High-intensity Storms Research Articles

Caracterización de la erosión en áreas acarcavadas en la Fm. Tudela (Bardenas Reales, Navarra)

At Bardenas Reales, erosion processes are due to hydric action and wind erosion. Climate, lithology and geomorphology are the main factors that control water erosion. Besides sediment yield by water, other forms exist to export material: mudslides and armoured mud balls. Clay material at high slopes and high dispersion index together with climate determine the presence of one type of erosion or another. On winter times, mudslides are developed while on summer high intensity storms provoke incision. Meanwhile armoured mud balls could coexist with both of them.

The importance of surface controls on overland flow connectivity in semi‐arid environments: results from a numerical experimental approach

AbstractIn semi‐arid environments, the characteristics of the land surface determine how rainfall is transformed into surface runoff and influences how this runoff moves from the hillslopes into river channels. Whether or not water reaches the river channel is determined by the hydrological connectivity. This paper uses a numerical experiment‐based approach to systematically assess the effects of slope length, gradient, flow path convergence, infiltration rates and vegetation patterns on the generation and connectivity of runoff. The experiments were performed with the Connectivity of Runoff Model, 2D version distributed, physically based, hydrological model. The experiments presented are set within a semi‐arid environment, characteristic of south‐eastern Spain, which is subject to low frequency high rainfall intensity storm events. As a result, the dominant hydrological processes are infiltration excess runoff generation and surface flow dynamics. The results from the modelling experiments demonstrate that three surface factors are important in determining the form of the discharge hydrograph: the slope length, the slope gradient and the infiltration characteristics at the hillslope‐channel connection. These factors are all related to the time required for generated runoff to reach an efficient flow channel, because once in this channel, the transmission losses significantly decrease. Because these factors are distributed across the landscape, they have a fundamental role in controlling the landscape hydrological response to storm events. Copyright © 2013 John Wiley & Sons, Ltd.

Temporal and spatial changes in dissolved organic carbon concentration and fluorescence intensity of fulvic acid like materials in mountainous headwater catchments

Dissolved organic carbon (DOC) such as humic substances are key to understanding the aquatic environment in catchments, because they, containing a large number of phenolic and carboxylic acid groups, adsorb many kinds of inorganic materials and also affect nutrition and carbon transport in catchments. To understand the detailed DOC dynamics, we conducted hydrological observations at mountainous headwater catchments dominated by different vegetation types (planted evergreen coniferous forest of 1.29 ha and natural deciduous broadleaf forest of 1.28 ha). The relationship between DOC concentrations and fluorescence intensity of fulvic acid-like materials (F-FAM) were positively correlated in both catchments but different between soil extracts, baseflow, and near surface flow represented by biomat flow. The ratios of change in F-FAM to that in DOC concentration (F-FAM/DOC) were higher in the baseflow (about 6 in both catchments) and lower in the soil extracts (about 4.5 in both catchments, respectively). However, the relationship in stormflow was distributed between the trends of baseflow and soil extracts. The higher F-FAM/DOC in baseflow may thus indicate that DOC (and FAM) in groundwater discharge mainly contributed to the stream flow, and the stormflow mainly reflect subsurface flow through soil during most rainstorms. In contrast, a high F-FAM/DOC ratio (>6) appeared in the stormflow of both catchments especially during large storms of short duration and high intensity following a dry antecedent period. The F-FAM/DOC in biomat flow developing distinctly in the coniferous catchment was high (about 6.5). Thus, rapid shallow subsurface flow through the biomat or near-surface of slopes might explain the unique transport dynamics of DOC and FAM in stormflows with the high F-FAM/DOC ratio. These results imply that the DOC and FAM relationship responds variably depending on both the distribution of soil organic matter and rainwater flow paths in steep slopes as well as on storm size and characteristics.

