Great Microwave Bursts and hard X-rays from solar flares     

Herbert J. Wiehl  David A. Batchelor  Carol Jo Crannell  Brian R. Dennis  Phillip N. Price  Andreas Magun 《Solar physics》1985,96(2):339-356

The microwave and hard X-ray characteristics of 13 solar flares that produced microwave fluxes greater than 500 solar flux units have been analyzed. These Great Microwave Bursts were observed in the frequency range from 3 to 35 GHz at Bern, and simultaneous hard X-ray observations were made in the energy range from 30 to 500 keV with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission spacecraft. The principal aim of this analysis is to determine whether or not the same distribution of energetic electrons can explain both emissions. The temporal and spectral behaviors of the microwaves as a function of frequency and the X-rays as a function of energy were tested for correlations, with results suggesting that optically thick microwave emission, at a frequency near the peak frequency, originates in the same electron population that produces the hard X-rays. The microwave emission at lower frequencies, however, is poorly correlated with emission at the frequency which appears to characterize this common source. A single-temperature and a multitemperature model were tested for consistency with the coincident X-ray and microwave spectra at microwave burst maximum. Four events are inconsistent with both of the models tested, and neither of the models attempts to explain the high-frequency part of the microwave spectrum. A source area derived on the basis of the single-temperature model agrees to within the uncertainties with the observed area of the one burst for which spatially resolved X-ray images are available.Swiss National Science Foundation Fellow from the University of Bern.Also Energy/Environmental Research Group, Incorporated, Tucson, Arizona, and Department of Physics and Astronomy, University of North Carolina, Chapel Hill. Present address: Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland.  相似文献   

High-Frequency Response of the Atmospheric Electric Potential Gradient Under Strong and Dry Boundary-Layer Convection     

Ricardo Conceição  Hugo Gonçalves Silva  Alec Bennett  Rui Salgado  Daniele Bortoli  Maria João Costa  Manuel Collares Pereira 《Boundary-Layer Meteorology》2018,166(1):69-81

The spectral response of atmospheric electric potential gradient gives important information about phenomena affecting this gradient at characteristic time scales ranging from years (e.g., solar modulation) to fractions of a second (e.g., turbulence). While long-term time scales have been exhaustively explored, short-term scales have received less attention. At such frequencies, space-charge transport inside the planetary boundary layer becomes a sizeable contribution to the potential gradient variability. For the first time, co-located (Évora, Portugal) measurements of boundary-layer backscatter profiles and the 100-Hz potential gradient are reported. Five campaign days are analyzed, providing evidence for a relation between high-frequency response of the potential gradient and strong dry convection.  相似文献   

Development of an Operational Hybrid Data Assimilation System at KIAPS     

In-Hyuk Kwon  Hyo-Jong Song  Ji-Hyun Ha  Hyoung-Wook Chun  Jeon-Ho Kang  Sihye Lee  Sujeong Lim  Youngsoon Jo  Hyun-Jun Han  Hanbyeol Jeong  Hui-Nae Kwon  Seoleun Shin  Tae-Hun Kim 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(1):319-335

This study introduces the operational data assimilation (DA) system at the Korea Institute of Atmospheric Prediction Systems (KIAPS) to the numerical weather prediction community. Its development history and performance are addressed with experimental illustrations and the authors’ previously published studies. Milestones in skill improvements include the initial operational implementation of three-dimensional variational data assimilation (3DVar), the ingestion of additional satellite observations, and changing the DA scheme to a hybrid four-dimensional ensemble-variational DA using forecasts from an ensemble based on the local ensemble transform Kalman filter (LETKF). In the hybrid system, determining the relative contribution of the ensemble-based covariance to the resultant analysis is crucial, particularly for moisture variables including a variety of horizontal scale spectra. Modifications to the humidity control variable, partial rather than full recentering of the ensemble for humidity further improves moisture analysis, and the inclusion of more radiance observations with higher-level peaking channels have significant impacts on stratosphere temperature and wind performance. Recent update of the operational hybrid DA system relative to the previous 3DVar system is described for detailed improvements with interpretation.  相似文献   

Engineering and environmental problems in karst — An introduction     

Mario Parise  Jo De Waele  Francisco Gutierrez 《Engineering Geology》2008,99(3-4):91

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Interaction between a dam site and karst springs: The case of Supramonte (Central-East Sardinia, Italy)     

