Storm Profile Research Articles

Infiltration and runoff generation processes in fire‐affected soils

AbstractPost‐wildfire runoff was investigated by combining field measurements and modelling of infiltration into fire‐affected soils to predict time‐to‐start of runoff and peak runoff rate at the plot scale (1 m2). Time series of soil‐water content, rainfall and runoff were measured on a hillslope burned by the 2010 Fourmile Canyon Fire west of Boulder, Colorado during cyclonic and convective rainstorms in the spring and summer of 2011. Some of the field measurements and measured soil physical properties were used to calibrate a one‐dimensional post‐wildfire numerical model, which was then used as a ‘virtual instrument’ to provide estimates of the saturated hydraulic conductivity and high‐resolution (1 mm) estimates of the soil‐water profile and water fluxes within the unsaturated zone.Field and model estimates of the wetting‐front depth indicated that post‐wildfire infiltration was on average confined to shallow depths less than 30 mm. Model estimates of the effective saturated hydraulic conductivity, Ks, near the soil surface ranged from 0.1 to 5.2 mm h−1. Because of the relatively small values of Ks, the time‐to‐start of runoff (measured from the start of rainfall), tp, was found to depend only on the initial soil‐water saturation deficit (predicted by the model) and a measured characteristic of the rainfall profile (referred to as the average rainfall acceleration, equal to the initial rate of change in rainfall intensity). An analytical model was developed from the combined results and explained 92–97% of the variance of tp, and the numerical infiltration model explained 74–91% of the variance of the peak runoff rates. These results are from one burned site, but they strongly suggest that tp in fire‐affected soils (which often have low values of Ks) is probably controlled more by the storm profile and the initial soil‐water saturation deficit than by soil hydraulic properties. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Max-stable processes for modeling extremes observed in space and time

Max-stable processes have proved to be useful for the statistical modeling of spatial extremes. For statistical inference it is often assumed that there is no temporal dependence; i.e., that the observations at spatial locations are independent in time. In a first approach we construct max-stable space–time processes as limits of rescaled pointwise maxima of independent Gaussian processes, where the space–time covariance functions satisfy weak regularity conditions. This leads to so-called Brown–Resnick processes. In a second approach, we extend Smith’s storm profile model to a space–time setting. We provide explicit expressions for the bivariate distribution functions, which are equal under appropriate choice of the parameters. We also show how the space–time covariance function of the underlying Gaussian process can be interpreted in terms of the tail dependence function in the limiting max-stable space–time process.

Two‐phase storm profile of global electron content in the ionosphere and plasmasphere of the Earth

The global electron content (GEC) derivation is initiated by summing up the total electron content of each cell of Global Positioning System GPS‐TEC global map multiplied by the cell area. Algorithm of GEC calculation is improved in the present paper using the electron density varying with height through the total volume of a spherical layer in near‐Earth space up to 20,200 km (GPS orbit) reconstructed from TEC with the International Reference Ionosphere model extended to the Plasmasphere (IRI‐Plas). An analytical model is first derived for two‐phase typical GEC storm profile by a common epoch analysis of 10 storms during 2001–2011 with the starting time put at the origin of the negative phase of GEC departure from the quiet reference (5 day median). It is found that GEC depletion occurs synchronously with decrease of the solar wind velocity and the outset of recovery of the magnetospheric ring current (the equatorial Dst index) and the auroral electrojet (AE index). Thus, the GEC is an indicator of the plasma injection in the ionosphere and plasmasphere with the solar wind energy inducing the positive phase of GEC storm during 24 h with electron number increased by 10–20% followed by a negative phase with GEC decrease by 10–20% during 40 h of a plasma release (ejection) into the magnetosphere tail beyond the three Earth radii (GPS orbit).

Use of observed scaled daily storm profiles in a copula based rainfall disaggregation model

It has been demonstrated in this paper that observed scaled daily storm profiles (OSDSPs) can be used at a different climatic site to disaggregate daily rainfall data into fine timescales by following some selection rules. For a given daily rainfall depth, the normal copula model predicts the total daily wet periods’ duration, capturing the seasonal variation of the copula and marginal lognormal model parameters by a first harmonic Fourier series. An OSDSP type, defined according to whether the first and/or last periods of the day are wet, is selected based on whether the day is an isolated wet day or in a cluster of wet days. For two consecutive wet Julian days, a transition probability is used to ascertain whether rainfall will cross midnight and spread to the next Julian day. A pool of the selected OSDSP type having the same, or close, numerical value of the copula predicted total daily wet periods’ duration is created. From the pool is selected one OSDSP that has the closest value of lag-1 autocorrelation of the natural logarithm of the wet period depths to a simulated value conditioned on the total daily wet periods’ duration. Multiplication of the OSDSP’s period depths by the daily rainfall depth gives the complete daily storm profile. The applicability of the OSDSP based disaggregation model is demonstrated by using two case study sites and OSDSPs from Australian State capital cities situated in different climates. Using the capital cities’ OSDSPs independently, and also together, predicted quite well the monthly gross rainfall statistics down to 6min.

