Intense Rainfall Episodes Research Articles

Diferencias geográficas de la fecundidad en España: Una perspectiva provincial

El objetivo de este trabajo es analizar las diferencias en la intensidad de la fecundidad existentes actualmente en el interior de las provincias españolas, particularmente la que se encuentra entre las capitales de provincia y sus restos provinciales, así como explicar la evolución reciente de dicho fenómeno en España. Mientras que la diferenciación en los valores de la fecundidad entre provincias ha sido objeto clásico de estudio, poco se sabe de las diferencias internas y de su evolución. Los resultados alcanzados en este trabajo indican la existencia de diferencias en dos direcciones: en las provincias más urbanas las capitales (especialmente aquellas con un término municipal reducido y que no incluyen, por lo tanto, nuevas áreas periféricas de expansión) experimentan menor fecundidad que el resto de sus respectivas provincias; en cambio, en las provincias más rurales, donde la población joven se concentra en la capital, es ésta la que muestra una mayor fecundidad que los municipios del resto de la provincia.

Spatial and Temporal Characteristics of Summer Precipitation over Central Europe in a Suite of High-Resolution Climate Models

AbstractHigh-impact, locally intense rainfall episodes represent a major socioeconomic problem for societies worldwide, and at the same time these events are notoriously difficult to simulate properly in climate models. Here, the authors investigate how horizontal resolution and model formulation influence this issue by applying the HIRLAM–ALADIN Regional Mesoscale Operational NWP in Europe (HARMONIE) Climate (HCLIM) regional model with three different setups: two using convection parameterization at 15- and 6.25-km horizontal resolution (the latter within the “gray zone” scale), with lateral boundary conditions provided by ERA-Interim and integrated over a pan-European domain, and one with explicit convection at 2-km resolution (HCLIM2) over the Alpine region driven by the 15-km model. Seven summer seasons were sampled and validated against two high-resolution observational datasets. All HCLIM versions underestimate the number of dry days and hours by 20%–40% and overestimate precipitation over the Alpine ridge. Also, only modest added value was found for gray-zone resolution. However, the single most important outcome is the substantial added value in HCLIM2 compared to the coarser model versions at subdaily time scales. It better captures the local-to-regional spatial patterns of precipitation reflecting a more realistic representation of the local and mesoscale dynamics. Further, the duration and spatial frequency of precipitation events, as well as extremes, are closer to observations. These characteristics are key ingredients in heavy rainfall events and associated flash floods, and the outstanding results using HCLIM in a convection-permitting setting are convincing and encourage further use of the model to study changes in such events in changing climates.

Environmental impact of phosphogypsum stockpile in remediated Schistos waste site (Piraeus, Greece) using a combination of γ-ray spectrometry with geographic information systems.

From 1979 to 1989, ten million tons of phosphogypsum, a waste by-product of the Greek phosphate fertilizer industry, was disposed into an abandoned limestone quarry in Schistos former waste site, Piraeus (Greece). The quarry has been recently closed and remediated using geomembranes and thick soil cover with vegetation. A part of the deposited phosphogypsum has been exposed due to intense rainfall episodes leading to concerns about how could potentially released radioactivity affect the surrounding environment. This study seeks to assess the environmental impact of the phosphogypsum deposited in the Schistos quarry, using laboratory-based γ-ray spectrometry measurements and geographical information systems. Radioactivity concentrations were mapped onto spatial-data to yield a spatial-distribution of radioactivity in the area. The data indicate elevated (226)Ra concentrations in a specific area on the steep south-eastern cliff of the remediated waste site that comprises uncovered phosphogypsum and is known to be affected by local weather conditions. (226)Ra concentrations range from 162 to 629Bq/kg, with an average activity being on the low side, compared to the global averages for phosphogypsum. Nevertheless, the low environmental risk may be minimized by remediating this area with geomembranes and thick soil cover with vegetation, a technique, which has worked successfully over the remainder of the remediated quarry.

