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1.
In the present paper, a methodology has been developed for the mapping of snow cover in Beas basin, Indian Himalaya using AWiFS (IRS-P6) satellite data. The complexities in the mapping of snow cover in the study area are snow under vegetation, contaminated snow and patchy snow. To overcome these problems, field measurements using spectroradiometer were carried out and reflectance/snow indices trend were studied. By evaluation and validation of different topographic correction models, it was observed that, the normalized difference snow index (NDSI) values remain constant with the variations in slope and aspect and thus NDSI can take care of topography effects. Different snow cover mapping methods using snow indices are compared to find the suitable mapping technique. The proposed methodology for snow cover mapping uses the NDSI (estimated using planetary reflectance), NIR band reflectance and forest/vegetation cover information. The satellite estimated snow or non-snow pixel information using proposed methodology was validated with the snow cover information collected at three observatory locations and it was found that the algorithm classify all the sample points correctly, once that pixel is cloud free. The snow cover distribution was estimated using one year (2004–05) cloud free satellite data and good correlation was observed between increase/decrease areal extent of seasonal snow cover and ground observed fresh snowfall and standing snow data.  相似文献   

2.
In this paper, an automated method for retrieval of snow surface temperature (SST) in Beas River Basin, India, using Landsat-8 thermal data is proposed. Digital number (DN) values of thermal data were converted into Top of Atmospheric (TOA) radiance. Surface radiance has been estimated from TOA radiance using a single channel method. The estimated surface radiance was then converted into SST. Cloud free Landsat-8 data for January and February 2017 has been used to estimate SST. Snow and Avalanche Study Establishment (SASE) has established a wireless sensor network (WSN) in an avalanche prone slope in Beas River Basin, India. Landsat-8 retrieved SST has been compared and validated with recorded SST at WSN stations. The retrieved SST using proposed algorithm was in good agreement with SST recorded on ground by sensor network. The mean absolute error (MAE) and root-mean-square error (RMSE) between estimated and recorded SST has been observed as ~?1.1 K and ~?1.5 K for 23 January 2017 and ~?0.7 and ~?1.6 K for 24 February 2017. Algorithm has shown a potential for automated mapping of snow and ice surface temperature using Landsat-8 data for snow cover and glaciers in Himalaya.  相似文献   

3.
Maximum and minimum temperatures are used in avalanche forecasting models for snow avalanche hazard mitigation over Himalaya. The present work is a part of development of Hidden Markov Model (HMM) based avalanche forecasting system for Pir-Panjal and Great Himalayan mountain ranges of the Himalaya. In this work, HMMs have been developed for forecasting of maximum and minimum temperatures for Kanzalwan in Pir-Panjal range and Drass in Great Himalayan range with a lead time of two days. The HMMs have been developed using meteorological variables collected from these stations during the past 20 winters from 1992 to 2012. The meteorological variables have been used to define observations and states of the models and to compute model parameters (initial state, state transition and observation probabilities). The model parameters have been used in the Forward and the Viterbi algorithms to generate temperature forecasts. To improve the model forecasts, the model parameters have been optimised using Baum–Welch algorithm. The models have been compared with persistence forecast by root mean square errors (RMSE) analysis using independent data of two winters (2012–13, 2013–14). The HMM for maximum temperature has shown a 4–12% and 17–19% improvement in the forecast over persistence forecast, for day-1 and day-2, respectively. For minimum temperature, it has shown 6–38% and 5–12% improvement for day-1 and day-2, respectively.  相似文献   

4.
Mass wasting and avalanche events substantially impact the landscape morphology and consequently human habitation throughout the Himalaya. There is, however, a paucity of snow avalanche documentation for the region. The application of dendrochronologic research methods introduces a sensitive approach to document the recurrence of snow avalanche events in a region where historical records are either non-existent or difficult to access. An exploratory dendrochronologic study was undertaken in the Lahul Himalaya of Northern India during the summer of 2006. Included within the fieldwork was an assessment of avalanche track morphology to enable identification of the slope characteristics that might be associated with an increase in avalanche activity. Thirty-six trees growing on the Ratoli avalanche track were sampled. The oldest tree was a Cedrus deodara with a pith date of 1950. A tree-ring-derived avalanche response curve highlights four avalanche events that occurred from 1972 to 2006. The successful scientific results based on the application of the method used provide the basis for local planners to quantify slope failure hazards in forested areas throughout the western Himalaya.  相似文献   