Permafrost as a factor of the dynamics of the coastal zone of the Russian East Arctic Seas

Some regularities that are generally accepted in the theory about the development of sea coasts as applied to the East Arctic coast of Russia do not conform to reality. To find out the reasons for these contradictions, the connection between the coastal processes and the perennially frozen sediment of the underwater coastal slope in the Laptev Sea and the East Siberian Sea was studied. The frozen state of the deposits of the coastal zone exerts a substantial influence on the coastal dynamics and determines several features of the thermoabrasion development. In particular, the subaqual permafrost does not allow the forming of a storm profile with dynamic balance. This fact causes the more effective action of the sea on the coastal cliffs and the more active recession of the frozen coasts as compared with their counterparts outside the cryolitozone.

An experimental study on geometric characteristics of beach erosion profiles

The beach profile and sediment transport are very important factors in the design of coastal structures, and the beach profile is mainly affected by a number of parameters, such as wave height and period, beach slope, and the material properties of the bed. In this study, considering wave height ( H 0=6.5, 11.5, 16, 20, 23, 26 and 30 cm), wave period ( T=1.46 and 2.03 s), beach slope ( m=1/10 and 1/15) and mean sediment diameter ( d 50=0.18, 0.26, 0.33 and 0.40 mm), an experimental investigation of coastal erosion profile (storm profile) was carried out in a wave flume using regular waves, and geometric characteristics of erosion profile were determined by the resultant erosion profile. Dimensional and non-dimensional equations were obtained by using linear and non-linear regression methods through the experimental data and were compared with previously developed equations in the literature. The results have shown that the experimental data fitted well to the proposed equations with respect to the previously developed equations.

Uncertainties in radar echo top heights used for hail detection

AbstractMost operational hail detection algorithms for single‐polarisation radars are based on the analysis of the vertical profiles of radar reflectivity. At KNMI (Royal Netherlands Meteorological Institute) and RMI (Royal Meteorological Institute of Belgium) the probability of hail is derived from the height of the freezing level and the 45‐dBZ radar echo top height (maximum height of the 45‐dBZ echo). Echo tops are affected by errors in the measured reflectivity itself and by errors in the height assigned to these reflectivities. This study investigates the quality of radar echo top heights as a function of range and explores the implications for hail detection.The method is based on the comparison between reflectivity measurements from two radars on the vertical cross‐section extending between these radars. In a first step, sampling errors related to the radar Volume Coverage Patterns are analysed using idealised storm profiles. Subsequently, real reflectivity data for 25 thunderstorm episodes are compared. It is found that the quality of the maximum reflectivity measurements strongly deteriorates with range and that about half of this degradation can be attributed to overshooting effects. Height assignment differences between the two radars are limited to about 0.5 km. Errors on the reflectivity measurements strongly affect the frequency of 45‐dBZ threshold exceedances. However, once the threshold is exceeded, errors in measuring the 45‐dBZ echo top heights generally affect the derived probability of hail by less than 20%. Copyright © 2006 John Wiley & Sons, Ltd.

Morphological and Sedimentological Impacts of Hurricane Ivan and Immediate Poststorm Beach Recovery along the Northwestern Florida Barrier-Island Coasts

Ivan, a strong Category 4 hurricane (downgraded to a Category 3 at landfall), caused widespread erosion and overwash along the northwestern Florida barrier-island beaches. This study examines the storm impact and short-term post-storm recovery along a 200-km stretch of coast from Fort Walton Beach eastward to St. George Island. One prestorm and three poststorm beach-profile surveys were conducted to quantify the storm-induced morphological changes and poststorm recovery. Forty-six trenches were excavated to study the characteristics and thickness of subaerial storm deposits.Extensive inundation and overwash occurred within 100 km from the storm center at landfall. Significant beach/dune erosion was measured as far as 300 km east of the storm center. The highest elevation of beach erosion extended considerably above the measured storm-surge level, indicating that storm-wave setup and swash run-up played significant roles in controlling the elevation of beach erosion. A simple empirical formula reproduced the wave setup and swash run-up reasonably well. Beach recovery began immediately after the storm. Within 90 days, the berm crest recovered to its prestorm elevation, although it was now located approximately 15 m landward for nonoverwashed sites and 30 to 40 m for overwashed sites. The steep prestorm foreshore slope was restored from the gentle storm profile within 30 days.An apparent erosional surface was observed along the impacted foredune and backbeach, extending over 300 km eastward from the storm center. This erosional surface represents a net elevation loss ranging from 0.5 to over 2.0 m. A storm layer of up to 50 cm thick was deposited above the erosional surface. Generally, the storm-layer thickness decreases away from the storm center, as well as landward from the high tide line. Local factors such as beach width and orientation, and sediment properties and supply caused variations in the thickness of storm deposit.

