A copula-based multivariate analysis of Canadian RCM projected changes to flood characteristics for northeastern Canada

In the present work, climate change impacts on three spring (March–June) flood characteristics, i.e. peak, volume and duration, for 21 northeast Canadian basins are evaluated, based on Canadian regional climate model (CRCM) simulations. Conventional univariate frequency analysis for each flood characteristic and copula based bivariate frequency analysis for mutually correlated pairs of flood characteristics (i.e. peak–volume, peak–duration and volume–duration) are carried out. While univariate analysis is focused on return levels of selected return periods (5-, 20- and 50-year), the bivariate analysis is focused on the joint occurrence probabilities P1 and P2 of the three pairs of flood characteristics, where P1 is the probability of any one characteristic in a pair exceeding its threshold and P2 is the probability of both characteristics in a pair exceeding their respective thresholds at the same time. The performance of CRCM is assessed by comparing ERA40 (the European Centre for Medium-Range Weather Forecasts 40-year reanalysis) driven CRCM simulated flood statistics and univariate and bivariate frequency analysis results for the current 1970–1999 period with those observed at selected 16 gauging stations for the same time period. The Generalized Extreme Value distribution is selected as the marginal distribution for flood characteristics and the Clayton copula for developing bivariate distribution functions. The CRCM performs well in simulating mean, standard deviation, and 5-, 20- and 50-year return levels of flood characteristics. The joint occurrence probabilities are also simulated well by the CRCM. A five-member ensemble of the CRCM simulated streamflow for the current (1970–1999) and future (2041–2070) periods, driven by five different members of a Canadian Global Climate Model ensemble, are used in the assessment of projected changes, where future simulations correspond to A2 scenario. The results of projected changes, in general, indicate increases in the marginal values, i.e. return levels of flood characteristics, and the joint occurrence probabilities P1 and P2. It is found that the future marginal values of flood characteristics and P1 and P2 values corresponding to longer return periods will be affected more by anthropogenic climate change than those corresponding to shorter return periods but the former ones are subjected to higher uncertainties.     

The internal structures and the relative rotation rates of Uranus and Neptune

The difference between the interior structures of Uranus and Neptune is presented, based on models which fit the observed mass, radius, and gravitational moments for the assumed rotation periods of these planets. If Uranus and Neptune are assumed to be as similar in internal structure as they are in mass and radius, the rotation period for Neptune must be shorter than that for Uranus. It is suggested that the true rotation period is given by Neptune's oblateness, while the photometric period corresponds to the motion of Rossby waves in the upper atmosphere.     

Simulations of magnetic-flux transport in solar active regions

We simulate the evolution of several observed solar active regions by solving a transport equation for magnetic flux at the photosphere. The rates of rotation, meridional flow, and diffusion of the flux are determined self-consistently in the calculations. Our findings are in good quantitative agreement with previous measures of the rotation rate and diffusion constant associated with photospheric magnetic fields. Although our meridional velocities are consistent in direction and magnitude with recently reported poleward flows, relatively large uncertainties in our velocity determinations make this result inconclusive.Laboratory for Computational Physics.E. O. Hulburt Center for Space Research.     

The Korean Integrated Model (KIM) System for Global Weather Forecasting

The Korea Institute of Atmospheric Prediction Systems (KIAPS) began a national project to develop a new global atmospheric model system in 2011. The ultimate goal of this 9-year project is to replace the current operational model at the Korea Meteorological Administration (KMA), which was adopted from the United Kingdom’s Meteorological Office’s unified model (UM) in 2010. The 12-km Korean Integrated Model (KIM) system, consisting of a spectral-element non-hydrostatic dynamical core on a cubed sphere grid and a state-of-the-art physics parameterization package, has been launched in a real-time forecast framework, with initial conditions obtained via the advanced hybrid four-dimensional ensemble variational data assimilation (4DEnVar) over its native grid. A development strategy for KIM and the evolution of its performance in medium-range forecasts toward a world-class global forecast system are described. Outstanding issues in KIM 3.1 as of February 2018 are discussed, along with a future plan for operational deployment in 2020.     

Wave Climatology in Coastal Maine for Aquaculture and Other Applications

Wind waves represent a significant hydrodynamic factor affecting many oceanographic studies such as sediment transport, design of structures, etc. In coastal Maine, wave information is needed, among other applications, for aquaculture-related activities. As few data sources exist, a question that confronts scientists pertains to the magnitudes of typical and extreme wave conditions at various times. To address this, numerical modeling was performed for a period of six and a half years (7/99–12/05) on a continuous basis by coupling National Oceanic and Atmospheric Administration’s outer ocean predictions to two coastal, high-resolution, regional domain grids encompassing the Penobscot Bay and Machias Bay regions where aquaculture activity is prevalent and expanding. As the modeling involves uncertainties because of bathymetric and wind field representations, their effect on the results was explored. It was found that although the uncertainties could create inaccuracies in real-time forecasts, their effect on the development of climatogies was minimal. Average modeled significant wave heights are found to vary between 0.6 and 1.5 m in the sub-domains. The maximum conditions are of the order of 6.5 m in the outer parts of the sub-domains and occurred in September and December. Estimated wave-induced bottom velocities were found in many areas to be in excess of the published estimates of resuspension thresholds for net-pen wastes. Estimates of “extreme” wave conditions, corresponding to a recurrence interval of 30 years (representing the nominal design life of the cage), were found to vary between 2 and 7 m in the modeled areas. Detailed contour maps have been developed for site-specific characterization of the wave climate.     

