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An ensemble study of extreme North Sea storm surges in a changing climate  [PDF]
A. Sterl,H. van den Brink,H. de Vries,R. Haarsma
Ocean Science Discussions (OSD) , 2009,
Abstract: The height of storm surges is extremely important for a low-lying country like the Netherlands. By law, part of the coastal defence system has to withstand a water level that on average occurs only once every 10 000 years. The question then arises whether and how climate change affects the heights of extreme storm surges. Published research points to only small changes. However, due to the limited amount of data available results are usually limited to relatively frequent extremes like the annual 99%-ile. We here report on results from a 17-member ensemble of North Sea water levels spaning the period 1950–2100. It was created by forcing a surge model of the North Sea with meteorological output from a state-of-the-art global climate model which has been driven by greenhouse gas emissions following the SRES A1b scenario. The large ensemble size enables us to calculate 10 000 year return water levels with a low statistical uncertainty. We find no statistically significant change in the 10 000 year return values of surge heights along the Dutch during the 21st century. Also a higher sea level resulting from global warming does not impact the height of the storm surges. As a side effect of our simulations we also obtain results on the interplay between surge and tide.
Changing Characteristics on Dust Storm in Jiangsu  [PDF]
Zhaotang Shang, Lin Cheng, Qingping Yu, Lang He, Zhigang Lu
Open Journal of Air Pollution (OJAP) , 2012, DOI: 10.4236/ojap.2012.13009
Abstract: Based on observation data of dust storm for the years 1960-2006 from weather stations across Jiangsu, this essay provides a statistical analysis on the characteristics and trends, including the timeframes and regions of the incidences of four weather phenomena: sandstorm, blowing sand, floating dust and haze in an effort to better understand the trend of dust storm changes in Jiangsu Province, China. The result indicates that, on average, the incidences of sandstorm, indi- cated with the total number of days in a year in Jiangsu is low and on a declining trend. With the improvement of the environment, no sandstorm has been observed for many years. In general, those of blowing sand and floating dust have been reducing, and showing a significant improvement during the recent years. What should be noted, however, is the accelerated increase in haze incidences, particularly, in Southern Jiangsu.
An ensemble study of extreme storm surge related water levels in the North Sea in a changing climate  [PDF]
A. Sterl,H. van den Brink,H. de Vries,R. Haarsma
Ocean Science (OS) & Discussions (OSD) , 2009,
Abstract: The height of storm surges is extremely important for a low-lying country like The Netherlands. By law, part of the coastal defence system has to withstand a water level that on average occurs only once every 10 000 years. The question then arises whether and how climate change affects the heights of extreme storm surges. Published research points to only small changes. However, due to the limited amount of data available results are usually limited to relatively frequent extremes like the annual 99%-ile. We here report on results from a 17-member ensemble of North Sea water levels spaning the period 1950–2100. It was created by forcing a surge model of the North Sea with meteorological output from a state-of-the-art global climate model which has been driven by greenhouse gas emissions following the SRES A1b scenario. The large ensemble size enables us to calculate 10 000 year return water levels with a low statistical uncertainty. In the one model used in this study, we find no statistically significant change in the 10 000 year return values of surge heights along the Dutch during the 21st century. Also a higher sea level resulting from global warming does not impact the height of the storm surges. As a side effect of our simulations we also obtain results on the interplay between surge and tide.
Relationships between statistics of rainfall extremes and mean annual precipitation: an application for design-storm estimation in northern central Italy
G. Di Baldassarre, A. Castellarin,A. Brath
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2006,
Abstract: Several hydrological analyses need to be founded on a reliable estimate of the design storm, which is the expected rainfall depth corresponding to a given duration and probability of occurrence, usually expressed in terms of return period. The annual series of precipitation maxima for storm duration ranging from 15 min to 1 day, observed at a dense network of raingauges sited in northern central Italy, are analyzed using an approach based on L-moments. The analysis investigates the statistical properties of rainfall extremes and detects significant relationships between these properties and the mean annual precipitation (MAP). On the basis of these relationships, we developed a regional model for estimating the rainfall depth for a given storm duration and recurrence interval in any location of the study region. The applicability of the regional model was assessed through Monte Carlo simulations. The uncertainty of the model for ungauged sites was quantified through an extensive cross-validation.