Morfodinâmica praial: uma breve revisão

Desde o início dos anos 30 perfis de praia foram classificados em um dos dois tipos: perfis de tempestade ou perfis de ondulação associados, respectivamente, com ondas de alta e baixa esbeltez. Mudanças no perfil praial envolvem muitas variáveis, tornando muito difícil a formulação de modelos de prediçâo de comportamento praial. Somente a partir da década de 70, as características dos sedimentos c os processos de transformação de ondas operantes na plataforma interna e antepraia, acoplados com a morfologia tridimensional e a hidrodinâmica da praia, começaram a ser estudados de maneira integrada. Tais estudos levaram a um melhor entendimento do comportamento de sistemas praiais e zonas de arrebentação e também à formulação de modelos seqüenciais de comportamento morfodinâmico daqueles sistemas. Apresenta-se aqui uma breve síntese dos principais trabalhos e modelos introduzidos pela escola australiana de geomorfologia costeira na área de morfodinâmica praial e o resultado de sua aplicação em algumas praias do sul e sudeste do Brasil.

Model predictions for the 2001 Leonids and implications for Earth-orbiting satellites

A numerical model of the Leonid stream is developed, based on an earlier model which has been applied to the Perseid stream. The results for this model are applied to the 2001 Leonid return. By examining the full three-dimensional dispersion of individual ‘streamlets’ released from the Leonid parent comet, 55P/Tempel–Tuttle, we have derived an estimate for the temporal change in spatial density of each trail. Using this result along with an estimate for the location of the centres for individual streamlets and fits to previous Leonid storm profiles, we estimate that the activity from the shower will be broad and relatively strong (zenithal hourly rates perhaps in excess of 1000). In particular, streamlets from the 1766 and 1799 ejections contribute to activity peaking near 10 and 12 ut on 2001 November 18, respectively. Additional older material from 1633, 1666 and 1699, as well as more recent ejections from 1866 and 1833, contributes to a much broader secondary maximum near 17.5 ut on November 18. Comparison with other published models of predicted Leonid activity in 2001 shows general agreement in terms of timing, but the models differ significantly in terms of the relative magnitude of the activity (which other models suggest will be larger). Significant anisotropy in the impact hazard exists for satellites in the geostationary belt, with those over western longitudes most likely to be affected. Integrated fluences for the 2001 Leonid return suggest a hazard of order one magnitude greater than occurred for the 1999 Leonid storm.

Mean and Near-Inertial Ocean Current Response to Hurricane Gilbert

The three-dimensional hurricane-induced ocean response is determined from velocity and temperature profiles acquired in the western Gulf of Mexico between 14 and 19 September 1988 during the passage of Hurricane Gilbert. The asymmetric wind structure of Gilbert indicated a wind stress of 4.2 N m−2 at a radius of maximum winds (Rmax) of 60 km. Using observed temperature profiles and climatological temperature–salinity relationships, the background and storm-induced geostrophic currents (re: 750 m) were 0.1 m s−1 and 0.2 m s−1, respectively. A Loop Current warm core ring (LCWCR) was also located to the right of the storm track at 4–5 Rmax, where anticyclonically rotating near-surface and 100-m currents decreased from 0.9 m s−1 to 0.6 m s−1 at depth. The relative vorticity in the LCWCR was shifted below the local Coriolis parameter by about 6%. In a storm-based coordinate system, alongtrack residual velocity profiles from 0 to 4 Rmax were fit to a dynamical model by least squares to isolate the near-inertial content over an e-folding timescale of four inertial periods (IP ≈ 30 h). Observed frequency shifts in the mixed layer currents ranged from 1.03 to 1.05f in agreement with both the backrotated velocity profiles at 1.04f relative to the storm profile (where maximum correlation coefficients were 0.8) and the predicted frequency shift from the mixed-layer Burger number. This frequency was increasingly blue shifted in the upper 100 m to 1.1f, decreasing toward f within the thermocline. Near-inertial currents rotated anticyclonically by 90°–180° in the upper ocean, providing the velocity shear for layer cooling and deepening observed on the right-hand side of the track. A summation of the first four baroclinic modes described up to 77% of this near-inertial current variability during the first 1.75 IP. However, the variance explained by this modal summation decreased to a minimum of 36% after 2.9 IP following passage due to phase separation between the first baroclinic mode and higher-order modes in the mixed layer. Although the response was complicated by the LCWCR, the evolving three-dimensional current structure can be described by linear, near-inertial wave dynamics.