Growth and linkage of a segmented normal fault zone; the Late Jurassic Murchison–Statfjord North Fault, northern North Sea

The structure of the 25 km long northeastern portion of the Murchison–Statfjord North Fault Zone and adjacent syn-rift stratigraphy are integrated to reconstruct the temporal and spatial evolution during c. 30.5 myr of Late Jurassic, North Sea rifting. Based on a structural analysis (D–d data) alone, approximately 14 precursor fault strands are identified. Incorporation of stratigraphic data shows that only six of these strands were important in controlling stratal architecture and distribution. Three main stages in the evolution of the fault zone are recorded in the syn-rift stratigraphy and are biostratigraphically constrained. These are: (1) following initiation of rifting, six isolated fault strands developed (each <4 km long) and controlled the stratigraphy for c. 13 myr; (2) the isolated strands linked along-strike forming two >9 km long fault segments separated by a 2 km wide relay ramp, that controlled the stratigraphy for at least the following c. 10.5 myr; and (3) the two fault segments hard-linked forming a single, continuous fault trace during the final c. 7 myr of rifting. The results of this study reveal the necessity to adopt an integrated structural and stratigraphic approach when reconstructing the evolution of normal fault zones. The results may also help to further constrain models of fault evolution.     

Prediction of nonstationary climatic series

Summary Most of the stochastic prediction methods are developed for stationary time series. However, many climatic series show clear evidence of non-stationarity. In such cases, methods based on the stationarity assumptions would be inappropriate. Alternative methods such as those based on stochastic approximation are preferable in these cases because they are based on adaptive learning principles. These methods have not been applied and their suitability not tested with nonstationary climatic time series.In the stochastic approximation method, the deterministic component of a nonstationary time series is estimated by first predicting the two steps ahead value of a time series. The two steps-ahead forecast may involve a term characterizing the trend in the time series. The two steps-ahead predictor is corrected to obtain the one step ahead prediction by using a gain sequence.The dynamic stochastic approximation method is used herein to predict non-stationary climatic time series. Daily minimum temperature series at West Lafayette, Indiana, U.S.A. and seasonal temperature and precipitation series at Evansville, Indiana, U.S.A. are used in the study. For data trends, an improved dynamic stochastic approximation method, called the modified dynamic stochastic approximation method gives more accurate predictions. If the method is used for seasonal data, then it can be used to track the time varying mean value.With 6 Figures     

Spectroscopic Observations of Comet C/1996 B2 (Hyakutake) with the Caltech Submillimeter Observatory

The apparition of Comet C/1996 B2 (Hyakutake) offered an unexpected and rare opportunity to probe the inner atmosphere of a comet with high spatial resolution and to investigate with unprecedented sensitivity its chemical composition. We present observations of over 30 submillimeter transitions of HCN, H¹³CN, HNC, HNCO, CO, CH₃OH, and H₂CO in Comet Hyakutake carried out between 1996 March 18 and April 9 at the Caltech Submillimeter Observatory. Detections of the H¹³CN (4–3) and HNCO (16_0,16–15_0,15) transitions represent the first observations of these species in a comet. In addition, several other transitions, including HCN (8–7), CO (4–3), and CO (6–5) are detected for the first time in a comet as is the hyperfine structure of the HCN (4–3) line. The observed intensities of the HCN (4–3) hyperfine components indicate a line center optical depth of 0.9 ± 0.2 on March 22.5 UT. The HCN/HNC abundance ratio in Comet Hyakutake at a heliocentric distance of 1 AU is similar to that measured in the Orion extended ridge— a warm, quiescent molecular cloud. The HCN/H¹³CN abundance ratio implied by our observations is 34 ± 12, similar to that measured in giant molecular clouds in the galactic disk but significantly lower than the Solar System¹²C/¹³C ratio. The low HCN/H¹³CN abundance ratio may be in part due to contamination by an SO₂line blended with the H¹³CN (4–3) line. In addition, chemical models suggest that the HCN/H¹³CN ratio can be affected by fractionation during the collapse phase of the protosolar nebula; hence a low HCN/H¹³CN ratio observed in a comet is not inconsistent with the solar system¹²C/¹³C isotopic ratio. The abundance of HNCO relative to water derived from our observations is (7 ± 3) × 10⁻⁴. The HCN/HNCO abundance ratio is similar to that measured in the core of Sagittarius B2 molecular cloud. Although a photo-dissociative channel of HNCO leads to CO, the CO produced by HNCO is a negligible component of cometary atmospheres. Production rates of HCN, CO, H₂CO, and CH₃OH are presented. Inferred molecular abundances relative to water are typical of those measured in comets at 1 AU from the Sun. The exception is CO, for which we derive a large relative abundance of 30%. The evolution of the HCN production rate between March 20 and March 30 suggests that the increased activity of the comet was the cause of the fragmentation of the nucleus. The time evolution of the H₂CO emission suggests production of this species from dust grains.