Jo De Waele   《Engineering Geology》2008,99(3-4):128

Sardinia is one of the Italian regions with the greatest number of dams per inhabitants, almost 60 for a population of only 1.5 million people. Many of these dam sites are located on non-carbonate rocks along the main rivers of the Island and their waters are used for irrigation, industrial, energy supply, drinking and flood regulation purposes.The Pedra 'e Othoni dam on the Cedrino river (Dorgali, Central-East Sardinia) is located along the threshold of the Palaeozoic basement on the Northern border of the Supramonte karst area, where water is forced to flow out of the system through several resurgences, the most famous of which is the Su Gologone vauclusian spring, used for drinking water supply. The other main outflows of the system, Su Tippari and San Pantaleo springs, are at present almost permanently submerged by the high water level of the Pedra 'e Othoni dam. In the near future water will be supplied also to other communities with a possible increase of water taken from the spring.The dam, originally meant to regulate the flooding of Cedrino river but actually used for all sorts of purposes (electricity supply, drinking water, irrigation of farmlands, industrial uses), has a maximum regulation altitude of 103 m a.s.l., only slightly less than a meter below the Su Gologone spring level (103.7 m), and 4 and 9 m respectively above the submerged Su Tippari and San Pantaleo springs.During floods of the Cedrino river, occurring on average twice a year, also the Su Gologone spring becomes submerged by the muddy waters of the lake for a time ranging between a couple of hours up to several days, making water supply impossible.The analysis of the available meteorological and hydrogeological data relative to the December 2004 flood, one of the severest of the past 100 years, suggests that the reservoir is filled in a few days time. Several flooding scenarios have been reconstructed using digital terrain models, showing that backflooding submerges most of the discharge area of the aquifer, having important repercussions also on the inland underground drainage system. The upstream flood prone areas prevalently comprise agricultural lands with some sparse houses, but also highly frequented tourist facilities. Fortunately flooding occurs outside the tourist season, thus limiting risk to a limited number of local inhabitants. Massive discharge at the dam site, instead, determines a more hazardous situation in the Cedrino coastal plain, where population density in low lying areas is much higher. To avoid flooding hazard upstream the water level in the lake should be regulated, keeping it low in the flood prone seasons, and having it filled from the end of the winter in order to have enough water stocked before the beginning of the summer. Discharge at the dam site, instead, should be done cautiously, preventing severe flooding of the coastal Cedrino plain.  相似文献   

Complex coastal change in response to autogenic basin infilling: An example from a sub‐tropical Holocene strandplain          下载免费PDF全文

Christopher J. Hein  Duncan M. FitzGerald  Luis H. P. de Souza  Ioannis Y. Georgiou  Ilya V. Buynevich  Antonio H. da F. Klein  João Thadeu de Menezes  William J. Cleary  Thelma L. Scolaro 《Sedimentology》2016,63(6):1362-1395

Thick bay‐fill sequences that often culminate in strandplain development serve as important sedimentary archives of land–ocean interaction, although distinguishing between internal and external forcings is an ongoing challenge. This study employs sediment cores, ground‐penetrating radar surveys, radiocarbon dates, palaeogeographic reconstructions and hydrodynamic modelling to explore the role of autogenic processes – notably a reduction in wave energy in response to coastal embayment infilling – in coastal evolution and shoreline morphodynamics. Following a regional 2 to 4 m highstand at ca 5·8 ka, the 75 km² Tijucas Strandplain in southern Brazil built from fluvial sediments deposited into a semi‐enclosed bay. Holocene regressive deposits are underlain by fluvial sands and a Pleistocene transgressive–regressive sequence, and backed by a highstand barrier‐island. The strandplain is immediately underlain by 5 to 16 m of seaward‐thickening, fluvially derived, Holocene‐age, basin‐fill mud. Several trends are observed from the landward (oldest) to the seaward (youngest) sections of the strandplain: (i) the upper shoreface and foreshore become finer and thinner and shift from sand‐dominated to mud‐dominated; (ii) beachface slopes decrease from >11° to ca 7°; and (iii) progradation rates increase from 0·4 to 1·8 m yr^?1. Hydrodynamic modelling demonstrates a correlation between progressive shoaling of Tijucas Bay driven by sea‐level fall and sediment infilling and a decrease in onshore wave‐energy transport from 18 to 4 kW m^?1. The combination of allogenic (sediment supply, falling relative sea‐level and geology) and autogenic (decrease in wave energy due to bay shoaling) processes drove the development of a regressive system with characteristics that are rare, if not unique, in the Holocene and rock records. These findings demonstrate the complexities in architecture styles of highstand and regressive systems tracts. Furthermore, this article highlights the diverse internal and external processes and feedbacks responsible for the development of these intricate marginal marine sedimentary systems.  相似文献   

Metagenomic characterization of viral communities in Goseong Bay,Korea     

Jinik Hwang  So Yun Park  Mirye Park  Sukchan Lee  Yeonhwa Jo  Won Kyong Cho  Taek-Kyun Lee 《Ocean Science Journal》2016,51(4):599-612

