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Natural Hazards and Earth System Sciences (NHESS)

Analysis of the French insurance market exposure to floods: a stochastic model combining river overflow and surface runoffNatural Hazards and Earth System Science, 14, 2469-2485, 2014Author(s): D. Moncoulon, D. Labat, J. Ardon, E. Leblois, T. Onfroy, C. Poulard, S. Aji, A. Rémy, and A. QuantinThe analysis of flood exposure at a national scale for the French insurance
market must combine the generation of a probabilistic event set of all
possible (but which have not yet occurred) flood situations with hazard and
damage modeling. In this study, hazard and damage models are calibrated on a
1995–2010 historical event set, both for hazard results (river flow, flooded
areas) and loss estimations. Thus, uncertainties in the deterministic
estimation of a single event loss are known before simulating a probabilistic
event set. To take into account at least 90 % of the insured flood losses,
the probabilistic event set must combine the river overflow (small and large
catchments) with the surface runoff, due to heavy rainfall, on the slopes of
the watershed. Indeed, internal studies of the CCR (Caisse Centrale de
Reassurance) claim database have shown that approximately 45 % of the
insured flood losses are located inside the floodplains and 45 % outside.
Another 10 % is due to sea surge floods and groundwater rise. In this
approach, two independent probabilistic methods are combined to create a
single flood loss distribution: a generation of fictive river flows based on
the historical records of the river gauge network and a generation of fictive
rain fields on small catchments, calibrated on the 1958–2010
Météo-France rain database SAFRAN. All the events in the
probabilistic event sets are simulated with the deterministic model. This
hazard and damage distribution is used to simulate the flood losses at the
national scale for an insurance company (Macif) and to generate flood areas
associated with hazard return periods. The flood maps concern river overflow
and surface water runoff. Validation of these maps is conducted by comparison
with the address located claim data on a small catchment (downstream Argens). 2014/09/20 - 18:28

Shallow landslide prediction and analysis with risk assessment using a spatial model in a coastal region in the state of São Paulo, BrazilNatural Hazards and Earth System Science, 14, 2449-2468, 2014Author(s): P. I. M. Camarinha, V. Canavesi, and R. C. S. AlvaláThis study presents a methodology for susceptibility mapping of shallow
landslides just from data and software from the public domain. The study was
conducted in a mountainous region located on the southeastern Brazilian
coast, in the state of São Paulo. The proposal is that the methodology
can be replicated in a practical and reliable way in several other
municipalities that do not have such mappings and that often suffer from
landslide-related disasters. The susceptibility mapping was generated based
on the following maps: geological, soils, slope, horizontal and vertical
curvatures, and land use. The thematic classes of these maps were weighted
according to technical and scientific criteria related to the triggering of
landslides, and were crossed by the fuzzy gamma technique. The mapping was
compared with the risk sector survey made by the Brazilian Geological Survey
(CPRM), which is the official database used by municipalities and civil
defense in risk management. The results showed positive correlations, so that
the critical risk sectors had higher proportions for the more susceptible
classes. To compare the approach with other studies using landslide-scar
maps, correlated indices were evaluated, which also showed satisfactory
results, thus indicating that the methodology presented is appropriate for
risk assessment in urban areas. 2014/09/20 - 18:28

Risk identification of agricultural drought for sustainable AgroecosystemsNatural Hazards and Earth System Science, 14, 2435-2448, 2014Author(s): N. R. Dalezios, A. Blanta, N. V. Spyropoulos, and A. M. TarquisDrought is considered as one of the major natural hazards with a significant
impact on agriculture, environment, society and economy. Droughts affect
sustainability of agriculture and may result in environmental degradation of
a region, which is one of the factors contributing to the vulnerability of
agriculture. This paper addresses agrometeorological or agricultural drought
within the risk management framework. Risk management consists of risk
assessment, as well as a feedback on the adopted risk reduction measures.
And risk assessment comprises three distinct steps, namely risk
identification, risk estimation and risk evaluation. This paper deals with
risk identification of agricultural drought, which involves drought
quantification and monitoring, as well as statistical
inference. For the quantitative assessment of agricultural drought,
as well as the computation of spatiotemporal features, one of the most
reliable and widely used indices is applied, namely the vegetation health
index (VHI). The computation of VHI is based on satellite data of
temperature and the normalized difference vegetation index (NDVI). The
spatiotemporal features of drought, which are extracted from VHI, are areal
extent, onset and end time, duration and severity. In this paper, a 20-year
(1981–2001) time series of the National Oceanic and Atmospheric Administration/advanced very high resolution radiometer (NOAA/AVHRR) satellite data is used, where monthly
images of VHI are extracted. Application is implemented in Thessaly, which
is the major agricultural drought-prone region of Greece, characterized by
vulnerable agriculture. The results show that agricultural drought appears
every year during the warm season in the region. The severity of drought is
increasing from mild to extreme throughout the warm season, with peaks
appearing in the summer. Similarly, the areal extent of drought is also
increasing during the warm season, whereas the number of extreme drought
pixels is much less than those of mild to moderate drought throughout the
warm season. Finally, the areas with diachronic drought persistence can be
located. Drought early warning is developed using empirical functional
relationships of severity and areal extent. In particular, two second-order
polynomials are fitted, one for low and the other for high severity drought
classes, respectively. The two fitted curves offer a forecasting tool on a
monthly basis from May to October. The results of this drought risk
identification effort are considered quite satisfactory offering a
prognostic potential. The adopted remote-sensing data and methods have
proven very effective in delineating spatial variability and features in
drought quantification and monitoring. 2014/09/12 - 22:15

Rainstorms able to induce flash floods in a Mediterranean-climate region (Calabria, southern Italy)Natural Hazards and Earth System Science, 14, 2423-2434, 2014Author(s): O. G. Terranova and S. L. GarianoHeavy rainstorms often induce flash flooding, one of the natural disasters
most responsible for damage to man-made infrastructures and loss of lives,
also adversely affecting the opportunities for socio-economic development of
Mediterranean countries. The frequently dramatic damage of flash floods are
often detected, with sufficient accuracy, by post-event surveys, but rainfall
causing them are still only roughly characterized. With the aim of improving
the understanding of the temporal structure and spatial distribution of
heavy rainstorms in the Mediterranean context, a statistical analysis was
carried out in Calabria (southern Italy) concerning rainstorms that mainly
induced flash floods, but also shallow landslides and debris flows. Thus, a
method is proposed – based on the overcoming of heuristically predetermined
threshold values of cumulated rainfall, maximum intensity, and kinetic
energy of the rainfall event – to select and characterize the rainstorms
able to induce flash floods in the Mediterranean-climate countries.
Therefore, the obtained (heavy) rainstorms were automatically classified and
studied according to their structure in time, localization, and extension.
Rainfall-runoff watershed models can consequently benefit from the enhanced
identification of design storms, with a realistic time structure integrated
with the results of the spatial analysis. A survey of flash flood events
recorded in the last decades provides a preliminary validation of the method
proposed to identify the heavy rainstorms and synthetically describe their
characteristics. The notable size of the employed sample, including data
with a very detailed resolution in time that relate to several rain gauges
well-distributed throughout the region, gives robustness to the obtained
results. 2014/09/11 - 17:16

Analysis of synoptic conditions for tornadic days over western GreeceNatural Hazards and Earth System Science, 14, 2409-2421, 2014Author(s): P. T. Nastos and I. T. MatsangourasTornadoes have been reported in Greece during the last few decades and recent
studies have given evidence that western Greece is an area vulnerable to
tornadoes, waterspouts and funnel clouds In this study, the composite means
and anomalies of synoptic conditions for tornadic events (tornadoes,
waterspouts and funnel clouds) over western Greece are analyzed and

The daily composite means of synoptic conditions were based on the National
Centers for Environmental Prediction–National Center for Atmospheric
Research (NCEP–NCAR) reanalysis data sets, for the period 12 August 1953 to
31 December 2012. The daily composite anomalies were calculated with respect
to 30 years of climatological study (1981–2010) of the synoptic conditions.
The analysis was carried out in terms of seasonal and monthly variability of
composite means and anomalies of synoptic conditions for specific isobaric
levels of 500, 700, 850, 925 hPa and the sea level pressure (SLP). In
addition, an analysis and discussion about the dynamic lifted index from
NCEP–NCAR reanalysis data sets is presented.

