Sounding Rocket Observations of Active Region Soft X-Ray Spectra Between 0.5 and 2.5 nm Using a Modified SDO/EVE Instrument

Spectrally resolved measurements of individual solar active regions (ARs) in the soft X-ray (SXR) range are important for studying dynamic processes in the solar corona and their associated effects on the Earth’s upper atmosphere. They are also a means of evaluating atomic data and elemental abundances used in physics-based solar spectral models. However, very few such measurements are available. We present spectral measurements of two individual ARs in the 0.5 to 2.5 nm range obtained on the NASA 36.290 sounding rocket flight of 21 October 2013 (at about 18:30 UT) using the Solar Aspect Monitor (SAM), a channel of the Extreme Ultaviolet Variability Experiment (EVE) payload designed for underflight calibrations of the orbital EVE on the Solar Dynamics Observatory (SDO). The EVE rocket instrument is a duplicate of the EVE on SDO, except the SAM channel on the rocket version was modified in 2012 to include a freestanding transmission grating to provide spectrally resolved images of the solar disk with the best signal to noise ratio for the brightest features, such as ARs. Calibrations of the EVE sounding rocket instrument at the National Institute of Standards and Technology Synchrotron Ultraviolet Radiation Facility (NIST/SURF) have provided a measurement of the SAM absolute spectral response function and a mapping of wavelength separation in the grating diffraction pattern. We discuss techniques (incorporating the NIST/SURF data) for determining SXR spectra from the dispersed AR images as well as the resulting spectra for NOAA ARs 11877 and 11875 observed on the 2013 rocket flight. In comparisons with physics-based spectral models using the CHIANTI v8 atomic database we find that both AR spectra are in good agreement with isothermal spectra (4 MK), as well as spectra based on an AR differential emission measure (DEM) included with the CHIANTI distribution, with the exception of the relative intensities of strong Fe?xvii lines associated with \(2p^{6}\)–\(2p^{5}3{s}\) and \(2p^{6}\)–\(2p^{5}3{d}\) transitions at about 1.7 nm and 1.5 nm, respectively. The ratio of the Fe?xvii lines suggests that the AR 11877 is hotter than the AR 11875. This result is confirmed with analysis of the active regions imaged by X-ray Telescope (XRT) onboard Hinode.     

A New Tool for Inundation Modeling: Community Modeling Interface for Tsunamis (ComMIT)

Almost 5 years after the 26 December 2004 Indian Ocean tragedy, the 10 August 2009 Andaman tsunami demonstrated that accurate forecasting is possible using the tsunami community modeling tool Community Model Interface for Tsunamis (ComMIT). ComMIT is designed for ease of use, and allows dissemination of results to the community while addressing concerns associated with proprietary issues of bathymetry and topography. It uses initial conditions from a precomputed propagation database, has an easy-to-interpret graphical interface, and requires only portable hardware. ComMIT was initially developed for Indian Ocean countries with support from the United Nations Educational, Scientific, and Cultural Organization (UNESCO), the United States Agency for International Development (USAID), and the National Oceanic and Atmospheric Administration (NOAA). To date, more than 60 scientists from 17 countries in the Indian Ocean have been trained and are using it in operational inundation mapping.     

Use of micro-XRF chemical analysis for mapping volcanogenic massive sulfide related hydrothermal alteration: Application to the subaqueous felsic dome-flow complex of the Cap d'Ours section,Glenwood rhyolite,Rouyn-Noranda,Québec,Canada

A new analytical method using micro-X-ray fluorescence (XRF) is presented for the in situ analysis of major elements in rock samples. This approach has allowed for a separate study of hydrothermal alteration of matrix versus fragments in volcaniclastic material (i.e. flow breccia). This is particularly important for volcanogenic massive sulfide (VMS) exploration in subaqueous felsic dome-flow complexes, where brecciated facies are omnipresent and the imprint of hydrothermal alteration is typically heterogeneous. In this study, eleven elements are measured with a 1.7 by 1.3 mm window considered to be representative of each sample, based on replicate analyses. An average is calculated for the analyzed window and yields a nearly complete analysis with the exception of loss of ignition (LOI). Micro-XRF data were validated using whole rock XRF analyses performed on the same sample block. The application of this chemical method has been tested successfully on thin sections from the Cap d'Ours section of the Glenwood rhyolite in the Rouyn-Noranda region of Québec, Canada. With 58 samples spaced at approximately 50 m intervals, two styles of alteration zoning were recognized: (1) a lateral and concordant zoning expressed by vent-proximal silicification in the west grading toward vent-distal chlorite–sericite alteration to the east, and (2) vertical and discordant zoning expressed by stronger sericitization in the upper part of later volcanic quartz- and feldspar-phyric endogenous lobes. The former is typical of cooling induced by seawater interaction at the lava–water interface at temperatures greater than 400 °C, whereas the latter is related to lower temperature (< 300 °C) hydrothermal mineralization associated with endogenous lobe emplacement within the volcanic pile. The presented results clearly demonstrate the potential use of the micro-XRF data for characterizing weak to intense hydrothermal alteration in highly fragmented volcanic rocks.     

