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1.
Abstract|Gjessing,

Y. T. 1968. On the Relation between the Meteorological Conditions and the Freezing of Lusterfjord. Norsk geogr. Tidsskr. 22, 200–208,

In most cases Lusterfjord freezes over in winter immediately after a period of mild weather conditions with some precipitation. It is sufficient to have temperatures just below 0°C for a relatively short period of time in order for ice to form. However, during extreme cold weather conditions where the temperatures are under -15°C for a lengthy period of time, the fjord is often free from ice formation.

In order for ice to form, there must be a stable gradient in the uppermost centimetres of the water masses. This stable cross-section is a result of a strong gradient of salinity and is formed by a supply of fresh water in the form of precipitation. Such a layer will easily be decomposed by a mechanical turbulence (wind).  相似文献   

2.
Climate anomalies in California associated with ENSO episodes between 1910 and 1984 are investigated using “Superposed Epoch Analysis” techniques tested against randomization for statistical significance of the identified signals. The results indicate that statistically significant temperature departures from seasonal normals are associated with ENSO events and are characterized by positive anomalies in all seasons but especially in the key season of the event year and in the winter following the key season. Temperature anomalies associated with ENSO increase inversely with latitude. The largest temperature anomalies in the station superpositions occur not in the key season but in the winter following. This two-year persistence of temperature anomalies may be important in long-range forecasting. The spring and summer of the second year of the cycle are significantly warmer than the preceding two springs and summers. From the station superpositions, significant positive precipitation anomalies accompany the key seasons of ENSO episodes and persist through the following winter while the winter preceding the key season is abnormally dry. Areally averaged superpositions depict a dry winter and spring preceding the key ENSO season, a wet winter and spring in the episode year persisting into the following winter and spring in the north. A similar pattern exists in the south except that the fall and winter following the key season are abnormally wet. A division of ENSO episodes into “wet” and “dry” events produces no significant foreshadowing characteristics but highlights the indeterminacy of weather types associated with ENSO teleconnections in California as latitude increases. [Key words: climate, climatic anomaly, El Nino/Southern Oscillation, ENSO, California.]  相似文献   

3.

In this issue THE PROFESSIONAL GEOGRAPHER presents the first two reports in a series on the Association's long-range planning process, which was described by Past President Marcus in May. David Morgan outlines here the results of a survey of members' attitudes on a number of important questions.  相似文献   

4.
Abstract

As interest in outdoor activities in remote areas is increasing, there is a strong need for improved avalanche forecasting at the regional scale. Due to important logistical and safety matters, avalanche terrain measurements (avalanche observations, snowpack profiles, and stability tests) are not always possible for practitioners/forecasters. An interesting alternative would be to analyze the snowpack without these challenges by using snow model outputs. The SNOWPACK model is currently used operationally for avalanche forecasting and research in the Swiss Alps. Thus, this paper presents a summary of analyses that have been conducted to assess the potential of using the SNOWPACK model driven with both in-situ and forecasted meteorological data in three different Canadian climate and geomorphological contexts. A comparison of meteorological data from in-situ and predicted datasets for two winters shows that the GEMLAM weather model is the most accurate for the three climatic contexts of this project, but also showed a bias proportional to precipitation intensity/rate. Snow simulations forced with GEMLAM are the closest to field measurements. Finally, predictions of persistent weak layers have been validated using the InfoEx platform from Avalanche Canada. Crust and surface hoar formation dates agree with the information reported in InfoEx.  相似文献   

5.
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6.
We investigated how both droughts and dzuds (severe winter weather) control livestock mortality in a non-equilibrium steppe ecosystem of Mongolia, Gobi Three Beauty National Park. These steppe ecosystems have developed under high interannual variability of rainfall and nomadic grazing systems. Interannual precipitation variation was 39%, with 128 mm mean annual precipitation. The effect of climate variability and extreme events on livestock mortality is a critical aspect for the Mongolian economy. Analysis of drought and precipitation variability on livestock mortality rate was not significantly influenced by the index of mean annual precipitation and annual winter temperature. Overall, unlike hot dry regions, pastoral livestock mortality in the cold dry regions was affected more by dzuds and annual growing seasonal rain than by droughts. Dzuds can be frequent events, occurring as often as once every 2 and 3 years within a decade. The average annual livestock mortality for the combined drought and dzuds years (18%) was 4.8% greater than the years with dzuds alone, and 7% greater than in years with only drought. Thus livestock mortality appears to be more sensitive to dzuds than to droughts, and that dzuds contributes more to livestock mortality even years where combined drought and winter storms occur.  相似文献   