Drought, Deluge and Declines: The Impact of Precipitation Extremes on Amphibians in a Changing Climate  [PDF]
Susan C. Walls,William J. Barichivich,Mary E. Brown
Biology , 2013, DOI: 10.3390/biology2010399
Abstract: The Class Amphibia is one of the most severely impacted taxa in an on-going global biodiversity crisis. Because amphibian reproduction is tightly associated with the presence of water, climatic changes that affect water availability pose a particularly menacing threat to both aquatic and terrestrial-breeding amphibians. We explore the impacts that one facet of climate change—that of extreme variation in precipitation—may have on amphibians. This variation is manifested principally as increases in the incidence and severity of both drought and major storm events. We stress the need to consider not only total precipitation amounts but also the pattern and timing of rainfall events. Such rainfall “pulses” are likely to become increasingly more influential on amphibians, especially in relation to seasonal reproduction. Changes in reproductive phenology can strongly influence the outcome of competitive and predatory interactions, thus potentially altering community dynamics in assemblages of co-existing species. We present a conceptual model to illustrate possible landscape and metapopulation consequences of alternative climate change scenarios for pond-breeding amphibians, using the Mole Salamander, Ambystoma talpoideum, as an example . Although amphibians have evolved a variety of life history strategies that enable them to cope with environmental uncertainty, it is unclear whether adaptations can keep pace with the escalating rate of climate change. Climate change, especially in combination with other stressors, is a daunting challenge for the persistence of amphibians and, thus, the conservation of global?biodiversity.
Evidences of relationships between statistics of rainfall extremes and mean annual precipitation: an application for design-storm estimation in northern central Italy
G. Di Baldassarre,A. Castellarin,A. Brath
Hydrology and Earth System Sciences Discussions , 2005,
Abstract: Several hydrological analyses need to be founded on a reliable estimate of the design storm, which is the expected rainfall depth corresponding to a given duration and probability of occurrence, usually expressed in terms of return period. The annual series of precipitation maxima for storm duration ranging from 15 min to 1 day are observed at a dense network of raingauges sited in northern central Italy are statistically analyzed using an approach based on L-moments. The study investigates the statistical properties of rainfall extremes and identifies important relationships between these properties and the mean annual precipitation (MAP). On the basis of these relationships, we develop a regional model for estimating the rainfall depth for a given storm duration and recurrence interval in any location of the study region. The reliability of the regional model is assessed through Monte Carlo simulations. The results are relevant given that the proposed model is able to reproduce the statistical properties of rainfall extremes observed for the study region.
Stochastic models of evidence accumulation in changing environments  [PDF]
Alan Veliz-Cuba,Zachary P. Kilpatrick,Kresimir Josic
Quantitative Biology , 2015,
Abstract: Organisms and ecological groups accumulate evidence to make decisions. Classic experiments and theoretical studies have explored this process when the correct choice is fixed during each trial. However, we live in a constantly changing world. What effect does such impermanence have on classical results about decision making? To address this question we use sequential analysis to derive a tractable model of evidence accumulation when the correct option changes in time. Our analysis shows that ideal observers discount prior evidence at a rate determined by the volatility of the environment, and the dynamics of evidence accumulation is governed by the information gained over an average environmental epoch. A plausible neural implementation of an optimal observer in a changing environment shows that, in contrast to previous models, neural populations representing alternate choices are coupled through excitation. Our work builds a bridge between statistical decision making in volatile environments and stochastic nonlinear dynamics.