Precipitation and Cloud Structures of Intense Rain during the 2013 Great Colorado Flood

Abstract Radar and disdrometer observations collected during the 2013 Great Colorado Flood are used to diagnose the spatial and vertical structure of clouds and precipitation during episodes of intense rainfall. The analysis focuses on 30 h of intense rainfall in the vicinity of Boulder, Colorado, during 2200–0400 UTC 11–13 September. The strongest rainfall occurred along lower parts of the Colorado Front Range at >1.6 km MSL and on the northern side of the Palmer Divide. The vertical structure of clouds and horizontal distribution of rainfall are strongly linked to upslope flow and low-level forcing, which resulted in surface convergence. During times of weak forcing, shallow convection produced rain at and below the melting layer through collision–coalescence and, to a lesser extent, riming. A mesoscale circulation interacting with the local terrain produced convective rainfall with high cloud tops that favored ice crystal production. During moderate forcing with cloud tops slightly exceeding the 0°C level, both cold- and warm-phase microphysical processes dominated. Less rain with weaker rainfall rates was observed over the higher-elevation stations compared to the lower-elevation stations across the foothills.

Remote impact of North Atlantic hurricanes on the Mediterranean during episodes of intense rainfall in autumn 2012

Autumn is the most favourable season for tropical cyclones to undergo extratropical transition and interact with the midlatitude flow over the North Atlantic. Autumn is also the season when intense rainfall over the Mediterranean is often triggered by Rossby wave breaking. The impact of tropical cyclones on downstream wave breaking is investigated here during three episodes of intense rainfall which were the target of HyMeX (Hydrological cycle in Mediterranean eXperiment) in autumn 2012. Five‐day simulations of hurricanes Leslie, Rafael and Sandy were performed with the Meso‐NH model in a domain encompassing the North Atlantic and the Mediterranean. Control simulations were compared to simulations in which the hurricanes were filtered out from the initial conditions. In each case, the hurricane locally impeded the forward progression of an upstream trough, then reintensified as an extratropical cyclone during the wrap‐up of the trough. The local impact of Leslie and Rafael on the midlatitude flow quickly propagated downstream along a polar jet and amplified Rossby wave breaking but decreased the intensity of the forecast precipitation over the Mediterranean. The local impact of Sandy propagated downstream along a subtropical jet in addition to the polar jet and resulted in a weak impact of the forecast precipitation on the Mediterranean. This study suggests that the interaction of tropical cyclones with the midlatitude flow over the western North Atlantic may be considered a perturbation to, rather than a source of, downstream wave breaking.

Climate, water and tourism: causes and effects of droughts associated with urban development and tourism in Benidorm (Spain).

In this paper, we analyse the relationship between climate, tourism and water in Benidorm (Spain), an international icon of Fordist tourism (mass tourism). In particular, we have studied the causes and effects of the water supply droughts Benidorm has suffered since becoming a major holiday destination. For this purpose, we consulted the local press in Benidorm over the period 1969-2003. Using qualitative and quantitative geographical techniques, we found that the water supply in the area has managed to keep up with rapidly increasing demand, with only occasional imbalances and periods of crisis. We focused in particular on the causes and effects of the water supply crisis of 1978, a moment of great uncertainty in the history of Benidorm as a holiday resort. We also examined the influence of atmospheric conditions on precipitation levels and how these precipitation levels affect the water supply. Our results highlight the importance of intense rainfall episodes associated with easterly winds, which provided large inputs for Benidorm's water supply system (Marina Baja Water Consortium). We also found that the water supply crisis of 1978 resulted in serious economic losses for Benidorm and damaged its image as a holiday destination and that the city is now less vulnerable to variations in the climate, as a result of its search for new water resources (both surface and ground water resources and from other nonconventional sources).

Direct pre-treatment of surface water through submerged hollow fibre ultrafiltration membranes

The most distinctive characteristic of the Mediterranean climate is its strong seasonality, dry summers and intense rainfall episodes concentrated in spring and autumn. This changeability is translated into a wide variability of the water resources in terms of quantity and quality. Barcelona, located in the northeast extreme of the Iberian Peninsula, shows all the characteristics of the Mediterranean climate. The Llobregat River, which is the main conventional water source for drinking water production in Barcelona region, presents a poor and variable quality as well as high flow variability. This study is focused on testing ultrafiltration (UF) membranes, based on a submerged outside-in configuration, as direct pre-treatment of such water at demonstration scale. A prototype with Zeeweed® 500D membranes was optimised for the different scenarios tested during 2 years of continuous operation. It was demonstrated to be able to stand the extreme feed quality limits, obtaining water yields in the range of 89–92% in all conditions used. The prototype worked better in terms of water production yield at high turbidity episodes (>70 NTU), probably due to a layer formation which prevented organic species and particles reaching the membrane. Permeate water was shown, in spite of feed water quality fluctuations, to be constant and appropriate in quality terms. Water quality results obtained are compared to the ones obtained in a conventional pre-treatment. The preliminary results of a technical comparison between direct UF and conventional pre-treatment are also detailed in the study.