7.
《自然地理学》2013,34(5):474-482
Our knowledge of winter leaf conductance and transpiration rates during the winter and early spring is especially weak for Pinus strobus L. (eastern white pine). Hence, the present study was conducted to: (1) measure and examine the winter leaf conductance and transpiration rates among 10 P. strobus trees to supply preliminary data for an understudied tree species; and (2) investigate whether observed leaf conductance and transpiration rates are large enough to merit incorporation into existing water balance models. The fieldwork was conducted at the Fair Hill Natural Resources Management Area in northeastern Maryland (39°42'N, 75°50'W) using a Li-Cor 1600M Steady State Porometer. Meteorological data were acquired from a continuously recording meteorological station on-site. Meteorological data were recorded at five-minute intervals to ensure that weather conditions could be temporally sequenced with porometer readings. The 10 co-occurring P. strobus sample trees were of similar age and health on uniform soils in an open field. Winter and early spring leaf conductance values of the selected trees reached 20 mmol m-2 s-1, whereas transpiration reached 0.13 mmol m-2 s-1. Results of the study indicate that there is statistically significant differences in leaf conductance rates among co-occurring P. strobus trees (H = 16.74, p = .05). Since the upper winter leaf conductance and transpiration rates measured in this study overlap with growing season leaf conductance and transpiration values reported by others, it is suggested that winter leaf conductance of and transpiration from P. strobus trees are significant enough to incorporate into water balance calculations.  相似文献   

8.
基于站点观测的沙尘暴数据和卫星遥感（FY-3A）的沙尘数据，分析了青藏高原及塔里木盆地-河西走廊沙尘天气的时空分布特征。结果表明：在空间分布上，沙尘天气发生的次数和强度自塔里木盆地-河西走廊往青藏高原的东南方向递减。季节变化上，沙尘暴在青藏高原主要发生在冬、春季，而在塔里木盆地-河西走廊主要发生在春、夏季，这主要是由于地表大风中心在3月北移、10月南移； FY-3A反演的沙尘天气在两个区域均主要发生在冬、春季，发生强度与观测结果在季节变化上也存在差异。在1980—2007年，青藏高原的沙尘暴发生次数和强度上均呈减弱趋势，塔里木盆地-河西走廊的沙尘暴发生次数减弱而强度增强。  相似文献   

9.
A study at the Penrice Soda Products Saltfields revealed that a “weed” blocking siphons in the lower salinity end of the fields was a bryozoan,Zoobotryon verticillatum (della Chiaje). Further observations showed that this bryozoan grows from early October to mid June, dying off for 3 months during winter, and that it was commonly found in salinities of up to 56 grams per litre.  相似文献   

10.
Despite more than 40 yr of research attributing temporal changes in streambank erosion rates to subaerial processes, little quantitative information is available on the relationships between streambank erodibility (kd) and critical shear stress (τc) and the environmental conditions and processes that enhance streambank erosion potential. The study goal was to evaluate temporal changes in kd and τc from soil desiccation and freeze–thaw cycling. Soil erodibility and τc were measured monthly in situ using a multiangle, submerged jet test device. Soil moisture, temperature, and bulk density as well as precipitation, air temperature, and stream stage were measured continuously to determine changes in soil moisture content and state. Pairwise Mann–Whitney tests indicted kd was 2.9 and 2.1 times higher (p < 0.0065) during the winter (December–March) than in the spring/fall (April–May, October–November) and the summer (June–September), respectively. Regression analysis showed 80% of the variability in kd was explained by freeze–thaw cycling alone. Study results also indicated soil bulk density was highly influenced by winter weather conditions (r2 = 0.86): bulk density was inversely related to both soil water content and freeze–thaw cycling. Results showed that significant changes in the resistance of streambank soils to fluvial erosion can be attributed to subaerial processes. Water resource professionals should consider the implications of increased soil erodibility during the winter in the development of channel erosion models and stream restoration designs.  相似文献   

11.
A traversing micro-erosion meter (TMEM) was used to measure micro-scale surface changes in a 45 cm2 area of an intertidal mudstone shore platform on Kaikoura Peninsula, New Zealand, with hourly readings taken over 5 days for two seasons, within 4 h either side of low tide. For all monitoring events, the relative height of a total of 120 co-ordinates were obtained, resulting in 4200 and 4800 measurements for the summer and winter seasons respectively. Within seasons, samples were grouped according to the presence of rain or no rain. Significant changes were found in the micro-topography with variations in temperature and among rain and no rain sample groups. For both seasons, in the absence of rain, there were positive linear relationships between rock surface temperatures and rock surface elevations, and regression analysis explained 42.3% and 46.5% of this variation for the summer (y = 0.098 + 0.004x; p-value = 0.007) and winter (y = 0.007 + 0.012x; p-value < 0.001) seasons respectively. It is suggested that incorporating weather readings alongside measurements of surface change could not only improve extrapolations of shore platform erosion from short-term studies, but also differentiate fluctuations in rock surfaces due to changes in rock surface temperatures from other processes involved in shore platform erosion.  相似文献   