5.
The occurrence of wet-snow avalanches is, in general, poorly understood. For 20 years (winters of 1975–1976 to 1994–1995), the avalanche activity has been observed in the Dischma valley near Davos (Eastern Swiss Alps). The study area comprises a large starting zone of north-easterly aspect (2,300 m a.s.l.) with several avalanche paths. We have analyzed the occurrence data in combination with meteorological and snowpack data collected at an elevation of 2,090 m a.s.l. During the 20-year observation period, almost 800 wet-snow avalanches were observed, about 4.5 times more loose snow avalanches than slab avalanches. Considering both types of avalanches jointly, snow depth, precipitation and air temperature showed the highest correlation with avalanche activity. Most loose snow avalanches occurred when air temperature was high and/or after a precipitation period. Slab avalanches occurrence was primarily related to warm air temperatures and snowpack properties such as the isothermal state and the existence of capillary barriers. Radiation did not show up as a significant variable. The results suggest that in a transitional snow climate wet-snow avalanches are, as dry snow avalanches, often related to precipitation events, and that wet slab instability strongly depends on snowpack properties in relation to warming of the snowpack and melt water production.  相似文献   

6.
奎屯河新龙口右岸山体崩塌原因及再次失稳可能性分析   总被引：1，自引：0，他引：1  
奎屯河新龙口段山体历史上多次发生山体塌滑破坏,最近一次山体崩塌较为反常地发生在1月寒冷季节,而不是通 常的7、8月雨季,针对该段山体频繁发生破坏而且还出现反季节崩塌这种特殊情况,从区域地质背景、地震作用、地形地貌、气 候及降水等几个方面分别详细论述了产生崩塌的原因,同时指出这次反季节崩塌产生的触发原因在于气候反常造成雪水入 渗、短时间内发生多次冻融,裂隙中液态水结冰产生膨胀力诱发了此次山体崩塌。采用赤平投影分析论证了潜在崩塌的可能 性问题,指出发生此次崩塌后的右岸山体仍然未达到稳定状态,还可能再次发生破坏,同时应用实体比例投影法圈定了最有 可能破坏的山体位置并对崩塌方量进行了计算,从而对山体潜在崩塌可能性及规模有了一定把握,对该段山体崩塌的防治具 有实际的工程意义。  相似文献   

7.
Seasonal snow cover is a vital natural resource in the Himalaya. Monitoring of the areal extent of seasonal snow cover is important for both climatological studies as well as hydrological applications. In the present paper, snow cover monitoring was carried out to evaluate the region-wise accumulation and ablation pattern of snow cover in Pir Panjal and Shamshawari ranges of Kashmir valley. The study was carried out for the winter period between November and April of 2004–05, 2005–06 and 2006–07, using multi-temporal WiFS sensor data of IRS-1C/1D satellites. The study shows reduction in the areal extent of seasonal snow cover and rising trend of maximum temperature in three winters for the entire Kashmir valley. This has been validated with 20 years (1988–89 to 2007–08) climatic conditions prevailed in both ranges of Kashmir valley. Region-wise study shows the spatial and temporal variability in seasonal snow cover within Kashmir valley. Advance melting was observed in Banihal and Naugam/Tangdhar regions than Gurez and Machhal regions. Different geographical parameters of these regions were studied to evaluate the influence on snow cover and it was observed that altitude and position of region with respect to mountain range are the deciding factors for retaining the seasonal snow cover for longer duration. Such region-wise study of snow cover monitoring, can provide vital inputs for planning the hydropower projects, development in habitat areas, recreational and strategic planning in the region.  相似文献   