The daily composite mean analysis of 500 hPa revealed a trough line across
the northern Adriatic Sea and central Italy, associated with a SW upper-air
stream over western Greece. The maximum composite anomalies were depicted at
the isobaric level of 500 hPa during autumn, spring and summer,
against winter when the anomaly appeared at 925 hPa isobaric level. In
addition, 48% of tornado events during the autumn season occurred in
pre-frontal weather conditions (cold fronts) and 27% developed after the
passage of the cold front. Furthermore, the main difference in synoptic
patterns between tornado and waterspout days along western Greece during the
autumn season is the maximum daily composite anomaly over the Gulf of
Taranto. 2014/09/11 - 17:16

Automated reconstruction of rainfall events responsible for shallow landslidesNatural Hazards and Earth System Science, 14, 2399-2408, 2014Author(s): G. Vessia, M. Parise, M. T. Brunetti, S. Peruccacci, M. Rossi, C. Vennari, and F. GuzzettiOver the last 40 years, many contributions have identified empirical rainfall
thresholds (e.g. rainfall intensity (I) vs. rainfall duration (D),
cumulated rainfall vs. rainfall duration (ED), cumulated rainfall vs.
rainfall intensity (EI)) for the possible initiation of shallow landslides,
based on local and global inventories. Although different methods to trace
the threshold curves have been proposed and discussed in literature, a
systematic study to develop an automated procedure to select the rainfall
event responsible for the landslide occurrence has only rarely been
addressed. Objective criteria for estimating the rainfall responsible for the
landslide occurrence play a prominent role on the threshold values. In this
paper, two criteria for the identification of the effective rainfall events
are presented. The first criterion is based on the analysis of the time
series of rainfall mean intensity values over 1 month preceding the landslide
occurrence. The second criterion is based on the analysis of the trend in the
time function of the cumulated mean intensity series calculated from the
rainfall records measured through rain gauges. The two criteria have been
implemented in an automated procedure that is written in the R language. A
sample of 100 shallow landslides collected in Italy from 2002 to 2012 was
used to calibrate the procedure. The cumulated event rainfall (E) and
duration (D) of rainfall events that triggered the documented landslides
are calculated through the new procedure and are fitted with power law in the
D, E diagram. The results are discussed by comparing the D, E pairs
calculated by the automated procedure and the ones by the expert method. 2014/09/11 - 17:16

Bayesian trend analysis of extreme wind using observed and hindcast series off the Catalan coast, NW Mediterranean SeaNatural Hazards and Earth System Science, 14, 2387-2397, 2014Author(s): M. I. Ortego, J. J. Egozcue, and R. Tolosana-DelgadoIt has been suggested that climate change might modify the occurrence rate
and magnitude of large ocean-wave and wind storms. The hypothesised reason is
the increase of available energy in the atmosphere–ocean system. Forecasting
models are commonly used to assess these effects, given that good-quality
data series are often too short. However, forecasting systems are often tuned
to reproduce the average behaviour, and there are concerns on their relevance
for extremal regimes. We present a methodology of simultaneous analysis of
observed and hindcast data with the aim of extracting potential time drifts
as well as systematic regime discrepancies between the two data sources. The
method is based on the peak-over-threshold (POT) approach and the generalized
Pareto distribution (GPD) within a Bayesian estimation framework. In this
context, storm events are considered points in time, and modelled as
a Poisson process. Storm magnitude over a reference threshold is modelled
with a GPD, a flexible model that captures the tail behaviour of the
magnitude distribution.

All model parameters, i.e. shape and location of the magnitude GPD and the
Poisson occurrence rate, are affected by a trend in time. Moreover, a
systematic difference between parameters of hindcast and observed series is
considered. Finally, the posterior joint distribution of all these trend
parameters is studied using a conventional Gibbs sampler. This method is
applied to compare hindcast and observed series of average wind speed at
a deep buoy location off the Catalan coast (NE Spain, western Mediterranean;
buoy data from 2001; REMO wind hindcasting from 1958 on). Appropriate scale
and domain of attraction are discussed, and the reliability of trends in time
is addressed. 2014/09/11 - 17:16

Agricultural losses related to frost events: use of the 850 hPa level temperature as an explanatory variable of the damage costNatural Hazards and Earth System Science, 14, 2375-2386, 2014Author(s): K. Papagiannaki, K. Lagouvardos, V. Kotroni, and G. PapagiannakisThe objective of this study is the analysis of damaging frost events in
agriculture, by examining the relationship between the daily minimum
temperature in the lower atmosphere (at an isobaric level of 850 hPa) and
crop production losses. Furthermore, the study suggests a methodological
approach for estimating agriculture risk due to frost events, with the aim of
estimating the short-term probability and magnitude of frost-related
financial losses for different levels of 850 hPa temperature. Compared with
near-surface temperature forecasts, temperature forecasts at the level of
850 hPa are less influenced by varying weather conditions or by local
topographical features; thus, they constitute a more consistent indicator of
the forthcoming weather conditions.

The analysis of the daily monetary compensations for insured crop losses caused by weather events in Greece shows that, during the period 1999–2011, frost caused more damage to crop production than any other meteorological phenomenon. Two regions of different
geographical latitudes are examined further, to account for the differences
in the temperature ranges developed within their ecological environment.
Using a series of linear and logistic regressions, we found that minimum
temperature (at an 850 hPa level), grouped into three categories according
to its magnitude, and seasonality, are significant variables when trying to
explain crop damage costs, as well as to predict and quantify the likelihood
and magnitude of damaging frost events. 2014/09/09 - 01:15

Corrigendum to "Modelling wildland fire propagation by tracking random fronts" published in Nat. Hazards Earth Syst. Sci., 14, 2249–2263, 2014Natural Hazards and Earth System Science, 14, 2373-2373, 2014Author(s): G. Pagnini and A. MentrelliNo abstract available. 2014/09/09 - 01:15