The spatial relationship between active regions and coronal holes and the occurrence of intense geomagnetic storms throughout the solar activity cycle

Abstract. We study the annual frequency of occurrence of intense geomagnetic storms (Dst < –100 nT) throughout the solar activity cycle for the last three cycles and find that it shows different structures. In cycles 20 and 22 it peaks during the ascending phase, near sunspot maximum. During cycle 21, however, there is one peak in the ascending phase and a second, higher, peak in the descending phase separated by a minimum of storm occurrence during 1980, the sunspot maximum. We compare the solar cycle distribution of storms with the corresponding evolution of coronal mass ejections and flares. We find that, as the frequency of occurrence of coronal mass ejections seems to follow very closely the evolution of the sunspot number, it does not reproduce the storm profiles. The temporal distribution of flares varies from that of sunspots and is more in agreement with the distribution of intense geomagnetic storms, but flares show a maximum at every sunspot maximum and cannot then explain the small number of intense storms in 1980. In a previous study we demonstrated that, in most cases, the occurrence of intense geomagnetic storms is associated with a flaring event in an active region located near a coronal hole. In this work we study the spatial relationship between active regions and coronal holes for solar cycles 21 and 22 and find that it also shows different temporal evolution in each cycle in accordance with the occurrence of strong geomagnetic storms; although there were many active regions during 1980, most of the time they were far from coronal holes. We analyse in detail the situation for the intense geomagnetic storms in 1980 and show that, in every case, they were associated with a flare in one of the few active regions adjacent to a coronal hole.

The spatial relationship between active regions and coronal holes and the occurrence of intense geomagnetic storms throughout the solar activity cycle

We study the annual frequency of occurrence of intense geomagnetic storms (Dst < –100 nT) throughout the solar activity cycle for the last three cycles and find that it shows different structures. In cycles 20 and 22 it peaks during the ascending phase, near sunspot maximum. During cycle 21, however, there is one peak in the ascending phase and a second, higher, peak in the descending phase separated by a minimum of storm occurrence during 1980, the sunspot maximum. We compare the solar cycle distribution of storms with the corresponding evolution of coronal mass ejections and flares. We find that, as the frequency of occurrence of coronal mass ejections seems to follow very closely the evolution of the sunspot number, it does not reproduce the storm profiles. The temporal distribution of flares varies from that of sunspots and is more in agreement with the distribution of intense geomagnetic storms, but flares show a maximum at every sunspot maximum and cannot then explain the small number of intense storms in 1980. In a previous study we demonstrated that, in most cases, the occurrence of intense geomagnetic storms is associated with a flaring event in an active region located near a coronal hole. In this work we study the spatial relationship between active regions and coronal holes for solar cycles 21 and 22 and find that it also shows different temporal evolution in each cycle in accordance with the occurrence of strong geomagnetic storms; although there were many active regions during 1980, most of the time they were far from coronal holes. We analyse in detail the situation for the intense geomagnetic storms in 1980 and show that, in every case, they were associated with a flare in one of the few active regions adjacent to a coronal hole.

The Modified Turning Bands (MTB) model for space-time rainfall. III. Estimation of the storm/rainband profile and a discussion of future model prospects

Methods are developed which project two-dimensional radar rainfall data into one dimension such that the overall storm profile can be measured. As a result, it is found that the storm width and velocity can be measured accurately, but the estimation of rainband width and rainband velocity remains elusive. Thus it is concluded that more work has to be done involving many real storms so that the problems of estimating these parameters may be understood more fully, leading, it is hoped, to suggestions for new approaches. As regards longer-term work, the various roles which the Modified Turning Bands (MTB) model may play in the estimation and forecasting of rainfall are discussed, and the potential for the model in the investigation of the rainfall-runoff characteristics of catchments is outlined.