Assessment of climate change impact on hydrological extremes in two source regions of the Nile River Basin
M. T. Taye,V. Ntegeka,N. P. Ogiramoi,P. Willems
Hydrology and Earth System Sciences Discussions , 2010, DOI: 10.5194/hessd-7-5441-2010
Abstract: The potential impact of climate change was investigated on the hydrology and hydrological extremes of Nyando River and Lake Tana catchments, located in two source regions of the Nile River basin. Climate change scenarios were developed for rainfall and potential evapotranspiration (ETo), considering 17 different General Circulation Model (GCM) simulations to better understand the range of possible future change. Projected changes under two future emission scenarios for the 2050s were extracted from an ensemble of selected GCM experiments. The future climate change scenarios were constructed by transferring the extracted climate change signals to the observed series using a frequency perturbation downscaling approach, which accounts for the effect on rainfall and ETo extremes, its dependence on the return period of rain storm depth, and the correlation between rainfall and ETo changes. Two conceptual hydrological models were calibrated and used for the impact assessment. Their difference in simulating the flows under future climate scenarios was investigated. The results reveal that the hydrological models project increasing runoff extremes for Nyando catchment towards the 2050s while unclear trend is observed for Lake Tana catchment for cumulative volumes as well as high and low flows.
Impacts on the Deep-Sea Ecosystem by a Severe Coastal Storm  [PDF]
Anna Sanchez-Vidal, Miquel Canals, Antoni M. Calafat, Galderic Lastras, Rut Pedrosa-Pàmies, Melisa Menéndez, Raúl Medina, Joan B. Company, Bernat Hereu, Javier Romero, Teresa Alcoverro
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0030395
Abstract: Major coastal storms, associated with strong winds, high waves and intensified currents, and occasionally with heavy rains and flash floods, are mostly known because of the serious damage they can cause along the shoreline and the threats they pose to navigation. However, there is a profound lack of knowledge on the deep-sea impacts of severe coastal storms. Concurrent measurements of key parameters along the coast and in the deep-sea are extremely rare. Here we present a unique data set showing how one of the most extreme coastal storms of the last decades lashing the Western Mediterranean Sea rapidly impacted the deep-sea ecosystem. The storm peaked the 26th of December 2008 leading to the remobilization of a shallow-water reservoir of marine organic carbon associated with fine particles and resulting in its redistribution across the deep basin. The storm also initiated the movement of large amounts of coarse shelf sediment, which abraded and buried benthic communities. Our findings demonstrate, first, that severe coastal storms are highly efficient in transporting organic carbon from shallow water to deep water, thus contributing to its sequestration and, second, that natural, intermittent atmospheric drivers sensitive to global climate change have the potential to tremendously impact the largest and least known ecosystem on Earth, the deep-sea ecosystem.
Long-Range Dispersal and High-Latitude Environments Influence the Population Structure of a “Stress-Tolerant” Dinoflagellate Endosymbiont  [PDF]
D. Tye Pettay, Todd C. LaJeunesse
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0079208
Abstract: The migration and dispersal of stress-tolerant symbiotic dinoflagellates (genus Symbiodinium) may influence the response of symbiotic reef-building corals to a warming climate. We analyzed the genetic structure of the stress-tolerant endosymbiont, Symbiodinium glynni nomen nudum (ITS2 - D1), obtained from Pocillopora colonies that dominate eastern Pacific coral communities. Eleven microsatellite loci identified genotypically diverse populations with minimal genetic subdivision throughout the Eastern Tropical Pacific, encompassing 1000’s of square kilometers from mainland Mexico to the Galapagos Islands. The lack of population differentiation over these distances corresponds with extensive regional host connectivity and indicates that Pocillopora larvae, which maternally inherit their symbionts, aid in the dispersal of this symbiont. In contrast to its host, however, subtropical populations of S. glynni in the Gulf of California (Sea of Cortez) were strongly differentiated from populations in tropical eastern Pacific. Selection pressures related to large seasonal fluctuations in temperature and irradiance likely explain this abrupt genetic discontinuity. We infer that S. glynni genotypes harbored by host larvae arriving from more southern locations are rapidly replaced by genotypes adapted to more temperate environments. The strong population structure of S. glynni corresponds with fluctuating environmental conditions and suggests that these genetically diverse populations have the potential to evolve rapidly to changing environments and reveals the importance of environmental extremes in driving microbial eukaryote (e.g., plankton) speciation in marine ecosystems.
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