the melting snow particles. The expected modeled attenuation is parametrized according to microphysical properties of snow at the top of the melting layer.
  • Salmi, Jatta; Laukkanen, Emmi; Latikka, Jenni (Finnish Meteorological Institute, 2017)
    Raportteja - Rapporter - Reports 2017:7
    Tämän työn tavoitteena oli määrittää yksinkertainen menetelmä, jolla voidaan mitoittaa pienille energiantuotantoyksiköille ilmanlaadun kannalta riittävä piipunkorkeus. Työssä arvioitiin päästöjen leviämismallilaskelmien avulla polttoaineteholtaan 1–5 MW kokoisten uusien energiantuotantoyksiköiden ilmanlaatuvaikutuksia ja selvitettiin niille sopivaa piipunkorkeutta. Leviämismallitarkastelut tehtiin erikseen seitsemän eri polttoaineen rikkidioksidi-, typenoksidi- ja hiukkaspäästöille. Polttoaineet olivat turve, puupelletit, kokopuuhake, bioöljy, raskas polttoöljy, kevyt polttoöljy ja maakaasu. Raskaasta polttoöljystä tarkasteltiin erikseen öljyä, joka sisältää 0,1 paino-% rikkiä ja öljyä, joka sisältää 0,2 paino-% rikkiä. Laskelmissa tarkasteltiin erikseen polttoaineteholtaan 1, 3 ja 5 MW kokoisten energiantuotantoyksiköiden päästöjen aiheuttamia ulkoilman pitoisuuksia laitosten ympäristössä. Laskelmissa käytettiin lähtötietoja, jotka parhaiten kuvaavat keskimääräisiä olosuhteita tyypillisissä tämän kokoisissa energiantuotantoyksiköissä. Päästöjen leviämislaskelmat tehtiin Ilmatieteen laitoksella kehitetyllä leviämismallilla UDM-FMI. Tarkastelujen avulla muodostettiin polttoainekohtaiset mitoituskäyrät polttoaineteholtaan 1–5 MW:n uusien energiantuotantoyksiköiden piipunkorkeuksille tasaisessa maastossa. Lisäksi tarkasteltiin erikseen läheisen maastoesteen tai lähirakennuksen vaikutusta syntyviin pitoisuuksiin ja määritettiin esteen vaikutuksesta piipunkorkeuteen tarvittava lisäkorkeus.
  • Nuottokari, Jaakko (Finnish Meteorological Institute, 2017)
    Finnish Meteorological Institute Contributions 137,
    Meteorological information and services supporting the various operations of air transport enable a safe, efficient and cost-effective operating environment for airspace users, air navigation service providers and air traffic management. The continuing pursuit towards an improved quality of observation, forecasting and decision support services is driven by an increasingly weather-sensitive society and growing impacts of hazardous weather events. This thesis provides an overview of the field of aeronautical meteorological research by introducing the organisations involved, global and regional strategies, impacts of weather on air transport, current state of the art in meteorological research and decision support systems serving air transport needs with a view of where the field should evolve next. This thesis is an attempt to highlight key findings and point the reader towards the direction of further research on the given topics. Research supporting air transport operations with the optimal use of weather information is a specialized field where advances are led by the needs of various airspace users. Research institutions for example in the United States have contributed greatly due to the severe weather impacts experienced by the National Airspace System (NAS), the ability of the Federal Aviation Aministration (FAA) and the National Oceanic and Atmospheric Administration (NOAA) to direct long-term funding to solve specific aviation-related research questions. The creation and maintenance of long-lived teams of scientists and engineers working together to produce end-toend solutions that meet the needs of the aviation industry is the key to improving meteorological information to aviation users while university research is typically shorter duration and typical does not result in operational systems. From a global perspective, research is yet to be organised in a way that would contribute to solving aviation issues beyond single research projects and/or programmes. There is a lot more the scientific community could do to develop tailored information to decision support systems used by the aviation sector, but it would require systematic investments and the establishment of research groups focusing on the applied science questions and technology transfer. This thesis provides an overview of recommended decision support system development topics with an outline of potential milestones.
  • Tsuruta, Aki (Finnish Meteorological Institute, 2017)
    Finnish Meteorological Institute Contributions 141
    Ensemble Kalman filter (EnKF) is a useful Bayesian inverse modelling method to make inference of the states of interest from observations, especially in non-linear systems with a large number of states to be estimated. This thesis presents an application of EnKF in estimation of global and regional methane budgets, where methane fluxes are inferred from atmospheric methane concentration observations. The modelling system here requires a highly non-linear atmospheric transport model to convert the state space on to the observation space, and an optimization in both spatial and temporal dimensions is desired. Methane is an important greenhouse gas, strongly influenced by anthropogenic activities, whose atmospheric concentration increased more than twice since pre-industrial times. Although its source and sink processes have been studied extensively, the mechanisms behind the increase in the 21st century atmospheric methane concentrations are still not fully understood. In this thesis, contributions of anthropogenic and natural sources to the increase in the atmospheric methane concentrations are studied by estimating the global and regional methane fluxes from anthropogenic and biospheric sources for the 21st century using an EnKF based data assimilation system (CarbonTracker Europe-CH4; CTE-CH4). The model was evaluated using assimilated in situ atmospheric concentration observations and various non-assimilated observations, and the model sensitivity to several setups and inputs was examined to assess the consistency of the model estimates. The key findings of this thesis include: 1) large enough ensemble size, appropriate prior error covariance, and good observation coverage are important to obtain consistent and reliable estimates, 2) CTE-CH4 was able to identify the locations and sources of the emissions that possibly contribute significantly to the increase in the atmospheric concentrations after 2007 (the Tropical and extra Tropical anthropogenic emissions), 3) Europe was found to have an insignificant or negative influence on the increase in the atmospheric CH4 concentrations in the 21st century, 4) CTE-CH4 was able to produce flux estimates that are generally consistent with various observations, but 5) the estimated fluxes are still sensitive to the number of parameters, atmospheric transport and spatial distribution of the prior fluxes.