Landslide inventory map for the Briga and the Giampilieri catchments, NE Sicily, Italy

On 1 October 2009, a high intensity storm hit the Ionian coast of Sicily, SW of Messina, Italy. The Santo Stefano di Briga rain gauge, located 2 km W of the Ionian coast, recorded 225 mm of rain in seven hours. The intense rainfall event triggered abundant slope failures, and resulted in widespread erosion and deposition of debris along ephemeral drainage channels, extensive inundation, and local modifications of the coastline. Landslides occurred in a territory prone to slope failures, due to the local geological and geomorphological settings. Many landslides were related to the presence of roads lacking adequate drainage. Abandoned terraced slopes lacking proper drainage, and unmaintained dry walls were also related to slope failures. Damage was particularly severe in small villages and at several sites along the transportation network. The shallow landslides and the inundation resulted in 37 fatalities, including 31 deaths and six missing persons, and innumerable injured people. After the event, an accurate landslide inventory map was prepared for the Briga and the Giampilieri catchments. The map shows: (i) the distribution of the event landslides triggered by the 1 October 2009 rainfall event; (ii) the distribution of the pre-existing slope failures; and (iii) other geomorphological features related to fluvial processes and slope movements. The landslide inventory map was prepared at 1:10,000 scale through a combination of field surveys and photo-interpretation of pre-event and post-event, stereoscopic and pseudo-stereoscopic, aerial photography. Different types of aerial photographs were analysed visually to prepare the landslide inventory map. The event landslides were mapped through the interpretation of pseudo-stereoscopic colour photographs taken shortly after the event at 1:3500 scale, combined with digital stereoscopic photographs at approximately 1:4500 scale, taken in November 2009. The pre-event landslides and the associated geomorphological features were mapped using 1:33,000 scale aerial photographs flown in 1954, 1955, and 2005. The event and pre-existing landslides were checked in the field in the period October–November 2009.

The impact of climate change on global tropical cyclone damage

One potential impact from greenhouse-gas emissions is increasing damage from extreme events. Here, we quantify how climate change may affect tropical cyclone damage. We find that future increases in income are likely to double tropical cyclone damage even without climate change. Climate change is predicted to increase the frequency of high-intensity storms in selected ocean basins depending on the climate model. Climate change doubles economic damage, but the result depends on the parameters of the damage function. Almost all of the tropical cyclone damage from climate change tends to be concentrated in North America, East Asia and the Caribbean‐Central American region. This paper provides a framework to combine atmospheric science and economics, but some effects are not yet modelled, including sea-level rise and adaptation.

Increasing occurrence of high-intensity rainstorm events relevant for the generation of soil erosion in a temperate lowland region in Central Europe

Summary Rainfall times series with a high temporal resolution of 1 min for the Emscher–Lippe catchment area were analysed for trends in regard to erosion-relevant storm events with intensities larger than 0.3 mm/min (>20 mm/h) for the last 70 years using the Mann–Kendall test. The analysis data showed for all investigated stations an increase of rainstorm events with erosion-relevant rainfall intensities; the trend was more pronounced over the last 35 years and was shown to be statistical significant for a critical zone with rainfall characteristics of: intensity iRain = 0.3–0.7 mm/min, duration tRain = 2–10 min and depth hRain = 1–3 mm. The increase of rainstorm events over the last 35 years was more pronounced in the summer season (July–September), but increases were detected also in the other seasons. The high-intensity storm events occured only ca. 4–15 times/year; the estimated trend increases of up to 0.5 events/year could therefore result in a multiplication of the occurrence of these storm events within only a few decades. This study has shown for the first time that the rainfall regime for temperate lowland regions in Germany has changed within its erosion-relevant spectrum over the last couple of decades. Parallel to the changes in the rainfall regime, increases in the annual and seasonal average temperature and changes in the occurrence of circulation patterns responsible for the generation of high-intensity storms were found, however not in the occurrence of thunderstorms. A climate-change driven increase of rain storm events over the last couple of decades and a potential future continuation of this trend may have several adverse effects for the study area and potentially for a larger region in Central Europe, for example an increase of soil erosion on slopes, the depletion of soil nutrients, an increased transport of nutrients and contaminants attached to sediment particles, their transfer into surface water bodies and consequential negative effects on stream habitats.

Measuring forest floor and canopy interception in a savannah ecosystem

Interception is one of the most underestimated processes of the hydrological cycle. However, it amounts to a substantial part of the terrestrial evaporation and forms a direct feedback of moisture to the atmosphere which is important to sustain continental rainfall. Most investigations on interception focus on canopy interception only, whereas the interception by the surface and forest floor may be of same order of magnitude. Moreover there is a regional bias. Most research has been carried out in Europe and America and little is known about interception in Africa. This paper presents a study on forest floor and canopy interception in a savannah ecosystem. The study deals with both interception storage capacity of different vegetation types and the related moisture fluxes. The interception storage capacity of Msasa leaf litter and of Thatching grass is 1.8mm and 1.5mm respectively. This water storage capacity is dependent on storm intensity, with high intensity storms resulting in smaller storage capacity than less intensive storms. Canopy interception for the study period averaged 25% of the total rainfall, which is comparable with other studies. More importantly, the study revealed that combining canopy and forest floor interception yields a total interception flux amounting to 37% of the rainfall, or close to 50% of the total evaporation. This is a significant amount which implies that interception of both canopy and forest floor should be included in hydrological modelling and that interception is relevant for water management.