8.
梅里雪山雪崩多发,但缺乏系统监测和研究。1991年1月3日梅里雪山发生了造成中日联合登山队17名队员遇难的巨大雪崩事件。2019年安装在明永冰川末端附近的物候相机拍摄到临近梅里雪山明永冰川的一次雪崩事件。两次事件类型不同,这对我们进行雪崩预测预警有良好的指示作用。本研究以RAMMS(Rapid Mass Movement System)模型为手段,利用经验值和经验公式确定影响模拟结果的主要模型参数和积雪可能断裂深度,在优化分析的基础上,对两次雪崩事件进行重建,定量分析雪崩堆积量、堆积范围等。结果显示:1991年雪崩共持续了192s,雪崩体从海拔5730m处断裂,沿坡面崩塌而下最终堆积在海拔约5000m的冰川粒雪盆地区,形成面积为0.6km^(2),体积约67×10^(4)m^(3)的堆积体。2019年雪崩共持续了158s,雪崩流最大高度35.91m,最大速度79.34m·s,堆积量76.2×10^(4)m^(3),雪崩堆积范围与野外观测到的一致。两次雪崩事件发生地位于雪崩极高危险区和高危险区,在一定程度上验证了风险评估的准确性。研究结果可为梅里雪山地区未来潜在雪崩灾害的风险评估提供依据,为雪崩预测预警提供良好的参考。  相似文献   

9.
Snow avalanches are a major natural hazard for road users and infrastructure in northern Gaspésie. Over the past 11 years, the occurrence of nearly 500 snow avalanches on the two major roads servicing the area was reported. No management program is currently operational. In this study, we analyze the weather patterns promoting snow avalanche initiation and use logistic regression (LR) to calculate the probability of avalanche occurrence on a daily basis. We then test the best LR models over the 2012–2013 season in an operational forecasting perspective: Each day, the probability of occurrence (0–100%) determined by the model was classified into five classes avalanche danger scale. Our results show that avalanche occurrence along the coast is best predicted by 2 days of accrued snowfall [in water equivalent (WE)], daily rainfall, and wind speed. In the valley, the most significant predictive variables are 3 days of accrued snowfall (WE), daily rainfall, and the preceding 2 days of thermal amplitude. The large scree slopes located along the coast and exposed to strong winds tend to be more reactive to direct snow accumulation than the inner-valley slopes. Therefore, the probability of avalanche occurrence increases rapidly during a snowfall. The slopes located in the valley are less responsive to snow loading. The LR models developed prove to be an efficient tool to forecast days with high levels of snow avalanche activity. Finally, we discuss how road maintenance managers can use this forecasting tool to improve decision making and risk rendering on a daily basis.  相似文献   

10.
Snow avalanche hazards in mountainous areas of developing countries have received scant attention in the scientific literature. The purpose of this paper is to describe this hazard and mitigative measures in Kaghan Valley, Pakistan Himalaya, and to review alternatives for future reduction of this hazard. Snow avalanches have long posed a hazard and risk to indigenous populations of the Himalaya and Trans-Himalaya mountains. Land use intensification due to population growth, new transportation routes, military activity and tourism is raising levels of risk. The history of land use in the study area is such that investigations of avalanche hazard must rely on different theoretical bases and data than in most industrialised countries. Despite the intensive use of valley-bottom land which is affected by avalanches, a number of simple measures are currently employed by the indigenous population to mitigate the hazard. Out-migration during the winter months is the most important one. During the intensive use period of summer avalanche-transported snow provides numerous resources for the population. In Kaghan the avalanche hazard is increasing primarily as a result of poorly located new buildings and other construction projects. The large scale of avalanche activity there rules out any significant improvement or protection of the currently difficult winter access. Instead, future mitigation of the hazard should focus on protecting the small number of winter inhabitants and minimising property damage.  相似文献   

11.
H. P. Hong  W. Ye 《Natural Hazards》2014,73(2):355-371
Snow depth records from daily measurements at climatological stations were obtained from Environment Canada and were processed and analyzed. It was identified that there are 549 stations, each with at least 20 years of useable annual maximum snow depth data. Both the Gumbel distribution and generalized extreme value distribution were used to fit the annual maximum snow depth, considering several distribution fitting methods. Statistical analysis results indicated that, according to the Akaike information criterion, the Gumbel distribution is preferred for 72 % stations. The estimated return period value of annual maximum snow depth at stations was used to calculate their corresponding ground snow load. The at-site analysis results were used as the basis to spatially interpolate the ground snow loads for locations tabulated in the National Building Code of Canada (NBCC) since a code location and a climatological site are usually not co-located. For the interpolation, the ordinary co-kriging method with elevation as co-variate was used because a cross-validation analysis by using several deterministic and probabilistic spatial interpolation techniques indicated that the ordinary co-kriging method is preferred. A comparison of the newly estimated ground snow loads to those locations tabulated in the 1995 edition and 2010 edition of the NBCC was also presented.  相似文献   