  • Svensson, Jonas (Finnish Meteorological Institute, 2017)
    Finnish Meteorological Institute Contributions 140
    Snow and ice are essential components of the Earth system, modulating the energy budget by reflecting sunlight back into the atmosphere, and through its importance in the hydrological cycle by being a reservoir for fresh water. Light-absorbing impurities (LAI), such as black carbon (BC) and mineral dust (MD), have a unique role in influencing the reflectance of the cryosphere. Deposition of the anthropogenic and natural LAI constituents onto these bright surfaces initiates powerful albedo feedbacks that will accelerate melt. This is important globally, but especially for regions such as the Arctic and the Himalaya. In this thesis, observations from both ambient and laboratory experiments are presented. The overarching research goal has been to better understand the climatic effect of LAI on snow. More specifically, an emphasis has been placed on exploring the process-level interactions between LAI and snow, which will enable better comprehension of LAI affecting the cryosphere. Key findings in this thesis involves the investigations on the horizontal variability of BC concentrations in the surface snow that indicate a larger variability on the order of meter scale at a pristine Arctic site compared to a polluted site nearby a major urban area. In outdoor experiments, where LAI were used to artificially dope natural snow surfaces, the snow albedo was observed to decrease following LAI deposition. The albedo decrease was on the same order as in situ measurements of LAI and albedo conducted elsewhere. As snow melted during the experiment, the snow density was observed to decrease with increasing LAI concentration, while this effect was not observed in non-melting snow. The water retention capacity in melting snow is likely to be decreased by the presence of LAI. Measurements examining the absorption of BC indicate that BC particles in the snow have less absorbing potential compared to BC particles generated in the laboratory. The LAI content of snow pit investigations from two glaciers in the Sunderdhunga valley, northern India, an area not previously examined for LAI, presented high BC and MD content, affecting the radiative balance of the glacier snow. At different points, MD may be greater than BC in absorbing light at the snow surface. A continued monitoring of LAI in the cryosphere, both on the detailed scale explored here, as well as on the larger modelling perspective is needed in order to understand the overall response of the cryosphere to climate change.
  • Päivärinta, Sanna-mari (Finnish Meteorological Institute, 2017)
    Finnish Meteorological Institute Contributions 136
    Odd nitrogen (NOx = N + NO + NO2) in the polar regions is mainly produced in the upper atmosphere through ionization processes by solar extreme ultraviolet radiation, soft X-rays and high energy particles originating from the space. During periods of high geomagnetic activity, normally close to the solar maximum, energetic particle precipitation (EPP) provides an in-situ source of NOx also in the middle atmosphere. Understanding the behaviour of NOx in the middle atmosphere is of great importance due to its capability to act as a catalyst in chemical reaction cycles destroying ozone in the stratosphere. This work considers EPP in the form of solar proton events (SPEs). Atmospheric dynamics play an important role in determining the distributions of long-lived trace gases in the middle atmosphere. The main loss mechanism for NOx is photolysis at the upper stratospheric and mesospheric altitudes, leading to long photochemical lifetime of NOx during the dark polar winter. NOx in the middle atmosphere, also if produced in-situ due to SPEs, is therefore affected by atmospheric dynamics, and transported from the mesosphere-lower hermosphere (MLT) region down to the middle atmosphere. This descent phenomenon can be intensified in the aftermath of sudden stratospheric warmings (SSWs), which are dynamical phenomena able to affect a wide range of altitudes in the Northern polar region atmosphere. The enhanced downward transport of NOx can thus strengthen the NOx-ozone connection in the stratosphere. In this work we used both space born observations from several satellite instruments and a chemistry transport model in the examination of the SSW and SPE caused effects in the stratosphere and mesosphere. The scientific objectives of this work were to find out the individual and combined effects of SSWs and SPEs on the NOx and ozone balance in the Northern middle atmosphere, and assess the relative contributions of dynamics (SSWs) and in-situ production of NOx (SPEs) on ozone in the stratosphere. The results showed dramatic increases in NOx in the middle atmosphere, even by a factor of 50, following both periods of enhanced NOx descent in connection with SSWs and in-situ production of NOx due to SPEs. A clear long-term (order of months) decrease in stratospheric ozone (10-90 %), coinciding with the enhanced amounts of NOx, was evident and affected mostly by dynamics in the upper stratosphere. The results of this work emphasize the importance of in-situ production of NOx (SPEs) on the ozone balance in the upper stratosphere, but also the key role of dynamics (SSWs) in transporting the SPE effect to even lower altitudes and its capability to strengthen the effect.
