排序方式： 共有23条查询结果，搜索用时 31 毫秒
1.
Natural Resources Research - Ecosystems and their services are essential to human well-being, but mining activities often cause adverse impacts on these services. Although impact of mining... 相似文献
2.
Stuart Bradley Yvette Perrott Paul Behrens Andy Oldroyd 《Boundary-Layer Meteorology》2012,143(1):37-48
The quality of lidar and sodar wind estimates is generally judged through comparisons with mast-mounted instruments, and the
resulting regressions. Evaluation of the relative merits of lidars versus sodars is complicated by the fact that lidars are
generally placed close to a mast whereas sodars are generally placed some distance from a mast so that acoustic reflections
off the mast are reduced. This leads to the two technologies, lidar and sodar, not being compared in similar situations. Differences
arising from the two geometries can be expected to be larger in complex terrain, where the wind regime can vary significantly
spatially. The current work explores these differences in moderately complex terrain. Lidar–mast comparisons are performed
with the lidar close to an 80 m mast, and sodar–mast comparisons performed with the sodar 300 m from the mast. Systematic
variations in estimated wind speed are found to occur with height, consistent with predictions from a simple flow model. When
the lidar was moved to the sodar location, further from the mast, there were significant changes in the estimated wind speeds
and a reduction in correlation with the mast-based wind speeds, as expected. However, the correlation between collocated lidar and sodar winds was high. This finding emphasizes that any comparison of two remote sensing instruments needs to be
through similar experiments, and that differences in accuracy often reported for the lidar and sodar technologies are likely
to be contaminated due to poor comparison configurations. A method was devised to simulate the sodar being collocated with
the mast, by using the lidar–sodar measurements and the lidar–mast measurements. It was found that there was then no statistically
detectable difference between lidar–mast regressions and sodar–mast regressions for the particular lidar and sodar tested.
Both remote sensing instruments were also found to be good estimators of Weibull parameters, as compared with those derived
from mast data. The conclusion is that the sodar measured the winds above the sodar with a similar accuracy to the lidar measuring
winds above the lidar. 相似文献
3.
Spectra of Nova Del 1967 have been obtained in the photographic infrared during the period March to November 1969. The gradient in the region 1.3–1.7 µ–1 has decreased from 3.06 in November 1968 to 2.57 in November 1969. The main spectral features occurring in the wavelength range 5800–9600 Å are described, while the profiles of some strong lines are displayed on Figures 2–6.
Les observations ont été effectuées à l'Observatoire de Haute-Provence (CNRS). 相似文献
Les observations ont été effectuées à l'Observatoire de Haute-Provence (CNRS). 相似文献
4.
Yvette Cuny 《Solar physics》1971,16(2):293-313
An interpretation is given of the observations of the continuous solar radiation in the spectral range 600–1700 Å. The model allows for deviations from LTE of H, C, Si and S, and is in hydrostatic equilibrium. The predicted intensity from 1680 to 1520 Å has virtually no dependence on the electron temperature variation in the optical depth range 10–3–4 × 10–5, at 5000 Å; the brightness temperature is compatible with a low electronic temperature minimum near the optical depth 10–4. The model of the low chromosphere is characterized by a steep temperature gradient. The model satisfies observations at millimeter wavelengths. 相似文献
5.
大陆岩石圈有效弹性厚度的计算及其地质意义 总被引：4，自引：1，他引：4
大陆范围内Te值有很大的范围，不同构造单元有不同的Te值。Te值的大小与岩石圈的热结构（热年龄）、壳幔耦合等因素有关。同时Te值和地壳厚度、地表有关矿产的分布、岩石圈地幔的物质组成等也有一定关系。 相似文献
6.
Luke P. Shoo Ary A. Hoffmann Stephen Garnett Robert L. Pressey Yvette M. Williams Martin Taylor Lorena Falconi Colin J. Yates John K. Scott Diogo Alagador Stephen E. Williams 《Climatic change》2013,119(2):239-246
Severe impacts on biodiversity are predicted to arise from climate change. These impacts may not be adequately addressed by conventional approaches to conservation. As a result, additional management actions are now being considered. However, there is currently limited guidance to help decision makers choose which set of actions (and in what order) is most appropriate for species that are considered to be vulnerable. Here, we provide a decision framework for the full complement of actions aimed at conserving species under climate change from ongoing conservation in existing refugia through various forms of mobility enhancement to ex situ conservation outside the natural environment. We explicitly recognize that allocation of conservation resources toward particular actions may be governed by factors such as the likelihood of success, cost and likely co-benefits to non-target species in addition to perceived vulnerability of individual species. As such, we use expert judgment of probable tradeoffs in resource allocation to inform the sequential evaluation of proposed management interventions. 相似文献
7.
Francis W.N. Nsubuga O.J. Botai Jane M. Olwoch C.J. deW Rautenbach Yvette Bevis Adebayo O. Adetunji 《水文科学杂志》2013,58(2):278-299
AbstractA study of rainfall trends and temporal variations within seven sub-basins of Uganda spanning from 1940 to 2009 has been made. Rainfall climatologies are constructed from observational data, using 36 station records which reflect hydroclimatic conditions. Long-term changes in rainfall characteristics were determined by non-parametric tests (Mann-Kendall and Sen’s T tests), coefficient of variation (CV), precipitation concentration index and drought severity index. Magnitude of change was estimated by applying Sen’s estimator of slope. Decadal variability of rainfall with marked seasonal cycles is evident. Temporal variability of drought patterns is detected. Variations in annual rainfall are low with no significant trends observed in the main drainage sub-basins. Significant trends occur in October, November, December and January. A noticeable decrease in the annual total rainfall was observed mostly in northwestern and southwestern sub-basins. Rainfall trend in the second normal of June–July–August (JJA) was decreasing in all the main drainage sub-basins.Editor Z.W. Kundzewicz; Associate editor S. YueCitation Nsubuga, F.W.N., Botai, O.J., Olwoch, J.M., Rautenbach, C.J.deW., Bevis, Y., and Adetunji, A.O., 2014. The nature of rainfall in the main drainage sub-basins of Uganda. Hydrological Sciences Journal, 59 (2), 278–299. 相似文献
8.