12.
Saudi Arabia is characterized as largely aseismic; however, the tectonic plate boundaries that surround it are very active. To improve characterization of seismicity and ground motion hazard, the Saudi Arabian Digital Seismic Network (SANDSN) was installed in 1998 and continues to be operated by the Saudi Geological Survey (SGS) and King Abdulaziz City for Science and Technology (KACST). This article describes research performed to improve seismic hazard parameters using earthquake location and magnitude calibration of the high-quality SANDSN data. The SANDSN consists of 38 seismic stations, 27 broadband, and 11 short period. All data are telemetered in real time to a central facility at KACST in Riyadh. The SANDSN stations show low background noise levels and have good signal detection capabilities; however, some stations show cultural noise at frequencies above 1.0 Hz. We assessed the SANDSN event location capabilities by comparing KACST locations with well-determined locations derived from ground truth or global observations. While a clear location bias exists when using the global average iasp91 earth model, the locations can be improved by using regional models optimized for different tectonic source regions. The article presents detailed analysis of some events and Dead Sea explosions where we found gross errors in estimated locations. New velocity models we calculated that should improve estimated locations of regional events in three specific regions include (1) Gulf of Aqabah—Dead Sea region, (2) Arabian Shield, and (3) Arabian Platform. Recently, these models were applied to the SANDSN to improve local and teleseismic event locations and to develop an accurate magnitude scale for Saudi Arabia. The Zagros Thrust presents the most seismic hazard to eastern Saudi Arabia because of the frequent occurrence of earthquakes. Although these events are 200 km or further from the Arabian coast, wave propagation through sedimentary structure of the Gulf causes long-duration ground motions for periods between 3 and 10 s. Such ground motions could excite response in large engineered structures (e.g., tall buildings and long bridges) such as was experienced after the November 22, 2005 Qeshm Island earthquake off the southern coast of Iran.  相似文献   

13.
Due to its geographical location, geology and topography, Turkey mainly undergoes three different types of natural disasters related to gravity flows. They are floods, landslides and snow avalanches.The heavy snow falls during winter pose the hazard of snow avalanches. According to statistics, 800 people were killed in snow avalanches during the period of 1960–1997. Within the program of the International Decade of Natural Disaster Reduction (1990–2000), an international cooperation has been initiated among SFISAR (Swiss Federal Institute for Snow and Avalanche Research), CEMAGREF (Centre National du Machinisme Agricole du Génie Rural des Eaux at des Forets) and AFET (Turkish Ministry of Public Works and Settlement, General Directorate of Disaster Affairs). This three-year project started in 1994 as a development project on avalanche forecasting, mapping, zoning and paravalanche construction technologies. For the pilot project area, the Soanli Mountains located in north-eastern Turkey were chosen, covering an area of approximately 40 by 30 km. After training the Turkish engineers, the basic technologies in avalanche forecasting and avalanche mapping were transferred from Switzerland and France to Turkey with the necessary infrastructure. The difficulties faced in meteorological data collection with the help of local observers and the limited data available caused some delay in avalanche forecasting. If automatic weather stations could take the place of manual work, the realization of a prognosis would be quicker. At present, avalanche-hit houses are rebuilt in new disaster-free zones by AFET. With this project, the idea of using paravalanche structures for protection is promoted. The physico-sociological impacts of avalanche disasters, avalanche mapping and zoning of disaster areas on local people are also studied.  相似文献   