12.
This paper examines how extreme weather events affect the mobility of low-income urban residents in Ghana. Bringing together scholarship on extreme weather and mobilities, it explores the differential impact of flooding on their everyday lives as they navigate the cities of Accra and Tamale. A range of qualitative methods were drawn on, including semi-structured interviews, focus group discussions, and follow-along-participant observations in selected communities of both cities. Three key themes emerged: disrupted road and transport infrastructure, everyday mobility challenges, and coping/adaptive strategies. In flooding conditions, residents experienced difficulties leaving/returning home, engaging in income-generating activities, and accessing transport services and other key urban infrastructure. Conceptually, the paper reveals how disruption to urban residents’ daily movements and activities (re)produces new forms of mobilities and immobilities, which have three relational elements: postponed, improvised and assisted. Throughout the analysis, we show how these mobilities/immobilities vary by age and gender: all urban residents, (though women in particular), experience postponed mobility; young people especially engage in improvised mobility; and children and the elderly are in greatest need of assisted mobility. The paper thus contributes to scholarship on extreme weather events and mobility by providing a more spatially nuanced understanding of the multi-faceted domains in which flooding, socio-economic conditions and adaptive strategies intersect to influence urban mobility in resource poor settings.  相似文献   

13.
基于CALIPSO星载激光雷达的中国沙尘气溶胶观测   总被引：2，自引：0，他引：2  
基于2006年6月至2012年5月无云条件下CALIPSO星载激光雷达观测资料,分析中国典型地区（塔克拉玛干沙漠、柴达木盆地、戈壁区和华北）沙尘气溶胶分布。结果表明：塔克拉玛干沙漠和戈壁区为沙尘天气发生频率高值区,且前者在各高度层的沙尘发生频率都大于后者。沙尘发生呈季节性分布。塔克拉玛干沙漠在春季沙尘发生频率最大,抬升最高可至10 km,冬季频率最小,高度最低,主要分布在3 km以下。戈壁区在春季沙尘发生频率、抬升高度最大,冬季抬升高度最低,但低层发生频率大于夏、秋两季。在塔克拉玛干沙漠,沙尘光学厚度春季最大约为0.44,冬季最小约为0.17,春,冬季消光系数峰值最大,可达0.25 km-1,且随高度的递减率大于夏,秋季。在戈壁区和柴达木盆地,沙尘光学厚度春季最大、秋季最小。在华北,沙尘光学厚度春季最大、夏季最小,消光系数在2 km以上春季最大,这主要是由于春季远距离高空传输到华北的沙尘量最多。塔克拉玛干沙漠与柴达木盆地的退偏比为0.2~0.35,戈壁区为0.16~0.28,可能是由于塔克拉玛干沙漠的物质组成与柴达木盆地相同,而与戈壁区不同。华北因低层沙尘与其他气溶胶混合导致退偏振比廓线随高度递增。4个区域对流层上部退偏比全为0.2,表明高空气溶胶可能为来自相同源区的沙尘。  相似文献   

14.
Abstract

Swiss-born Arnold Henri Guyot (1807–1884) was the first professionally trained geographer to hold an academic position in the United States. After his migration to this country in 1848 he lived for several years in Massachusetts. During this period he introduced contemporary German-Swiss ideas of geography to key opinion leaders in an important series of lectures (published as Earth and Man), established a system of weather stations, and lectured on methods of teaching geography in Massachusetts teachers' institutes and normal schools. This article discusses Guyot's work in the reform of school geography in Massachusetts as the seedbed for his later, better-known work as the author of innovative textbooks and other teaching aids.  相似文献   

15.

Current long-range planning activities affect future characteristics and functions of the Association of American Geographers. This commentary addresses the need for such planning, describes planning issues that should be faced by the membership, and suggests some themes for future action. Several problem areas are discussed. The key debate is seen between proponents of a scholarly society and advocates of a professional association. This, in turn, raises a variety of lesser related issues, such as the program for the Annual Meeting, the role of regional divisions, academic and non-academic constituencies, and the benefits and dangers involved in Association grantsmanship. This statement by President Marcus is the first of a series to appear in THE PROFESSIONAL GEOGRAPHER on the subject of the Association's long-range planning efforts.  相似文献   

16.

