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Wind and waves are major forces affecting the geomorphology and biota in coastal areas. We present a generally applicable method for measuring and calculating fetch length, fetch direction and wave exposure. Fetch length and direction, measured by geographic information system-based methods, are used along with wind direction and wind speed data to estimate wave height and period by applying forecasting curves. The apparent power of waves approaching the shore, used as a proxy for wave exposure, is then calculated by a linear wave model. We demonstrate our method by calculating fetch lengths and wave exposure indices for five areas with varying exposure levels and types of meteorological conditions in the Finnish Archipelago Sea, situated in the northern Baltic Sea. This method is a rapid and accurate means of estimating exposure, and is especially applicable in areas with geomorphologically varying and complicated shorelines. We expect that our method will be useful in several fields, such as basic biogeographical and biodiversity research, as well as coastal land-use planning and management. 相似文献
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Leena Järvi Ari-Juhani Punkka David M. Schultz Tuukka Petäjä Harri Hohti Janne Rinne Toivo Pohja Markku Kulmala Pertti Hari Timo Vesala 《Boundary-Layer Meteorology》2007,125(2):343-359
On the afternoon of 3 July 2004 in Hyytiälä (Juupajoki, Finland), convective cells produced a strong downburst causing forest damage. The SMEAR II field station, situated near the damage site, enabled a unique micrometeorological analysis of a microburst with differences above and inside the canopy. At the time of the event, a squall line associated with a cold front was crossing Hyytiälä with a reflectivity maximum in the middle of the squall line. A bow echo, rear-inflow notch, and probable mesovortex were observed in radar data. The bow echo moved west-north-west, and its apex travelled just north of Hyytiälä. The turbulence data were analysed at two locations above the forest canopy and at one location at sub-canopy. At 1412 EET (Eastern European Time, UTC+2), the horizontal and vertical wind speed increased and the wind veered, reflecting the arrival of a gust front. At the same time, the carbon dioxide concentration increased due to turbulent mixing, the temperature decreased due to cold air flow from aloft and aerosol particle concentration decreased due to rain scavenging. An increase in the number concentration of ultra-fine particles (< 10 nm) was detected, supporting the new particle formation either from cloud outflow or due to rain. Five minutes after the gust front (1417 EET), strong horizontal and downward vertical wind speed gusts occurred with maxima of 22 and 15 m s?1, respectively, reflecting the microburst. The turbulence spectra before, during and after the event were consistent with traditional turbulence spectral theory. 相似文献
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Pasi Hakala Gavin Ramsay Panu Muhli Phil Charles Diana Hannikainen Koji Mukai Osmi Vilhu 《Monthly notices of the Royal Astronomical Society》2005,356(3):1133-1138
UW CrB (MS 1603+2600) is a peculiar short-period X-ray binary that exhibits extraordinary optical behaviour. The shape of the optical light curve of the system changes drastically from night to night, without any changes in overall brightness. Here we report X-ray observations of UW CrB obtained with XMM–Newton . We find evidence for several X-ray bursts, confirming a neutron star primary. This considerably strengthens the case that UW CrB is an accretion disc corona system located at a distance of at least 5–7 kpc (3–5 kpc above the Galactic plane). The X-ray and Optical Monitor (ultraviolet–optical) light curves show remarkable shape variation from one observing run to another, which we suggest are due to large-scale variations in the accretion disc shape resulting from a warp that periodically obscures the optical and soft X-ray emission. This is also supported by the changes in phase-resolved X-ray spectra. 相似文献
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Pasi Hakala Linnea Hjalmarsdotter Diana C. Hannikainen Panu Muhli † 《Monthly notices of the Royal Astronomical Society》2009,394(2):892-899
Since its discovery in 1990, UW CrB (also known as MS1603+2600) has remained a peculiar source without firm classification. Our current understanding is that it is an accretion disc corona (ADC) low-mass X-ray binary. In this paper, we present results from our photometric campaign dedicated to studying the changing morphology of the optical light curves. We find that the optical light curves show remarkable evidence for strongly evolving light curve shapes. In addition, we find that these changes show a modulation at a period of ∼5 d. We interpret these changes as either due to strong periodic accretion disc warping or due to other geometrical changes because of disc precession at a period of 5 d. Finally, we have detected 11 new optical bursts, the phase distribution of which supports the idea of a vertically extended asymmetric accretion disc. 相似文献
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Hannu Marttila Annalea Lohila Pertti Ala-Aho Kashif Noor Jeffrey M. Welker Danny Croghan Kaisa Mustonen Leo-Juhani Meriö Anna Autio Filip Muhic Hannah Bailey Mika Aurela Jussi Vuorenmaa Timo Penttilä Valtteri Hyöky Eric Klein Anton Kuzmin Pasi Korpelainen Timo Kumpula Anssi Rauhala Bjørn Kløve 《水文研究》2021,35(9):e14350
Subarctic ecohydrological processes are changing rapidly, but detailed and integrated ecohydrological investigations are not as widespread as necessary. We introduce an integrated research catchment site (Pallas) for atmosphere, ecosystems, and ecohydrology studies in subarctic conditions in Finland that can be used for a new set of comparative catchment investigations. The Pallas site provides unique observational data and high-intensity field measurement datasets over long periods. The infrastructure for atmosphere- to landscape-scale research in ecosystem processes in a subarctic landscape has recently been complemented with detailed ecohydrological measurements. We identify three dominant processes in subarctic ecohydrology: (a) strong seasonality drives ecohydrological regimes, (b) limited dynamic storage causes rapid stream response to water inputs (snowmelt and intensive storms), and (c) hydrological state of the system regulates catchment-scale dissolved carbon dynamics and greenhouse (GHG) fluxes. Surface water and groundwater interactions play an important role in regulating catchment-scale carbon balances and ecosystem respiration within subarctic peatlands, particularly their spatial variability in the landscape. Based on our observations from Pallas, we highlight key research gaps in subarctic ecohydrology and propose several ways forward. We also demonstrate that the Pallas catchment meets the need for sustaining and pushing the boundaries of critical long-term integrated ecohydrological research in high-latitude environments. 相似文献
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Granitoid rock samples from the assumed center of the Keurusselkä impact site were subjected to a systematic study of fluid‐inclusion compositions and densities in various microstructures of the shocked quartz. The results are consistent with the following impact‐induced model of formation. After cessation of all major regional tectonic activity and advanced erosional uplift of the Fennoscandian shield, a meteorite impact (approximately 1.1 Ga) caused the formation of planar fractures (PFs) and planar deformation features (PDFs) and the migration of shock‐liberated metamorphic fluid (CO2 ± H2O) to the glass in the PDFs. Postimpact annealing of the PDFs led to the formation of CO2 (±H2O) fluid‐inclusion decorated PDFs. The scarce fluid‐inclusion implosion textures (IPs) suggest a shock pressure of 7.6–10 GPa. The postimpact pressure release and associated heating initiated hydrothermal activity that caused re‐opening of some PFs and their partial filling by moderate‐salinity/high temperature (>200 °C) H2O (+ chlorite + quartz) and moderate‐density CO2. The youngest postimpact endogenic sub‐ and nonplanar microfractures (MFs) are characterized by low‐density CO2 and low‐salinity/low‐temperature (<200 °C) H2O. 相似文献