A stochastic differential equation model for assessing drought and flood risks

Droughts and floods are two opposite but related hydrological events. They both lie at the extremes of rainfall intensity when the period of that intensity is measured over long intervals. This paper presents a new concept based on stochastic calculus to assess the risk of both droughts and floods. An extended definition of rainfall intensity is applied to point rainfall to simultaneously deal with high intensity storms and dry spells. The mean-reverting Ornstein–Uhlenbeck process, which is a stochastic differential equation model, simulates the behavior of point rainfall evolving not over time, but instead with cumulative rainfall depth. Coefficients of the polynomial functions that approximate the model parameters are identified from observed raingauge data using the least squares method. The probability that neither drought nor flood occurs until the cumulative rainfall depth reaches a given value requires solving a Dirichlet problem for the backward Kolmogorov equation associated with the stochastic differential equation. A numerical model is developed to compute that probability, using the finite element method with an effective upwind discretization scheme. Applicability of the model is demonstrated at three raingauge sites located in Ghana, where rainfed subsistence farming is the dominant practice in a variety of tropical climates.

On the importance of accurate depiction of infiltration processes on modelled soil moisture and vegetation water stress

AbstractThe description of soil moisture dynamics is a challenging problem for the hydrological community, as it is governed by complex interactions between climate, soil and vegetation. Recent research has achieved significant advances in the description of temporal dynamics of soil water balance through the use of a stochastic differential equation proposed by Laio et al. (2001). The assumptions of the Laio et al. model simplify the mathematical form of the soil water loss functions and the infiltration process. In particular, runoff occurs only for saturation excess, the probability distribution function (PDF) of which is well‐represented by a simple expression, but the model does not consider the limited infiltration capacity of soil. In the present work, we extend the soil moisture model to include limitations on soil infiltration capacity with the aim of understanding the impact of varying infiltration processes on the soil water balance and vegetation stress. A comparison between the two models (the original version and the modified one) is carried out via numerical simulations. The limited infiltration capacity influences the soil moisture PDF by reducing its mean and variance. Major changes in the PDFs are found for climates characterized by storms of short duration and high rainfall intensity, as well as in humid climates and in cases where soils have moderate permeability (e.g. loam and clay soils). In the case of limited infiltration capacity, modifications to the dynamics of soil moisture generally lead to higher amounts of vegetation water stress. An investigation of the role of soil texture on vegetation water stress demonstrates that loam soil provides the most favorable condition for plant‐growth under arid and semi‐arid conditions, while vegetation may benefit from the presence of more permeable soils (e.g. loamy sand) in humid climates. Copyright © 2009 John Wiley & Sons, Ltd.

The impact of slope length on the discharge of sediment by rain impact induced saltation and suspension

AbstractSimulations using a mechanistic model of raindrop driven erosion in rain‐impacted flow were performed with particles travelling by suspension, raindrop induced saltation and flow driven saltation. Results generated by both a high intensity storm, and a less intense one, indicate that, because of the effect of flow depth on the delivery of raindrop energy to the bed, there is a decline in sediment concentration, and hence soil loss per unit area, with slope length when particles are transported by raindrop induced saltation. However, that decline is reversed when the critical velocities that lead to flow driven saltation are episodically exceeded during an event. The simulations were performed on smooth surfaces and a single drop size but the general relationships are likely to apply for rain made up of a wide range of drop size. Although runoff is not always produced uniformly, as a general rule, flow velocities increase with slope length so that, typically, the distance particles travel before being discharged during an event increase with slope length. The effect of slope length on soil loss per unit area is often considered to vary with slope length to a power greater than zero and less that 1·0. The simulations show that effect of slope length on sediment discharge is highly dependent on the variations in runoff response resulting from variations in rainfall duration‐intensity‐infiltration conditions rather than plot length per se. Consequently, predicting soil loss per unit area using slope length with positive powers close to zero when sheet erosion occurs may not be as effective as commonly expected. Erosion by rain‐impacted flow is a complex process and that complexity needs to be considered when analysing the results of experiments associated with rain‐impacted flow under both natural and artificial conditions. Copyright © 2009 John Wiley & Sons, Ltd.

