A neurocomputing approach to the forecasting of monthly maximum temperature over Kolkata, India using total ozone concentration as predictor

The association between the monthly total ozone concentration and monthly maximum temperature over Kolkata (22.56° N, 88.30° E), India, has been explored in this paper. For this, the predictability of monthly maximum temperature based on the total ozone as predictor is investigated using Artificial Neural Network. The presence of persistence and similar cyclic patterns are revealed through autocorrelation and cross-correlation coefficients. Common cycles of length 12 and 6 have been identified through periodogram. Hence, a predictive model has been generated by Artificial Neural Network in the form of Multi Layer Perceptron (MLP) using scaled conjugate gradient learning with sigmoid non-linearity. After training and testing the network, an MLP with total ozone of month n as predictor and maximum temperature of month (n + 1) as the target output is found as the best model. Performance of the model has been judged statistically. Finally, the MLP model has been compared with linear and non-linear regressions and the efficiency of MLP has been established over the regression models.     

A 50-year record of NO<Subscript>x</Subscript> and SO<Subscript>2</Subscript> sources in precipitation in the Northern Rocky Mountains,USA

Ice-core samples from Upper Fremont Glacier (UFG), Wyoming, were used as proxy records for the chemical composition of atmospheric deposition. Results of analysis of the ice-core samples for stable isotopes of nitrogen (δ¹⁵N, ) and sulfur (δ³⁴S, ), as well as and deposition rates from the late-1940s thru the early-1990s, were used to enhance and extend existing National Atmospheric Deposition Program/National Trends Network (NADP/NTN) data in western Wyoming. The most enriched δ³⁴S value in the UFG ice-core samples coincided with snow deposited during the 1980 eruption of Mt. St. Helens, Washington. The remaining δ³⁴S values were similar to the isotopic composition of coal from southern Wyoming. The δ¹⁵N values in ice-core samples representing a similar period of snow deposition were negative, ranging from -5.9 to -3.2 ‰ and all fall within the δ¹⁵N values expected from vehicle emissions. Ice-core nitrate and sulfate deposition data reflect the sharply increasing U.S. emissions data from 1950 to the mid-1970s.     

Nutrient Inputs, Phytoplankton Response, and CO2 Variations in a Semi-Enclosed Subtropical Embayment, Kaneohe Bay, Hawaii

The marine shelf areas in subtropical and tropical regions represent only 35% of the total shelf areas globally, but receive a disproportionately large amount of water (65%) and sediment (58%) discharges that enter such environments. Small rivers and/or streams that drain the mountainous areas in these climatic zones deliver the majority of the sediment and nutrient inputs to these narrow shelf environments; such inputs often occur as discrete, episodic introductions associated with storm events. To gain insight into the linked biogeochemical behavior of subtropical/tropical mountainous watershed-coastal ocean ecosystems, this work describes the use of a buoy system to monitor autonomously water quality responses to land-derived nutrient inputs and physical forcing associated with local storm events in the coastal ocean of southern Kaneohe Bay, Oahu, Hawaii, USA. The data represent 2.5 years of near-real time observations at a fixed station, collected concurrently with spatially distributed synoptic sampling over larger sections of Kaneohe Bay. Storm events cause most of the fluvial nutrient, particulate, and dissolved organic carbon inputs to Kaneohe Bay. Nutrient loadings from direct rainfall and/or terrestrial runoff produce an immediate increase in the N:P ratio of bay waters up to values of 48 and drive phytoplankton biomass growth. Rapid uptake of such nutrient subsidies by phytoplankton causes rapid declines of N levels, return to N-limited conditions, and subsequent decline of phytoplankton biomass over timescales ranging from a few days to several weeks, depending on conditions and proximity to the sources of runoff. The enhanced productivity may promote the drawing down of pCO₂ and lowering of surface water column carbonate saturation states, and in some events, a temporary shift from N to P limitation. The productivity-driven CO₂ drawdown may temporarily lead to air-to-sea transfer of atmospheric CO₂ in a system that is on an annual basis a source of CO₂ to the atmosphere due to calcification and perhaps heterotrophy. Storms may also strongly affect proximal coastal zone pCO₂ and hence carbonate saturation state due to river runoff flushing out high pCO₂ soil and ground waters. Mixing of the CO₂-charged water with seawater causes a salting out effect that releases CO₂ to the atmosphere. Many subtropical and tropical systems throughout the Pacific region are similar to Kaneohe Bay, and our work provides an important indication of the variability and range of CO₂ dynamics that are likely to exist elsewhere. Such variability must be taken into account in any analysis of the direction and magnitude of the air?Csea CO₂ exchange for the integrated coastal ocean, proximal and distal. It cannot be overemphasized that this research illustrates several examples of how high frequency sampling by a moored autonomous system can provide details about ecosystem responses to stochastic atmospheric forcing that are commonly missed by traditional synoptic observational approaches. Finally, the work exemplifies the utility of combining synoptic sampling and real-time autonomous observations to elucidate the biogeochemical and physical responses of coastal subtropical/tropical coral reef ecosystems to climatic perturbations.     