14.
Snow avalanches,which are widely and frequently developed at high elevations,seriously threatens the built traffic corridors in the Tibetan Plateau. Susceptibility evaluation of snow avalanche via machine learning model with a high forecast accuracy can be appled to quickly and effectively assess the regional avalanche risk. This paper took the central Shaluli Mountain region as the study area,in which the snow avalanche inventory was established through remote sensing interpretation and field investigation verification. We quantitatively extracted 17 evaluation factors via GIS-based analysis,and these factors were selected through the variance expansion factor（VIF）. Four machine learning models containing SVM,DT,MLP and KNN were used to compile the susceptibility index map of snow avalanches,and kappa coefficient and ROC curve were used to verify the accuracy. The results suggested that the susceptibility indexes obtained from SVM,DT,MLP and KNN were in the range of［0,0. 964］,［0,815］,［0,0. 995］and［0,1］,respectively. The accuracy test results show that these four models all have good prediction accuracy. Among them,the SVM model is the best. The results also indicated that the areas with the high snow avalanche susceptibility mainly distributed in Genie Mountain and Rigong Mountain,most of which were above the planation surface of the Tibetan Plateau. The average altitude of the extremely high snow-avalanche-prone areas is 4 939 m,while the average altitude of the high snow avalanche-prone areas is 4 859 m. The snow avalanche has low perniciousness on the Sichuan-Tibet Highway and the Sichuan-Tibet Railway in the study area. This study can provide theoretical basis and method reference for disaster prevention and mitigation of snow avalanche along Sichuan-Tibet Railway and other major projects across Shaluli Mountains region. © 2022 Science Press (China).  相似文献   

15.
Through the late Quaternary, the global climate system ranged from full glacial to temperate interglacial conditions. On a smaller spatial scale, regional climates of the late Quaternary exhibited fluctuations that were at times asynchronous to these global changes. For example, glacier expansion in the Himalayas during the mid-Holocene appears to be at odds with the notion of increased global temperature. A clear understanding of the dynamical processes governing regional climate is therefore essential to the correct interpretation of proxy climate data. We summarize results from numerical simulations of the Last Glacial Maximum (LGM) and the mid-Holocene, and focus on the multiple processes that control regional climate of the Himalaya and surrounding areas, with emphasis on monsoon dynamics and variability. It is shown that changes in the south Asian monsoon (caused by fluctuations in Earth's orbital parameters, by tropical Pacific Ocean temperatures, or by exposure of the Sunda shelf) alter the hydrological balance in regions bordering the Tibetan Plateau, a balance for which there are extensive continental proxy records. Numerical results correlate with the expansion/contraction cycles of deserts near the Chinese Loess Plateau. In addition, the LGM monsoon exhibits significant snow accumulation in the eastern Himalaya, whereas the mid-Holocene monsoon exhibits increased accumulation in the northwestern Himalaya. Simulated changes are therefore in accord with field data and demonstrate that numerical simulations can be a useful tool in the interpretation of regional proxy data, particularly when those data are asynchronous to global records.  相似文献   

16.
The Himalayas has experienced varying rates of earthquake occurrence in the past in its seismo-tectonically distinguished segments which may be attributed to different physical processes of accumulation of stress and its release, and due diligence is required for its inclusion for working out the seismic hazard. The present paper intends to revisit the various earthquake occurrence models applied to Himalayas and examines it in the light of recent damaging earthquakes in Himalayan belt. Due to discordant seismicity of Himalayas, three types of regions have been considered to estimate larger return period events. The regions selected are (1) the North-West Himalayan Fold and Thrust Belt which is seismically very active, (2) the Garhwal Himalaya which has never experienced large earthquake although sufficient stress exists and (3) the Nepal region which is very seismically active region due to unlocked rupture and frequently experienced large earthquake events. The seismicity parameters have been revisited using two earthquake recurrence models namely constant seismicity and constant moment release. For constant moment release model, the strain rates have been derived from global strain rate model and are converted into seismic moment of earthquake events considering the geometry of the finite source and the rates being consumed fully by the contemporary seismicity. Probability of earthquake occurrence with time has been estimated for each region using both models and compared assuming Poissonian distribution. The results show that seismicity for North-West region is observed to be relatively less when estimated using constant seismicity model which implies that either the occupied accumulated stress is not being unconfined in the form of earthquakes or the compiled earthquake catalogue is insufficient. Similar trend has been observed for seismic gap area but with lesser difference reported from both methods. However, for the Nepal region, the estimated seismicity by the two methods has been found to be relatively less when estimated using constant moment release model which implies that in the Nepal region, accumulated strain is releasing in the form of large earthquake occurrence event. The partial release in second event of May 2015 of similar size shows that the physical process is trying to release the energy with large earthquake event. If it would have been in other regions like that of seismic gap region, the fault may not have released the energy and may be inviting even bigger event in future. It is, therefore, necessary to look into the seismicity from strain rates also for its due interpretation in terms of predicting the seismic hazard in various segments of Himalayas.  相似文献   