Comparison of conventional and no-tillage corn and soybean production on runoff and erosion in the southeastern US Piedmont

Soil erosion on southern Piedmont soils remains a problem without application of sound conservation practices. This study was conducted to compare a no-tillage (NT) system with a conventional-tillage (CT) system in row-cropped land under natural rainfall conditions for six continuous years. Runoff and soil loss were continuously monitored from May 1995 to April 2001 from four erosion plots (7.3 m × 12.2 m [24 ft × 40 ft]) in CT and four plots in NT under a corn (Zea mays L.)-soybean (Glycine max L.) rotation in a Mecklenburg sandy clay loam and Enon clay loam (fine mixed, active, thermic, Ultic Hapludalfs) at a Piedmont location. Runoff was significantly less for NT than for CT in three study years; in the other three years no differences between treatments where found. The NT six-year runoff average was 33% lower than the six-year runoff average of CT. The tolerable soil loss level of 7.0 Mg ha-1 y-1 (3.1 tn ac-1 yr-1) was exceeded in CT in four study years, while annual NT losses were always below 7.0 Mg ha-1 y-1 The six-year soil loss average was 74.7 Mg ha-1 (33.3 tn ac-1) and 2.6 Mg ha-1 (1.2 tn ac-1) for CT and NT, respectively. In CT, most of the soil lost during the six-year study period occurred during rain storms of high intensity. No-till was highly effective at protecting against soil loss during these rain storms.

Thunderstorm nowcasting by means of lightning and radar data: algorithms and applications in northern Italy

Abstract. Thunderstorms and their ground effects, such as flash floods, hail, lightning, strong winds, and tornadoes, are responsible for most weather damages in northern Italy, especially in the warm season from May to September. A nowcasting and warning system focused on severe thunderstorm events would be useful to reduce risks for people involved in outside activities and for electric, telecommunication, and sensitive industrial business. C-band radar and Lighting Location Systems provide useful, fast and high resolution data for the detection of convective systems and for following their dynamics. The whole of northern Italy is covered by radar with a resolution of 1 km and by a lightning network with a mean accuracy of 0.5 km on the single point of impact. The authors present an algorithm developed for tracking high intensity storm cells by means of radar and lightning data. Application to northern Italy reveals that tracking thunderstorm cells can be used as an alert system that may help prevent damages from extreme weather, as well as allowing for studying the correlation among lightning, rainfall and tornado occurrence. Assessing the algorithm skill is also discussed, and a forecast verification method is described and applied for the duration of a thunderstorm season.

Lacustrine turbidites as indicators of Holocene storminess and climate: Lake Tahoe, California and Nevada

Sediment cores from Lake Tahoe permit the discrimination of turbidites initiated by seismic-induced debris flows from those generated by severe storms and associated hyperpycnal currents over the last 7000 years using integrated textural, magnetic, and geochemical signatures. Relative to fine-grained ‘background’ sediments, the majority of Tahoe turbidites exhibit coincident trends of increased mean grain size, increased magnetic susceptibility, decreased TOC, higher δ13Corg and variable C/N. We interpret these characteristics to record the rapid influx of terrigenous sediments within runoff from the watershed triggered by high-intensity storms. Correlation of multiple, individual turbidites between cores suggests a synchronicity of occurrence, supporting the model of extreme hydrologic events as the trigger for most turbidity currents into Lake Tahoe. In contrast, turbidites generated by seismic collapse of steep lake margins would have textural, magnetic and geochemical signatures that would reflect a homogenized mix of autochthonous biogenic debris and multiple older turbidites. Only one of the turbidites in the cores appears to be seismically generated. A second component of this study tested the hypothesis that turbidite clustering reflects phases of increased storminess, paleoprecipitation and lake level. We correlated broad patterns of turbidite frequency in the Tahoe cores with climate proxies from (1) elsewhere in the Tahoe watershed, (2) the western Great Basin (primarily Pyramid Lake) and (3) the San Francisco bay estuary. The reasonable degree of temporal overlap suggests that apparent trends in severe storm frequency recorded by clusters of turbidites provides a measure of long-term regional paleoprecipitation and lake level. A key finding is an extended phase of dryness and a near absence of major storms between ~3000 and ~900 cal yr B.P. in the Tahoe watershed.