Neogene-Quaternary tectonic evolution of the Leeward Antilles islands (Aruba, Bonaire, Curaçao) from fault kinematic analysis

Aruba, Bonaire, and Curaçao are islands aligned along the crest of a 200-km-long segment of the east-west-trending Leeward Antilles ridge within the broad Caribbean-South America plate boundary zone presently characterized by east-west, right-lateral strike-slip motion. The crust of the Leeward Antilles ridge represents the western segment of the Cretaceous-early Cenozoic Great Arc of the Caribbean, which obliquely collided, with the continental margin of northern South America in early Cenozoic time. Following the collision, the ridge was affected by folding and was segmented by oblique, northwest-striking normal faults that have produced steep-sided, northwest-trending, elongate islands and narrow shelves separated by deepwater, sediment-filled and fault-controlled basins. In this paper, we present the first fault slip observations on the Neogene carbonate rocks that cover large areas of all three islands. Our main objective is to quantify the timing and nature of Neogene to Quaternary phases of faulting and folding that have affected the structure and topography of this area including offshore sedimentary basins that are being explored for their petroleum potential. These data constrain three fault phases that have affected Aruba, Bonaire, and Curaçao and likely the adjacent offshore areas: 1) NW-SE-directed late Paleogene compression; 2) middle Miocene syndepositional NNW-SSE to NNE-SSW extension that produced deep rift basins transverse to the east-west-trending Leeward Antilles ridge; and 3) Pliocene-Quaternary NNE-trending compression that produced NW-SE-trending anticlines present on Aruba, Curaçao and Bonaire islands. Our new observations - that include detailed relationships between striated fault planes, paleostress tensors, and bedding planes - show that prominent bedding dips of Neogene limestone on Aruba, Bonaire and Curaçao were produced by regional tectonic shortening across the entire Leeward Antilles ridge rather than by localized, syndepositional effects as proposed by previous workers. We interpret Pliocene-Quaternary NNE-directed shortening effects on the Leeward Antilles ridge as the result of northeastward extrusion or “tectonic escape” of continental areas of western Venezuela combined with southeastward shallow subduction of the Caribbean plate beneath the ridge.     

Structural controls on Quaternary deepwater sedimentation, mud diapirism, and hydrocarbon distribution within the actively evolving Columbus foreland basin, eastern offshore Trinidad

Eastward migration of the Caribbean plate relative to the South American plate has caused lithospheric loading along the northern margin of South America, which is recorded by an 1100-km-long foreland basin which is oldest in the west (Maracaibo basin, 65-55 Ma) and youngest in the east (Columbus basin, eastern offshore Trinidad, 15-0 Ma). The Orinoco River has been the primary source of sediment for the basin since early Miocene. We have integrated approximately 775 km of deep-penetration 2D seismic lines acquired in the area of eastern offshore Trinidad as part of the 2004 “Broadband Ocean-Land Investigations of Venezuela and the Antilles arc Region” (BOLIVAR) project, 8000 km² of shallow industry 3D seismic data, and published industry well data from offshore eastern Trinidad. Active mud diapirism in the Columbus basin is widespread and is related to overthrusting and tectono-sedimentary loading of upper Miocene-lower Pliocene age mud. Analysis of the shallow 3D seismic data reveals the presence of extensive gravity-flow depositional elements on the Columbus basin slope and the deepwater area. These stacked gravity-flow deposits are characterized by mass-transport deposits at the base, turbidite frontal-splay deposits, leveed-channel deposits, and capped by fine-grained condensed-section deposits. Exploration targets in the deepwater area are located towards the center of the Columbus basin, where northeast-trending fault-propagation folds are important Plio-Pleistocene trap-forming elements. Deep basin wells drilled in recent years have proven that turbidites were transported into the deepwater Columbus basin during the Plio-Pleistocene. Analysis of these well results suggests that a deeper oil charge is present within the deepwater Columbus basin area. The primary uncertainty for this variable hydrocarbon system is whether fault or diapiric pathways connect or divert the petroleum charge at depth with shallower reservoir rocks.     

