We present new VLA H I spectral line imaging of five sources discovered by the ALFALFA extragalactic survey. These targets are drawn from a larger sample of systems that were not uniquely identified with optical counterparts during ALFALFA processing, and as such have unusually high H I mass to light ratios. The candidate "Almost Dark" objects fall into four broad categories: 1) objects with nearby H I neighbors that are likely of tidal origin; 2) objects that appear to be part of a system of multiple H I sources, but which may not be tidal in origin; 3) objects isolated from nearby ALFALFA H I detections, but located near a gas-poor early-type galaxy; 4) apparently isolated sources, with no object of coincident redshift within ∼400 kpc. Roughly 75% of the 200 objects without identified counterparts in the α.40 database (Haynes et al. 2011) fall into category 1 (likely tidal), and were not considered for synthesis follow-up observations. The pilot sample presented here (AGC 193953, AGC 208602, AGC 208399, AGC 226178, and AGC 233638) contains the first five sources observed as part of a larger effort to characterize H I sources with no readily identifiable optical counterpart at single dish resolution (3.5 ′ ). These objects span a range of H I mass [7.41 < log(M HI ) < 9.51] and H I mass to B-band luminosity ratios (3 < M HI /L B < 9). We compare the H I total intensity and velocity fields to optical imaging drawn from the Sloan Digital Sky Survey and to ultraviolet imaging drawn from archival GALEX observations. Four of the sources with uncertain or no optical counterpart in the ALFALFA data are identified with low surface brightness optical counterparts in Sloan Digital Sky Survey imaging when compared with VLA H I intensity maps, and appear to be galaxies with clear signs of ordered rotation in the H I velocity fields. Three of these are detected in far-ultraviolet GALEX images, a likely indication of star formation within the last few hundred Myrs. One source (AGC 208602) is likely tidal in nature, associated with the NGC 3370 group. Consistent with previous efforts, we find no "dark galaxies" in this limited sample. However, the present observations do reveal complex sources with suppressed star formation, highlighting both the observational difficulties and the necessity of synthesis follow-up observations to understand these extreme objects.

A general drop size distribution (DSD) normalization method is formulated in terms of generalized power series relating any DSD moment to any number and combination of reference moments. This provides a consistent framework for comparing the variability of normalized DSD moments using different sets of reference moments, with no explicit assumptions about the DSD functional form (e.g., gamma). It also provides a method to derive any unknown moment plus an estimate of its uncertainty from one or more known moments, which is relevant to remote sensing retrievals and bulk microphysics schemes in weather and climate models. The approach is applied to a large dataset of disdrometer-observed and bin microphysics-modeled DSDs. As expected, the spread of normalized moments decreases as the number of reference moments is increased, quantified by the logarithmic standard deviation of the normalized moments, σ. Averaging σ for all combinations of reference moments and normalized moments of integer order 0–10, 42.9%, 81.3%, 93.7%, and 96.9% of spread are accounted for applying one-, two-, three-, and four-moment normalizations, respectively. Thus, DSDs can be well characterized overall using three reference moments, whereas adding a fourth reference moment contributes little independent information. The spread of disdrometer-observed DSD moments from uncertainty associated with drop count statistics generally lies between values of σ using two- and three-moment normalizations. However, this uncertainty has little impact on the derived DSD scaling relationships or σ when considered.

There is growing interest in combining microphysical models and polarimetric radar observations to improve our understanding of storms and precipitation. Mapping model-predicted variables into the radar observational space necessitates a forward operator, which requires assumptions that introduce uncertainties into model–observation comparisons. These include uncertainties arising from the microphysics scheme a priori assumptions of a fixed drop size distribution (DSD) functional form, whereas natural DSDs display far greater variability. To address this concern, this study presents a moment-based polarimetric radar forward operator with no fundamental restrictions on the DSD form by linking radar observables to integrated DSD moments. The forward operator is built upon a dataset of &gt;200 million realistic DSDs from one-dimensional bin microphysical rain-shaft simulations, and surface disdrometer measurements from around the world. This allows for a robust statistical assessment of forward operator uncertainty and quantification of the relationship between polarimetric radar observables and DSD moments. Comparison of “truth” and forward-simulated vertical profiles of the polarimetric radar variables are shown for bin simulations using a variety of moment combinations. Higher-order moments (especially those optimized for use with the polarimetric radar variables: the sixth and ninth) perform better than the lower-order moments (zeroth and third) typically predicted by many bulk microphysics schemes.

Carbon intensity of ship emissions is a cornerstone of contemporary regulatory actions, with measurable targets of reduction being enforced in the coming decade. Short term measures to achieve them include voyage optimization. Therefore, the VISIR ship routing model was upgraded for computing least-CO2 routes depending on ocean analysis products related to waves and sea currents. The speed loss in waves and the CO2 emission rate of a medium size Ro-Pax ship were obtained from a coupled command-bridge engine-room simulator. The geographical and topological features of least-CO2 routes resulting from VISIR were characterised by means of various types of isolines. A case study in the Adriatic Sea leads to bundles of optimal routes with significant spatial diversions even on short-sea routes. The carbon intensity savings were compared to the CO2 savings, highlighting also their dependence on both route lengthening and fractional engine load. For a case study in winter, carbon intensity reductions up to 11% were computed with respect to least-distance routes between the same couple of ports of call. This is promising, as a reduction of this magnitude represents a significant amount of the carbon intensity curbing target required at International level.

Starbursts are finite periods of intense star formation (SF) that can dramatically impact the evolutionary state of a galaxy. Recent results suggest that starbursts in dwarf galaxies last longer and are distributed over more of the galaxy than previously thought, with star formation efficiencies (SFEs) comparable to spiral galaxies, much higher than those typical of non-bursting dwarfs. This difference might be explainable if the starburst mode is externally triggered by gravitational interactions with other nearby systems. We present new, sensitive neutral hydrogen observations of 18 starburst dwarf galaxies, which are part of the STARburst IRregular Dwarf Survey (STARBIRDS) and each were mapped with the Green Bank Telescope (GBT) and/or Parkes Telescope in order to study the low surface brightness gas distributions, a common tracer for tidal interactions.