SST and circulation trend biases cause an underestimation of European precipitation trends   总被引：2，自引：0，他引：2  

Ronald van Haren  Geert Jan van Oldenborgh  Geert Lenderink  Matthew Collins  Wilco Hazeleger 《Climate Dynamics》2013,40(1-2):1-20

Clear precipitation trends have been observed in Europe over the past century. In winter, precipitation has increased in north-western Europe. In summer, there has been an increase along many coasts in the same area. Over the second half of the past century precipitation also decreased in southern Europe in winter. An investigation of precipitation trends in two multi-model ensembles including both global and regional climate models shows that these models fail to reproduce the observed trends. In many regions the model spread does not cover the trend in the observations. In contrast, regional climate model (RCM) experiments with observed boundary conditions reproduce the observed precipitation trends much better. The observed trends are largely compatible with the range of uncertainties spanned by the ensemble, indicating that the boundary conditions of RCMs are responsible for large parts of the trend biases. We find that the main factor in setting the trend in winter is atmospheric circulation, for summer sea surface temperature (SST) is important in setting precipitation trends along the North Sea and Atlantic coasts. The causes of the large trends in atmospheric circulation and summer SST are not known. For SST there may be a connection with the well-known ocean circulation biases in low-resolution ocean models. A quantitative understanding of the causes of these trends is needed so that climate model based projections of future climate can be corrected for these precipitation trend biases.  相似文献   

Characterization and assessment of the devastating natural hazards across the Canadian Prairie Provinces from 2009 to 2011     

Julian Brimelow  Ronald Stewart  John Hanesiak  Bohdan Kochtubajda  Kit Szeto  Barrie Bonsal 《Natural Hazards》2014,73(2):761-785

From 2009 to 2011, the Canadian Prairies were subjected to exceptionally variable precipitation regimes, ranging between record drought and unprecedented flooding. Adjacent regions concurrently experienced droughts and floods, and individual areas transitioned rapidly from pluvial to drought conditions and vice versa. Such events had major impacts; for example, damages from floods in the Assiniboine River Basin (ARB) have exceeded $1 billion, and forest fires ravaged the town of Slave Lake, Alberta. This study first characterizes, and then assesses, these devastating natural hazards in terms of their physical processes (across multiple spatial and temporal scales) related to both the spatially contrasting precipitation states and rapid temporal transitions between these states. Subtle differences in large-scale atmospheric flow had marked impacts on precipitation. Primary factors controlling the distribution and amount of precipitation included the location and persistence of key surface and upper-air features, as well as their interaction. Additionally, multiple events—rather than individual extremes—were responsible for the flooding over the Saskatchewan River Basin and the ARB. Very heavy rainfall events (≥25 mm d^?1) accounted for up to 55 % of warm season rain at some locations, and the frequency of heavy rainfall events was critical for determining whether a region experienced drought or pluvial conditions. This study has increased our knowledge of the characteristics, impacts and mechanisms of rapidly transitioning disparate precipitation states on the Canadian Prairies and will aid in better understanding both past and projected future hydro-climatic extremes in the region.  相似文献   

Microbiological monitoring and classification of karst springs     

Michael Sinreich  Michiel Pronk  Ronald Kozel 《Environmental Earth Sciences》2014,71(2):563-572

The use of groundwater as a drinking water resource requires knowledge of its microbiological status and quality. In contrast to conventional microbiological monitoring of groundwater, the present study not only considers faecal indicator bacteria, but also covers a wide spectrum of microorganisms, including bacterial pathogens (verotoxin-producing E. coli, Campylobacter spp. and Salmonella spp., as well as Pseudomonas aeruginosa), human enteric viruses (norovirus, enterovirus, rotavirus and adenovirus) and parasitic protozoa (Cryptosporidium oocysts and Giardia cysts). Samples collected at karst sites of the Swiss National Groundwater Monitoring network revealed the presence of a large diversity of microorganisms of faecal origin, the occurrence of which could be linked to specific hydrogeological settings and situations. The findings represent a ‘snapshot’ of the microbiological status at the monitoring sites and provide a national overview of the types and presence of microorganisms in Swiss karst groundwater. In addition to microbiological parameters related to faecal contamination, the overall bacterial load in groundwater was assessed using cell density measurements (i.e. total cell count), which yielded typical ranges for this ecological parameter. The study highlights differential vulnerability of karst groundwater to microbiological contamination, as well as its relationship with the microbial biocenoses, i.e. the interplay of allochthonous and autochthonous microbial components. On the basis of this data set, a microbiological classification of karst aquifers is proposed and discussed with respect to spring dynamics and vulnerability.  相似文献   

Hidden Components in Tropical Seascapes: Deep-Estuary Habitats Support Unique Fish Assemblages     

Michael Bradley  Ronald Baker  Marcus Sheaves 《Estuaries and Coasts》2017,40(4):1195-1206

Tropical coastal seascapes are biodiverse and highly productive systems composed of an interacting mix of habitats. They provide crucial ecosystem services that support people’s livelihoods, yet key components of these seascapes remain unstudied. We know little about the deep (>2 m) subtidal areas of tropical estuaries, because, due to gear restrictions, there have been no detailed studies of the habitats they contain and the fish that use them. Consequently, potentially important functions and linkages with surrounding habitats remain unknown. Using unbaited videos, an approach capable of sampling the full breadth of benthic habitats and whole fish assemblages, we investigated patterns of fish occupancy of the deep subtidal habitats (2–20 m) in one of Australia’s largest tropical estuaries. We identified 19 taxa not previously recorded from estuaries of tropical eastern Australia, along with 36 previously identified estuary taxa. Three recognisable fish assemblages were associated with distinct benthic habitat types: open bottom fine sediment, seagrass and structurally complex rocky areas. In deep water, habitats often overlooked in shallow water become important, and there are sharp differences in habitat function. Deep subtidal habitats are potentially an important zone for direct interaction between estuary and marine fauna, with a range of consequences for intertidal habitat use and nursery ground functioning. The interface between marine areas and the shallow-water estuary may be richer and more complex than previously recognised.  相似文献   

A new species of the genus <Emphasis Type="Italic">Ammonicera</Emphasis> (Prosobranchia,Omalogyridae) in a coralline algae community from Jeju Island,off the south coast of Korea     

Tsukasa Waki  Emilio Rolán  Ronald G. Noseworthy  Hyun-Sil Kang  Kwang-Sik Choi 《Ocean Science Journal》2017,52(4):587-591

A species of the genus Ammonicera Vayssière, 1893 collected from coralline algae communities in Jeju Island, South Korea, is described as a new species, A. aurea, for science. Its morphological characters are described and illustrated by SEM micrographs. This new species can be clearly distinguished from other Ammonicera species from the Pacific Ocean by the presence of a spiral cord and about 25 slightly-elevated axial ribs, resulting in about 25 nodules at intersecting points of the cord and ribs on the last whorl of the teleoconch.  相似文献