Effective UV surface albedo of seasonally snow-covered lands

International audienceAt ultraviolet wavelengths the albedo of most natural surfaces is small with the striking exception of snow and ice. Therefore, snow cover is a major challenge for various applications based on radiative transfer modelling. The aim of this work was to determine the characteristic effective UV range surface albedo of various land cover types when covered by snow. First we selected 1 by 1 degree sample regions that met three criteria: the sample region contained dominantly subpixels of only one land cover type according to the 8 km global land cover classification product from the University of Maryland; the average slope of the sample region was less than 2 degrees according to the USGS's HYDRO1K slope data; the sample region had snow cover in March according to the NSIDC Northern Hemisphere weekly snow cover data. Next we generated 1 by 1 degree gridded 360 nm surface albedo data from the Nimbus-7 TOMS Lambertian equivalent reflectivity data, and used them to construct characteristic effective surface albedo distributions for each land cover type. The resulting distributions showed that each land cover type experiences a characteristic range of surface albedo values when covered by snow. The result is explained by the vegetation that extends upward beyond the snow cover and masks the bright snow covered surface

Relation between substorm characteristics and rapid temporal variations of the ground magnetic field

Auroral substorms are one of the major causes of large geomagnetically induced currents (GIC) in technological systems. This study deals with different phases of the auroral substorm concerning their severity from the GIC viewpoint. Our database consists of 833 substorms observed by the IMAGE magnetometer network in 1997 (around sunspot minimum) and 1999 (rising phase of the sunspot cycle), divided into two classes according to the <i>D<sub>st</sub></i> index: non-storm (<i>D<sub>st</sub></i>>-40 nT, 696 events) and storm-time ones (<i>D<sub>st</sub></i><-40 nT, 137 events). The key quantity concerning GIC is the time derivative of the horizontal magnetic field vector (<i>d</i><i><b>H</b></i>/<i>dt</i>) whose largest values during substorms occur most probably at about 5 min after the onset at stations with CGM latitude less than 72 deg. When looking at the median time of the occurrence of the maximum <i>d</i><i><b>H</b></i>/<i>dt</i> after the expansion onset, it increases as a function of latitude from about 15 min at CGM lat=56 deg to about 45 min at CGM lat=75 deg for non-storm substorms. For storm-time events, these times are about 5 min longer. Based on calculated ionospheric equivalent currents, large <i>d</i><i><b>H</b></i>/<i>dt</i> occur mostly during the substorm onset when the amplitude of the westward electrojet increases rapidly

The impact of grandparental investment on mothers' fertility intentions in four European countries

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Sukupolvien ketju : Suuret ikäluokat ja sukupolvien välinen vuorovaikutus Suomessa

Tutkimuksessa selvitään sukulaisten välistä vuorovaikutusta sekä avunantoa suomalaisissa perheissä ja suvuissa. Tutkimuskohteena on kolme perhesukupolvea: suuret ikäluokat, heidän aikuiset lapsensa ja vanhempansa, joista on kerätty laaja postikysely-, lomakehaastattelu- ja teemahaastatteluaineisto. Tutkimuskysymysten muodostamisessa ja tulosten tarkastelussa hyödynnetään aikaisempaa sosiologista sukupolvi- ja perhetutkimusta sekä evoluutioteorian esittämiä vastavuoroisuutta ja altruismia koskevia teorioita ja tuloksia. Tutkimuksessa kysytään, miten eri sukupolvet auttavat toisiaan, millaisia sukupolvikohtaisia eroja auttamiskäytännöissä esiintyy ja mitkä taustatekijät selittävät auttamista. Lisäksi selvitetään sukulaisten auttamisasenteita ja tyytyväisyyttä saatuun apuun sekä auttamiseen liittyviä ristiriitoja. Näiden ohella tarkastellaan, miten sukupolvien väliset sosiaaliset suhteet kytkeytyvät auttamiskäytäntöihin. Tutkimustulokset osoittavat, että sukulaisapu on tärkeä tekijä ihmisten välisessä vuorovaikutuksessa. Ihmiset ovat eniten yhteydessä biologisiin sukulaisiinsa, auttavat heitä eniten ja saavat heiltä eniten apua. Mitä keskeisemmästä avun muodosta on kysymys, sitä tärkeämpiä lähisukulaiset ovat. Toisaalta apua annetaan useille eri sukulaisille, mutta avun nettovirta kulkee sukulinjassa vanhemmilta nuoremmille polville. Keskeinen tulos onkin se, että suuret ikäluokat antavat apua enemmän lapsilleen kuin vanhemmilleen. Sukupolvien väliset erot auttamisessa liittyvät yleensä vastaajien ikään tai elämänvaiheeseen. Vastaajat ovat tavallisesti saaneet pyytäessään apua ja ovat yleensä myös tyytyväisiä saamaansa apuun. Sukulaisten auttaminen onkin valtaosalle itsestään selvää riippumatta siitä, koetaanko sitä varsinaisesti velvollisuudeksi. Huolimatta siitä, että sukulaisten auttaminen on runsasta, vain harvat mieltävät esimerkiksi vanhusten auttamisen yksinomaan perheen velvollisuudeksi.11,00 euro

Multigenerational Effects on Children's Cognitive and Socioemotional Outcomes: A Within-Child Investigation

Associations between grandparental investment and child outcomes were investigated using three waves of a longitudinal British Millennium Cohort Study that included children between the ages of 9 months and 5 years (n = 24,614 person-observations from 13,744 children). Grandparental investment was measured by parent–grandparent contact frequency and grandparental financial support. Child cognitive development was measured using the British Ability Scale and socioemotional outcomes using the Strength and Difficulties Questionnaire. Grandparental investment was associated with improved cognitive and socioemotional outcomes among children. However, these associations occurred because of between-person effects and did not exist in within-person analyses that compared the same children over time. The results are discussed in terms of their contribution to multigenerational relationships research.</p

Auroral electrojets during deep solar minimum at the end of solar cycle 23

We investigate the auroral electrojet activity during the deep minimum at the end of solar cycle 23 (2008–2009) by comparing data from the IMAGE magnetometer chain, auroral observations in Fennoscandia and Svalbard, and solar wind and interplanetary magnetic field (IMF) observations from the OMNI database from that period with those recorded one solar cycle earlier. We examine the eastward and westward electrojets and the midnight sector separately. The electrojets during 2008–2009 were found to be weaker and at more poleward latitudes than during other times, but when similar driving solar wind and IMF conditions are compared, the behavior in the morning and evening sectors during 2008–2009 was similar to other periods. On the other hand, the midnight sector shows distinct behavior during 2008–2009: for similar driving conditions, the electrojets resided at further poleward latitudes and on average were weaker than during other periods. Furthermore, the substorm occurrence frequency seemed to saturate to a minimum level for very low levels of driving during 2009. This analysis suggests that the solar wind coupling to the ionosphere during 2008–2009 was similar to other periods but that the magnetosphere-ionosphere coupling has features that are unique to this period of very low solar activity.Peer reviewe