Roughness of the lunar soil     

Kari Lumme  Hannu Karttunen  William M. Irvine 《Earth, Moon, and Planets》1985,33(1):19-29

In situ measurements at the lunar surface at millimeter resolution by the Apollo astronauts have been analyzed. Several statistical parameters have been determined for the landing site. The surface roughness has been found to be very nearly gaussian. The root-mean-square slopes have been obtained over scales between 0.5 mm and 5 cm. They steadily decrease with increasing scale length from 58° to 2° and are in reasonable agreement with radar-measured values. The autocorrelation coefficient of the height distribution has also been obtained. It has a scale-length of 0.7 mm.Adjunct Professor at the University of Massachusetts.Visiting Scholar at the University of Massachusetts.  相似文献   

Sm−Nd and Pb isotopic study of mafic rocks associated with early Proterozoic continental rifting: the Peröpohja schist belt in northern Finland     

Hannu Huhma  Robert A. Cliff  Vesa Perttunen  Matti Sakko 《Contributions to Mineralogy and Petrology》1990,104(3):369-379

The Peräpohja schist belt in northern Finland rests unconformably on Archaean granitoids, and marks the early stages of Proterozoic crustal evolution in the Fennoscandian (Baltic) shield. 2440 Ma old layered mafic intrusions predate the supracrustal , and ca. 2200 Ma old sills of the gabbro-wehrlite association intrude the lowest quartzites and volcanics (Runkaus) of the sequence. The Sm-Nd mineral isochron of the Penikat layered intrusion gives an age of 2410±64 Ma. The initial _Nd-values of the Penikat intrusion (_Nd(2440) = –1.6) and the Runkausvaara sill (_Nd(2200) 0) suggest that these mafic magmas were contaminated by older crustal material. The Sm-Nd and Pb isotopic results on the 2.44–2.2 Ga old Runkaus volcanics indicate mobility of Pb, fractionation of Sm/Nd during late greenschist facies metamorphism, and crustal contamination. The Pb-Pb data provide an age of 1972±80 Ma with a high initial ²⁰⁷Pb/²⁰⁴Pb ratio (₁ = 8.49), while scattered Sm-Nd data result in an imprecise age of 2330±180 Ma, with an initial _Nd-value of about zero. Secondary titanite gives an U-Pb age of ca. 2250 Ma. The Jouttiaapa basalts, in contrast, ascended from the mantle without interaction with older crust. These LREE depleted tholeiites mark a break in continental sedimentation, and yield a Sm-Nd age of 2090±70 Ma. Their initial _Nd = + 4.2 ±0.5 implies that the subcontinental early Proterozoic mantle had been depleted in LREE for a long period of time. The first lava flows are strongly depleted in LREE, suggesting that their source was significantly more depleted than the source of mid-ocean ridge basalts today.  相似文献   

Meteorology of the terrestrial planets     

Hannu Savijärvi 《Surveys in Geophysics》1994,15(6):755-773

The thermodynamics, dynamics, weather and general circulation (climate) of the atmospheres of Venus, Earth and Mars is reviewed, in the light of present knowledge. These three terrestrial planets each have a gaseous sunlit envelope, but the realizations of motions in them are quite different. This makes comparisons of their meteorology very interesting and challenging.  相似文献   

Blind Source Separation for Spatial Compositional Data     

Klaus Nordhausen  Hannu Oja  Peter Filzmoser  Clemens Reimann 《Mathematical Geosciences》2015,47(7):753-770

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Petrology and structure of the Palaeoproterozoic (1.9 Ga) Rytky nickel sulphide deposit,Central Finland: a comparison with the Kotalahti nickel deposit     

Jari?M?kinenEmail author  Hannu?V.?Makkonen 《Mineralium Deposita》2004,39(4):405-421

The Palaeoproterozoic (1.9 Ga) Rytky and Kotalahti mafic-ultramafic intrusions are located in the contact zone between the Archaean craton and Proterozoic supracrustal rocks. During the second deformation event (D₂) the surrounding country rocks were subjected to intensive metamorphism and deformation associated with the Svecofennian orogeny; the Archaean/Proterozoic boundary controlled both D₂ thrusting and magma ascent. Emplacement of the Rytky and Kotalahti intrusions took place at the culmination of D₂, as shown by the gneiss inclusions with S₂ schistosity within the intrusions. Overthrusting continued after emplacement, with detached fragments of the bodies incorporated into the Archaean gneisses. During the third deformation event (D₃) the originally subhorizontal intrusions were rotated into a subvertical position, so that they now have their stratigraphic top towards the west. The Rytky intrusion is composed mainly of medium- and coarse-grained lherzolite, websterite and gabbronorite. The nickel deposit with pentlandite as the main nickel mineral is associated with the lherzolite and websterite. The coarse-grained lherzolite, websterite and melagabbro represent the first rocks to form, and they contain the nickel sulphide mineralisation. Country rock contamination, as indicated by high TiO₂, P₂O₅, Rb, Zr and light rare earth element contents (LREE), is most pronounced in the marginal part of the intrusion, which was the first to form. The variation in olivine composition (Fo 78.6-84.77 mole %; Ni 630–2386 ppm) and the metal ratio of the sulphide (Ni/Co 19.3 – 50.3) along with the internal stratigraphy of the intrusion indicate an in-situ process of sulphide ore formation.Editorial handling: P. LightfootAn erratum to this article can be found at  相似文献   

Subarctic catchment water storage and carbon cycling – Leading the way for future studies using integrated datasets at Pallas,Finland     

