Browsing by Subject "vuodenajat"

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  • Oja, Heikki (Yliopiston almanakkatoimisto, 2013)
    Aikakirja sisältää keskeistä kalenteritietoa, josta Yliopiston almanakkatoimistoon tulee jatkuvasti kyselyjä.
  • Granberg, Kaj (University of Helsinki, 1968)
  • Viitanen, Pertti J. (University of Helsinki, 1954)
  • Salonen, Kalevi (University of Helsinki, 1972)
  • Lehtinen, Sirpa (University of Helsinki, 2000)
  • Lotsari, Eliisa; Dietze, Michael; Kämäri, Maria; Alho, Petteri; Kasvi, Elina (MDPI, 2020)
    Water 12 7 (2020)
    Macro-turbulent flows (i.e., coherent flow structures reaching through the whole water column), have not been studied widely in northern seasonally frozen rivers during both open-channel and ice-covered flow conditions. Thus, we aim: (1) to detect and compare the macro-turbulent flow, both at open-channel and ice-covered flow conditions; (2) to explore spatial variation of macro-turbulent flow characteristics within a meander bend; and (3) to detect the effects of near-bed layer velocity fluctuation on bedload transport during differing overall flow conditions. The analyses are based on 5–10 min-long acoustic Doppler current profiler (ADCP) measurements from a subarctic river. The ice-covered low flow, and open-channel higher and lower flow conditions were measured over the period of 2016 to 2020. This study found that macro-turbulent flow existed at all measurement locations under both open-channel and ice-covered flow conditions. Macro-turbulent flow was most consistent and obvious in the streamwise velocity component, and in particular at the inlet and outlet of the investigated meander bend. During all seasons, the near-bed velocities consistently exceeded the sufficient amount for sediment transport. At inlet and outlet areas, the greatest near-bed velocity fluctuation across the critical threshold for sediment transport coincided with the measurement times having frequent macro-turbulent flow.
  • Räisänen, Petri; Merikanto, Joonas; Makkonen, Risto; Savolahti, Mikko; Kirkevåg, Alf; Sand, Maria; Seland, Øyvind; Partanen, Antti-Ilari (Copernicus GmbH, 2022)
    Atmospheric Chemistry and Physics
    For short-lived climate forcers such as black carbon (BC), the atmospheric concentrations, radiative forcing (RF), and, ultimately, the subsequent effects on climate, depend on the location and timing of the emis sions. Here, we employ the NorESM1-Happi version of the Norwegian Earth System Model to systematically study how the RF associated with BC emissions depends on the latitude, longitude, and seasonality of the emis sions. The model aerosol scheme is run in an offline mode to allow for an essentially noise-free evaluation of the RF associated with even minor changes in emissions. A total of 960 experiments were run to evaluate the BC direct RF (dirRF) and the RF associated with BC in snow/ice (snowRF) for emissions in 192 latitude–longitude boxes covering the globe, both for seasonally uniform emissions and for emissions in each of the four seasons separately. We also calculate a rough estimate of the global temperature response to regional emissions and provide a Fortran-based tool to facilitate the further use of our results. Overall, the results demonstrate that the BC RFs strongly depend on the latitude, longitude, and season of the emissions. In particular, the global mean dirRF normalized by emissions (direct specific forcing; dirSF) depends much more strongly on the emission location than suggested by previous studies that have considered emissions from continental-/subcontinental-scale regions. Even for seasonally uniform emissions, dirSF varies by more than a factor of 10, depending on the emission location. These variations correlate strongly with BC lifetime, which varies from less than 2 to 11 d. BC dirSF is largest for emissions in tropical convective regions and in subtropical and midlatitude continents in summer, both due to the abundant solar radiation and strong convective transport, which increases BC lifetime and the amount of BC above clouds. The dirSF is also relatively large for emissions in high-albedo, high-latitude regions such as Antarctica and Greenland. The dependence of snow specific forcing (snowSF) on the emission location is even larger. While BC emissions originating from most low-latitude regions result in negligible snowSF, the maxima of snowSF for emissions in polar regions greatly exceed the largest values of dirSF for low-latitude emissions. The large magnitude of snowSF for high-latitude BC emissions suggests that, for a given mass of BC emitted, the climate impacts are also largest for high-latitude emissions. The additivity of the RFs resulting from BC emissions in different regions and seasons is also investigated. It is found that dirRF is almost additive for current-day emissions, so that summing the RFs computed for individual regions/seasons without considering BC emissions from elsewhere overestimates dirRF by less than 10 %. For snowRF, the overestimate is somewhat larger, at ∼ 20 %.