Analysis of the Marmara flood in Turkey, 7–10 September 2009: an assessment from hydrometeorological perspective

Turkey often suffers from flood-related damages and causalities as a result of intense and prolonged storms that are usually convective or cyclonic in origin. The impact is more distinctive in Aegean and Mediterranean coasts of the country where quantity and distribution of rainfall is influenced by Mediterranean cyclones, especially in late autumn and early winter. The floods sometimes became very hazardous when combined with urbanization effects, especially in the densely populated coastal communities and major cities. Severe weather was marked in the early parts of September 2009 that produced record-setting rainfall amounts across the Marmara region of Turkey and led a series of flash floods which affected Istanbul and Tekirdag provinces especially. The overall flooding was the result of successive and persistent intense rainfall episodes over a 3-day period which produced more than 250-mm rainfall over portions of the region. The floods resulted in death of 32 people and caused extensive environmental and infrastructural damage in the region. This study provides in-depth analysis of hydrometeorological conditions that led to the occurrence of flash floods in Marmara region during 7–10 September 2009 period and also discusses non-meteorological factors that exacerbated the flooding conditions. Main meteorological settings that led to intense storms were presence of cold air in the upper atmosphere, a slow-moving quasi-stationary trough, and continuous resupply of moisture to the surface low from the warm Aegean Sea. Radar images showed the development of clusters of convective cells that remained quasi-stationary over portions of the region. The 24-h rainfall amounts varied between 100 and 253 mm in most parts of the region during the flooding period with diverse spatial patterns. The southern locations received the highest amount of the rainfall as compared to stations located in northern slopes of the region. Typical effects of orography that enhance rainfall in the coastal areas, however, were not observed during the Marmara flood. Some features of the synoptic pattern observed prior and during the flooding period, supported the back door cold front concept. This is characterized with easterly to northeasterly surface flows forced by an anticyclone, advection of cold continental air over the warm Black Sea which provided anomalous moisture to trigger cyclogenesis over the Marmara region, and falling of core of the intense rainfall over the Marmara Sea. The study concluded that although the meteorological settings were favorable for the convective rainfalls, urbanization factors, such as land use changes and occupation of flood plains, played major role in aggravating the worst flood observed in the region in recent decades.

Regional-scale high-plasticity clay-bearing formation as controlling factor on landslides in Southeast Spain

Complex landslides in clay-bearing sediments are investigated in two moderate-relief regions of Southeast Spain. Both regions, more than 100 km apart show landslides affecting the same Flysch formation, which outcrops widely in the central and western Betic Cordillera along the contact between the External (South Iberian Domain) and Internal (Alborán Domain) zones. Intense rainfall episodes can be considered as the main triggering factor for slope failures in these two areas. We have chosen two landslides (Diezma and Riogordo landslides), one from each area of study, to investigate their morphological and geotechnical features in order to establish the relative importance of the different controlling factors. From a kinematic point of view, the two features studied in detail can be referred as to rotational failures, evolving downhill to slow earthflows. The movement was concentrated on several surfaces developed on a clay-rich layer mostly constituted by smectite. This clay mineral is of critical relevance to the mechanical behaviour of soils and Flysch-like formations, being very consistent at dry conditions, but rapidly losing its strength at wet conditions. Thus, softened smectite-rich clay layers with high water contents can approach the properties of a lubricant, which, in turn, can be critical for slope stability. In addition to their high plasticity, these clays have a high swelling potential, which can induce significant vertical overpressure, thus reducing even more the strength properties of the Flysch formation. In Southeast Spain, a region with a Mediterranean rainfall regime, slope stability can be seriously influenced by the presence of these smectite-rich clay layers in a formation of regional extent, as is the case of the Flysch formation. Therefore, this lithologically-controlled factor should be taken into account when evaluating landslide hazard in the Betic Cordillera.

