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Snowmelt makes an essential component of the hydrological system of Kashmir Himalayas. The present study was carried out to examine the status of Snow Cover Area (SCA) using Moderate Resolution Imaging Spectroradiometer (MODIS) 8-day Snow Cover Product between 2000 and 2016. The intra- and inter-annual variability in SCA and in meteorological parameters was observed and various statistical tests were used to study the interrelationship. Results of statistical analysis indicate decrease in maximum temperature (?0.05 °C/year) and minimum temperatures (?0.02 °C/year) while rise in precipitation (19.13 mm/year). It also showed an increase in annual mean SCA (43.5 sq km) during the study period. The analysis was also carried out on a seasonal basis. The results revealed that in Kashmir Himalayas, climate plays a dominating role in controlling the SCA. The results depict the short-term fluctuations in SCA and show the magnitude of change between two successive values being very large in SCA. 相似文献
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GeoJournal - Horticulture plays a pivotal role in the economy of Jammu and Kashmir. Owing to favourable agro-climatic conditions, temperate horticulture is fast expanding in the state which is... 相似文献
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The economy of the Jammu and Kashmir state depends mostly on traditional forms of occupation. Unaffected and unaltered by modern day industrial developments and changing times, the indigenous traditional occupations of farming, animal husbandry and horticulture forms the backbone of the state economy. But in the last few decades, Agriculture in the state as well as the study area is receiving a set back and Horticulture is flourishing leaps and bounds. The present study aims to analyze various determinants responsible for this change. Climatic as well as field data was thoroughly analyzed to comprehend the situation. A Mann–Kendall test was done on the climatic data to support the hypotheses. It was observed that initially changing climatic trends proved to be the triggering factor supporting this change, but in due course of time, the determinants took an economic and psychological turn. The perusal of Indian Meteorological Data reveals an increasing trend of annual mean maximum temperature from 16.78 °C in 1985 to 17.58 °C in 1995 and an increase from 5.30 °C to 7.00 °C in the annual mean minimum temperature, and as such acting as a triggering factor for the land use conversion. Further, the mean annual rainfall shows a decrease from 100.75 mm in 1981 to 79.43 mm in 1991. The greater economic returns from horticulture as well as the changing behavioral patterns of people over the time further cemented its growth. The farmers have since persisted with the horticulture activity as it has proven to be an economically a much better lucrative enterprise. 相似文献
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印度河扇更新世发育的沉积物波结构复杂、形态多样,其形成过程的认识程度低。本次研究通过高分辨率地震数据和地震解释技术,研究了印度河扇沉积物波的波长、形态、波峰变化等形态特征;阐述了沉积物波与沉积物变形特征的差异、识别了两者的区分标志;总结了水道堤岸斜坡和区域斜坡上沉积物波的分布规律;在此基础上,讨论了沉积物波的形成机理和控制因素,分析了沉积物波的形成过程,并建立了印度河扇沉积物波的形成模式。研究表明: (1)研究区沉积物波波长平均为486.84 m,最大1473 m;波高在10~60 m之间,平均30 m。(2)沉积物波的形态有对称型和非对称型,其迁移方式有上坡迁移型、加积型和下坡迁移型;沉积物波主要发育在水道堤岸的斜坡上,在区域斜坡上也发育少量的沉积物波,这2种沉积物波波脊的走向差异很大,水道堤岸斜坡上的沉积物波主要分布于水道凹岸堤岸的外侧,距离水道越远其规模(波长、波高)越小,波脊走向近于NE-SW方向,与水道的走向平行或斜交;区域斜坡上的沉积物波波脊的走向多为NW-SE向,平行于区域斜坡的走向,离源区越远规模越大。(3)水道堤岸斜坡上的沉积物波是由水道型浊流在离心力的作用下,溢出水道的凹岸,在堤岸外侧的斜坡上沉积形成的,堤岸斜坡的角度对沉积物波的发育规模影响不大,浊流的强度和输沙量对其规模影响大;区域斜坡上发育的沉积物波是由顺坡而下的非水道化的浊流沉积形成;滑塌变形造成的起伏地貌以及早期沉积物波的存在,也都影响了后期沉积物波的发育。 相似文献
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J.?M.?F.?NogueiraEmail author B.?Simplício M.?H.?Floréncio A.?M.?M.?Bettencourt 《Estuaries and Coasts》2003,26(3):798-802
Concentrations of tributyltin in sediments from 9 selected stations located in the upper Tagus River estuary nature reserve, Portugal, were determined. Tributyltin (TBT) concentrations in the sediments ranged from 5 to 35 ng g−1 on a dry weight basis. The persistent TBT contamination observed in the sediments from this important European ecosystem is primarily related to shipping activities as well as the naval industrial complexes located downstream. This exploratory survey suggests that both dumping and dredging, or the effects of tidal transport of resuspended sediments, are likely the main sources for the TBT contamination observed in the upper estuary. Although the TBT contents found in the sediments studied are low relative to concentrations reported from other parts of the world, they appear to represent a potential risk for some resident marine populations. 相似文献