17.
The tropopause height and tropopause temperature are sensitive to temperature changes in troposphere and stratosphere. These are the measures of global climatic variability. Atmospheric profiles of temperature, refractivity and water vapour are always needed for communication, navigation and atmospheric modeling studies. The tropopause characteristics over the Indian region have been studied using radio occultation measurements (CHAMP) on the basis of cold point criterion. Tropopause height shows large variation in the latitude range ∼30°–40°N during winter. Tropopause temperature less than −82°C, assumed to facilitate troposphere to stratosphere air transport, is observed at a number of tropical Indian locations and no seasonal pattern is observed in its occurrence. The bias in temperature and refractivity deduced from radiosonde and radio occultation measurements is also presented.  相似文献   

18.
Naaim  Mohamed  Gurer  Ibrahim 《Natural Hazards》1998,17(2):129-145
In this paper the powder snow avalanche is considered as a two-phase flow (air and snow particles). The equations governing this flow are the fluid mechanics conservation laws. The mass and the momentum conservation are considered for each phase. The interaction between the two phases takes into account the drag force between the particle and the air. Owing to high turbulence in the powder flow, a closure model was used based on a modified k - model in order to take into account the reduction of turbulence energy by the particles. The dense avalanche is modeled using the shallow water equations. The formation and the development of the powder avalanche is modeled using a mass and momentum exchanges between the powder flow and the dense flow. The flow area is digitized horizontally and vertically using a finite elements mesh. The numerical scheme is obtained by integrating the equations on each cell. The model thus built was calibrated using laboratory measurements of density current carried out in a flume. The model was successfully applied to reproduce many avalanches observed in France. At the end of this paper, an application of this model to an engineering case study is presented. It concerns the Uzengili path where an avalanche occurred in 1993. In this paper we use the integrated dense/powder avalanche model to define the effect of a powder avalanche flow in this path. Different simulations allow display of maps of the exposed zones for different available snow depths in the starting zone. The results were mapped in terms of dynamic pressure field and recommendations are proposed to the local authorities.  相似文献   

19.
Investigation on Snow Characteristics and Their Distribution in China   总被引：3，自引：3，他引：0  
The background, scientific objective, investigation contents and scheme of project “Investigation on snow characteristics and their distribution in China” was introduced in this paper. The general objective of the investigation is to build comprehensive and systematic database of snow characteristics in China, at the service of providing data for the climate change, water resource and snow disaster studies. The investigation will be performed on the three fields including the compilation of historical data, in situ measurement of snow characteristics in the typical regions, and investigation of snow characteristics using remote sensing methods. For the compilation of historical data, the historical snow data from the meteorological stations and research institutes will be firstly collected, and then they will be compiled based on a standard rule. In situ observation will be performed at point, line and area-scale on the typical regions which include Northeast region, Xinjiang Degion, and Qinghai-Tibet Plateau. The observation content will contain snow depth, snow density, snow water equivalent, snow particle shape, hardness of snowpack surface, liquid water content, grain size, snow temperature, snow/soil temperature, dielectric constant, and some chemical parameters. These snow characteristics are the priority information used for the modification of retrieval algorithm on snow parameters. Remote sensing methods will be used to build long-time series of snow cover, snow albedo and snow water equivalent datasets based on these modified algorithms. Finally, the snow characteristics from both in situ and remote sensing investigation will be used to classify snow types in China, and produce distribution maps of snow characteristic and other thematic maps.  相似文献   

20.
Long-term conditional probabilities of occurrence of great earthquakes along the Himalaya plate boundary seismic zone have been estimated. The chance of occurrence of at least one great earthquake along this seismic zone over a period of 100 years (beginning the year 1999) is estimated to be about 0.89. The 100-year probability of such an earthquake occurring in the Kashmir seismic gap is about 0.27, in the central seismic gap about 0.52 and in the Assam gap about 0.21. The 25-year probabilities of their occurrence in these gaps are 0.07, 0.17, and 0.05 respectively. These probability estimates may be used profitably to assess the seismic hazard in the Himalaya and the adjoining Ganga plains.  相似文献   

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