Retrospective analysis of a nonforecasted rain-on-snow flood in the Alps – a matter of model limitations or unpredictable nature?

Abstract. A rain-on-snow flood occurred in the Bernese Alps, Switzerland, on 10 October 2011, and caused significant damage. As the flood peak was unpredicted by the flood forecast system, questions were raised concerning the causes and the predictability of the event. Here, we aimed to reconstruct the anatomy of this rain-on-snow flood in the Lötschen Valley (160 km2) by analyzing meteorological data from the synoptic to the local scale and by reproducing the flood peak with the hydrological model WaSiM-ETH (Water Flow and Balance Simulation Model). This in order to gain process understanding and to evaluate the predictability. The atmospheric drivers of this rain-on-snow flood were (i) sustained snowfall followed by (ii) the passage of an atmospheric river bringing warm and moist air towards the Alps. As a result, intensive rainfall (average of 100 mm day-1) was accompanied by a temperature increase that shifted the 0° line from 1500 to 3200 m a.s.l. (meters above sea level) in 24 h with a maximum increase of 9 K in 9 h. The south-facing slope of the valley received significantly more precipitation than the north-facing slope, leading to flooding only in tributaries along the south-facing slope. We hypothesized that the reason for this very local rainfall distribution was a cavity circulation combined with a seeder-feeder-cloud system enhancing local rainfall and snowmelt along the south-facing slope. By applying and considerably recalibrating the standard hydrological model setup, we proved that both latent and sensible heat fluxes were needed to reconstruct the snow cover dynamic, and that locally high-precipitation sums (160 mm in 12 h) were required to produce the estimated flood peak. However, to reproduce the rapid runoff responses during the event, we conceptually represent likely lateral flow dynamics within the snow cover causing the model to react "oversensitively" to meltwater. Driving the optimized model with COSMO (Consortium for Small-scale Modeling)-2 forecast data, we still failed to simulate the flood because COSMO-2 forecast data underestimated both the local precipitation peak and the temperature increase. Thus we conclude that this rain-on-snow flood was, in general, predictable, but requires a special hydrological model setup and extensive and locally precise meteorological input data. Although, this data quality may not be achieved with forecast data, an additional model with a specific rain-on-snow configuration can provide useful information when rain-on-snow events are likely to occur.

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Retrospective analysis of a non-forecasted rain-on-snow flood in the Alps – a matter of model-limitations or unpredictable nature?

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-10-12861-2013 ◽

2013 ◽

Vol 10 (10) ◽

pp. 12861-12904 ◽

Cited By ~ 1

Author(s):

O. Rössler ◽

P. Froidevaux ◽

U. Börst ◽

R. Rickli ◽

O. Martius ◽

...

Keyword(s):

Temperature Increase ◽

Input Data ◽

Hydrological Model ◽

Hydrological Process ◽

Northern Flank ◽

Flood Peak ◽

Synoptic Conditions ◽

Forecast Data ◽

Meteorological Input ◽

Southern Flank

Abstract. On 10 October 2011, a rain-on-snow flood occurred in the Bernese Alps, Switzerland, and caused significant damage. As this flood peak was unpredicted by the flood forecast system, questions were raised concerning what has caused this flood and whether it was predictable at all. In this study, we focused on one valley that was heavily hit by the event, the Loetschen valley (160 km2), and aimed to reconstruct the anatomy of this rain-on-snow flood from the synoptic conditions represented by European Centre for Medium-Range Weather Forecasts ECWMF analysis data, and the local meteorology within the valley recorded by an extensive met-station network. In addition, we applied the hydrological model WaSiM-ETH to improve our hydrological process understanding about this event and to demonstrate the predictability of this rain-on-snow flood. We found an atmospheric river bringing moist and warm air to Switzerland that followed an anomalous cold front with sustained snowfall to be central for this rain-on-snow event. Intensive rainfall (average 100 mm day−1) was accompanied by a drastic temperature increase (+8 K) that shifted the zero degree line from 1500 m a.s.l. to 3200 m a.s.l. in 12 h. The northern flank of the valley received significantly more precipitation than the southern flank, leading to an enormous flood in tributaries along the northern flank, while the tributaries along the southern flank remained nearly unchanged. We hypothesized that the reason for this was a cavity circulation combined with a seeder-feeder-cloud system enhancing both local rainfall and snow melt by condensation of the warm, moist air on the snow. Applying and adjusting the hydrological model, we show that both the latent and the sensible heat fluxes were responsible for the flood and that locally large amounts of precipitation (up to 160 mm rainfall in 12 h) was necessary to produce the estimated flood peak. With considerable adjustments to the model and meteorological input data, we were able to reproduce the flood peak, demonstrating the ability of the model to reproduce the flood. However, driving the optimized model with COSMO-2 forecast data, we still failed to simulate the flood precisely because COSMO-2 forecast data underestimated both the local precipitation peak and the temperature increase. Thus, this rain-on-snow flood was predictable, but requires a special model set up and extensive and locally precise meteorological input data, especially in terms of both precipitation and temperature.