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We present RPWS Langmuir probe data from the third Enceladus flyby (E3) showing the presence of dusty plasma near Enceladus’ South Pole. There is a sharp rise in both the electron and ion number densities when the spacecraft traverses through Enceladus plume. The ion density near Enceladus is found to increase abruptly from about 102 cm−3 before the closest approach to 105 cm−3 just 30 s after the closest approach, an amount two orders of magnitude higher than the electron density. Assuming that the inconsistency between the electron and ion number densities is due to the presence of dust particles that are collecting the missing electron charges, we present dusty plasma characteristics down to sub-micron particle sizes. By assuming a differential dust number density for a range in dust sizes and by making use of Langmuir probe data, the dust densities for certain lower limits in dust size distribution were estimated. In order to achieve the dust densities of micrometer and larger sized grains comparable to the ones reported in the literature, we show that the power law size distribution must hold down to at least 0.03 μm such that the total differential number density is dominated by the smallest sub-micron sized grains. The total dust number density in Enceladus’ plume is of the order of 102 cm−3 reducing to 1 cm−3 in the E-ring. The dust density for micrometer and larger sized grains is estimated to be about 10−4 cm−3 in the plume while it is about 10−6-10−7 cm−3 in the E-ring. Dust charge for micron sized grains is estimated to be about eight thousand electron charges reducing to below one hundred electron charges for 0.03 μm sized grains. The effective dusty plasma Debye length is estimated and compared with inter-grain distance as well as the electron Debye length. The maximum dust charging time of 1.4 h is found for 0.03 μm sized grains just 1 min before the closest approach. The charging time decreases substantially in the plume where it is only a fraction of a second for 1 μm sized grains, 1 s for 0.1 μm sized grains and about 10 s for 0.03 μm sized grains. 相似文献
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Middle Jurassic Coptoclavidae (Insecta:Coleoptera:Dytiscoidea) from China:a Good Example of Mosaic Evolution 总被引：2，自引：2，他引：0
<正>Adults of the aquatic coptoclavid beetles(Coleoptera:Adephaga:Dytiscoidea),described from four Middle Jurassic fossil localities in Inner Mongolia and Liaoning in northeastern China,are attributed to Daohugounectes primitives Wang,Ponomarenko and Zhang,2009,which was previously proposed after study of larvae.The generic name Timarchopsis Brauer,Redtenbacher and Ganglbauer,1889 is proposed as a substitute for the preoccupied and junior homonym Necronectes Ponomarenko,1977,non Milne-Edwards,1881. Furthermore,the subfamily name Necronectinae Ponomarenko,1977 is substituted by the available name Timarchopsinae.Daohugounectes is placed into Timarchopsinae because its adults have long,slightly apically widened tibiae and small femoral plates.The adults of this genus differ from those of other Timarchopsinae in the following features:antennae short and widened in the middle part;basal segments of protarsi not cut apically; metaventrite with a triangular plate.The larvae look like somewhat primitive forms in the subfamily Timarchopsinae.In contrast to these primitive larvae,the adults with some advanced characters can be regarded as among the most advanced forms in the subfamily Timarchopsinae,and probably represent a transition between the Timarchopsinae and Charanoscaphinae.Such mosaic evolution within Daohugounectes indicates that the evolutionary process of aquatic beetles is far more complex than previously thought. 相似文献
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The Influence of the North Atlantic Oscillation on Rainfall Triggering of Landslides near Lisbon 总被引：1，自引：0，他引：1
Ricardo?M.?TrigoEmail author José L.?Zêzere Maria?L.?Rodrigues Isabel?F.?Trigo 《Natural Hazards》2005,36(3):331-354
The majority of landsliding episodes in the area north of Lisbon are associated with rainfall events of short (less than 5
days) medium (5–20 days) or long duration (more than 20 days). The precipitation regime in Portugal is highly irregular, with
large differences between wet and dry years. We have assessed the impact of the North Atlantic Oscillation (NAO) on both the
winter precipitation and the timing and magnitude of associated landslide events. Results show that the large inter-annual
variability of winter precipitation is largely modulated by the NAO mode. The precipitation composite corresponding to high
NAO index presents a considerable lower median value (47 mm/month) than the corresponding low NAO index class (134 mm/month).
The entire precipitation distribution associated with the low NAO index composite encompasses a wider range of values than
the corresponding high NAO index composite. This non-linear behavior is reflected in the probability of occurrence of a very
wet month (precipitation above the 90% percentile) that is just 1% for the positive NAO class and 23% for low NAO index months.
Results for the low NAO class are crucial because these months are more likely associated with long-lasting rainfall episodes
responsible for large landslide events. This is confirmed by the application of a 3-month moving average to both NAO index
and precipitation time series. This procedure allowed the identification of many months with landslide activity as being characterized
by negative average values of the NAO index and high values of average precipitation (above 100 mm/month). Finally, using
daily data we have computed the return periods associated with the entire set of landslide episodes and, based on these results,
obtained a strong linear relationship between critical cumulative rainfall and the corresponding critical rainfall event duration. 相似文献