Rainfall-triggered landslides in the Lisbon region over 2006 and relationships with the North Atlantic Oscillation

Abstract. Landslides occurred in the Lisbon area during the last 50 years were almost always induced by rainfall and have been used to establish rainfall thresholds for regional landslide activity. In 2006, three new rainfall-triggered landslide events occurred in the study area, namely on the 20 March, the 25–27 October, and the 28 November. Landslide events occurred in March and October 2006 include shallow translational slides and few debris flows, and the corresponding absolute antecedent rainfall was found to be above the threshold for durations ranging from 4 to 10 days. These events also fit the combined threshold of daily precipitation and 5 days calibrated antecedent rainfall values. Likewise the landslide event that took place in late November 2006 includes some slope movements with deeper slip surfaces, when compared with landslides dating from March and October. Moreover, the corresponding absolute antecedent rainfall was also found to be above the 40-day period rainfall threshold. Here we characterize in detail the short and long-term atmospheric circulation conditions that were responsible for the intense rainfall episodes that have triggered the corresponding landslide events. It is shown that the three rainfall episodes correspond to considerably different synoptic atmospheric patterns, with the March episode being associated to an intense cut-off low system while the October and November episodes appear to be related to more typical Atlantic low pressure systems (and associated fronts) travelling eastwards. Finally, we analyse the role played by the North Atlantic Oscillation (NAO) during those months marked by landslide activity. It is shown that the NAO index was consistently negative (usually associated with above average precipitation) for the months prior to the landslide events, i.e. between October 2005 and March 2006, and again between August and October 2006.

ENSO tropical–extratropical climate teleconnections and mechanisms for Holocene debris flows along the hyperarid coast of western South America (17°–24°S)

El Niño, the warm phase of the ENSO cycle, involves ocean-climate anomalies in the tropical Pacific Ocean and in the extratropics, which frequently result in heavy rainfall episodes along the equatorial and subtropical regions of western South America. Here, we investigate meteorological mechanisms producing heavy rains, floods and debris flows along the less-known hyperarid coasts of southern Peru and northern Chile, to evaluate the paleoclimate significance of Holocene debris flow deposits. Our results reveal that heavy rainfall over the coast of southernmost Peru occurs either during austral summer, at the mature stage of El Niño in connection with warmer sea surface temperatures and anomalous jet streams off northern Chile, or during the previous austral winter–spring associated with equatorward-shifted Pacific South America (PSA) atmospheric teleconnection patterns. At Antofagasta, in northern Chile, such events occur almost exclusively in the latter season when deeper PSA-related anomaly poles extend their influence equatorwards beyond central Chile. During non-El Niño conditions short-lived heavy rainfall episodes in southernmost Peru can be associated with similar, albeit weaker or less persistent, circulation anomalies. In addition to that, a seasonally-enhanced low-level southerly flow provides orographic uplift (rainfall-favourable conditions) by the Andes at the 18 °S coastal bend. Ultimately, the trigger for rainfall events in all seasons and phases of the ENSO cycle was invariably connected with mid-troposphere wave disturbances from mid-latitudes. The chronostratigraphy of debris flow deposits from both areas and its comparison with other paleoclimate records at the western side of the Andes, suggests that the ENSO-related teleconnection patterns operated only during the second half of the Holocene, supporting an onset of modern El Niño manifestations at 5300–5500 cal BP and increased frequency of major events during recent times. We suggest that several debris flows dated between 12,900 and 8400 cal BP in southernmost Peru, previously interpreted as an indication of strong El Niño events, were associated with short and intense heavy rainfall episodes similar to those described here during the late winter–spring season in non-El Niño conditions, concomitant with stronger low-level southerlies, strengthened South-Eastern Pacific Subtropical Anticyclone and intensified coastal upwelling.

Analysis and simulation of local and regional conditions for the rainfall over the Lago Maggiore Target Area during MAP IOP 2b

AbstractThe Mesoscale Alpine Programme (MAP) operational and research network collected a large variety of measurements during the two days of Intensive Observing Period (IOP) 2b (19 and 20 September 1999), which is one of the most intense rainfall episodes during the Special Observing Period over the Lago Maggiore area. The synoptic situation is a typical one of a southerly flow and associated convection over Alpine orography. Simulations with the non‐hydrostatic Meso‐NH model are used to describe the rainfall conditions and are successfully validated at the different scales allowed by the MAP data. The two types of pre‐frontal orographically triggered convective episodes are described: (1) Sporadic and shallow convection occurs over the coastal mountains and propagates over the Po Valley. The chronology and the intensity of these convective episodes are driven by two main features: the low‐level humidity anomalies and the middle‐troposphere dry anomaly present over the Mediterranean Sea. (2) The Lago Maggiore orographic convection has a very long duration and is mainly controlled by both the intensity of the easterly low‐level wind in the north part of the Po Valley and the upper‐level clouds of the cold front. The different origins of the air masses transported by this easterly barrier wind and the associated local circulations are detailed. Copyright © 2003 Royal Meteorological Society.

