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High frequency distributed temperature sensing and eddy covariance data observed at Hyytiälä measurement station during summer 2019
No full textThis record contains high frequency distributed temperature sensing and eddy covariance data observed at Hyytiälä measurement station and used in the following study:
Peltola, O., Aurela, M., Launiainen, S. and Katul, G. (2022), Probing the eddy size and its effective mixing length in stably stratified roughness sublayer flows. Q J R Meteorol Soc. Accepted Author Manuscript. https://doi.org/10.1002/qj.4386
Hyytiala_DTS_mm_yyyy.zip
These zip-files contain continuous high frequency potential temperature profiles measured along the Hyytiälä127-metre tall mast. See more information on the data in the netCDF-file attributes and on the measurement setup in the related scientific article.
EC27.zip
This zip-file contains high frequency data from an eddy covariance measurement setup located at 27 m height in the measurement height. See more information in EC27_readme.txt and on the measurement setup in the related scientific article.
EC67.zip
This zip-file contains high frequency data from an eddy covariance measurement setup located at 68 m height in the measurement height. See more information in EC67_readme.txt and on the measurement setup in the related scientific article.
codes_Hyytiala.zip
Matlab codes to produce similar figure as Fig. 2 in the abovementioned article
Latvusprosessit, aine ja energiavuot ja mikroilmasto mäntymetsässä
Full text linkInteraction between forests and the atmosphere occurs by radiative and turbulent transport. The fluxes of energy and mass between surface and the atmosphere directly influence the properties of the lower atmosphere and in longer time scales the global climate. Boreal forest ecosystems are central in the global climate system, and its responses to human activities, because they are significant sources and sinks of greenhouse gases and of aerosol particles. The aim of the present work was to improve our understanding on the existing interplay between biologically active canopy, microenvironment and turbulent flow and quantify. In specific, the aim was to quantify the contribution of different canopy layers to whole forest fluxes. For this purpose, long-term micrometeorological and ecological measurements made in a Scots pine (Pinus sylvestris) forest at SMEAR II research station in Southern Finland were used.
The properties of turbulent flow are strongly modified by the interaction between the canopy elements: momentum is efficiently absorbed in the upper layers of the canopy, mean wind speed and turbulence intensities decrease rapidly towards the forest floor and power spectra is modulated by spectral short-cut . In the relative open forest, diabatic stability above the canopy explained much of the changes in velocity statistics within the canopy except in strongly stable stratification. Large eddies, ranging from tens to hundred meters in size, were responsible for the major fraction of turbulent transport between a forest and the atmosphere. Because of this, the eddy-covariance (EC) method proved to be successful for measuring energy and mass exchange inside a forest canopy with exception of strongly stable conditions. Vertical variations of within canopy microclimate, light attenuation in particular, affect strongly the assimilation and transpiration rates. According to model simulations, assimilation rate decreases with height more rapidly than stomatal conductance (gs) and transpiration and, consequently, the vertical source-sink distributions for carbon dioxide (CO2) and water vapor (H2O) diverge. Upscaling from a shoot scale to canopy scale was found to be sensitive to chosen stomatal control description. The upscaled canopy level CO2 fluxes can vary as much as 15 % and H2O fluxes 30 % even if the gs models are calibrated against same leaf-level dataset.
A pine forest has distinct overstory and understory layers, which both contribute significantly to canopy scale fluxes. The forest floor vegetation and soil accounted between 18 and 25 % of evapotranspiration and between 10 and 20 % of sensible heat exchange. Forest floor was also an important deposition surface for aerosol particles; between 10 and 35 % of dry deposition of particles within size range 10 30 nm occurred there. Because of the northern latitudes, seasonal cycle of climatic factors strongly influence the surface fluxes. Besides the seasonal constraints, partitioning of available energy to sensible and latent heat depends, through stomatal control, on the physiological state of the vegetation. In spring, available energy is consumed mainly as sensible heat and latent heat flux peaked about two months later, in July August. On the other hand, annual evapotranspiration remains rather