Increasing evidence from fission track studies in Sweden indicate that large parts of the Fennoscandian Shield have been affected by a large-scale thermotectonic event in the Palaeozoic. In this study the results of 17 apatite fission track analyses from central Sweden are presented collected along three NW–SE transects trending from the Bothnian Sea to the Caledonides. On the Bothnian coast samples have been collected directly from the Sub-Cambrian Peneplain. The sedimentary cover protecting this surface until recently is responsible for the thermal increase detected through apatite fission track (FT) thermochronology.The apatite FT ages range between 516 ± 46 Ma (±1σ) on the Bothnian coast around sea level to 191 ± 11 Ma in the Caledonides (～500–1500 m.a.s.l.). The mean track lengths vary from 11.3 ± 2.2 μm (±1σ) in the east to 14.2 ± 2.8 μm in the west, indicating a longer stay in the PAZ in the east, versus a continuous cooling pattern in the west. This pattern in combination with other geological constraints indicates that the crystalline basement rocks near the Caledonian deformation front in the west experienced higher temperatures after the formation of the Sub-Cambrian Peneplain followed by denudation, compared with the basement rocks in the east near the Bothnian coast.The apatite FT data near the Caledonian deformation front indicates prevailing temperatures of more than 110 ± 10 °C prior to the Mid Palaeozoic, causing a resetting of the apatite fission track clock. The temperatures were progressively lower away from the deformation front. Apatite fission track analysis of samples collected from the Sub-Cambrian Peneplain along the Bothnian coast indicate maximum temperatures of 90 ± 15 °C during Late Silurian–Early Devonian time. This heating event is argued to be the result of burial beneath a developing foreland basin in front of the Caledonian orogeny. Assuming a geothermal gradient of 20 °C/km, this temperature increase can be converted to a total burial of the samples. The resulting geometry of this basin can be described as an asymmetrical basin at least 3.5 km deep in the vicinity of the Caledonian deformation front decreasing to about 2.5 km on the Bothnian coast, continuing further onto Finland. The width of this basin was in thus in the order of 600 km. Whether this was formed completely synorogenic or partly synorogenic, broadening after cessation of the orogeny, could not be revealed.The Late Palaeozoic and Mesozoic thermal evolution of this area is related to the extensional tectonics in the North Atlantic Domain. 相似文献
9.
北冰洋-欧亚大陆-太平洋地学断面东南段岩石圈有效弹性厚度 总被引：4，自引：1，他引：4
大陆岩石圈有效弹性厚度（Te）是表示岩石圈强度的参数，计算该参数对研究岩石圈大规模构造，分析大陆板块内的均衡补偿机制有一定意义。利用Forsyth提出的相关技术计算的北冰洋－欧亚大陆－太平洋地学断面东南段自黑水到泉州的Te值，并分析了重力和地形波长的相关性特征，初步认为：计算Te值所选的每个数据块在短波长（6.6-100km)内岩石圈板块的强度足以平衡地形负载，重力和地形不相关；在长波长（100－250km)内，地形及地下负载由弯曲模型补偿，岩石圈板块在地形及地下负载作用下而挠曲。断面通过地段具有较低热流密度值的陆核有较高的Te值，具有较高热流密度值的宁化，大田地区有较低的Te值，反映了较高的热流密度值对应较低的Te值，较低的热流密度值对应较高Te 值的关系，Te可分为南东低值段和北西高值段，地壳厚度大体上与Te值呈正相关关系。 相似文献
10.
Two important atmospheric features affecting El Niño-Southern Oscillation (ENSO) are atmospheric noise and a nonlinear atmospheric response to SST. In this article, we investigate the roles of these atmospheric features in ENSO in observations and coupled Global Climate Models (GCMs). We first quantify the most important linear couplings between the ocean and atmosphere. We then characterize atmospheric noise by its patterns of standard deviation and skewness and by spatial and temporal correlations. GCMs tend to simulate lower noise amplitudes than observations. Additionally, we investigate the strength of a nonlinear response of wind stress to SST. Some GCMs are able to simulate a nonlinear response of wind stress to SST, although weaker than in observations. These models simulate the most realistic SST skewness. The influence of the couplings and noise terms on ENSO are studied with an Intermediate Climate Model (ICM). With couplings and noise terms fitted to either observations or GCM output, the simulated climates of the ICM versions show differences in ENSO characteristics similar to differences in ENSO characteristics in the original data. In these model versions the skewness of noise is of minor influence on ENSO than the standard deviation of noise. Both the nonlinear response of wind stress to SST anomalies and the relation of noise to the background SST contribute to SST skewness. The ICM is not yet fully evolved, the results rather show that this is a promising route. Overall, atmospheric noise with realistic standard deviation pattern and spatial correlations seems to be important for simulating an irregular ENSO. Both a nonlinear atmospheric response to SST and the dependence of noise on the background SST influence the El Niño/La Niña asymmetry. 相似文献