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   

8000-year history of palaeoproductivity in a large boreal lake     

Arto Itkonen  Virpi Marttila  Jarno Meriläinen  Veli-Pekka Salonen 《Journal of Paleolimnology》1999,21(3):271-294

An 8000-year record of palaeoproductivity, based on the chemical and chironomid stratigraphies from Lake Päijänne, S. Finland, was assessed with respect to known morphometric, climatic and anthropogenic events. A gradual trend of dystrophication and an associated decrease in aquatic production was detected during the Holocene, with the following exceptions: (1) high diatom and chironomid production around 8000-6000 cal yr BP, (2) eutrophication around 2000 cal yr BP, and (3) an anthropogenic signal during the last few decades.The changes in chironomid assemblages, before the past few decades, have mainly been shifts in concentration, but not in species composition. Variation in chironomid production was mainly explained by the accumulations of biogenic silicon, carbon and organic matter. Nutrient availability seems to be important in controlling biogenic silicon, which we use to infer past diatom production. The high production ca. 8000-6000 cal yr BP and the fluctuation in chironomid influx after ca. 2000 cal yr BP, however, were probably caused by the proposed warm/dry and cold/wet conditions during these times, respectively. These results highlight the sensitivity of boreal shield lake ecosystems to climatic forcing. In contrast, the pronounced change in the morphometry of the basin around 7000 cal yr BP had little effect on the trophic state of the lake. The human-induced trophic change during the past few decades has affected the Lake Päijänne ecosystem to an extent never experienced before during the last 8000-years.  相似文献   

Aspects of the Fine-Scale Climatology Over Lake Tanganyika as Resolved by a Mesoscale Model   总被引：1，自引：0，他引：1  

Hannu Savijärvi  Simo Järvenoja 《Meteorology and Atmospheric Physics》2000,73(1-2):77-88

Summary  An hourly averaged climatology at 0.05 ° horizontal resolution over the Lake Tanganyika region was created by making simulations with a mesoscale model (HIRLAM) using a high resolution physiography to represent the surface. Initial and boundary values were interpolated from ECMWF analyses. Climatologies for a typical dry season month (July 1994) and wet season month (March 1994) were created by 7-day segmenting. Model results were validated by utilizing a special coastal observation network. A number of experiments were made with changes to the physiography (mountains/no mountains, lake/no lake). The results reveal local channelling and blocking effects of the near-surface southeasterly trade winds by the high mountain chains in the region of the East African rift. Furthermore, surface winds display regular diurnal cycles in many places, due to slope winds over hills and lake-land-type breezes near the coast. The diurnal coastal winds (defined by the observation network) are reasonably well simulated. Precipitation patterns display the semi-annual march of the ITCZ across the area, plus considerable topographic effects. There is high evaporation from lakes and wetlands during the windy dry season, while evaporation from the moist land surface dominates the rainy season. Received October 15, 1998/Revised September 2, 1999  相似文献   

Short-code paleolimnological investigation of Lake Pihlajavesi in the Saimaa Lake complex, eastern Finalnd: assessment of habitat quality of an endemic and endangered seal population     

Olavi Sandman  Jarmo Meriläinen  Heikki Simola  Juhani Hynynen  Jaana Lahtinen  Virpi Marttila  Pasi Reinikainen 《Journal of Paleolimnology》2000,24(3):317-329

A short-core paleolimnological investigation was carried out to acquire knowledge of the recent history of Lake Pihlajavesi, Saimaa Lake complex, and define its natural state before cultural disturbances. In the natural state, with negligible human interference, the basin was oligotrophic and oxygen-rich. The bioproductivity in the littoral zone was low and the profundal benthic quality was good according to Wiederholm's Benthic Quality Index.Based on diatom analyses, no significant changes have taken place in the phytoplankton communities during the past decades. Sedimentary chironomid communities reveal, however, slight changes on profundal life in the Pihlajavedenselkä basin, near the main pollution sources, whereas there were no significant changes in the outer basin. Three stages could be distinguished in the pollution history of Pihlajavedenselkä: (1) 'The natural state' up until the 1960s, (2) 'the period of increasing loading' during the 1960s and 1970s, and (3) 'the recovery of the basin' during the past two decades.Untreated municipal waste water from the town of Savonlinna was partly responsible for the commencement of eutrophication in the Pihlajavedenselkä basin in the 1960s. The paper and pulp industry in Varkaus, some 40 kilometres upstream from Lake Pihlajanvesi, has also increased eutrophication, especially during the worst period of water quality in the 1960s and 1970s. More effective waste water purification has markedly reduced effluent loading and led to a general recovery of the area. Neverthless the effects of slight nutrient loading can still be seen, especially in littoral bioproductivity.Our paleolimnological data indicate that the present ecosystem will offer living conditions for the endemic Saimaa ringed seal population that are similar to those that existed prior to human disturbances.  相似文献   

On the parameterization of precipitation in warm clouds     

Priit Tisler  Hannu Savijrvi 《Atmospheric Research》2002,63(3-4)

The Sundqvist parameterization for warm rain production by autoconversion processes as the function of cloud liquid water mixing ratio m is tested by defining a realistic ‘driving’ profile m(z) for a maritime low, warm stratocumulus cloud, and comparing with various recent observations. The results show that the parameterization is acceptable, especially after tuning its rain collection constant C₁. It is somewhat sensitive to the vertical resolution of the host model, though. Extending the calculations by considering typical cloud and raindrop size spectra, extra variables such as drizzle amounts and droplet effective radii (forced by the bulk Sundqvist rain rates) could be estimated by numerical integration. Also, these seem to agree fairly well with the available observations.  相似文献