stable over range of environmental conditions and thus any increase of accumulated radiation affects primarily the sensible heat exchange. Finally, autumn temperature had strong effect on ecosystem respiration but its influence on photosynthetic CO2 uptake was restricted by low radiation levels. Therefore, the projected autumn warming in the coming decades will presumably reduce the positive effects of earlier spring recovery in terms of carbon uptake potential of boreal forests.Maanpinnan ja ilmakehän välinen massan ja energian vaihto vaikuttaa suoraan ilmakehän alimman kerroksen, rajakerroksen, paikallisiin ominaisuuksiin ja pitemmällä aikajänteellä globaaliin ilmastoon. Boreaaliset metsät ovat keskeinen osa ilmastosysteemiä mm. merkittävinä hiilivarastoina ja aerosolihiukkasten lähteinä. Työssä tarkasteltiin latvuston rakenteen vaikutusta turbulenttisen, kaoottisen ja satunnaisen, virtauskentän ominaisuuksiin metsän sisällä sekä mikroilmaston ja latvusprosessien kuten fotosynteesin, kasvien lävitse tapahtuvan haihdunnan (transpiraatio) sekä aerosolihiukkasten deposition välisiä yhteyksiä. Erityisenä tavoitteena oli selvittää miten metsikön eri osat vaikuttavat ja osallistuvat koko metsikön ja ilmakehän välisiin vuorovaikutusprosesseihin. Työssä hyödynnettiin mikrometeorologisia mittauksia Helsingin Yliopiston Hyytiälän (Juupajoki) mittausasemalta (SMEAR II). Energian ja aineiden, kuten kasvihuonekaasujen, kuljetus metsän ja ilmakehän välillä tapahtuu pääasiassa säteilynä sekä turbulenssin ajamana. Turbulenttisen virtauksen ominaisuuksien tunteminen latvuston sisällä onkin tärkeää tutkittaessa ja mallinnettaessa näitä ainevirtoja. Työssä havaittiin virtauksen ominaisuuksien latvuksen sisällä vaihtelevan voimakkaasti pystysuunnassa mutta riippuvan kvalitatiivisesti metsän yllä vallitsevasta kerrostuneisuudesta. Tutkitussa tyypillistä kasvatusmännikköä edustavassa metsässä turbulenssi on suhteellisen voimakasta pois lukien öiset ja talviset tilanteet, jolloin rajakerros on voimakkaan stabiilisti kerrostunut. Voimakkaan sekoittumisen vuoksi pystysuuntaiset pitoisuuserot (CO2, kosteus, lämpötila) ilmassa pysyvät pieninä metsän sisällä. Mikroilmaston ja latvusrakenteen vaikutuksia fotosynteesin ja transpiraation voimakkuuteen latvuksen eri osissa selvitettiin mallintamalla metsikkö yksiulotteisena. Mallitulokset tukevat käsitystä että pystysuuntaiset muutokset fotosynteesinopeudessa ja transpiraation voimakkuudessa aiheutuvat ensisijassa valon pystyjakaumasta latvuston sisällä ja muitten ympäristötekijöiden pystyvaihtelu on vähemmän merkityksellistä. Työssä havaittiin metsikkötason fotosynteesin ja erityisesti transpiraation olevan huomattavan herkkiä erilaisille verso- tai lehtitason ilmarakosäätömallille. Mikrometeorologisten vuonmittausten ja mallitulosten perusteella tyypillisen kasvatusmännikön fotosynteesistä noin 10 % ja haihdunnasta noin 20 25 % on peräisin aluskasvillisuudesta. Vastaavasti noin 10 30 % aerosolihiukkasten kuivadepositiosta tapahtuu latvuston alapuolelle. Pohjoisilla leveysasteilla ympäristötekijöiden vuodenaikaisvaihtelu on voimakasta, mikä luonnollisesti heijastuu myös ekosysteemien toimintaan. Tästä syystä myös energia- ja ainevirtojen suuruudet ja suunta metsän ja ilmakehän välillä vaihtelevat vuodenajoittain. Vastaavasti eri ympäristötekijöiden rooli biologisten ja fysikaalisten prosessien säätelijöinä riippuu vuodenajasta. Ympäristötekijöiden lisäksi havupuiden vuosisyklillä on suuri merkitys latvustoon absorboituvan säteilyenergian jakautumiselle. Keväällä mäntyjen ilmarakosäätö on voimakasta, haihdunta pysyy vähäisenä ja valtaosa energiasta kuluu havaittavan lämmön vuohon pinnasta ilmakehään. Kevään edetessä fotosynteesikoneiston tehokkuus kasvaa ja haihdunta kasvillisuudesta lisääntyy huomattavasti ja loppukesästä latentin ja havaittavan lämmön vuot ovat likimain yhtä suuria. On huomionarvoista että ilmakehän kannalta boreaaliset havumetsät ovat dynaamisia rakenteita ja tulosten perusteella havupuiden vuosisykli ja sen vaikutukset pinnan energiataseeseen tulisi huomioida entistä tarkemmin mm. säänennustus- ja ilmakehämalleissa. Laajemmin työn tulokset ovat hyödynnettävissä lähinnä tarkennettaessa boreaalisten metsien kuvausta ilmakehämallien dynaamisissa kasvillisuusmalleissa sekä metsähydrologisissa malleissa.ei saavutettav
Impact of the crown layer to snow accumulation, ablation and snow model parameters
No full textTyön tarkoituksena oli tutkia metsän latvuston peittävyyden vaikutusta lumen määrään ja lumimallin parametrien arvoihin. Metsikön peittävyyden kuvaamiseen on käytetty lehtialaindeksiä tai aukkoisuuden määrää, joihin verrattavia suureita ovat olleet lumen syvyys, tiheys ja vesiarvo sekä sulamisnopeus. Lisäksi on tutkittu, miten lumimallin parametrin arvot muuttuvat lehtialaindeksiltään erilaisissa metsissä. Työssä on keskitytty havumetsiin.