Stochastic storm profiles for strain accumulation in clay : K.O. Ronold & S.R. Winterstein, Transactions - ASME: Journal of Offshore Mechanics & Arctic Engineering, 116(1), 1994, pp 28–34

Stochastic storm profiles for strain accumulation in clay : K.O. Ronold & S.R. Winterstein, Transactions - ASME: Journal of Offshore Mechanics & Arctic Engineering, 116(1), 1994, pp 28–34

Stochastic Storm Profiles for Strain Accumulation in Clay

For offshore gravity platforms founded on clay, an important foundation failure mode arises from cumulative shear strain under cyclic loads. The major contribution to this cyclic strain accumulation comes from wave loads in sea states of high intensities. To analyze this and similar cumulative damage mechanisms, a probabilistic storm profile model is developed. Slepian random process models are used to estimate the temporal evolution of the significant wave height HS during a storm, during which HS exceeds a specified threshold. To predict storm profiles associated with any threshold, the model requires only conventional marginal wave statistics along with limited correlation information. Numerical results are shown for a North Sea location, where rare, high-threshold events can be verified by long hindcast histories. For an example foundation, predicted strain accumulation is compared with results from conventional storm profile models.

Magnetic Storm Development and Its Quantification for Aims of Modeling.

Using a large sample of storms of different intensity the ring current magnetic field development is followed in terms of varying interplanetary conditions. It is shown that although the storm depression field is associated with energy input into the magnetosphere, the sustained IEF intensity <-5 mV/m as a condition for the occurrence of intense storms appears not to be of general validity. Quantification of the magnetic storm development indicates the role of the actual state of the magnetosphere in the development of its response on interplanetary medium forcing. Ring current energization is considered for some storm models represented by pairs of energy injection rate and time decay parameter. A number of models are juxtaposed quantitatively. The adequacy of modeling of storm profiles and the significance of decay parameter in the magnetic storm development is discussed from the viewpoint of consistency of energy injection rate and energy decay rate and also with regard to an adequate distribution of dissipated energy within the ring current region and auroral ionosphere.

The hyperbolic shape triangle as a tool for discriminating populations of sediment samples of closely connected origin

ABSTRACTThis paper describes a new method for discriminating populations of sediment samples of closely connected origin. It provides a dynamical interpretation to grain size data. The descriptive modelling power of the hyperbolic distribution, the hyperbolic shape triangle and the population concept have been applied to several hundred beach sand samples from the Mediterranean coast of southern Israel. The investigated samples are from a 60 km stretch of beach, from Rafah to Ashqelon, and represent an autumn storm profile. The domain of variation of the hyperbolic shape parameters χ and ξ is a triangle referred to as the hyperbolic shape triangle. The distribution of the estimated (χ, ξ) shape positions in the hyperbolic shape triangle was studied graphically and statistically using the newly developed tools described here to present, evaluate and compare hyperbolic shape position data for analysed grain size populations. The graphical methods of contouring the scatter diagrams of the samples in the domain of the hyperbolic shape triangle and chi‐squared tests are demonstrated. They were performed on two sedimentary environments normal to the beach, namely inshore and mid‐swash zone. The qualitative and quantitative estimated changes in the populations (χ, ξ) shape positions in the shape triangle suggest that they are subjected mainly to ε erosion‐deposition processes. Their modes are located along one of the upper ‘hammock’curves in the shape triangle. The location and scale invariant hyperbolic shape parameter ρ indicates a change of the grain size distribution across the left part of the hyperbolic shape triangle, which is the domain of predominantly depositional processes. However, the mid‐swash zone sediments reflect that they are subjected more to depositional processes and the inshore sediments more to erosional ones.

Foundation Safety of Gravity-Based Systems During Severe Storms

The temporal evolutions of the most important sea state characteristics during storms are presented together with the corresponding uncertainties. Storm data from the Northern North Sea are used for this purpose. The influence of the uncertainties associated with an extreme storm on the foundation safety is demonstrated for a gravity-based structural system founded on a clay. The stability is analyzed with respect to failure in large cyclic displacements accumulated during the storm. The failure probability is estimated by a first-order reliability method and the most important variables concerning their contribution to the failure probability are indicated. In most practical foundation safety investigations, an idealized deterministic storm profile is adopted. The adequacy of this profile is considered by calibrating a “load factor” to be used in connection with the idealized profile.

Classification of storm profiles using crossing properties

Temporal characteristics of rainfall are classified by means of crossing properties of the storm profile. A method based on the number of crossings is proposed for the identification of storm patterns for use in simulation models. This enables local synoptic features and seasonal variations to be represented. Storm duration and depth are shown to be correlated with the type of classification. The classification is also an aid in identifying spatial characteristics such as storm movement. A case study was made using autographic rainfall data from a region of 1800 km 2 around the city of Birmingham.