The Regional Ocean Modeling System (ROMS) 4-dimensional variational data assimilation systems: Part I - System overview and formulation

The Regional Ocean Modeling System (ROMS) is one of the few community ocean general circulation models for which a 4-dimensional variational data assimilation (4D-Var) capability has been developed. The ROMS 4D-Var capability is unique in that three variants of 4D-Var are supported: a primal formulation of incremental strong constraint 4D-Var (I4D-Var), a dual formulation based on a physical-space statistical analysis system (4D-PSAS), and a dual formulation representer-based variant of 4D-Var (R4D-Var). In each case, ROMS is used in conjunction with available observations to identify a best estimate of the ocean circulation based on a set of a priori hypotheses about errors in the initial conditions, boundary conditions, surface forcing, and errors in the model in the case of 4D-PSAS and R4D-Var. In the primal formulation of I4D-Var the search for the best circulation estimate is performed in the full space of the model control vector, while for the dual formulations of 4D-PSAS and R4D-Var only the sub-space of linear functions of the model state vector spanned by the observations (i.e. the dual space) is searched. In oceanographic applications, the number of observations is typically much less than the dimension of the model control vector, so there are clear advantages to limiting the search to the space spanned by the observations. In the case of 4D-PSAS and R4D-Var, the strong constraint assumption (i.e. that the model is error free) can be relaxed leading to the so-called weak constraint formulation. This paper describes the three aforementioned variants of 4D-Var as they are implemented in ROMS. Critical components that are common to each approach are conjugate gradient descent, preconditioning, and error covariance models, which are also described. Finally, several powerful 4D-Var diagnostic tools are discussed, namely computation of posterior errors, eigenvector analysis of the posterior error covariance, observation impact, and observation sensitivity.     

Drivers of Change in Shallow Coastal Photic Systems: An Introduction to a Special Issue

Coastal ecosystems are characterized by relatively deep, plankton-based estuaries and much shallower systems where light reaches the bottom. These latter systems, including lagoons, bar-built estuaries, the fringing regions of deeper systems, and other systems of only a few meters deep, are characterized by a variety of benthic primary producers that augment and, in many cases, dominate the production supplied by phytoplankton. These “shallow coastal photic systems” are subject to a wide variety of both natural and anthropogenic drivers and possess numerous natural “filters” that modulate their response to these drivers; in many cases, the responses are much different from those in deeper estuaries. Natural drivers include meteorological forcing, freshwater inflow, episodic events such as storms, wet/dry periods, and background loading of optically active constituents. Anthropogenic drivers include accelerated inputs of nutrients and sediments, chemical contaminants, physical alteration and hydrodynamic manipulation, climate change, the presence of intensive aquaculture, fishery harvests, and introduction of exotic species. The response of these systems is modulated by a number of factors, notably bathymetry, physical flushing, fetch, sediment type, background light attenuation, and the presence of benthic autotrophs, suspension feeding bivalves, and fringing tidal wetlands. Finally, responses to stressors in these systems, particularly anthropogenic nutrient enrichment, consist of blooms of phytoplankton, macroalgae, and epiphytic algae, including harmful algal blooms, subsequent declines in submerged aquatic vegetation and loss of critical habitat, development of hypoxia/anoxia particularly on short time scales (i.e., “diel-cycling”), fish kills, and loss of secondary production. This special issue of Estuaries and Coasts serves to integrate current understanding of the structure and function of shallow coastal photic systems, illustrate the many drivers that cause change in these systems, and synthesize their varied responses.     

Counterfactual reasoning in space and time: Integrating graphical causal models in computational movement analysis

Movement analysis is distinguished by an emphasis on understanding via observation and association. However, an important component of movement from the human and computer modeling perspective is the processes that bring about movement behavior in the first place. This article contextualizes the graphical causal modeling framework (for association, intervention, and counterfactual causal analysis) in GIScience, and more specifically within movement analysis studies. This is done by modeling the movement behavior of football players, applied to spatiotemporal data generated by an agent-based simulation. The movement dataset is thoroughly analyzed to infer the statistical associations among its variables, to estimate the effect of an intervention on some of those variables, and to answer a few counterfactual questions from the observations. We conclude that causal graphs (i.e., directed acyclic graphs), if implemented correctly, can assist analysts in infering causal relations from movement data. This research suggests the integration of causal graphs and agent-based paradigms as one solution for computational movement analysis.     

The Visualisation of Uncertainty for Spatially Referenced Census Data Using Hierarchical Tessellations

This paper explains why it is vital to account for uncertainty when utilising socioeco‐nomic data in a GIS, focusing on a novel and intuitive method to visually represent the uncertainty. In common with other data, it is not possible to know exactly how far from the truth socioeconomic data are. Therefore, when such data are used in a decision‐making environment an approximate measure given for correctness of data is an essential component. This is illustrated, using choropleth mapping techniques on census data as an example. Both attribute and spatial uncertainty are considered, with Monte Carlo statistical simulations being used to model attribute uncertainty. An appropriate visualisation technique to manage certain choropleth issues and uncer‐tainty in census type data is introduced, catering for attribute and spatial uncertainty simultaneously. This is done using the output from hierarchical spatial data structures, in particular the region quadtree and the HoR (Hexagon or Rhombus) quadtree. The variable cell size of these structures expresses uncertainty, with larger cell size indicating large uncertainty, and vice versa. This technique is illustrated using the New Zealand 2001 census data, and the TRUST (The Representation of Uncertainty using Scale‐unspecific Tessellations) software suite, designed to show spatial and attribute uncertainty whilst simultaneously displaying the original data.     

Carbon content and carbonate 13C abundances in the Early Precambrian Swaziland sediments of South Africa

Carbon content (0.02–0.68% organic), carbonate content (0–69.7%) and carbonate ¹³C abundances (${}^{\mathrm{?}}\text{7.5?+2.3‰}$) were obtained on samples from the Swaziland sediments of South Africa, which are among the oldest known sedimentary rocks on earth (> 3·10⁹ years old). The carbon chemistry of these sediments may serve as evidence for early life and/or for products of chemical evolution. The variation of organic and carbonate carbon concentrations in different sedimentary horizons seems to be controlled by differences in depositional and diagenetic histories. The carbonate δ ¹³C values did not vary significantly from the ordinary range of Phanerozoic limestone values.