Resolving vorticity-driven lateral fire spread using the WRF-Fire coupled atmosphere–fire numerical modelNatural Hazards and Earth System Science, 14, 2359-2371, 2014Author(s): C. C. Simpson, J. J. Sharples, and J. P. EvansVorticity-driven lateral fire spread (VLS) is a form of
dynamic fire behaviour, during which a wildland fire spreads rapidly across a
steep leeward slope in a direction approximately transverse to the background
winds. VLS is often accompanied by a downwind extension of the active flaming
region and intense pyro-convection. In this study, the WRF-Fire
(WRF stands for Weather Research and Forecasting) coupled
atmosphere–fire model is used to examine the sensitivity of resolving VLS to
both the horizontal and vertical grid spacing, and the fire-to-atmosphere
coupling from within the model framework. The atmospheric horizontal and
vertical grid spacing are varied between 25 and 90 m, and the
fire-to-atmosphere coupling is either enabled or disabled. At high spatial
resolutions, the inclusion of fire-to-atmosphere coupling increases the
upslope and lateral rate of spread by factors of up to 2.7 and 9.5,
respectively. This increase in the upslope and lateral rate of spread
diminishes at coarser spatial resolutions, and VLS is not modelled for a
horizontal and vertical grid spacing of 90 m. The lateral fire spread is
driven by fire whirls formed due to an interaction between the background
winds and the vertical circulation generated at the flank of the fire front
as part of the pyro-convective updraft. The laterally advancing fire fronts
become the dominant contributors to the extreme pyro-convection. The results
presented in this study demonstrate that both high spatial resolution and
two-way atmosphere–fire coupling are required to model VLS with WRF-Fire. 2014/09/06 - 14:29

Reducing volcanic risk on Fogo Volcano, Cape Verde, through a participatory approach: which outcome?Natural Hazards and Earth System Science, 14, 2347-2358, 2014Author(s): P. Texier-Teixeira, F. Chouraqui, A. Perrillat-Collomb, F. Lavigne, J. R. Cadag, and D. GrancherThis research paper
presents the outcomes of Work Package 5 (socio-economical vulnerability
assessment and community-based disaster risk reduction) of the MIAVITA
(MItigate and Assess risk from Volcanic Impact on Terrain and human
Activities) research programme conducted on Fogo Volcano, Cape Verde. The
study lasted for almost 3 years (May 2010 to January 2012), of which most of
the time was spent in the village of Chã das Caldeiras, situated within
the 9 km wide caldera of the volcano inside Fogo Natural Park. The
objectives of the programme included assessment of the vulnerability of the
community at risk in terms of livelihoods, access to resources, and power
relations between the local people and the different public and private
institutions. These are important factors that need to be investigated in
order to understand the root causes of vulnerability of the local people.
This case study shows that the voluntary exposure of people to volcanic
threats is linked to daily access to sources of livelihood, especially
agriculture and tourism. This is despite the perception of people of the risk
to their lives and properties. In order to counter the factors of
vulnerability, the study also aimed to identify and enhance local capacities.
To achieve such an objective, a participatory three-dimensional mapping
(P3DM) activity was conducted to facilitate the dialogue between the local
people and the different stakeholders as well as to prepare plans and
measures to reduce volcanic risk. The P3DM was a half success considering
that it has not yet led to an operational plan which takes into account the
local capacities. The main reasons included (1) the non-participatory aspect
of the project at the beginning which should have identified priorities for
people and let them lead the project to ensure the sustainability of (2) deep
conflicts within the community which complicated the focus group discussions
around the 3-D map, and the difficulties in involving more marginalised
people like women and the youth, and (3) the fact that volcanic risk is not a
priority for the people, who are more concerned with daily difficulties due
to unsustainable livelihoods, a lack of access to water, land tenure, and the
restrictions by the Fogo Natural Park administration and the municipal

Still, the study was successful in creating a space for dialogue between the
local people and the outside stakeholders such as the Natural Park
Administration, the Civil Protection, and the Municipality of Santa Catarina,
who have all participated actively during the course of the project. 2014/09/06 - 14:29

PM1 measurements at a site close to an oil/gas pre-treatment plant (Agri Valley – southern Italy): a preliminary studyNatural Hazards and Earth System Science, 14, 2337-2346, 2014Author(s): S. Trippetta, R. Caggiano, and S. SabiaA PM1 (i.e. particulate matter with an aerodynamic
diameter less than 1.0 μm) short-term monitoring campaign was
carried out in the Agri Valley (southern Italy) in September 2012. This area
is of international concern, since it houses one of the largest European
on-shore reservoirs and the largest oil/gas pre-treatment plant (i.e. the
Centro Olio Val d'Agri – COVA) within an anthropised context. PM1
measurements were performed in Viggiano, the nearest town to the COVA plant
and one of the most populated towns of the Agri Valley. During the study
period, the PM1 daily concentrations ranged from 1.2 to
8.4 μg m−3, with a mean value of 4.6 μg m−3.
Regarding the PM1 chemical composition, it can be observed that S and
typical crustal elements were the most abundant constituents of the PM1
collected. By applying principal component analysis (PCA), it was pointed out
that crustal soil, biomass and wood burning, secondary atmospheric reactions
involving COVA plant emissions and local soil particles, and traffic were the
main sources contributing to the PM1 measured in the area under study.
Moreover, a possible contribution of the long-range transport of African dust
was observed. 2014/09/03 - 20:13

Stochastic daily precipitation model with a heavy-tailed componentNatural Hazards and Earth System Science, 14, 2321-2335, 2014Author(s): N. M. Neykov, P. N. Neytchev, and W. ZucchiniStochastic daily precipitation
models are commonly used to generate scenarios of climate variability or
change on a daily timescale. The standard models consist of two components
describing the occurrence and intensity series, respectively. Binary logistic
regression is used to fit the occurrence data, and the intensity series is
modeled using a continuous-valued right-skewed distribution, such as gamma,
Weibull or lognormal. The precipitation series is then modeled using the
joint density, and standard software for generalized linear models can be
used to perform the computations. A drawback of these precipitation models is
that they do not produce a sufficiently heavy upper tail for the distribution
of daily precipitation amounts; they tend to underestimate the frequency of
large storms. In this study, we adapted the approach of
Furrer and Katz (2008) based on hybrid distributions in order to correct for
this shortcoming. In particular, we applied hybrid gamma–generalized Pareto
(GP) and hybrid Weibull–GP distributions to develop a stochastic
precipitation model for daily rainfall at Ihtiman in western Bulgaria. We
report the results of simulations designed to compare the models based on the
hybrid distributions and those based on the standard distributions. Some
potential difficulties are outlined. 2014/09/03 - 20:13

Development of models for maximum and time variation of storm surges at the Tanshui estuaryNatural Hazards and Earth System Science, 14, 2313-2320, 2014Author(s): C.-P. Tsai and C.-Y. YouIn this study, artificial neural networks, including both
multilayer perception and the radial basis function neural networks, are
applied for modeling and forecasting the maximum and time variation of
storm surges at the Tanshui estuary in Taiwan. The physical parameters,
including both the local atmospheric pressure and the wind field factors,
for finding the maximum storm surges, are first investigated based on the
training of neural networks. Then neural network models for forecasting the
time series of storm surges are accordingly developed using the major
meteorological parameters with time variations. The time series of storm
surges for six typhoons were used for training and testing the models, and
data for three typhoons were used for model forecasting. The results show
that both neural network models perform very well for the forecasting of the
time variation of storm surges. 2014/09/03 - 20:13