In this study, seawater samples were collected from Goseong Bay, Korea in March 2014 and viral populations were examined by metagenomics assembly. Enrichment of marine viral particles using FeCl₃ followed by next-generation sequencing produced numerous sequences. De novo assembly and BLAST search showed that most of the obtained contigs were unknown sequences and only 0.74% of sequences were associated with known viruses. As a result, 138 viruses, including bacteriophages (87%), viruses infecting algae and others (13%) were identified. The identified 138 viruses were divided into 11 orders, 14 families, 34 genera, and 133 species. The dominant viruses were Pelagibacter phage HTVC010P and Roseobacter phage SIO1. The viruses infecting algae, including the Ostreococcus species, accounted for 9.4% of total identified viruses. In addition, we identified pathogenic herpes viruses infecting fishes and giant viruses infecting parasitic acanthamoeba species. This is a comprehensive study to reveal the viral populations in the Goseong Bay using metagenomics. The information associated with the marine viral community in Goseong Bay, Korea will be useful for comparative analysis in other marine viral communities.  相似文献   

Hydroelastic response of a very large floating structure over a variable bottom topography   总被引：1，自引：0，他引：1  

Jo Hyun Kyoung  Sa Young Hong  Byoung Wan Kim  Seok Kyu Cho 《Ocean Engineering》2005,32(17-18):2040-2052

An influence of sea-bottom topography on the hydroelastic response of a Very Large Floating Structure (VLFS) is considered. When the floating structure is constructed near the shore, the sea-bottom topographical effect should be considered. In this study, the effect of sea-bottom topography is investigated for four different bottom cases. To calculate the sea-bottom effects rigorously, the finite-element method based on the variational formulation is used in the fluid domain. The pontoon-type floating structure is modeled as the Kirchhoff plate. The mode superposition method is adopted for the hydroelastic behavior of the floating structure.  相似文献   

Bioaccumulation and depuration of Zn and Cd in mangrove oysters (Crassostrea rhizophorae, Guilding, 1828) transplanted to and from a contaminated tropical coastal lagoon   总被引：2，自引：0，他引：2  

Rebouças do Amaral MC  de Freitas Rebelo M  Torres JP  Pfeiffer WC 《Marine environmental research》2005,59(4):277-285

In order to study Zn and Cd accumulation and depuration, a set of oysters, Crassostrea rhizophorae, were transplanted to a metal contaminated coastal lagoon and another one was harvested there and transplanted to a non-polluted site. C. rhizophorae oysters and Perna perna mussels native from both sites were collected in order to monitor variability of metal concentration in resident populations. After three months exposure, oysters transplanted to the polluted site accumulated fourfold Zn (307-1319 microgg(-1)) without reaching the concentration level of resident oysters (9770 microgg(-1)). Cadmium concentrations had a slight but significant decrease during the same period (1.25-0.54 microgg(-1)). Oysters transplanted to the non-polluted site, showed threefold Zn depuration (6727-2404 microgg(-1)), while Cd had no significant variation (0.90-1.45 microgg(-1)). Results showed that transplanted oysters do not reach heavy metal concentrations in indigenous populations suggesting transplanted organisms would be better used to evaluate bioavailability instead of environmental concentrations.  相似文献   

Coastal uplift rate at Matanzas (Cuba) inferred from MIS5e phreatic overgrowths on speleothems          下载免费PDF全文

Jo De Waele  Ilenia M. D'Angeli  Nicola Tisato  Paola Tuccimei  Michele Soligo  Joaquín Ginés  Angel Ginés  Joan J. Fornós  Igor M. Villa  Esteban R. Grau González  Stefano M. Bernasconi  Tomaso R. R. Bontognali 《地学学报》2017,29(2):98-105

Many morphological elements in Cuba's landscape (e.g. marine terraces, tidal notches) demonstrate that coastal uplift has taken place, but the rate at which this occurs is not known. Carbonate phreatic overgrowths on speleothems have been found in a cave in Central North Cuba, ~1 km from the present coastline at 16 m asl. They form exceptional and unique mushroom‐shaped speleothems and balconies decorating the walls of the rooms. These phreatic overgrowths on speleothems (POS) formed at the oscillating air–water interface in sea‐level controlled anchialine lakes. U/Th dating of these overgrowths suggests ages that are compatible with the Marine Isotope Stage 5e (i.e. 130–115 ka). These POS have fixed this sea‐level highstand and demonstrate that this part of Cuba has been subjected to a much lower uplift rate than previously reported, that is, less than 0.1 mm/year since the last interglacial.  相似文献