Long-term snow and weather observations at Weissfluhjoch and its relation to other high-altitude observatories in the Alps   总被引：1，自引：1，他引：0  

Christoph Marty  Roland Meister 《Theoretical and Applied Climatology》2012,110(4):573-583

Snow and weather observations at Weissfluhjoch were initiated in 1936, when a research team set a snow stake and started digging snow pits on a plateau located at 2,540?m asl above Davos, Switzerland. This was the beginning of what is now the longest series of daily snow depth, new snow height and bi-monthly snow water equivalent measurements from a high-altitude research station. Our investigations reveal that the snow depth at Weissfluhjoch with regard to the evolution and inter-annual variability represents a good proxy for the entire Swiss Alps. In order to set the snow and weather observations from Weissfluhjoch in a broader context, this paper also shows some comparisons with measurements from five other high-altitude observatories in the European Alps. The results show a surprisingly uniform warming of 0.8°C during the last three decades at the six investigated mountain stations. The long-term snow measurements reveal no change in mid-winter, but decreasing trends (especially since the 1980s) for the solid precipitation ratio, snow fall, snow water equivalent and snow depth during the melt season due to a strong temperature increase of 2.5°C in the spring and summer months of the last three decades.  相似文献   

Martian gravity field model and its time variations from MGS and Odyssey data     

J.C. Marty  G. Balmino  P. Rosenblatt  S. Le Maistre  A. Rivoldini  V. Dehant  T. Van Hoolst 《Planetary and Space Science》2009,57(3):350-1027

We present results of several years of research and data processing aimed at modelling the Mars gravity field and its longest wavelength time variations. The new solution includes tracking data from Mars Global Surveyor (MGS) from 1998 to 2006 (end of mission) and from Mars Odyssey from 2002 to the spring of 2008; this is the longest analyzed data set from these two orbiter missions as compared to previous works. The new model has been obtained by a team working in Europe, independently from the works of groups at NASA Jet Propulsion Laboratory (JPL) and Goddard Space Flight Center (GSFC), also with totally independent software. Observations consist in two and three-way Doppler measurements (also one way for MGS), and range tracking data collected by the Deep Space Network and have been processed in 4 day arcs, taking into account all disturbing forces of gravitational and non-gravitational origins; for each arc the state vector, drag and solar pressure model multiplying factors, and angular momentum dump parameters are adjusted. The static field (MGGM08A) is represented in spherical harmonics up to degree and order 95 and is very close to previously published models (in terms of spectral components and also over specific features); correlations with the global Mars topography are established and apparent depths of compensation by degree are derived. Lumped zonal harmonics of degree two and three are solved for every 10 days, exhibiting variations in line with previous results (including authors’ ones); the work also shows the difficulty of finding clean signatures (annual and semi-annual) for the zonal coefficient of second degree. The k₂ Love number is also derived from the ensemble of data, as well as from subsets of them; values between 0.110 and 0.130 are found, which are consistent with the existence of a Martian fluid core of significant radius.  相似文献   

First ever in situ observations of Venus’ polar upper atmosphere density using the tracking data of the Venus Express Atmospheric Drag Experiment (VExADE)     

P. Rosenblatt  S.L. Bruinsma  I.C.F. Müller-Wodarg  B. Häusler  H. Svedhem  J.C. Marty 《Icarus》2012,217(2):831-838

On its highly elliptical 24 h orbit around Venus, the Venus Express (VEX) spacecraft briefly reaches a periapsis altitude of nominally 250 km. Recently, however, dedicated and intense radio tracking campaigns have taken place in August 2008, October 2009, February and April 2010, for which the periapsis altitude was lowered to the 186–176 km altitude range in order to be able to probe the upper atmosphere of Venus above the North Pole for the first time ever in situ. As the spacecraft experiences atmospheric drag, its trajectory is measurably perturbed during the periapsis pass, allowing us to infer total atmospheric mass density at the periapsis altitude. A Precise Orbit Determination (POD) of the VEX motion is performed through an iterative least-squares fitting process to the Doppler tracking data, acquired by the VEX radioscience experiment (VeRa). The drag acceleration is modelled using an initial atmospheric density model (VTS3 model, Hedin, A.E., Niemann, H.B., Kasprzak, W.T., Seiff, A. [1983]. J. Geophys. Res. 88, 73–83). A scale factor of the drag acceleration is estimated for each periapsis pass, which scales Hedin’s density model in order to best fit the radio tracking data. Reliable density scale factors have been obtained for 10 passes mainly from the second (October 2009) and third (April 2010) VExADE campaigns, which indicate a lower density by a factor of about 1.8 than Hedin’s model predicts. These first ever in situ polar density measurements at solar minimum have allowed us to construct a diffusive equilibrium density model for Venus’ thermosphere, constrained in the lower thermosphere primarily by SPICAV-SOIR measurements and above 175 km by the VExADE drag measurements (Müller-Wodarg et al., in preparation). The preliminary results of the VExADE campaigns show that it is possible to obtain with the POD technique reliable estimates of Venus’ upper atmosphere densities at an altitude of around 175 km. Future VExADE campaigns will benefit from the planned further lowering of VEX pericenter altitude to below 170 km.  相似文献   