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“WEBSNOW”: ESTIMATION OF SNOW COVER FROM FREELY ACCESSIBLE WEBCAM IMAGES IN THE ALPS

ISPRS Annals of Photogrammetry Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-annals-v-2-2020-695-2020 ◽

2020 ◽

Vol V-2-2020 ◽

pp. 695-701

Author(s):

S. Flöry ◽

C. Ressl ◽

M. Hollaus ◽

G. Pürcher ◽

L. Piermattei ◽

...

Keyword(s):

Spatial Variability ◽

Snow Cover ◽

Temporal Resolution ◽

Small Scale ◽

Mountain Areas ◽

Processing Times ◽

Temporal And Spatial Variability ◽

The Alps ◽

Temporal And Spatial ◽

Aerial Platforms

Abstract. The alpine snow cover exhibits a high spatial variability in the horizontal and vertical directions even on a very small scale, mainly caused by the high variability of alpine terrain. To quantify the annual and inter-annual snow dynamics continuously reliable measurements of the temporal and spatial variability are required. While remote sensing from satellite and aerial platforms have been successfully used to estimate snow cover at larger scales, especially in mountain areas spatial and temporal resolution are too low to capture local changes. In the alpine region, webcam images are freely available for touristic purposes capturing images at high frequency intervals. Within the WebSnow project the feasibility of using such images for the detection of snow was investigated. With the developed workflow, processing times could be reduced and satisfactory results obtained. Our results show, that webcam networks have the potential for monitoring snow at high spatial and temporal resolution.

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Active, Small-Scale, Periglacial Features on the South Coast of Newfoundland

Géographie physique et Quaternaire ◽

10.7202/032485ar ◽

2007 ◽

Vol 36 (3) ◽

pp. 327-329 ◽

Cited By ~ 1

Author(s):

D. A. Leckie ◽

S. B. McCann

Keyword(s):

Snow Cover ◽

Short Duration ◽

South Coast ◽

Small Scale ◽

High Humidity ◽

The South ◽

Patterned Ground ◽

Freeze Thaw ◽

Marine Influence ◽

Marine Climate

ABSTRACT Small-scale, patterned ground is currently forming on the south coast of Newfoundland. Small, sorted circles and stripes form in the vicinity of the coast under the influence of marine climate with numerous, short duration, freeze-thaw cycles, high humidity, abundant rainfall and a thin snow cover throughout the winter, inland, no more than 15 to 25 km from the coast, the marine influence has decreased sufficiently that the patterned ground is no longer forming.

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Exploring the South African Government Communication on Land Expropriation without Compensation

Journal of Human Ecology ◽

10.31901/24566608.2020/72.1-3.3275 ◽

2020 ◽

Vol 72 (1-3) ◽

Author(s):

Lungisani Moyo

Keyword(s):

South Africa ◽

Food Security ◽

South African ◽

Small Scale ◽

South African Government ◽

Eastern Cape ◽

The South ◽

Land Expropriation ◽

African Government ◽

Government Communication

ABSTRACT This paper used qualitative methodology to explore the South African government communication and land expropriation without compensation and its effects on food security using Alice town located in the Eastern Cape Province South Africa as its case study. This was done to allow the participants to give their perceptions on the role of government communication on land expropriation without compensation and its effects on South African food security. In this paper, a total population of 30 comprising of 26 small scale farmers in rural Alice and 4 employees from the Department of Agriculture (Alice), Eastern Cape, South Africa were interviewed to get their perception and views on government communications and land expropriation without compensation and its effects on South African food security. The findings of this paper revealed that the agricultural sector plays a vital role in the South African economy hence there is a great need to speed up transformation in the sector.