A multi-scale risk assessment for tephra fallout and airborne concentration from multiple Icelandic volcanoes – Part 2: Vulnerability and impactNatural Hazards and Earth System Science, 14, 2289-2312, 2014Author(s): C. Scaini, S. Biass, A. Galderisi, C. Bonadonna, A. Folch, K. Smith, and A. HöskuldssonWe perform a multi-scale impact assessment of tephra fallout and dispersal
from explosive volcanic activity in Iceland. A companion paper (Biass et al.,
2014; "A multi-scale risk assessment of tephra fallout and airborne
concentration from multiple Icelandic volcanoes – Part I: hazard
assessment") introduces a multi-scale probabilistic assessment of tephra
hazard based on selected eruptive scenarios at four Icelandic volcanoes (Hekla,
Askja, Eyjafjallajökull and Katla) and presents probabilistic hazard maps
for tephra accumulation in Iceland and tephra dispersal across Europe. Here,
we present the associated vulnerability and impact assessment that describes
the importance of single features at national and European levels and
considers several vulnerability indicators for tephra dispersal and
deposition. At the national scale, we focus on physical, systemic and economic
vulnerability of Iceland to tephra fallout, whereas at the European scale we
focus on the systemic vulnerability of the air traffic system to tephra
dispersal. This is the first vulnerability and impact assessment analysis of
this type and, although it does not include all the aspects of physical and
systemic vulnerability, it allows for identifying areas on which further specific
analysis should be performed. Results include vulnerability maps for Iceland
and European airspace and allow for the qualitative identification of the
impacts at both scales in the case of an eruption occurring. Maps produced at
the national scale show that tephra accumulation associated with all eruptive
scenarios considered can disrupt the main electricity network, in particular in
relation to an eruption of Askja. Results also show that several power plants
would be affected if an eruption occurred at Hekla, Askja or Katla, causing a substantial systemic impact due to their
importance for the Icelandic economy. Moreover, the Askja and Katla eruptive
scenarios considered could have substantial impacts on agricultural
activities (crops and pastures). At the European scale, eruptive scenarios at
Askja and Katla are likely to affect European airspace, having
substantial impacts, in particular, in the Keflavík and London flight
information regions (FIRs), but also at FIRs above France, Germany and
Scandinavia. Impacts would be particularly intense in the case of long-lasting
activity at Katla. The occurrence of eruptive scenarios at Hekla is likely to produce high impacts at Keflavík FIR and London FIRs,
and, in the case of higher magnitude, can also impact France's FIRs. Results could
support land use and emergency planning at the national level and risk management
strategies of the European air traffic system. Although we focus on Iceland,
the proposed methodology could be applied to other active volcanic areas,
enhancing the long-term tephra risk management. Moreover, the outcomes of
this work pose the basis for quantitative analyses of expected impacts and
their integration in a multi-risk framework. 2014/08/30 - 21:21

A multi-scale risk assessment for tephra fallout and airborne concentration from multiple Icelandic volcanoes – Part 1: Hazard assessmentNatural Hazards and Earth System Science, 14, 2265-2287, 2014Author(s): S. Biass, C. Scaini, C. Bonadonna, A. Folch, K. Smith, and A. HöskuldssonIn order to assist the elaboration of proactive measures for the management
of future volcanic eruptions in Iceland, we developed a new scenario-based approach to
assess the hazard associated with tephra dispersal and sedimentation at
various scales and for multiple sources. The target volcanoes are Hekla,
Katla, Eyjafjallajökull and Askja, selected either for their high
probabilities of eruption and/or their high potential impact. By coupling
tephrostratigraphic studies, probabilistic techniques and modelling, we
developed comprehensive eruption scenarios for both short- and long-lasting
eruptions and compiled hazard maps for tephra ground deposition at a national
scale and air concentration at a European scale using the TEPHRA2 and FALL3D
models, respectively. New algorithms for the identification of realistic sets
of eruptive source parameters are investigated, which assist the generation
of probability density functions of eruption source parameters for the
selected scenarios. Aggregation processes were accounted for using various
empirical models. Outcomes, i.e. probabilities conditioned to the occurrence of an eruption,
help the assessment and comparison of hazard levels at
different scales. For example, at a national scale Askja has a 5–10%
probability of blanketing the easternmost half of the country with a tephra
accumulation of at least 1 kg m−2. At a continental scale, Katla
has a 5–10% probability of producing ash clouds with concentrations of
2 mg m−3 over the UK, Scandinavia and northern Europe with a mean
arrival time of 48–72 h and a mean persistence time of 6–18 h. In a
companion paper, Scaini et al. (2014) present a vulnerability assessment for
Iceland to ground deposition of tephra and for the European air traffic to
airborne ash which, combined with the outcomes of the present paper,
constitute one of the first comprehensive multi-scale risk assessment associated with
tephra dispersal and sedimentation. 2014/08/30 - 21:21

Modelling wildland fire propagation by tracking random frontsNatural Hazards and Earth System Science, 14, 2249-2263, 2014Author(s): G. Pagnini and A. MentrelliWildland fire propagation is studied in the literature by two alternative
approaches, namely the reaction–diffusion equation and the level-set method.
These two approaches are considered alternatives to each other because the
solution of the reaction–diffusion equation is generally a continuous smooth
function that has an exponential decay, and it is not zero in an infinite
domain, while the level-set method, which is a front tracking technique,
generates a sharp function that is not zero inside a compact domain. However,
these two approaches can indeed be considered complementary and reconciled.
Turbulent hot-air transport and fire spotting are phenomena with a random nature and
they are extremely important in wildland fire propagation.
Consequently, the fire front gets a random character, too; hence, a tracking
method for random fronts is needed. In particular, the level-set contour is
randomised here according to the
probability density function of the interface particle displacement.
Actually, when the level-set method is developed for tracking a front
interface with a random motion, the resulting averaged process emerges to be
governed by an evolution equation of the reaction–diffusion type. In this
reconciled approach, the rate of spread of the fire keeps the same key and
characterising role that is typical of the level-set approach. The resulting
model emerges to be suitable for simulating effects due to turbulent
convection, such as fire flank and backing fire, the faster fire spread being
because of the actions by hot-air pre-heating and by ember landing, and also
due to the fire overcoming a fire-break zone, which is a case not resolved by models based on the
level-set method. Moreover, from the proposed formulation, a correction follows
for the formula of the rate of spread which is due to the mean jump length of
firebrands in the downwind direction
for the leeward sector of the fireline contour. The presented
study constitutes a proof of concept, and it needs to be subjected to a future validation. 2014/08/29 - 02:07

Computational snow avalanche simulation in forested terrainNatural Hazards and Earth System Science, 14, 2233-2248, 2014Author(s): M. Teich, J.-T. Fischer, T. Feistl, P. Bebi, M. Christen, and A. Grêt-RegameyTwo-dimensional avalanche simulation software operating in three-dimensional
terrain is widely used for hazard zoning and engineering to predict runout
distances and impact pressures of snow avalanche events. Mountain forests are
an effective biological protection measure against avalanches; however, the
protective capacity of forests to decelerate or even to stop avalanches that
start within forested areas or directly above the treeline is seldom
considered in this context. In particular, runout distances of small- to
medium-scale avalanches are strongly influenced by the structural conditions
of forests in the avalanche path. We present an evaluation and
operationalization of a novel detrainment function implemented in the
avalanche simulation software RAMMS for avalanche simulation in forested
terrain. The new approach accounts for the effect of forests in the avalanche
path by detraining mass, which leads to a deceleration and runout shortening
of avalanches. The relationship is parameterized by the detrainment
coefficient K [kg m−1 s−2] accounting for differing forest
characteristics. We varied K when simulating 40 well-documented small- to
medium-scale avalanches, which were released in and ran through forests of
the Swiss Alps. Analyzing and comparing observed and simulated runout
distances statistically revealed values for K suitable to simulate the
combined influence of four forest characteristics on avalanche runout: forest
type, crown closure, vertical structure and surface cover, for
example, values for K were higher for dense spruce and mixed spruce-beech
forests compared to open larch forests at the upper treeline. Considering
forest structural conditions within avalanche simulations will improve
current applications for avalanche simulation tools in mountain forest and
natural hazard management. 2014/08/29 - 02:07