Barnett (“Barney”) Shanson

Soil erosion on southern Piedmont soils remains a problem without application of sound conservation practices. This study was conducted to compare a no-tillage (NT) system with a conventional-tillage (CT) system...

Performance of in situ rainwater conservation tillage techniques on dry spell mitigation and erosion control in the drought-prone North Wello zone of the Ethiopian highlands

Grain production shortfalls in northern Ethiopia are commonly associated with occurrence of intra-seasonal dry spells or droughts and rapid land degradation which adversely impact crop yields. Suitable practices that use available rainwater more efficiently to mitigate impact of dry spells on crops and that protect soil are needed to stabilize and improve grain yields in the predominately rainfed agriculture. During three cropping seasons on-farm experiments tested conservation tillage techniques implemented with oxen-drawn plows on clay loam soil. Tested tillage techniques are subsoiling, open and tied ridges, no till, and conventional tillage with the local maresha plow (the control). Effectiveness in improving root zone soil moisture, limiting soil erosion, and improving sorghum ( Sorghum bicolor (L.) Moench.) and chickpea ( Cicer arietinum L.) grain yield were determined. Results demonstrate that performance of the tillage techniques varied with seasonal rainfall distribution and intensity and land slope gradient. Tied and open ridge increased seasonal root zone soil moisture 15–24%. Subsoiling slightly (3%) increased and no till slightly decreased soil moisture but were not statistically different from conventional tillage. Tied ridge and no till significantly reduced seasonal soil loss by up to 11 Mg ha −1 during seasons with moderate intensity storms, but during a season with high intensity storms tied ridge on over 9% slope gradient increased soil loss (up to 35 Mg ha −1). The increased soil disturbance of subsoiling led to higher soil loss rates (up to 32 Mg ha −1) than conventional tillage during all seasons. Grain yield decreased and runoff and erosion rates increased rapidly with increasing land slope gradient. During a season with moderate intensity rainfall open and tied ridge increased sorghum yield by 67–73% over the control (730 kg ha −1) while no till decreased yield by 25%. During a season when high intensity rainfall events damaged the ridges, subsoiling had the best sorghum yield with 42% increase over the control (1430 kg ha −1). Poor early season rainfall and fungus attacks resulted in low chickpea yields (200–320 kg ha −1) and statistically insignificant differences between tillage methods. Overall results of the study suggest that on slopes below 8% gradient oxen-drawn ridge tillage and subsoiling, to a lesser degree, can effectively improve conditions that mitigate impact of short dry spells especially during seasons with less intense rainfall events.

Application of a steady-state nutrient model and inferences for load reduction strategy in two public water supply reservoirs in eastern Connecticut

Mansfield Hollow Lake (MHL) and Willimantic Reservoir (WR) are two reservoir lakes located in eastern Connecticut in the northeastern United States. MHL formed behind the Mansfield Hollow Dam constructed by the U.S. Army Corps of Engineers in 1952 and is primarily fed by the Fenton, Mount Hope and Natchaug Rivers. The WR lies approximately 1-km downstream from the Mansfield Hollow Dam. Total dissolved nitrogen, phosphorus and chlorophyll a measurements indicate the water bodies could be classified as borderline mesotrophic/eutrophic. A steady-state numerical software package (Bathtub) designed to facilitate application of empirical eutrophication models to morphometrically complex reservoirs was used to determine the trophic status in MHL and WR based on different phosphorus and nitrogen loading budgets. The short hydraulic residence times and rapid flushing rates in MHL and WR are directly related to the flow rates in the streams discharging into MHL. The low flow period could significantly increase the hydraulic residence times of these two reservoirs. Therefore, the sampling design emphasized periods of low flow in late August and early September to assess the impact of nutrient inputs to MHL and WR during dry periods. The results of a low flow sampling period (August 2002) were used to calibrate and test the Bathtub model developed for these water bodies. Application of the Bathtub model to differing flow regimes, notably average flows, suggested that nitrogen or phosphorus could limit the productivity and cause eutrophication in the two lakes. Results of this study indicated that the Bathtub model could be used to predict total nitrogen and total phosphorus concentrations with reasonable accuracy, but it might not be a suitable tool for predicting organic nitrogen or algae in rapidly flushing lake systems. To further investigate and validate the assumptions made in this study, more sampling data are needed, especially during high intensity storm events to investigate possible sources of nutrient flow into the two lake system and further calibrate the Bathtub model for the MHL-WR watershed.