Pelagic processes in extensive shrimp ponds of the Mekong delta, Vietnam

Rates of pelagic primary production, respiration, and bacterioplankton dynamics were measured in relation to water quality parameters in three extensive shrimp ponds in the Mekong delta, Vietnam. There were few consistent differences in pelagic characteristics among different locations within these ponds, among the three ponds, or between the ponds and adjacent river water. Rates of primary production ( 14 C uptake) ranged from <1 to 94 mg C m −3 d −1. Rates of gross primary production (light–dark bottle technique) ranged from −184 to 2697 mg C m −3 d −1. Rates of pelagic respiration ranged from 60 to 3783 mg C m −3 d −1. Primary production rates measured by oxygen flux were greater than those measured via 14 C uptake, with P/ R ratios varying widely (−0.45 to 3.4), but the mean P/ R at each site was <1 with a grand mean among ponds of 0.7. Bacterioplankton numbers (mean range: 0.2 to 27.2×10 8 cells ml −1) and productivity (range: 2.5 to 297.3 mg C m −3 d −1) did not vary consistently among ponds with season. Mean bacterioplankton growth rates were fastest ( μ=0.29 d −1) in the pond with highest shrimp production and slowest in the poorest yielding pond ( μ=0.08 d −1). The primary production and respiration rates, and bacterioplankton dynamics, indicate that these pond waters are net heterotrophic. Plankton measurements rarely correlated with changes in physicochemistry (pH, dissolved O 2, salinity, temperature) or nutrient concentrations as within-site and temporal variability were large for most parameters. The diurnal cycles of physicochemical characteristics were similar to those measured in other unfertilized, low-alkalinity ponds, but these cycles were dampened by intense rainfall. Our data indicate that low net primary production, high rates of respiration, moderate rates of bacterioplankton production, high suspended solid and nutrient concentrations, low and very variable pH and dissolved O 2 concentrations, and variations in salinity due to intense rainfall episodes limit shrimp production in these extensive ponds.

Geomorphic effects of a 10‐year storm on a small drainage Basin in the Texas Panhandle

AbstractBedded Permian salt in the Palo Duro Basin of the Texas Panhandle is being considered for isolation of nuclear waste. Studies underway to evaluate the geomorphic processes affecting any waste repository that may be sited in the region include studies of the geomorphic events associated with individual storms. On 26 May, 1978, thunderstorms occurred near Canyon, Texas, which received 130mm of rain, and on a small instrumented watershed at Buffalo Lake, 16 km to the southwest, which received 71 mm of rain. Rainfall at Buffalo Lake was concentrated in a period of 3 hours, representing a return period of approximately 10 years and a maximum 30‐minute intensity of 64 mm/hour.Erosion‐pin fields, topographic surveys, and stakes for headcut monitoring had been established 2 to 3 months before the storm in a 640‐m long tributary canyon to Tierra Blanca Creek downstream of Buffalo Lake. Canyon slopes of moderately to slightly calichified sands and gravels of the Ogallala Formation are capped by well‐indurated caliche on the canyon rim. Erosion‐pin fields showed average net erosion of 2·4 cm (0° to 9° slope) to 2·7 cm (10° to 19° slope) and a single‐pin maximum value of 6·2 cm in the 20° to 29° slope class. Headcuts 1 to 2 m deep in alluvial‐colluvial material on the floor of the canyon migrated as much as 12 m upstream. Canyon floor deposition occurred as a series of elongate bars, 16m long and longer, located at the mouth of tributary gullies, downstream from scours, and at slope breaks. Grain sizes ranged from boulders up to 70cm in intermediate axis deposited in the upper canyon to fine to very fine sand deposited as a sheet up to 25cm thick beyond the mouth of the canyon at Tierra Blanca Creek.In an adjacent canyon a sequence of irregular beds of caliche gravel, mixed sand and gravel, and fine sand up to 3 m thick is exposed. Comparison of this sequence with deposits resulting from the 26 May, 1978, storm suggests that the coarse fraction of the alluvial sequence is deposited by repetitive major storm events. Cobble and boulder units 30 to 70cm thick can evidently be deposited in a few hours. Under the continental climate of the Texas Panhandle, erosion, deposition, and stream incision are taking place primarily in discrete steps related to episodes of intense rainfall.