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Factors that Inhibit Sustainable Adoption of Industry 4.0 in the South African Manufacturing Industry

Sustainability ◽

10.3390/su13031013 ◽

2021 ◽

Vol 13 (3) ◽

pp. 1013

Author(s):

Whisper Maisiri ◽

Liezl van Dyk ◽

Rojanette Coeztee

Keyword(s):

South African ◽

Education System ◽

Industry 4.0 ◽

Manufacturing Industry ◽

Youth Unemployment ◽

Small Scale ◽

The South ◽

Qualitative Descriptive ◽

Cultural Construct ◽

Sub Saharan

Industry 4.0 (I4.0) adoption in the manufacturing industry is on the rise across the world, resulting in increased empirical research on barriers and drivers to I4.0 adoption in specific country contexts. However, no similar studies are available that focus on the South African manufacturing industry. Our small-scale interview-based qualitative descriptive study aimed at identifying factors that may inhibit sustainable adoption of I4.0 in the country’s manufacturing industry. The study probed the views and opinions of 16 managers and specialists in the industry, as well as others in supportive roles. Two themes emerged from the thematic analysis: factors that inhibit sustainable adoption of I4.0 and strategies that promote I4.0 adoption in the South African manufacturing industry. The interviews highlighted cultural construct, structural inequalities, noticeable youth unemployment, fragmented task environment, and deficiencies in the education system as key inhibitors. Key strategies identified to promote sustainable adoption of I4.0 include understanding context and applying relevant technologies, strengthening policy and regulatory space, overhauling the education system, and focusing on primary manufacturing. The study offers direction for broader investigations of the specific inhibitors to sustainable I4.0 adoption in the sub-Saharan African developing countries and the strategies for overcoming them.

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Relief shapes and precipitation on the south side of the Alps Part I: Relief characteristics and dry sensitivity simulations

Meteorologische Zeitschrift ◽

10.1127/0941-2948/2004/0013-0083 ◽

2004 ◽

Vol 13 (2) ◽

pp. 83-90 ◽

Cited By ~ 6

Author(s):

Jože Rakovec ◽

Saša Gaberšek ◽

Tomaž Vrhovec

Keyword(s):

The South ◽

South Side ◽

The Alps

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Experiments on wind-driven heat exchange processes over melting snow

10.5194/egusphere-egu21-10182 ◽

2021 ◽

Author(s):

Michael Haugeneder ◽

Tobias Jonas ◽

Dylan Reynolds ◽

Michael Lehning ◽

Rebecca Mott

Keyword(s):

Snow Cover ◽

Surface Wind ◽

Infrared Camera ◽

Snow Accumulation ◽

Internal Boundary ◽

Small Scale ◽

Snow Melt ◽

Two Dimensional ◽

Atmospheric Conditions ◽

Near Surface

Snowmelt runoff predictions in alpine catchments are challenging because of the high spatial variability of the snow cover driven by various snow accumulation and ablation processes. In spring, the coexistence of bare and snow-covered ground engages a number of processes such as the enhanced lateral advection of heat over partial snow cover, the development of internal boundary layers, and atmospheric decoupling effects due to increasing stability at the snow cover. The interdependency of atmospheric conditions, topographic settings and snow coverage remains a challenge to accurately account for these processes in snow melt models. In this experimental study, we used an Infrared Camera (VarioCam) pointing at thin synthetic projection screens with negligible heat capacity. Using the surface temperature of the screen as a proxy for the air temperature, we obtained a two-dimensional instantaneous measurement. Screens were installed across the transition between snow-free and snow-covered areas. With IR-measurements taken at 10Hz, we capture the dynamics of turbulent temperature fluctuations over the patchy snow cover at high spatial and temporal resolution. From this data we were able to obtain high-frequency, two-dimensional windfield estimations adjacent to the surface.Preliminary results show the formation of a stable internal boundary layer (SIBL), which was temporally highly variable. Our data suggest that the SIBL height is very shallow and strongly sensitive to the mean near-surface wind speed. Only strong gusts were capable of penetrating through this SIBL leading to an enhanced energy input to the snow surface.With these type of results from our experiments and further measurements this spring we aim to better understand small scale energy transfer processes over patch snow cover and it&#8217;s dependency on the atmospheric conditions, enabling to improve parameterizations of these processes in coarser-resolution snow melt models.