Quantization analysis of weather radar data with synthetic rainfall

Quantization is a process by where continuous signals are transformed into discrete values. It is an important part of the signal processing involved in using weather radar. Technological advances have made it easier to increase the number of quantization levels, as witnessed by the replacement of a 3 bit system by an 8 bit system by the UK Meteorological Office. Research has been conducted in the past demonstrating the error statistics of quantized rainfall, although these studies have used real radar data. The novelty of this study is in using synthetic rain, generated with a Poisson cluster model to represent hourly rainfall, and subsequently disaggregated using a fractal cascade to a fine 5 min time scale. The advantage of this approach is the length of time series that can be generated far outweighs the limited duration of historical rainfall series, especially at such fine time scales. This provides sufficient rainfall data, especially high intensity rainfall, to say something statistically significant about the error statistics. The models are parameterised for different months and also for a non-seasonal set. Rainfall is then generated for a summer case, a winter case, and for the non-seasonal case. It is discovered that the error distribution varies significantly as the parameters change for 3 bit rainfall. This error distribution is relatively constant for 8 bit data, within its working range (up to 126 mm/h). At a fine time scale, such high intensity events are not uncommon. This knowledge is useful when investigating historical radar data at lower quantization levels, for the purpose of flood frequency analysis, and remains relevant, especially, if as some studies have shown, the occurrence of high intensity storms is likely to increase.

Ionospheric disturbances in the East-Asian region during geomagnetic storm in November, 2004

Results of the study into variations of the ionospheric parameters during the intense geomagnetic storm on November 7–11, 2004 in the 20–80°N, 80–160°E sectors are presented. These used data from ionospheric stations and total electron content (TEC) measurements obtained from the network of the GPS ground-based receivers and the receiver onboard the CHAMP satellite. Periods of total absorption and blanketing sporadic E layers were observed at high latitudes, whereas long-lasting negative disturbances which are typical of geomagnetic storms of high intensity were detected at midlatitudes. In the afternoon hours of local time on November 8, 2004, a large-scale ionospheric disturbance was detected on the basis of foF2 and TEC measurements. The disturbance was propagating southwestward at a mean velocity of about 200 m/s. Comparison of the relative amplitude of this large-scale disturbance according to the total electron content (∼70%) and foF2 (∼80%) measurements made it possible to assume that the disturbance was extended in height. A similar disturbance of smaller intensity was observed on November 10.

Tillage-crop residue management and rainfall-runoff relationships for the Alemaya catchment in Eastern Ethiopia

A field study was conducted in the Alemaya catchment, Eastern Ethiopia, with the objective of determining the effect of tillage practices, crop reside cover and rainfall characteristics on runoff during two rainfall seasons on a clayey Regosol with 5% slope. Relationships between runoff and rainfall characteristics, such as the amount, intensity and erosivity were established from a two-year data set. The results on fields without crop showed that a minimum of 21 ha−1 of fresh wheat residue is required to reduce runoff from low intensity storms and 4 t ha−1 of residue for high intensity storms with peak intensities of more than 55 mm h−1. These norms can be used for estimating runoff under comparable soil and climatic conditions. A technique was also developed to estimate runoff from the rainfall intensity-duration curve and the mean soil infiltration rate.

Ionospheric disturbances in the east-Asian region during the geomagnetic period in November 2004

Results of the studies of ionospheric parameter variations during the intense geomagnetic storm on November 7–11, 2004, in the 20°–80° N, 60°–180° E sector are presented. The data of ionospheric stations and the results of total electron content (TEC) measurements at the network of the GPS ground-based receivers and of the GPS receiver onboard the CHAMP satellite were used. Periods of total absorption and blanketing sporadic E layers were observed at high latitudes, whereas durable negative disturbances typical of geomagnetic storms of high intensity were detected at midlatitudes. In the afternoon hours of local time on November 8, 2004, a large-scale ionospheric disturbance of a frontal type was detected on the basis of foF2 and TEC measurements. The disturbance propagated southwestward at a mean velocity of about 200 m/s. The comparison of the relative amplitude of this large-scale disturbance according to the total electron content (∼70%) and foF2 (∼80%) measurements made it possible to assume a large vertical scale of the disturbance.