Non-susceptible landslide areas in Italy and in the Mediterranean regionNatural Hazards and Earth System Science, 14, 2215-2231, 2014Author(s): I. Marchesini, F. Ardizzone, M. Alvioli, M. Rossi, and F. GuzzettiWe used landslide information for 13 study areas in Italy and morphometric
information obtained from the 3-arcseconds shuttle radar topography mission digital elevation model (SRTM DEM) to determine areas where
landslide susceptibility is expected to be negligible in Italy and in the
landmasses surrounding the Mediterranean Sea. The morphometric information
consisted of the local terrain slope which was computed in a square 3 × 3-cell
moving window, and in the regional relative relief computed in a circular
15 × 15-cell moving window. We tested three different models to
classify the "non-susceptible" landslide areas, including a linear model
(LNR), a quantile linear model (QLR), and a quantile, non-linear model (QNL).
We tested the performance of the three models using independent landslide
information presented by the Italian Landslide Inventory
(Inventario Fenomeni Franosi in Italia – IFFI). Best results were
obtained using the QNL model. The corresponding zonation of
non-susceptible landslide areas was intersected in a geographic information system (GIS) with
geographical census data for Italy. The result determined that 57.5% of
the population of Italy (in 2001) was located in areas where landslide
susceptibility is expected to be negligible. We applied the QNL model to the
landmasses surrounding the Mediterranean Sea, and we tested the synoptic
non-susceptibility zonation using independent landslide information for three
study areas in Spain. Results showed that the QNL model was capable of
determining where landslide susceptibility is expected to be negligible in
the validation areas in Spain. We expect our results to be applicable in
similar study areas, facilitating the identification of non-susceptible
landslide areas, at the synoptic scale. 2014/08/29 - 02:07

Developing an index for heavy convective rainfall forecasting over a Mediterranean coastal areaNatural Hazards and Earth System Science, 14, 2205-2214, 2014Author(s): M. Korologou, H. Flocas, and H. MichalopoulouHeavy convective rainfall incidents that occurred over western coastal Greece
and led to flash floods are analyzed with respect to mesoscale analysis for
the period from January 2006 to June 2011. The synoptic scale circulation is
examined throughout the troposphere along with satellite images, lightning
data and synoptic observations of weather stations. Well-known instability
indices are calculated and tested against synoptic observations. Taking into
account the severity of the incidents, the performance of the indices was not
as good as expected. Further detailed analysis resulted in the development of
a new index that incorporates formalized experience of local weather and
modeled knowledge of mechanisms of severe thunderstorms. The proposed index
named Local Instability Index (LII), is then evaluated and its performance is
found to be quite satisfactory. 2014/08/29 - 02:07

Comment on "Rip current related drowning deaths and rescues in Australia 2004–2011" by Brighton et al. (2013)Natural Hazards and Earth System Science, 14, 2203-2204, 2014Author(s): B. C. Brewster and R. GouldNo abstract available. 2014/08/29 - 02:07

Medicanes in an ocean–atmosphere coupled regional climate modelNatural Hazards and Earth System Science, 14, 2189-2201, 2014Author(s): N. Akhtar, J. Brauch, A. Dobler, K. Béranger, and B. AhrensSo-called medicanes (Mediterranean hurricanes) are meso-scale, marine, and
warm-core Mediterranean cyclones that exhibit some similarities to tropical
cyclones. The strong cyclonic winds associated with medicanes threaten the
highly populated coastal areas around the Mediterranean basin. To reduce the
risk of casualties and overall negative impacts, it is important to improve
the understanding of medicanes with the use of numerical models. In this
study, we employ an atmospheric limited-area model (COSMO-CLM) coupled with
a one-dimensional ocean model (1-D NEMO-MED12) to simulate medicanes. The aim
of this study is to assess the robustness of the coupled model in simulating
these extreme events. For this purpose, 11 historical medicane events are
simulated using the atmosphere-only model, COSMO-CLM, and coupled model, with
different setups (horizontal atmospheric grid spacings of 0.44, 0.22, and
0.08°; with/without spectral nudging, and an ocean grid spacing of
1/12°). The results show that at high resolution, the coupled model is
able to not only simulate most of medicane events but also improve the track
length, core temperature, and wind speed of simulated medicanes compared to
the atmosphere-only simulations. The results suggest that the coupled model
is more proficient for systemic and detailed studies of historical medicane
events, and that this model can be an effective tool for future projections. 2014/08/26 - 18:30

The efficiency of the Weather Research and Forecasting (WRF) model for simulating typhoonsNatural Hazards and Earth System Science, 14, 2179-2187, 2014Author(s): T. Haghroosta, W. R. Ismail, P. Ghafarian, and S. M. BarekatiThe Weather Research and Forecasting (WRF) model includes various configuration
options related to physics parameters, which can affect the performance of
the model. In this study, numerical experiments were conducted to determine
the best combination of physics parameterization schemes for the simulation
of sea surface temperatures, latent heat flux, sensible heat flux,
precipitation rate, and wind speed that characterized typhoons. Through
these experiments, several physics parameterization options within the Weather Research and Forecasting
(WRF) model were exhaustively tested for typhoon Noul, which originated in the
South China Sea in November 2008. The model domain consisted of one coarse
domain and one nested domain. The resolution of the coarse domain was 30 km,
and that of the nested domain was 10 km. In this study, model simulation
results were compared with the Climate Forecast System Reanalysis (CFSR)
data set. Comparisons between predicted and control data were made through
the use of standard statistical measurements. The results facilitated the
determination of the best combination of options suitable for predicting
each physics parameter. Then, the suggested best combinations were examined
for seven other typhoons and the solutions were confirmed. Finally, the best
combination was compared with other introduced combinations for wind-speed
prediction for typhoon Washi in 2011. The contribution of this study is to
have attention to the heat fluxes besides the other parameters. The outcomes
showed that the suggested combinations are comparable with the ones in the literature. 2014/08/26 - 18:30

Application and prospect of a high-resolution remote sensing and geo-information system in estimating earthquake casualtiesNatural Hazards and Earth System Science, 14, 2165-2178, 2014Author(s): T. Feng, Z. Hong, Q. Fu, S. Ma, X. Jie, H. Wu, C. Jiang, and X. TongAn accurate estimation of a casualty rate is critical in response to
earthquake disasters, and could allow an increase in the survival rate.
Building damage is considered to be a major cause of earthquake casualties in
developing countries. High-resolution satellite imagery (HRSI) can be used to
detect the building damage in a period of a short time. This makes it
possible to use a model to estimate earthquake casualties immediately after
the occurrence of an earthquake. With respect to the capability of HRSI, this
study built a new model for estimating the casualty rate in an earthquake
disaster based on remote sensing and a geographical information system. Three
groups of earthquake data, the 2003 Bam earthquake, the 2008 Wenchuan
earthquake, and the 2010 Yushu earthquake, were used to evaluate this model.
The results indicated that our new model significantly improved the accuracy
in predicting the casualty rate. The parameters used in the model vary
between developed and developing countries. This study could provide valuable
information for a more efficient rescue operation in response to earthquakes. 2014/08/26 - 18:30

