On the boundary-layer flow over a Canadian Archipelago polynya

A numerical model is presented for predicting boundary-layer parameters for flow over a polynya, i.e., an isolated lead of open water that recurs annually at the same geographical location during Arctic winters. As the flow encounters a polynya, it experiences a sudden change from a cold, dry, rough, snow-covered ice surface to a warmer, wetter, and smoother open water surface. The present model includes both the heat balance equation and the vapor conservation equation in addition to the usual mass continuity equation, x-momentum equation, and the turbulent energy equation. In addition, the buoyancy term is added to the energy equation to account for the buoyancy force introduced by the underlying warmer surface. To close the system, the present model uses the Glushko-type mixing length relationship. During the numerical calculations, a fully implicit finite-difference method was used, and stable numerical solutions were obtained for a fetch over 1 km. Comparison of model results with measured results over a polynya in the Canadian Archipelago show good agreement.     

Seasonal agricultural land use patterns in China's Pearl River Delta from multi-date landsat images

Landsat images of the Pearl River delta region of SE China were interpreted manually in combination with other data sources to identify, measure and to map agricultural land use in a 25,775 km² study area during three growing seasons of 1978. Areal measurements for different land uses were compiled. Paddy lands, which accounted for 6,340 km², were evaluated and classified on the basis of quality, yield and production. Rice production for the study area was then estimated at 5.9 million metric tons based on average yields for the different grades of paddy land.     

Using Active Faults and Seismicity for the Strong Motion Modeling in the Eastern Rif (Northern Morocco)

— The aim of this study is to conduct a probabilistic seismic hazard analysis for the eastern Rif area in northern Morocco. The source zones were established on the basis of the seismicity database, the fracturing analysis deduced from Landsat7 ETM digital enhancement and marine seismic reflection profiles. By the use of this information together with the selected attenuation relationship, the peak ground acceleration contour maps are produced for specific return periods. The map has been divided into intervals of 0.1 degrees in both latitude and longitude to calculate the values at each grid point and draw the seismic hazard curves. The results of seismic hazard assessment are displayed as iso-acceleration contours expected to be exceeded during typical economic life times of structures.     

Crustal-scale boudinage and migmatization of gneiss during their exhumation in the UHP Province of Western Norway

ABSTRACT A field study in the coesite province, the deepest unit of the Norwegian Caledonides, gives new constraints on the rheological behaviour of the continental crust during exhumation. Lithological heterogeneities and differential retrogression led to crustal-scale boudinage during the late-orogenic intense E–W stretching event in the footwall of the Nordfjord-Sogn Detachment. The main gneissic lithologies display a modest but widespread syn-exhumation migmatization. Textural criteria allow estimation of a 30% fusion rate. Partial melting mostly post-dates eclogitization and is synchronous with ductile stretching and top-to-west shearing. Presented observations suggest that the melt reactions and migmatization resulted in a soft rheology. During subduction to ~ 100 km depth and subsequent exhumation, crustal viscosity can be reduced by up to four orders of magnitude. Models are discussed that consider a transition from a small internal strain of the crust to viscous flow during exhumation.     

Large-area rice yield forecasting using satellite imageries

Ability to make large-area yield prediction before harvest is important in many aspects of agricultural decision-making. In this study, canopy reflectance band ratios (NIR/RED, NIR/GRN) of paddy rice (Oryza sativa L.) at booting stage, from field measurements conducted from 1999 to 2005, were correlated with the corresponding yield data to derive regression-type yield prediction models for the first and second season crop, respectively. These yield models were then validated with ground truth measurements conducted in 2007 and 2008 at eight sites, of different soil properties, climatic conditions, and various treatments in cultivars planted and N application rates, using surface reflectance retrieved from atmospherically corrected SPOT imageries. These validation tests indicated that root mean square error of predicting grain yields per unit area by the proposed models were less than 0.7 T ha⁻¹ for both cropping seasons. Since village is the basic unit for national rice yield census statistics in Taiwan, the yield models were further used to forecast average regional yields for 14 selected villages and compared with officially reported data. Results indicate that the average yield per unit area at village scale can be forecasted with a root mean square error of 1.1 T ha⁻¹ provided no damaging weather occurred during the final month before actual harvest. The methodology can be applied to other optical sensors with similar spectral bands in the visible/near-infrared and to different geographical regions provided that the relation between yield and spectral index is established.     

Trophic structure and functioning in a eutrophic and poorly flushed lagoon in southwestern Taiwan

Tapong Bay, a eutrophic and poorly flushed tropical lagoon, supports intensive oyster culture. Using the Ecopath approach and network analysis, a mass-balanced trophic model was constructed to analyze the structure and matter flows within the food web. The lagoon model is comprised of 18 compartments with the highest trophic level of 3.2 for piscivorous fish. The high pedigree index (0.82) reveals the model to be of high quality. The most-prominent living compartment in terms of matter flow and biomass in the lagoon is cultured oysters and bivalves, respectively. The mixed trophic impacts indicate that phytoplankton and periphyton are the most-influential living compartments in the lagoon. Comparative analyses with the eutrophic and well-flushed Chiku Lagoon and non-eutrophic tropical lagoons show that high nutrient loadings might stimulate the growth and accumulation of phytoplankton and periphyton and therefore support high fishery yields. However, net primary production, total biomass, fishery yields per unit area, and mean transfer efficiency of Tapong Bay were remarkably lower than those of Chiku Lagoon. The lower transfer efficiency likely results from the low mortality of cultured oysters and invasive bivalves from predation or the lower density of benthic feeders constrained by the hypoxic bottom water as a result of poor flushing. This might therefore result in a great proportion of flows to detritus. However, the hypoxic bottom water might further reduce the recycling of the entering detritus back into the food web. In contrast to many estuaries and tropical lagoons, poor flushing of this eutrophic tropical lagoon might induce a shift from detritivory to herbivory in the food web.     

Comparison of the QBO and F10.7 Solar Flux Effects on Total Mass Density

Geomagnetism and Aeronomy - The comparison of the Quasi Biennial Oscillation (QBO) and F10.7 solar flux effects on Total Mass Density (TMD) obtained from NRLMSIS-00 model for 90 km altitude of...     

Coupling Effect of Riser on Integrated FPS in Deepwater Area

The main challenge in predicting global responses of floating vessels in deepwater and ultra-deepwater areas comes from the system's coupled effect.In this paper,the coupled approach is used to analyze effects of riser on floating system in deepwater.The analysis results show that the coupling effects of risers will mainly affect the low frequency (LF) motions of the system.That is because risers will provide the system with a significant low frequency (LF) damping which will vary with the sea states.Under ...     

Assessing optical earth observation systems for mapping and monitoring temporary ponds in arid areas

Remote sensing methods for locating and monitoring temporary ponds over large areas in arid lands were tested on a study site in Northern Senegal. Three main results are presented, validated with field data and intended to highlight different spectral, spatial and temporal characteristics of the methods: (1) Among several water indices tested, two Middle Infrared-based indices (MNDWI—Modified Normalized Difference Water Index and NDWI₁—Normalized Difference Water Index) are found to be most efficient; (2) an objective method is given prescribing the necessary sensor spatial resolution in terms of minimal detected pond area; and (3) the potential of multi-temporal MODIS imagery for tracking the filling phases of small ponds is illustrated. These results should assist in epidemiological studies of vector-borne diseases that develop around these ponds, but also more generally for land and water management and preservation of threatened ecosystems in arid areas.