Seasonal transition of hydrological processes in a slow‐moving landslide in a snowy region

A comprehensive understanding of seasonal hydrological dynamics is required to describe the influence of pore‐water pressure on the stability of landslides in snowy regions. This study reports on the results of continuous meteorological and hydrological observations over 2 years on a landslide body comprising Neogene sedimentary rocks in northern Japan, where a thick (3–5 m) seasonal snowpack covers the land surface. Monitoring of the volumetric water content in shallow unsaturated zones (<0.8 m depth) and pore‐water pressure in saturated bedrock at depths of 2.0 and 5.2 m revealed clear seasonality in hydrological responses to rainfall and meltwater supply. During snow‐free periods, both the shallow soil moisture and deep pore‐water pressure responded rapidly to intense rainwater infiltration. In contrast, during snowmelt, the deep pore pressure fluctuated in accordance with the daily cycle of meltwater input, without notable changes in shallow moisture conditions. During occasional foehn events that cause intense snow melting in midwinter, meltwater flows preferentially through the layered snowpack, converging to produce a localized water supply at the ground surface. This episodically triggers a significant rise in pore‐water pressure. The seasonal differences in hydrological responses were characterized by a set of newly proposed indices for the magnitude and quickness of increases in the pressure head near the sliding surface. Under snow‐covered conditions, the magnitude of the pressure increase tends to be suppressed, probably owing to a reduction in infiltration caused by a seasonal decrease in the permeability of surface soils, and effective pore‐water drainage through the highly conductive colluvial layer. Deep groundwater flow within bedrock remained in a steady upwelling state, enhanced by increasing moisture in shallow soils under snow cover, reflecting the convergence of subsurface water from surrounding hillslopes.     

Study on chemical composition of snowpack in southeast and southwest of Tibetan Plateau in winter北大核心CSCD

According to 73 snow samples collected in the southeast and southwest of Tibetan Plateau in January,2021,the characteristics of hydrogen and oxygen stable isotopes（δD and δ18O）fractionation in dry season and the influence of water vapor migration on the chemical composition change of snow profile were revealed by measuring the stable isotopes of hydrogen and oxygen and soluble inorganic ions in snow,and the relationship between stable isotopes of hydrogen and oxygen and climate and the composition and source of soluble inorganic ions were discussed. The results show that the local meteoric waterline of snowpack in the whole study area is δD=7. 86δ18O+11. 8（R2=0. 95）,which is close to the Lhasa winter meteoric waterline,and the slope and inter⁃ cept of the meteoric waterline in the southeast are slightly lower than those in the southwest. δD and δ18O fluctu⁃ ates from -178. 11% to -68. 07% and -23. 80% to -9. 61%,respectively,and the d-excess values fluctuate from 11. 03% to 23. 49%,showing low values of δD and δ18O in winter,and high d-excess values. The surface layer is relatively enriched in heavy isotopes,and the isotope values are higher than those of the lower snow sam⁃ ples,and the water vapor migration inside the snow makes the slope of the relationship between δD and δ18O dif⁃ ferent. The concentration sequence of the main soluble inorganic ions is Ca2+>SO42->Na+>NO3->Cl->K+>Mg2+> NH4+,of which Ca2+（42. 47%）,SO42-（23. 53%）accounted for the largest proportion of cation and anion,re⁃ spectively,and the average concentration of ions in the southeast was higher than that in the southwest. The re⁃ sults of principal component analysis show that terrigenous sources are the main source of ions in snow,and NH4+ and some NO3- are related to human activities. The backward air mass trajectory shows that the source of water vapor is related to the water vapor transport controlled by the upper-altitude westerly circulation,and most of the ions are terrestrial mineral dust carried by westerly winds in winter. © 2023 The Author(s).     

栾城王家庄井水位异常分析

2012年8月栾城王家庄井水位短时间内多次出现快速、大幅下降变化,调研发现,下降异常由距离该井约860 m的新井抽水引起.利用抽水试验模型,定量模拟抽水对王家庄井水位的变化影响,模拟结果与实际变化量相当,进一步确定该井水位下降异常为抽水影响.     

Uncertainties in the SNOWPACK multilayer snow model for a Canadian avalanche context: sensitivity to climatic forcing data

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.     

Pre-Melt Energy Budget of an Arctic Snowpack on Landfast First-Year Sea Ice

The pre-melt energy budget of a snowpack on landfast first-year sea ice at a remote site in the Canadian Arctic Archipelago was analyzed. Over a 19-day period, the total heat conducted into the snowpack at the snow–sea-ice interface was the largest single energy transfer to the snowpack, while each of the turbulent heat fluxes removed comparable amounts of energy. The total energy transferred from the snowpack (∑Q?≈??7027?kJ?m^?2) should have reduced its temperature; however, the opposite occurred. The snowpack’s temperature at both the 7 and 13?cm depths increased over the pre-melt period. The total change in internal energy and latent heat of the snowpack (ΔU_snowpack)_, derived from 15-minute changes in the snowpack’s temperature over the pre-melt period, was approximately 672?kJ?m^?2. Closure of the energy budget was not achieved for either the daily or the total pre-melt period. The terms of the energy budget were determined independently; thus, the failure to close the energy budget was the result of the accumulation of errors associated with all the terms. However, for snow on first-year sea ice, the parameterization of the salinity and temperature dependence of the “specific heat” of the basal layer of the snowpack was likely the primary source of error. The snowpack plays a central role in the transfer of energy across the ocean–sea-ice–atmosphere interface, but an adequate method for modelling the evolution of snow on Arctic sea ice including the energy budget, which determines the warming rate and subsequent melt rate of the snow, has yet to be developed.     