Brief Communication: CATALYST – a multi-regional stakeholder think tank for fostering capacity development in disaster risk reduction and climate change adaptationNatural Hazards and Earth System Science, 14, 2157-2163, 2014Author(s): M. P. Hare, C. van Bers, P. van der Keur, H. J. Henriksen, J. Luther, C. Kuhlicke, F. Jaspers, C. Terwisscha van Scheltinga, J. Mysiak, E. Calliari, K. Warner, H. Daniel, J. Coppola, and P. F. McGrathThis brief communication presents the work and objectives of the CATALYST
project on "Capacity Development for Hazard Risk Reduction and Adaptation"
funded by the European Commission (October 2011–September 2013). CATALYST
set up a multi-regional think tank covering four regions (Central America and
the Caribbean, East and West Africa, the European Mediterranean, and South
and Southeast Asia), intending to strengthen capacity development for
stakeholders involved in disaster risk reduction (DRR) and climate change
adaptation, in the context of natural hazards. This communication concludes
with a selection of recommendations for capacity development in DRR and
climate change adaptation from the perspective of governance issues. 2014/08/22 - 19:43

Automated classification of the atmospheric circulation patterns that drive regional wave climatesNatural Hazards and Earth System Science, 14, 2145-2155, 2014Author(s): J. Pringle, D. D. Stretch, and A. BárdossyWave climates are fundamental drivers of coastal vulnerability;
changing trends in wave heights, periods and directions can severely impact a
coastline. In a diverse storm environment, the changes in these parameters
are difficult to detect and quantify. Since wave climates are linked to
atmospheric circulation patterns, an automated and objective classification
scheme was developed to explore links between synoptic-scale circulation
patterns and wave climate variables, specifically wave heights. The algorithm
uses a set of objective functions based on wave heights to guide the
classification and find atmospheric classes with strong links to wave
behaviour. Spatially distributed fuzzy numbers define the classes and are
used to detect locally high- and low-pressure anomalies. Classes are derived
through a process of simulated annealing. The optimized classification
focuses on extreme wave events. The east coast of South Africa was used as a
case study. The results show that three dominant patterns drive extreme wave
events. The circulation patterns exhibit some seasonality with one pattern
present throughout the year. Some 50–80% of the extreme wave events are
explained by these three patterns. It is evident that strong low-pressure
anomalies east of the country drive a wind towards the KwaZulu-Natal
coastline which results in extreme wave conditions. We conclude that the
methodology can be used to link circulation patterns to wave heights within a
diverse storm environment. The circulation patterns agree with qualitative
observations of wave climate drivers. There are applications to the
assessment of coastal vulnerability and the management of coastlines worldwide. 2014/08/22 - 19:43

An integrated approach for the evaluation of technological hazard impacts on air quality: the case of the Val d'Agri oil/gas plantNatural Hazards and Earth System Science, 14, 2133-2144, 2014Author(s): M. Calvello, F. Esposito, and S. TrippettaThe Val d'Agri area (southern Italy) hosts one of the biggest onshore European reservoir
and the largest oil/gas pre-treatment plant, named Centro Olio Val
d'Agri (COVA), located in a rural/anthropized context. Several hazards are
associated with this plant. These are mainly represented by possible impacts
of the COVA atmospheric emissions on the local air quality and human health.
This work uses a novel approach based on the integration of air quality
measurements from the regional monitoring network, additional experimental
measurements (i.e. sub-micrometre particulate matter (PM1) and black
carbon (BC)) and advanced statistical analyses to provide a preliminary
evaluation of the Val d'Agri air quality state and give some indication of
specific areas potentially affected by COVA hazards. Results show that the
COVA plant emissions have a particular impact on the air quality of the
area closest to it. In this area several pollutants specifically related to
the COVA combustion processes (i.e. nitrogen oxides, benzene and toluene)
show the highest concentration values and significant correlations. The
proposed approach represents a first step in the assessment of the risks
associated with oil/gas exploration and pre-treatment activities and a
starting point for the development of effective and exportable air quality
monitoring strategies. 2014/08/22 - 19:43

An explanation of large-scale coal and gas outbursts in underground coal mines: the effect of low-permeability zones on abnormally abundant gasNatural Hazards and Earth System Science, 14, 2125-2132, 2014Author(s): F. H. An and Y. P. ChengLarge-scale coal and gas outbursts pose a risk of fatal disasters in
underground mines. Large-scale outbursts (outburst of coal and rock greater
than 500 t) in recent years in China indicate that there is abundant gas in
areas of outbursts containing large amounts of potential energy. The
adequate sealing properties of the roof and floor of a coal seam are
required for local abundant gas around the site of an outburst, but an
annular low-permeability zone in a coal seam, which prevents the loss by gas
migration through the coal seam itself, is also required. The distribution
of coal gas with this annular zone of low permeability is described, and it
is proposed that the annular zone of low permeability creates conditions for
confining the coal gas. The effect of this low-permeability zone on the gas
distribution is analyzed after allowing for simplifications in the model.
The results show that the permeability and length of the low-permeability
zone have a great impact on the gas distribution, and the permeability is
required to be several orders of magnitude less than that of normal coal and
enough length is also in demand. A steep gradient of gas pressure in the
low-permeability zone and the high-pressure gas in the abundant zone of gas
can promote coal mass failure and coal wall deformation, thereby
accelerating the coal and gas outburst. The high-pressure gas in abundant
zone of gas will lead to a large-scale outburst if an outburst occurs. 2014/08/22 - 19:43

Stochastic relation between anomalous propagation in the line-of-sight VHF radio band and occurrences of earthquakesNatural Hazards and Earth System Science, 14, 2119-2124, 2014Author(s): K. Motojima and N. HagaThis paper was intended to find out any relation between anomalous
line-of-sight propagation on the very high frequency (VHF) band and occurrences of earthquakes
near the VHF propagation paths. The television and FM radio broadcasting
waves on the VHF band were monitored continuously over the long term. For
that purpose, a multidirectional VHF band monitoring system was established
and utilized. Anomalous line-of-sight propagation on the VHF band was
distinguished from the monitored wave by using a statistical analysis. After
the stochastic consideration, it was found out that earthquakes associated
with anomalous propagation were characterized by magnitude of earthquakes
M ≥ 4.5, and distances from epicenters L ≤ 75 km. The anomalous
propagation was monitored on the VHF band a few days before the associated
earthquakes occurred. Moreover, the anomaly appeared on multidirectional
propagation paths simultaneously. The anomaly on the line-of-sight
propagation indicates the possibility of narrowly focusing the area of the epicenter
of earthquake. 2014/08/22 - 19:43

