The "Little Ice Age" and its Geomorphological Consequences in Mediterranean Europe   总被引：1，自引：0，他引：1  

A.T. Grove 《Climatic change》2001,48(1):121-136

Alpine glacier advances in the "Little Ice Age" took place in the decades around 1320, 1600, 1700 and 1810. They were the outcome of snowier winters and cooler summers than those of the twentieth century. Documentary records from Crete in particular, and also from Italy, southern France and southeast Spain point to a greater frequency in Mediterranean Europe's mountainous regions of severe floods, droughts and frosts at times of "Little Ice Age" Alpine glacier advances. Deluges, when more than 200 mm of rain fall within 24 hours, are most frequent on mountainous areas near the coast. An instance is given of the geomorphological consequences of a great deluge which struck the Tech valley in the eastern Pyrenees on 17 October 1940. An increased frequency of deluges, probably at times when Alpine glaciers were advancing in the "Little Ice Age" and earlier in the Holocene, in areas known to be tectonically unstable and underlain by soft sediments, could better explain the occurrence of fluvial terraces in Mediterranean Europe sometimes known as the "younger fill", than soil erosion resulting from deforestation.  相似文献   

On the relationship of thunderstorm ice hydrometeor characteristics and total lightning measurements   总被引：1，自引：0，他引：1  

Wiebke Deierling  John Latham  Walter A. Petersen  Scott M. Ellis  Hugh J. Christian  Jr.   《Atmospheric Research》2005,76(1-4):114

Satellite-borne and ground-based devices for the detection of lightning offer the opportunity to explore relationships–on all significant scales up to global–between lightning frequency, f, and other thundercloud parameters. Calculations predict that f is proportional to the product of the downflux p of solid precipitation and the upward mass flux, I, of ice crystals. This prediction has received support from limited computational studies. The physical reasons for such a relationship are explained in terms of the paramount role of ice in the electrification of thunderstorms. Herein, this prediction is subjected to further, preliminary examination through analysis of lightning and dual-polarimetric radar data collected during the STERAO experiment conducted in Northern Colorado during the summer of 1996. The analysis has yielded some highly provisional support for this flux hypothesis. Computed trends of radar derived hydrometeor fractions of solid precipitation and small ice show correlation to the total lightning frequency and raise the possibility of determining values of p and/or I from lightning measurements.It is shown that the extent to which the observed correlations between f and both solid precipitation and small ice trends are or are not strong can provide an indication as to whether the lightning activity is limited by the available concentrations of precipitating or non-precipitating ice in the upper regions of the charging zone of the thundercloud, where most of the charge transfer occurs. It is demonstrated that the most accurate determinations of precipitation rate p from measurements of lighting frequency f are likely to be for conditions where the field-growth is limited by the availability of graupel pellets. It is shown that the simultaneous time variations of f and solid precipitation trends of the type obtained in the STERAO experiment could enable us to determine the nature of the dominant glaciation process operative in the thunderclouds studied.  相似文献   

Why is Shirase Glacier turning its flow direction eastward?     

Kazuki Nakamura  Koichiro Doi  Kazuo Shibuya 《Polar Science》2007,1(2-4):63-71

We applied an image correlation method to Japanese Earth Resources Satellite-1 (JERS-1) synthetic aperture radar (SAR) data obtained from 1996 to 1998 to examine flow velocity within Shirase Glacier, Antarctica. From the grounding line to the downstream region of the glacier, the obtained ice-flow velocity was systematically higher on the western streamline than the eastern. The differences between the two streamlines were 0.31 km/a in 1996 and 0.37 km/a in 1998, significantly larger than the error estimate of 0.03 km/a. The direction of ice flow was about 312° at the grounding line and changed to 327° at 10 km, 346° at 20 km and 2° at 30 km downstream from the grounding line. The total accumulated deflection is 50° to the east. Under the assumption of the conservation of ice mass across the glacier, the observed eastward change in flow direction can be explained by an asymmetric deepening of bedrock topography, that is, across the 8 km width of the glacier, the eastern side is 50 m (10%) deeper than the western side. This eastward turning of flow direction appears to be accelerated by tributary inlets, that flow to the north and northeast at 60–75% of the velocity of inlets on the western streamline.  相似文献   

青藏高原崇测冰芯氯离子、硫酸根离子记录     

刘业祥  刘永建  韩建康 《云南地理环境研究》2007,19(3):11-14

通过对青藏高原崇测冰帽一支18．70m冰芯中Cl^-、SO4^2-离子含量变化的分析表明，20世纪90年来Cl^-、SO4^2-离子含量在波动中呈下降趋势，两种离子的周期性波动变化相似，20世纪晚期比早期和中期的波动幅度小，总体上离子含量逐渐减少与温度在波动中上升相一致，但每一次温度的升高与离子含量的下降并非一一对应。陆源物质和青藏高原上的盐湖是冰芯中Cl^-、SO4^2-离子的主要贡献者。揭示了研究地区大气成分和环境变化与气候变化的关系及亚洲粉尘在全球环境变化中的源区地位。  相似文献   