The southeastern United States, including Florida, has been identified as a region of homogeneous response to the El Niño/Southern Oscillation (ENSO) climatic anomaly, in which mean monthly precipitation and discharge during winter is above or below normal following the onset of the warm (El Niño) or cold (La Niña) phase of ENSO, respectively. However, this understanding of the response is expanded through a study of the effects of the ENSO phenomenon on the probability distributions of mean monthly streamflows of the Santa Fe river. The Santa Fe river basin is situated between one region, which experiences the greatest proportion of annual streamflow during winter, and another where the largest percentage of annual flow occurs during late summer. The basin experiences both winter and summer peaks in precipitation and (subsequent) streamflow and may therefore display responses to ENSO during each season. A two-parameter lognormal distribution is employed to model these streamflows during warm and cold phases of ENSO. Increases in both the mean and the variance detected during warm phase winters are compatible with previous observations. Increases in variance apparent during cold phase summers have not been previously identified. These results, which have considerable bearing upon predictions of high and low flow probabilities during the year, suggest that the response in streamflow is not spatially homogeneous across the state.  相似文献   

17.
《The Journal of geography》2012,111(6):278-290
Abstract

This issue brings to a close my 10 years as editor of the Journal ofGeography. It has been ajob that, with very few exceptions, I have enjoyed. Many of my colleagues have offered me sympathy for what they perceive must be the huge workload and responsibility associated with editing ajournal. Depending on one's preferences and abilities, however, many aspects of the editor's job are rewarding. Forgive me for beginning with a few personal observations about the last 10 years.  相似文献   

18.
Titles Of Theses     

This essay questions the effectiveness of nuclear winter modeling as a means of impacting nuclear policy and changing public attitudes about nuclear issues. In nuclear winter modeling, humanistic concern over the possibility of global environmental destruction is cloaked in the ostensibly neutral language of science. Nuclear winter modeling attempts to apply rational argument to an issue that is rooted instead in human affect and morality. The implications of this misappropriation are discussed in terms of the dehumanizing nature of the images conjured up by nuclear winter, its attention to the effects of nuclear weapons rather than deeper structural problems, and its political ambiguity as a function of unresolvable uncertainty in model results.  相似文献   

19.
This paper interprets a stone‐banked lobe on the upper western face of Mt Rufus, at an altitude of 1380 m in western Tasmania, Australia. The morphology of the deposit resembles that of a solifluction lobe. Field observations show vertical and downslope movement of pebbles, cobbles and small boulders over a single winter season. The movement is largely related to frost pull (10–15 cm) and shallow freeze–thaw processes promoting the downslope (up to 50 cm yr–1) creep of material and the accumulation of coarse clasts at the lobe riser. The climate of Mt Rufus is strongly maritime and this is reflected in the limited duration and depth of penetration of frozen ground at this site during the 2013 winter. Despite the relatively mild climatic conditions, freeze–thaw processes are clearly the dominant geomorphic force operating at the site. These findings support observations of active stone‐banked lobes on sub‐Antarctic islands where intense freezing is absent. Both there and at Mt Rufus, movement is dominated by freeze–thaw processes operating in the upper c. 20 cm of the regolith. These are typical landforms of marginal freeze–thaw settings.  相似文献   

20.
Surface-process models (SPMs) have the potential to become an important tool in predicting sediment flux to basins, but currently suffer from a lack of quantitative understanding of their controlling parameters, as well as difficulties in identifying landscape properties that can be used to test model predictions. We attempt to constrain the parameter values that enter a SPM by comparing predictions of landscape form (as expressed by hypsometric and fractal measures) and process rates obtained for different parameter sets with observations from the south-eastern Australian highlands, a rifted margin mountain belt that has remained tectonically stable during Cenozoic times. We map the hypsometry and fractal characteristics of south-eastern Australia and find that the roughness amplitude (G) correlates well with local relief, whereas the hypsometric integral (H ) correlates slightly better with elevation than with relief. The fractal dimension (D) does not correlate with any other morphometric measure and varies randomly throughout the region. Variograms generally show three kinds of scaling behaviour of topography with increasing wavelength, with topography only being truly self-affine at wavelengths between ～1 and 10 km. From a review of the available data on long-term denudation rates in south-eastern Australia, we infer that these have been 1–10 m Myr?1, and average escarpment retreat rates 0.2–1.0 km Myr?1, throughout the Cenozoic. Model predictions, using a SPM that includes hillslope diffusion and long-range fluvial transport, suggest that landscape form evolves with time; after an initial phase where D, G and relief increase, all morphometric measures decrease with increasing denudation. The behaviour of GandH in the models is qualitatively compatible with the observations; D, however, varies predictably in the models, in contrast with its random behaviour in the real world. The observed present-day morphology of SE Australia does not impose quantitative constraints on parameter values. The fractal analyses do impose general conditions of relative parameter values that have to be met in order to create ‘realistic’ topographies. They also suggest that there is no theoretical basis for including hillslope diffusion in SPMs with a spatial resolution coarser than 1 km. A comparison of the observed denudation and retreat rates with model predictions places order-of-magnitude constraints on parameter values. Thus, data pertaining to landscape evolution are much more valuable than static present-day topography data for calibrating SPMs.  相似文献   

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