Assessment of the physical flood susceptibility of buildings on a large scale – conceptual and methodological frameworksNatural Hazards and Earth System Science, 14, 2105-2117, 2014Author(s): A. Blanco-Vogt and J. SchanzeThere are various approaches available for assessing the flood
vulnerability and damage to buildings and critical infrastructure. They cover
pre- and post-event methods for different scales. However, there can hardly
be found any method that allows for a large-scale pre-event assessment of the
built structures with a high resolution. To make advancements in this
respect, the paper presents, first, a conceptual framework for understanding
the physical flood susceptibility of buildings and, second, a methodological
framework for its assessment. The latter ranges from semi-automatic
extraction of buildings, mainly from remote sensing with a subsequent
classification and systematic characterisation, to the assessment of the
physical flood susceptibility on the basis of depth–impact functions. The
work shows results of the methodology's implementation and testing in a
settlement of the city of Magangué, along the Magdalena River in
Colombia. 2014/08/22 - 19:43

Spatiotemporal multifractal characteristics of electromagnetic radiation in response to deep coal rock burstsNatural Hazards and Earth System Science, 14, 2089-2103, 2014Author(s): S. Hu, E. Wang, and X. LiuDynamic collapses of deeply mined coal rocks are severe
threats to miners; in order to predict collapses more accurately using
electromagnetic radiation (EMR), we investigate the spatiotemporal
multifractal characteristics and formation mechanism of EMR induced by
underground coal mining. Coal rock in the burst-prone zone often exchanges
materials (gas, water and coal) and energy with its environment and
gradually transitions from its original stable equilibrium structure to a
nonequilibrium dissipative structure with implicit spatiotemporal
complexity or multifractal structures, resulting in temporal variation in
multifractal EMR. The inherent law of EMR time series during damage
evolution was analyzed by using time-varying multifractal theory. Results
show that the time-varying multifractal characteristics of EMR are
determined by damage evolution processes. Moreover, the dissipated energy caused by
the damage evolutions, such as crack propagation, fractal sliding and
shearing, can be regarded as the fingerprint of various EMR micro-mechanics.
The dynamic spatiotemporal multifractal spectrum of EMR considers both spatial
(multiple fractures) and temporal (dynamic evolution) characteristics of
coal rocks and records the dynamic evolution processes of rock bursts.
Thus, it can be used to evaluate the coal deformation and fracture process.
The study is of significance for us to understand the EMR mechanism in detail and
to increase the accuracy of the EMR method in forecasting dynamic disasters. 2014/08/16 - 18:23

New improvement of the combined optical fiber transducer for landslide monitoringNatural Hazards and Earth System Science, 14, 2079-2088, 2014Author(s): Z.-W. Zhu, Q.-Y. Yuan, D.-Y. Liu, B. Liu, J.-C. Liu, and H. LuoLandslide monitoring is important in predicting the behavior of landslides,
thereby ensuring environmental, life, and property safety. On the basis of
our previous studies, we conducted the double shear test by using a
third-generation optical fiber transducer that uses expandable polystyrene
(EPS) as base material. However, the third-generation transducer has poor
performance when cohesive force is present between the grout and capillary
stainless steel pipe of the transducer. Thus, the fourth-generation optical
fiber transducer was invented. Similar to the third-generation transducer,
the fourth-generation transducer also used EPS as its base material. Single
shear test was conducted on the fourth-generation transducer after being
grouted with cement mortar (1 : 1 mix ratio). The micro-bend loss mechanism
of the optical fiber was considered, and the optical time domain
reflectometry instrument was used. The fact that the loss sequence of
optical fibers subjected to loading is different at various locations is
found. The relationship of the loading-point displacement vs. optical fiber
sliding distance and optical loss were measured. Results show that the
maximum initial measurement precision of the newly proposed device is 1 mm,
the corresponding sliding distance is 21 mm, and the dynamic range is 0–20 mm.
The fourth-generation transducer can measure the movement direction of
loadings, thus making this transducer applicable for landslide monitoring. 2014/08/15 - 08:37

Palaeoclimate and palaeoseismic events discovered in Diexi barrier lake on the Minjiang River, ChinaNatural Hazards and Earth System Science, 14, 2069-2078, 2014Author(s): X. Q. Wang, Y. R. Li, Y. Yuan, Z. Zhou, and L. S. WangStudies on the formation of the ancient Diexi barrier lake on the
Mingjiang River, southwestern China, have long been carried out.
However, investigations into the correlation between the
palaeoclimate and palaeoenvironment and the palaeoseismic events in
this area are rarely found in literature. The present study took
sediments from the ancient Diexi barrier lake to investigate the
palaeoclimate, palaeoenvironment and palaeoseismic events. A drilling
at the centre of the barrier lake was conducted and the core of
about 260 m long was examined. The palaeoclimate and
palaeoenvironment indicators (sporopollen, carbon and oxygen
isotopes, organic matter, calcium carbonate, granularity) from the
sediments have been tested and analysed, and indicate that there
were 10 climatic and environmental periods between
30 000 and 15 000 a BP (before present). The discovered disturbance
segments in the core indicate there were at least 10 seismic events
during that period. The consistency between climate change and
seismic events indicates that a strong seismicity is normally
accompanied by a climatic variation. This may be a useful
supplement for climate and geohazard predictions in the future. 2014/08/15 - 08:37

Extreme storm surges: a comparative study of frequency analysis approachesNatural Hazards and Earth System Science, 14, 2053-2067, 2014Author(s): Y. Hamdi, L. Bardet, C.-M. Duluc, and V. RebourIn France, nuclear facilities were designed around very low probabilities of
failure. Nevertheless, some extreme climatic events have given rise to
exceptional observed surges (outliers) much larger than other observations,
and have clearly illustrated the potential to underestimate the extreme water
levels calculated with the current statistical methods. The objective of the
present work is to conduct a comparative study of three approaches to extreme
value analysis, including the annual maxima (AM), the peaks-over-threshold
(POT) and the r-largest order statistics (r-LOS). These methods are
illustrated in a real analysis case study. All data sets were screened for
outliers. Non-parametric tests for randomness, homogeneity and stationarity
of time series were used. The shape and scale parameter stability plots, the
mean excess residual life plot and the stability of the standard errors of
return levels were used to select optimal thresholds and r values for the
POT and r-LOS method, respectively. The comparison of methods was based on
(i) the uncertainty degrees, (ii) the adequacy criteria and tests, and
(iii) the visual inspection. It was found that the r-LOS and POT methods
have reduced the uncertainty on the distribution parameters and return level
estimates and have systematically shown values of the 100 and 500-year return
levels smaller than those estimated with the AM method. Results have also
shown that none of the compared methods has allowed a good fit at the right
tail of the distribution in the presence of outliers. As a perspective, the
use of historical information was proposed in order to increase the
representativeness of outliers in data sets. Findings are of practical
relevance, not only to nuclear energy operators in France, for applications
in storm surge hazard analysis and flood management, but also for the optimal
planning and design of facilities to withstand extreme environmental
conditions, with an appropriate level of risk. 2014/08/15 - 08:37