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The South Georgia Wave Experiment: A Means for Improved Analysis of Gravity Waves and Low-Level Wind Impacts Generated from Mountainous Islands

Bulletin of the American Meteorological Society ◽

10.1175/bams-d-16-0151.1 ◽

2018 ◽

Vol 99 (5) ◽

pp. 1027-1040 ◽

Cited By ~ 7

Author(s):

D. R. Jackson ◽

A. Gadian ◽

N. P. Hindley ◽

L. Hoffmann ◽

J. Hughes ◽

...

Keyword(s):

High Resolution ◽

Gravity Waves ◽

Numerical Models ◽

Small Island ◽

Small Scale ◽

The South ◽

South Georgia ◽

Low Level ◽

Wave Experiment ◽

Realistic Representation

AbstractGravity waves (GWs) play an important role in many atmospheric processes. However, the observation-based understanding of GWs is limited, and representing them in numerical models is difficult. Recent studies show that small islands can be intense sources of GWs, with climatologically significant effects on the atmospheric circulation. South Georgia, in the South Atlantic, is a notable source of such “small island” waves. GWs are usually too small scale to be resolved by current models, so their effects are represented approximately using resolved model fields (parameterization). However, the small-island waves are not well represented by such parameterizations, and the explicit representation of GWs in very-high-resolution models is still in its infancy. Steep islands such as South Georgia are also known to generate low-level wakes, affecting the flow hundreds of kilometers downwind. These wakes are also poorly represented in models.We present results from the South Georgia Wave Experiment (SG-WEX) for 5 July 2015. Analysis of GWs from satellite observations is augmented by radiosonde observations made from South Georgia. Simulations were also made using high-resolution configurations of the Met Office Unified Model (UM). Comparison with observations indicates that the UM performs well for this case, with realistic representation of GW patterns and low-level wakes. Examination of a longer simulation period suggests that the wakes generally are well represented by the model. The realism of these simulations suggests they can be used to develop parameterizations for use at coarser model resolutions.

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Benefits and limitations of data assimilation for discharge forecasting using an event-based rainfall–runoff model

Natural Hazards and Earth System Science ◽

10.5194/nhess-13-583-2013 ◽

2013 ◽

Vol 13 (3) ◽

pp. 583-596 ◽

Cited By ~ 15

Author(s):

M. Coustau ◽

S. Ricci ◽

V. Borrell-Estupina ◽

C. Bouvier ◽

O. Thual

Keyword(s):

Data Assimilation ◽

Hydrological Model ◽

Peak Discharge ◽

State Variables ◽

Rainfall Runoff ◽

Discharge Data ◽

Southern France ◽

Flood Peak ◽

Event Based ◽

The Impact

Abstract. Mediterranean catchments in southern France are threatened by potentially devastating fast floods which are difficult to anticipate. In order to improve the skill of rainfall-runoff models in predicting such flash floods, hydrologists use data assimilation techniques to provide real-time updates of the model using observational data. This approach seeks to reduce the uncertainties present in different components of the hydrological model (forcing, parameters or state variables) in order to minimize the error in simulated discharges. This article presents a data assimilation procedure, the best linear unbiased estimator (BLUE), used with the goal of improving the peak discharge predictions generated by an event-based hydrological model Soil Conservation Service lag and route (SCS-LR). For a given prediction date, selected model inputs are corrected by assimilating discharge data observed at the basin outlet. This study is conducted on the Lez Mediterranean basin in southern France. The key objectives of this article are (i) to select the parameter(s) which allow for the most efficient and reliable correction of the simulated discharges, (ii) to demonstrate the impact of the correction of the initial condition upon simulated discharges, and (iii) to identify and understand conditions in which this technique fails to improve the forecast skill. The correction of the initial moisture deficit of the soil reservoir proves to be the most efficient control parameter for adjusting the peak discharge. Using data assimilation, this correction leads to an average of 12% improvement in the flood peak magnitude forecast in 75% of cases. The investigation of the other 25% of cases points out a number of precautions for the appropriate use of this data assimilation procedure.

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