Constraints on the flux of meteoritic and cometary water on the Moon from volatile element (N–Ar) analyses of single lunar soil grains,Luna 24 core     

Evelyn Füri  Bernard Marty  Sergey S. Assonov 《Icarus》2012,218(1):220-229

We report new nitrogen and argon isotope and abundance results for single breccia clasts and agglutinates from four different sections of the Luna 24 drill core in order to re-evaluate the provenance of N trapped in lunar regolith, and to place limits on the flux of planetary material to the Moon’s surface. Single Luna 24 grains with ⁴⁰Ar/³⁶Ar ratios <1 show δ¹⁵N values between ?54.5‰ and +123.3‰ relative to terrestrial atmosphere. Thus, low-antiquity lunar soils record both positive and negative δ¹⁵N signatures, and the secular increase of the δ¹⁵N value previously postulated by Kerridge (Kerridge, J.F. [1975]. Science 188(4184), 162–164. doi:10.1126/science.188.4184.162) is no longer apparent when the Luna and Apollo data are combined. Instead, the N isotope signatures, corrected for cosmogenic ¹⁵N, are consistent with binary mixing between isotopically light solar wind (SW) N and a planetary N component with a δ¹⁵N value of +100‰ to +160‰. The lower δ¹⁵N values of Luna 24 grains compared to Apollo samples reflect a higher relative proportion of solar N, resulting from the higher SW fluence in the region of Mare Crisium compared to the central near side of the Moon. Carbonaceous chondrite-like micro-impactors match well the required isotope characteristics of the non-solar N component trapped in low-antiquity lunar regolith. In contrast, a possible cometary contribution to the non-solar N flux is constrained to be ?3–13%. Based on the mixing ratio of SW to planetary N obtained for recently exposed lunar soils, we estimate the flux of micro-impactors to be (2.2–5.7) × 10³ tons yr^?1 at the surface of the Moon. Our estimate for Luna 24 agrees well with that for young Apollo regolith, indicating that the supply of planetary material does not depend on lunar location. Thus, the continuous influx of water-bearing cosmic dust may have represented an important source of water for the lunar surface over the past ～1 Ga, provided that water removal rates (i.e., by meteorite impacts, photodissociation, and sputtering) do not exceed accumulation rates.  相似文献   

Intercomparison of measurements of bulk snow density and water equivalent of snow cover with snow core samplers: Instrumental bias and variability induced by observers     

J. Ignacio López-Moreno  Leena Leppänen  Bartłomiej Luks  Ladislav Holko  Ghislain Picard  Alba Sanmiguel-Vallelado  Esteban Alonso-González  David C. Finger  Ali N. Arslan  Katalin Gillemot  Aynur Sensoy  Arda Sorman  M. Cansaran Ertaş  Steven R. Fassnacht  Charles Fierz  Christoph Marty 《水文研究》2020,34(14):3120-3133

Manually collected snow data are often considered as ground truth for many applications such as climatological or hydrological studies. However, there are many sources of uncertainty that are not quantified in detail. For the determination of water equivalent of snow cover (SWE), different snow core samplers and scales are used, but they are all based on the same measurement principle. We conducted two field campaigns with 9 samplers commonly used in observational measurements and research in Europe and northern America to better quantify uncertainties when measuring depth, density and SWE with core samplers. During the first campaign, as a first approach to distinguish snow variability measured at the plot and at the point scale, repeated measurements were taken along two 20 m long snow pits. The results revealed a much higher variability of SWE at the plot scale (resulting from both natural variability and instrumental bias) compared to repeated measurements at the same spot (resulting mostly from error induced by observers or very small scale variability of snow depth). The exceptionally homogeneous snowpack found in the second campaign permitted to almost neglect the natural variability of the snowpack properties and focus on the separation between instrumental bias and error induced by observers. Reported uncertainties refer to a shallow, homogeneous tundra-taiga snowpack less than 1 m deep (loose, mostly recrystallised snow and no wind impact). Under such measurement conditions, the uncertainty in bulk snow density estimation is about 5% for an individual instrument and is close to 10% among different instruments. Results confirmed that instrumental bias exceeded both the natural variability and the error induced by observers, even in the case when observers were not familiar with a given snow core sampler.  相似文献   

The Greening of Baltimore's Asphalt Schoolyards          下载免费PDF全文

Geoffrey L. Buckley  Christopher G. Boone  J. Morgan Grove 《Geographical review》2017,107(3):516-535

Asphalt was becoming an integral part of the urban American landscape by the end of the nineteenth century. Not only was it emerging as the preferred alternative for street paving, its promoters were endorsing it for other purposes as well. Although Baltimore was not in the vanguard when it came to adopting asphalt for road surfaces, it soon followed the trend. Like other cities, it too found other applications for this versatile petroleum product, including the paving of playgrounds and schoolyards. Despite low maintenance costs, widespread use of asphalt as a recreational surface started to meet resistance in Baltimore during the 1960s. Fifty years later, stringent storm‐water runoff requirements are causing city officials to rethink how they deploy asphalt in an urban setting. In an effort to meet these new requirements, while at the same time improve recreational opportunities for school children, an alliance of government agencies, nonprofit organizations, and private developers has developed a strategy to remove asphalt from schoolyards—one that may serve as a model for other cities facing financial and sustainability challenges similar to those of Baltimore.  相似文献   

Climate Change Policy: Facts, Issues and Analysis, by Catrinus J. Jepma and Mohan Munasinghe, Cambridge University Press (Cambridge, UK; New York, US; Melbourne, Australia), 1998, 349 pp., hardback: $74.95 (ISBN 0-521-59314-x), paperback: $29.95 (ISBN 0-521-59688-2).     