On the clustering of winter storm loss events over GermanyNatural Hazards and Earth System Science, 14, 2041-2052, 2014Author(s): M. K. Karremann, J. G. Pinto, P. J. von Bomhard, and M. KlawaDuring the last decades, several windstorm series hit Europe leading to large
aggregated losses. Such storm series are examples of serial clustering of
extreme cyclones, presenting a considerable risk for the insurance industry.
Clustering of events and return periods of storm series for Germany are
quantified based on potential losses using empirical models. Two reanalysis
data sets and observations from German weather stations are considered for
30 winters. Histograms of events exceeding selected return levels (1-, 2-
and 5-year) are derived. Return periods of historical storm series are
estimated based on the Poisson and the negative binomial distributions. Over
4000 years of general circulation model (GCM) simulations forced with current
climate conditions are analysed to provide a better assessment of historical
return periods. Estimations differ between distributions, for example 40 to
65 years for the 1990 series. For such less frequent series, estimates
obtained with the Poisson distribution clearly deviate from empirical data.
The negative binomial distribution provides better estimates, even though a
sensitivity to return level and data set is identified. The consideration of
GCM data permits a strong reduction of uncertainties. The present results
support the importance of considering explicitly clustering of losses for an
adequate risk assessment for economical applications. 2014/08/08 - 20:29

Flood analysis of the Limpopo River basin through past evolution reconstruction and a geomorphological approachNatural Hazards and Earth System Science, 14, 2027-2039, 2014Author(s): M. Spaliviero, M. De Dapper, and S. MalóThis research reconstructs the past evolution of the Limpopo River, a
transboundary system located in south-eastern Africa, and describes its
geomorphological settings through a literature review and field work
activities, with the aim of analysing flood hazard in the basin. Major
changes have occurred since the late Jurassic–early Cretaceous period due to
successive tectonic events. The paper demonstrates that the apparently
abandoned drainage conformation of the palaeo-Limpopo in the upper and middle
stretches of the river today constitutes preferential flood-prone areas in
the case of major rainfall events. An important palaeo-delta is identified in
the lower Limpopo, which imposes a particular drainage pattern onto the
floodplain in Mozambique and influences the flood dynamics at present. The
adopted method is helpful in determining flood hazard in a data-scarce area
showing complex fluvial dynamics, and allows for the identification of
unsuitable locations for human settlements. 2014/08/08 - 20:29

Sensitivity of the WRF model to the lower boundary in an extreme precipitation event – Madeira island case studyNatural Hazards and Earth System Science, 14, 2009-2025, 2014Author(s): J. C. Teixeira, A. C. Carvalho, M. J. Carvalho, T. Luna, and A. RochaThe advances in satellite
technology in recent years have made feasible the acquisition of
high-resolution information on the Earth's surface. Examples of such
information include elevation and land use, which have become more detailed.
Including this information in numerical atmospheric models can improve their
results in simulating lower boundary forced events, by providing detailed
information on their characteristics. Consequently, this work aims to study
the sensitivity of the weather research and forecast (WRF) model to different
topography as well as land-use simulations in an extreme precipitation event.
The test case focused on a topographically driven precipitation event over
the island of Madeira, which triggered flash floods and mudslides in the
southern parts of the island. Difference fields between simulations were
computed, showing that the change in the data sets produced statistically
significant changes to the flow, the planetary boundary layer structure and
precipitation patterns. Moreover, model results show an improvement in model
skill in the windward region for precipitation and in the leeward region for
wind, in spite of the non-significant enhancement in the overall results with
higher-resolution data sets of topography and land use. 2014/08/06 - 21:42

Chlorophyll increases off the coasts of Japan after the 2011 tsunami using NASA/MODIS dataNatural Hazards and Earth System Science, 14, 1999-2008, 2014Author(s): E. Sava, B. Edwards, and G. CervoneLarge chlorophyll anomalies are observed after the 2011 Japanese tsunami
using the NASA MODIS instrument onboard the TERRA and AQUA satellites. These
anomalies are observed both along the eastern coast of Japan, where the
tsunami wave hit with maximum force, and in the deep water surrounding the
epicentral region. Although both satellites show agreeing spatio-temporal
patterns, larger anomalies are detected using the AQUA satellite. A temporal
analysis shows increased chlorophyll concentrations immediately after the
tsunami, and higher values are observed for nearly one month before reversing
to pre-tsunami levels. 2014/08/06 - 21:42

The characteristics of lightning risk and zoning in Beijing simulated by a risk assessment modelNatural Hazards and Earth System Science, 14, 1985-1997, 2014Author(s): H. Hu, J. Wang, and J. PanIn this study, the cloud-to-ground (CG) lightning flash/stroke density was
derived from the lightning location finder (LLF) data recorded between 2007
and 2011. The vulnerability of land surfaces was then assessed from the
classification of the study areas into buildings, outdoor areas under the
building canopy and open-field areas, which makes it convenient to deduce the
location factor and confirm the protective capability. Subsequently, the
potential number of dangerous lightning events at a location could be
estimated from the product of the CG stroke density and the location's
vulnerability. Although the human beings and all their material properties
are identically exposed to lightning, the lightning casualty risk and
property loss risk was assessed respectively due to their vulnerability
discrepancy. Our analysis of the CG flash density in Beijing revealed that
the valley of JuMaHe to the southwest, the ChangPing–ShunYi zone downwind of
the Beijing metropolis, and the mountainous PingGu–MiYun zone near the coast
are the most active lightning areas, with densities greater than
1.5 flashes km−2 year−1. Moreover, the mountainous
northeastern, northern, and northwestern rural areas are relatively more
vulnerable to lightning because the high-elevation terrain attracts lightning
and there is little protection. In contrast, lightning incidents by induced
lightning are most likely to occur in densely populated urban areas, and the
property damage caused by lightning here is more extensive than that in
suburban and rural areas. However, casualty incidents caused by direct
lightning strokes seldom occur in urban areas. On the other hand, the
simulation based on the lightning risk assessment model (LRAM) demonstrates
that the casualty risk is higher in rural areas, whereas the property loss
risk is higher in urban areas, and this conclusion is also supported by the
historical casualty and damage reports. 2014/08/06 - 21:42

MEDEX: a general overviewNatural Hazards and Earth System Science, 14, 1965-1984, 2014Author(s): A. Jansa, P. Alpert, P. Arbogast, A. Buzzi, B. Ivancan-Picek, V. Kotroni, M. C. Llasat, C. Ramis, E. Richard, R. Romero, and A. SperanzaThe general objective of the international MEDiterranean
EXperiment (MEDEX) was the better understanding and forecasting of cyclones
that produce high impact weather in the Mediterranean. This paper reviews the
motivation and foundation of MEDEX, the gestation, history and organisation
of the project, as well as the main products and scientific achievements
obtained from it. MEDEX obtained the approval of World Meteorological Organisation (WMO) and can be considered as
framed within other WMO actions, such as the ALPine EXperiment (ALPEX),
the Mediterranean Cyclones Study Project (MCP) and, to a certain extent,
THe Observing System Research and Predictability EXperiment (THORPEX) and the
HYdrological cycle in Mediterranean EXperiment (HyMeX). Through two phases (2000–2005 and 2006–2010), MEDEX has
produced a specific database, with information about cyclones and severe or
high impact weather events, several main reports and a specific data targeting system field
campaign (DTS-MEDEX-2009). The scientific achievements are significant in
fields like climatology, dynamical understanding of the physical processes
and social impact of cyclones, as well as in aspects related to the location
of sensitive zones for individual cases, the climatology of sensitivity zones
and the improvement of the forecasts through innovative methods like
mesoscale ensemble prediction systems. 2014/08/06 - 21:42