Käytössä on ollut kaksi hyvin erilaista aineistoa. Aineistoista vanhempi on vuosilta 1931–58 ja se koostuu pienillä valuma-alueilla ympäri Suomea tehdyistä hydrologisista mittauksista. Toisen aineiston mittaukset on tehty vuosien 2007–2010 aikana Iso-Kauhealla Kainuun Sotkamossa.
Lumen tiheys kasvaa talven aikana metsätyypistä riippumatta, mutta eroja tiheydeltään erilaisten metsien välillä ei voida havaita. Aukealla tiheyden kasvu on kuitenkin keskimäärin metsää edellä. Lumen syvyys ja vesiarvo kasvavat keskimäärin metsän peittävyyden vähetessä. Iso-Kauhella lumen syvyys ja vesiarvo saivat suurimmat arvonsa metsissä, joiden lehtialaindeksi oli alhaisin sekä aukealla. Vuosien 1931–58 aineistossa suurimmat arvot mitattiin pääosin metsäisillä linjoilla. Lumen sulamisnopeus on kummankin aineiston mukaan aukealla nopeampaa kuin metsässä ja sulamisnopeus keskimäärin hidastui latvuston peittävyyden lisääntyessä.
Iso-Kauhelta kerättyjä mittauksia käytettiin myös astepäivämallin ajamiseen. Lumisateen korjauskerroin ja astepäivätekijä kasvoivat lehtialaindeksin pienentyessä. Vedenpidätysparametrin osalta yhteyttä lehtialaindeksiin ei voitu vetää. Muilla parametreilla ei ollut merkittävää vaikutusta mallin toimintaan.The aim of this study was to examine the impact of crown layer coverage on snow accumulation, ablation and snow model parameter values. Leaf area index (LAI) and the number of openings in the foliage were used to represent the coverage of the crown layer. These were compared to snow depth, snow density, snow water equivalent (SWE) and snow ablation rate. In addition it has been studied the effect of LAI on snow model parameter values. The study focused on conifer forests.
The study employed data that was collected in two snow course surveys, conducted in years 1931–58 and 2007–2010. The older data set includes hydrological measurements from small catchments from different parts of Finland. The more recent survey is from a small study site located in Iso-Kauhea in the north-eastern part of Finland.
Snow density increases during the melting period regardless of the forest type and there are no significant differences between forested snow courses of different foliage density. On average snow depth and SWE increased as the density of the forest decreased. In Iso-Kauhea the maximum values of snow depth and SWE were measured on sites that had the lowest LAI values and on openings. According to the older survey data the corresponding maximum values were measured in forests rather than on openings. Both surveys suggest that the snow ablation rate is usually higher on openings than in the nearby forest. Ablation rate also decreased as the density of the foliage increased.
Snow course data collected from Iso-Kauhea was also used to run a degree-day model. The snowfall correction factor and the degree-day parameter had negative correlation with LAI. There was no correlation between the retention parameter and the LAI. Other parameters had no significant effect on the results given by the snow model
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
High frequency distributed temperature sensing and eddy covariance data observed at Sodankylä measurement station during summer/winter 2020
No full textThis record contains high frequency distributed temperature sensing and eddy covariance data observed at Sodankylä measurement station and used in the following study:
Peltola, O., Aurela, M., Launiainen, S. and Katul, G. (2022), Probing the eddy size and its effective mixing length in stably stratified roughness sublayer flows. Q J R Meteorol Soc. Accepted Author Manuscript. https://doi.org/10.1002/qj.4386
Sodankyla_DTS_mm_yyyy.zip
These zip-files contain continuous high frequency potential temperature profiles measured along the Sodankylä 48-metre tall mast. See more information on the data in the netCDF-file attributes and on the measurement setup in the related scientific article.
ECa.zip
This zip-file contains high frequency data from an eddy covariance measurement setup located at 24.5 m height in the measurement height. See more information in ECa_readme.txt and on the measurement setup in the related scientific article.
ECb.zip
This zip-file contains high frequency data from an eddy covariance measurement setup located at 3 m height in the measurement height. See more information in ECb_readme.txt and on the measurement setup in the related scientific article.
codes_Sodankyla.zip
Matlab codes to produce similar figure as Fig. 2 in the abovementioned article, but for Sodankylä
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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