Temporal observations of a seasonal snowpack using upward‐looking GPR

An increase of the spatial and temporal resolution of snowpack measurements in Alpine or Arctic regions will improve the predictability of flood and avalanche hazards and increase the spatial validity of snowpack simulation models. In the winter season 2009, we installed a ground‐penetrating radar (GPR) system beneath the snowpack to measure snowpack conditions above the antennas. In comparison with modulated frequency systems, GPR systems consist of a much simpler technology, are commercially available and therefore are cheaper. The radar observed the temporal alternation of the snow height over more than 2·5 months. The presented data showed that with moved antennas, it is possible to record the snow height with an uncertainty of less than 8% in comparison with the probed snow depth. Three persistent melt crusts, which formed at the snow surface and were buried by further new snow events, were used as reflecting tracers to follow the snow cover evolution and to determine the strain rates of underlaying layers between adjacent measurements. The height in two‐way travel time of each layer changed over time, which is a cumulative effect of settlement and variation of wave speed in response to densification and liquid water content. The infiltration of liquid water with depth during melt processes was clearly observed during one event. All recorded reflections appeared in concordance with the physical principles (e.g. in phase structure), and one can assume that distinct density steps above a certain threshold result in reflections in the radargram. The accuracy of the used impulse radar system in determining the snow water equivalent is in good agreement with previous studies, which used continuous wave radar systems. The results of this pilot study encourage further investigations with radar measurements using the described test arrangement on a daily basis for continuous destruction‐free monitoring of the snow cover. Copyright © 2010 John Wiley & Sons, Ltd.     

季节背景对ENSO循环过程中SSTA增/减幅作用的数值试验研究

利用热带太平洋地区 2层区域海洋模式和再分析资料探讨了大气 /海洋的季节背景对ENSO时间尺度上海温异常的增幅或减幅作用。结果表明 :不论什么季节背景下 ,就海洋变化而言 ,El Nino/La Nina事件均可存在 ,说明 El Nino/La Nina事件的存在和维持并没有季节性选择 ;模式海洋的西太平洋赤道地区次表层海水温度异常变化位相明显超前于东太平洋SSTA且在空间上自西向东传播 ,同时有位相超前的量还包括模式第 1层厚度异常及热容量异常 ,这些对 ENSO的预测和机制研究具有重要意义。 SSTA的振幅在不同的季节背景下可受到不同的调节。以春季为背景 ,同样的异常风应力作用于海洋 ,可使 NINO3区 SSTA较正常季节背景下该区的 SSTA振幅明显增大 ;而在冬季背景下可使 SSTA受到一定程度的减幅 ,这说明 El Nino/L a Nina现象的发生和消亡有季节选择倾向。与春季背景下 NINO 3区SSTA的增幅倾向相反 ,模式第 1层厚度异常的振幅则受到削弱。而西太平洋赤道地区 ,模式海洋混合层的厚度异常则有所增强。这种与 SSTA增 /减幅反相关的现象需要进一步研究     

湖/陆风过程中湍流摩擦作用的数值分析(英文)

本文利用一个湍流能量闭合的二维原始方程模式分析讨论了湍流交换对湖/陆风过程的影响。文中较详细地介绍了湍能闭合方法,分析了在湖(陆)风发展的不同阶段湍流交换强度的分布特征并讨论了大尺度风场对湍流交换系数场的影响。     

One‐year‐long runoff forecast by a single snowpack evaluation

A degree‐day‐based model is presented for a 1 year ahead runoff forecast, with 1 day time steps. The input information is a single snowpack evaluation collected at the beginning of the snowmelt season. The snow‐cover dynamics, the key information for long‐term snowmelt forecast, are described by the snow‐line dynamics, i.e. by the movements of the downhill snowpack limit. The snowmelt volume, estimated by the snow‐line dynamics, is the exogenous input of an autoregressive transformation model. The model is calibrated by a least‐squares procedure on the basis of observed daily runoff data and the corresponding measurements of the snowpack volume (one measurement per year). A real‐world case study on the Alto Tunuyan River basin (2380 km², Argentinean Andes) is presented. The 1 year ahead Alto Tunuyan River runoff patterns, computed for both calibration and validation periods, reveal high agreement with observed streamflows. Copyright © 2004 John Wiley & Sons, Ltd.