Marty Hoffert 《Global and Planetary Change》1999,21(4):237

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Book Review: Desertification in Developed Countries,edited by David A. Mouat and Charles F. Hutchinson,Kluwer Academic Publishers,Dordrecht, The Netherlands, 1996. No. of pages: 363. Price: £99.00. ISBN 0792339193.     

A. T. Grove 《地球表面变化过程与地形》1997,22(8):795-796

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Integrated Deep Soil N and Groundwater Isotope Investigation of N Sources Captured by Municipal Wells     

Roy F. Spalding  Aaron J. Hirsh  Mary E. Exner  Marty Stange  Ramon Aravena 《Ground Water Monitoring & Remediation》2019,39(2):22-31

Identification of major nitrate sources that adversely impact groundwater quality in municipal well capture zones in areas of emerging nitrate contamination is essential to minimize leaching and prevent exceedance of the nitrate drinking water standard. Vertical profiles of nitrate leachate in deep soils provide an estimate of the amount of nitrate in transit beneath irrigated, row-cropped fields; depths of peak leachate; and the approximate rate of downward movement. Profiles of pore-water soil-nitrate concentrations in thick 60-feet (~18 m), fine-textured soils near Hastings, Nebraska clearly indicate that considerably more nitrate leached beneath furrow-irrigated than center-pivot irrigated fields. Peak leaching appeared to correlate with recorded periods of poor weather conditions during some growing seasons and may best be controlled by “spoon feeding” fertilizer to the crop through the sprinkler irrigation system at times of nutrient need. The presence of trace levels of atrazine and deethylatrazine to 60 feet (18 m) in core samples indicates that larger, more complex anthropogenic molecules also leach through the fine-textured soils. The light δ¹⁵N_NO3 values in the surficial groundwater beneath fertilized and irrigated cropland indicate that ammonium fertilizer is a major N source and suggest that the natural soil-N contribution is negligible. δ¹⁵N_NO3 values were most enriched in irrigation wells located within municipal well capture zones downgradient of a large feedlot. Dual isotope method (DIM) δ¹⁵N_NO3 and δ¹⁸O_NO3 values suggest that the Hastings’ municipal wells farther downgradient are contaminated with a mixture of nitrate from manure and commercial ammonium-based fertilizer. DIM values indicate an absence of denitrification, which has implications for long-term management of the water resources.  相似文献   

Evidence of Self‐Organized Criticality in riverbank mass failures: a matter of perspective?          下载免费PDF全文

Jacky Croke  Robert Denham  Chris Thompson  James Grove 《地球表面变化过程与地形》2015,40(7):953-964

A growing body of field, theoretical and numerical modelling studies suggests that predicting river response to even major changes in input variables is difficult. Rivers are seen to adjust rapidly and variably through time and space as well as changing independently of major driving variables. Concepts such as Self‐Organized Criticality (SOC) are considered to better reflect the complex interactions and adjustments occurring in systems than traditional approaches of cause and effect. This study tests the hypothesis that riverbank mass failures which occurred both prior to, and during, an extreme flood event in southeast Queensland (SEQ) in 2011 are a manifestation of SOC. Each wet‐flow failure is somewhat analogous to the ‘avalanche’ described in the initial sand‐pile experiments of Bak et al. (Physical Review Letters, 1987, 59(4), 381–384) and, due to the use of multitemporal LiDAR, the time period of instability can be effectively constrained to that surrounding the flood event. The data is examined with respect to the key factors thought to be significant in evaluating the existence of SOC including; non‐linear temporal dynamics in the occurrence of disturbance events within the system; an inverse power‐law relation between the magnitude and frequency of the events; the existence of a critical state to which the system readjusts after a disturbance; the existence of a cascading processes mechanism by which the same process can initiate both low‐magnitude and high‐magnitude events. While there was a significant change in the frequency of mass failures pre‐ and post‐flood, suggesting non‐linear temporal dynamics in the occurrence of disturbance events, the data did not fit an inverse power‐law within acceptable probability and other models were found to fit the data better. Likewise, determining a single ‘critical’ state is problematic when a variety of feedbacks and multiple modes of adjustment are likely to have operated throughout this high magnitude event. Overall, the extent to which the data supports a self‐organized critical state is variable and highly dependent upon inferential arguments. Investigating the existence of SOC, however, provided results and insights that are useful to the management and future prediction of these features. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献