The Middle Miocene to Recent Davis Strait Drift Complex: implications for Arctic�CAtlantic water exchange

A large-scale contourite drift complex has been recognised on multi-channel 2D reflection seismic data acquired in the south-eastern Davis Strait and adjacent Labrador Sea slope offshore West Greenland between 63°?C66°N. Based on well-tie data, the drift complex developed from the Middle Miocene to the Recent. It has been mapped in a wide variety of water depths ranging from about 700?m, at a NNW-ESE-elongated crest located above structural highs in the Davis Strait, to more than 2,000?m beyond the slope to the Labrador Sea. The overall drift geometry has been described by subdivision into two first-order seismic units, enabling the generation of time-isochore maps. The reflection patterns demonstrating current-related deposition are illustrated by seismic examples. The time-isochores of the two first-order seismic units show lateral changes in their depocentres: the lower unit is absent in a zone slightly displaced south-westwards of the present-day crest, indicating changes in the prevailing deepwater current system during the Early Pliocene. The observations can be explained by two alternative palaeoceanographic scenarios: (1) either the present-day oceanographic setting with Arctic?CAtlantic water exchange across the Davis Strait was largely established by the mid-Miocene, with only minor adjustments during the Early Pliocene caused by tectonic movements, or (2) it became established during the Early Pliocene as a consequence of enhanced northward flow across the Davis Strait due to lowering of the sill depth.     

Measurement and modeling of bed shear stress under solitary waves

Direct measurements of bed shear stresses (using a shear cell apparatus) generated by non-breaking solitary waves are presented. The measurements were carried out over a smooth bed in laminar and transitional flow regimes (~ 10⁴ < R_e < ~ 10⁵). Measurements were carried out where the wave height to water depth (h/d) ratio varied between 0.12 and 0.68; maximum near bed velocity varied between 0.16 m/s and 0.51 m/s and the maximum total shear stress (sum of skin shear stress and Froude–Krylov force) varied between 0.386 Pa and 2.06 Pa. The total stress is important in determining the stability of submarine sediment and in sheet flow regimes. Analytical modeling was carried out to predict total and skin shear stresses using convolution integration methods forced with the free stream velocity and incorporating a range of eddy viscosity models. Wave friction factors were estimated from skin shear stress at different instances over the wave (viz., time of maximum positive total shear stress, maximum skin shear stress and at the time of maximum velocity) using both the maximum velocity and the instantaneous velocity at that phase of the wave cycle. Similarly, force coefficients obtained from total stress were estimated at time of maximum positive and negative total stress and at maximum velocity. Maximum positive total shear stress was approximately 1.5 times larger than minimum negative total stress. Modeled and measured positive bed shear stresses are well correlated using the best convolution model, but the model underestimates the data by about 4%. Friction factors are dependent on the choice of normalizing using the maximum velocity, as is conventional, or the instantaneous velocity. These differ because the stress is not in phase with the velocity in general. Friction factors are consistent with previous data for monochromatic waves, and vary inversely with the square-root of the Reynolds number. The total shear stress leads the free stream fluid velocity by approximately 50°, whereas the skin friction shear stress leads by about 30°, which is similar to that reported by earlier researchers.     

Solar Flare Prediction Using Advanced Feature Extraction, Machine Learning, and Feature Selection

Novel machine-learning and feature-selection algorithms have been developed to study: i) the flare-prediction-capability of magnetic feature (MF) properties generated by the recently developed Solar Monitor Active Region Tracker (SMART); ii) SMART’s MF properties that are most significantly related to flare occurrence. Spatiotemporal association algorithms are developed to associate MFs with flares from April 1996 to December 2010 in order to differentiate flaring and non-flaring MFs and enable the application of machine-learning and feature-selection algorithms. A machine-learning algorithm is applied to the associated datasets to determine the flare-prediction-capability of all 21 SMART MF properties. The prediction performance is assessed using standard forecast-verification measures and compared with the prediction measures of one of the standard technologies for flare-prediction that is also based on machine-learning: Automated Solar Activity Prediction (ASAP). The comparison shows that the combination of SMART MFs with machine-learning has the potential to achieve more accurate flare-prediction than ASAP. Feature-selection algorithms are then applied to determine the MF properties that are most related to flare occurrence. It is found that a reduced set of six MF properties can achieve a similar degree of prediction accuracy as the full set of 21 SMART MF properties.     

Lunar atmospheric H2 detections by the LAMP UV spectrograph on the Lunar Reconnaissance Orbiter

We report on the detection of H₂ as seen in our analysis of twilight observations of the lunar atmosphere observed by the LAMP instrument aboard NASA’s Lunar Reconnaissance Orbiter. Using a large amount of data collected on the lunar atmosphere between September 2009 and March 2013, we have detected and identified, the presence of H₂ in the native lunar atmosphere, for the first time. We derive a surface density for H₂ of 1.2 ± 0.4 × 10³ cm⁻³ at 120 K. This is about 10 times smaller than originally predicted, and several times smaller than previous upper limits from the Apollo era data.