  • Hytönen, Joni-Petteri (Helsingin yliopisto, 2019)
    Tanka (suom. lyhyt laulu) on yksi japanilaisen runouden tunnetuimpia lajeja. Se sai alkunsa jo 600-luvulla nara-kauden (710–794) Japanissa, mutta kohosi korvaamattomaan asemaansa kultakautenaan heian-kaudella (794–1185), jolloin tätä runouden lajia kutsuttiin nimellä waka (suom. japanilainen laulu). Wakarunoilla oli tärkeä asema keisarillisessa hovissa, sillä niitä käytettiin eleganttina kommunikaatiotapana hovin jäsenten kesken. Wakalla oli myös rooli hovin sosiaalisen hierarkian määrittymisessä ja taidokkaita runoilijoita pidettiin arvossa. Konventionaalisia teemoja, kuten vuodenaikoja ja luontoa, käyttäen wakarunoja kirjoitettiin niin yksityiseen kuin myös julkiseen tarkoitukseen. Yksityiset wakat olivat usein esimerkiksi viestejä toiselle henkilölle. Julkisissa tilanteissa runoja kirjoitettiin esimerkiksi hovissa järjestetyissä runonkirjoituskilpailuissa. Runoista koottiin myös useita keisarillisia runokokoelmia. Tankarunoja kirjoitetaan yhä nykypäivänä ja ne ovat muuttuneet paljon vapaamuotoisemmiksi, kuin mitä ne olivat tuhat vuotta sitten. Sen sijaan, että runoja kirjoitettaisiin tiettyjen kriteerien ja kauniiden hovirunoudelle tyypillisten luontoteemojen mukaisesti, nykytankan aiheissa vain taivas on rajana. Tämä pro gradu -tutkielma havainnoi aineistorunojen vuodenaikoihin, luontoon ja vuorokaudenkiertoon liittyvän sanaston kielikuvia ja metaforia rakkauskontekstissa. Aineistonani käytin tunnetun tankarunoilijan Tawara Machin toimittamaa kokoelmateosta, joka sisältää sata rakkausteemaista nykytankarunoa sadalta eri runoilijalta. Jaoin aineiston yhteentoista eri vuodenaika- ja luontoteeman, joiden kielikuvia pohdin ja analysoin japaninkielisiä sanakirjoja apuna käyttäen. Tutkielman teoreettinen viitekehys rajautuu kielikuvien ja metaforien tutkimukseen metodinaan sisällönanalyysi. Tutkielman perusteella voidaan päätellä, että aineistorunojen luontoon ja vuodenaikoihin liittyvät sanat toimivat monenlaisten tunteiden ja kokemusten, esimerkiksi ensi-ihastuksen, kaipuun tai hyvästien kielikuvina ja/tai metaforina. Yksi sama aineistorunossa esiintynyt sana saattoi sisältää tulkinnasta, runosta ja kontekstista riippuen useita eri kielikuvia.
  • Maliniemi, Einar (Suomen metsätieteellinen seura, 1933)
  • Elovaara, Samu; Degerlund, Maria; Franklin, Daniel J.; Kaartokallio, Hermanni; Tamelander, Tobias (Springer Link, 2020)
    Hydrobiologia 847 11 (2020)
    Cell death drives the magnitude and community composition of phytoplankton and can result in the conversion of particulate organic carbon to dissolved organic carbon (DOC), thereby affecting carbon cycling in the aquatic food web. We used a membrane integrity probe (Sytox Green) to study the seasonal variation in the percentage of viable cells in the phytoplankton population in an estuary in the northern Baltic Sea for 21 months. The associated dissolved and particulate organic matter concentrations were also studied. The viable fraction of phytoplankton cells varied from < 20% to almost 100%, with an average of 62%. Viability was highest when a single phytoplankton group (diatoms or dinoflagellates) dominated the community. Viability of sinking phytoplankton cells, including some motile species, was in general as high as in surface water. Changes in viability were not closely related to nutrient concentrations, virus-like particle abundance, seawater temperature or salinity. There was a weak but significant negative correlation between viability and DOC, although at this location, the DOC pool was mainly influenced by the inflow of riverine water. This study demonstrates that cell viability, and its relationship with carbon export, is highly variable in the complex microbial populations common within estuarine and coastal marine ecosystems.
  • Bonsdorff, A. J. (Suomen metsätieteellinen seura, 1917)
  • Candolin, Ulrika (University of Helsinki, 1991)
  • Parviainen, Leena (1976)
  • Eklund, Jan (University of Helsinki, 1976)
  • Nummelin, Matti (University of Helsinki, 1977)