The Tallinn Temperature Series Reconstructed Back Half a Millennium by Use of Proxy Data     

A. Tarand  P.Ø. Nordli 《Climatic change》2001,48(1):189-199

In order to extend the Tallinn temperature series backward in time, three different climate proxies were used. These were: the first day of ice break-up in Tallinn port, a proxy for the mean winter air temperature (December to March); the first day of ice break-up on the rivers in northern Estonia, a proxy for the beginning of spring; and, the first day of the rye harvest, a proxy for the mean air temperature in spring and summer (April to July). On the basis of these proxies the mean winter temperature could be extended back to the year AD 1500, and the spring and summer temperature back to 1731. The series of winter temperatures was analysed for long-term trends and variations on different timescales. The most striking feature is the warming of the winters from about the mid nineteenth century to the present. The warming is especially noticeable over the latest decades. The climate from the start of the series (AD 1500) to the mid nineteenth century was in general somewhat colder, and should be recognised as a part of the Little Ice Age, though the period was intercepted by warmer winters in the first half of the eighteenth century.  相似文献   

Behaviour of H₂O₂, NH₃, and black carbon in mixed-phase clouds during CIME     

Paolo Laj  Andrea I. Flossmann  Wolfram Wobrock  Sandro Fuzzi  Giordano Orsi  Loretta Ricci  Stephan Mertes  Alfons Schwarzenbck  Jost Heintzenberg  Harry Ten Brink 《Atmospheric Research》2001,58(4):256

We investigated the partitioning of trace substances during the phase transition from supercooled to mixed-phase cloud induced by artificial seeding. Simultaneous determination of the concentrations of H₂O₂, NH₃ and black carbon (BC) in both condensed and interstitial phases with high time resolution showed that the three species undergo different behaviour in the presence of a mixture of ice crystals and supercooled droplets. Both H₂O₂ and NH₃ are efficiently scavenged by growing ice crystals, whereas BC stayed predominantly in the interstitial phase. In addition, the scavenging of H₂O₂ is driven by co-condensation with water vapour onto ice crystals while NH₃ uptake into the ice phase is more efficient than co-condensation alone. The high solubility of NH₄⁺ in the ice could explain this result. Finally, it appears that the H₂O₂–SO₂ reaction is very slow in the ice phase with respect to the liquid phase. Our results are directly applicable for clouds undergoing limited riming.  相似文献   

小冰期以来中国十年尺度气候变化时空分布特征的初步研究   总被引：8，自引：2，他引：8  

杨保 《干旱区地理》2001,24(1):67-73

依据10年际的冰芯、树轮和历史文献记录，首先进行了聚类分析，近400年来中国温度变化大体上可分为两类：第一类包括高原南部、高原西部、东北和闽台地区；第二类包括西南、华南、华中、华东、西北和华北地区。接着分析了近600年、500年和400年三种不同时间尺度上中国气温的时空分布，第一特征向量显示中国东部温度值高于西部，第二特征向量中高原南部、高原东北部与高原西部的反位相变化趋势在不同时间惊讶的EOF结果中都有表现。西南、华南区与华北、华东区在后两种时间尺度上温度变化位相相反。以上这些变化型在近40年来的年际变化中同样发生。小冰期在不同时间尺度的第一特征向量的权重系数中均有明显表现。将中国温度变化与北半球和北极进行比较，发现它们变化非常类似，且以北半球和北级滞后中国温度20年时相关相关最好。  相似文献   

ICE Particle Size and Shape Effect on Solar Energy Scattering Angular Distribution     

Yao Key  Liu Chunlei 《大气科学进展》1996,13(4):505-510

The rare occurrence of te halos produced by cirrus ice crystals in nature has been investigated by modelling the incident solar (visible) light scattering angular distribution using the Monte Carlo/ray tracing method.The results show that the irregular shapes of ice crystals and large population of small ice particles in cirrus are responsible forthe rare occurrence of halos.  相似文献   

古里雅冰帽区天气气候特征的分析     

章新平  姚檀栋 《冰川冻土》1993,15(3):460-466

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Assessment of potential transport of pollutants into the Barents Sea via sea ice--an observational approach     

Korsnes R  Pavlova O  Godtliebsen F 《Marine pollution bulletin》2002,44(9):861-869

The present estimates of ice drift in the Arctic include utilization of satellite imagery data (special sensor microwave/imager) and a reconstruction of air pressure for the period 1899-1998. A significant part of the sea ice in the Arctic Ocean has its origin in the Kara Sea and melts in the Greenland and the Barents Sea (BS). Consequently there may be a particular risk of pollutants in the Kara Sea entering the food webs of the Greenland and BS. The ice export from the Kara Sea between 1988 and 1994 was about 208,000 km2 (154 km3) per year. The import of ice into the BS was during the same period 161,000 km2 (183 km3) per year while the ice drift through the Fram Strait into the Greenland Sea was 583,000 km2 (1859 km3) per year. Ice which formed adjacent to the Ob and Yenisey rivers in early January, drifted into the BS within two years (with a probability of about 50%.  相似文献