  • Komppula, Birgitta; Waldén, Jari; Lusa, Kaisa; Kyllönen, Katriina; Saari, Helena; Vestenius, Mika; Salmi, Jatta; Latikka, Jenni (Finnish Meteorological Institute, 2017)
    Raportteja - Rapporter - Reports 2017:6
    Suomen ilmanlaadun seurantaa säätelevät suurelta osin EU:n ilmanlaatua koskevat direktiivit. Ilman epäpuhtauksien pitoisuuksia säädellään sitovien raja-arvojen ja tavoitearvojen avulla. Myös kansalliset ohjearvot ovat edelleen voimassa ja niitä käytetään suunnittelun tukena, mutta niiden merkitys on vähenemässä. Raja-arvoja valvoviksi asemiksi kutsutaan niitä ilmanlaadun mittausasemia, jotka täyttävät ilmanlaatudirektiivien kriteerit ja joiden pitoisuustiedot toimitetaan EU:lle. Rajaarvopitoisuuksia valvovien mittausasemien lisäksi ilmanlaatua seurataan mittausverkoissa laajalti erilaisista paikallisista tarpeista, mikä on ollut aikanaan lähtökohta useimpien ilmanlaatumittausten aloittamiselle. Ilmanlaatua seurataan ensisijaisesti hyvän ilmanlaadun turvaamiseksi paikallisille asukkaille ja ympäristölle. Ilmanlaatua mitataan lisäksi muun muassa yksittäisten päästölähteiden vaikutusten arvioimiseksi, asukkaiden valitusten vuoksi, ympäristölupaehtojen täyttämiseksi sekä jatkuvan ilmanlaadun seurannan tarvetta arvioitaessa. Tämä ohje koskee ilmanlaadun mittaamista osana ilmanlaadun seurantaa. Ohjeessa käsitellään ilmanlaatulainsäädäntöä, mittaustarpeen arviointia, mittausten suunnittelua, tekemistä ja laadunvarmennustoimenpiteitä, laatujärjestelmän sisältöä, raportointia sekä tiedottamista. Ohjeen tarkoituksena on kehittää mittausten laatua, luotettavuutta, edustavuutta ja vertailtavuutta sekä luoda edellytyksiä ilmanlaadun mittaustulosten monipuoliselle hyödyntämiselle. Ilmatieteen laitos päivitti ilmanlaadun mittausohjetta edellisen kerran vuonna 2004 ja nyt mittausohjetta on edelleen laajennettu ja päivitetty ajan tasalle.
  • Salminen, Miia (Finnish Meteorological Institute, 2017)
    Finnish Meteorological Institute Contributions 139
    Monitoring of snow cover in northern hemisphere is highly important for climate research and for operational activities, such as those related to hydrology and weather forecasting. The appearance and melting of seasonal snow cover dominate the hydrological and climatic patterns in the boreal and arctic regions. Spatial variability (in particular during the spring and autumn transition months) and long-term trends in global snow cover distribution are strongly interconnected to changes in Earth System (ES). Satellite data based estimates on snow cover extent are utilized e.g. in near-real-time hydrological forecasting, water resource management and to construct long-term Climate Data Records (CDRs) essential for climate research. Information on the quantitative reliability of snow cover monitoring is urgently needed by these different applications as the usefulness of satellite data based results is strongly dependent on the quality of the interpretation. This doctoral dissertation investigates the factors affecting the reliability of snow cover monitoring using optical satellite data and focuses on boreal regions (zone characterized by seasonal snow cover). Based on the analysis of different factors relevant to snow mapping performance, the work introduces a methodology to assess the uncertainty of snow cover extent estimates, focusing on the retrieval of fractional snow cover (within a pixel) during the spring melt period. The results demonstrate that optical remote sensing is well suited for determining snow extent in the melting season and that the characterizing the uncertainty in snow estimates facilitates the improvement of the snow mapping algorithms. The overall message is that using a versatile accuracy analysis it is possible to develop uncertainty estimates for the optical remote sensing of snow cover, which is a considerable advance in remote sensing. The results of this work can also be utilized in the development of other interpretation algorithms. This thesis consists of five articles predominantly dealing with quantitative data analysis, while the summary chapter synthesizes the results mainly in the algorithm accuracy point of view. The first four articles determine the reflectance characteristics essential for the forward and inverse modeling of boreal landscapes (forward model describes the observations as a function of the investigated variable). The effects of snow, snow-free ground and boreal forest canopy on the observed satellite scene reflectance are specified. The effects of all the error components are clarified in the fifth article and a novel experimental method to analyze and quantify the amount of uncertainty is presented. The five articles employ different remote sensing and ground truth data sets measured and/or analyzed for this research, covering the region of Finland and also applied to boreal forest region in northern Europe.