Association of an ice-nucleating pseudomonad with cultures of the marine dinoflagellate, Heterocapsa niei

The observations that terrestrial ice nuclei can have a biogenic origin and that certain bacteria can initiate freezing at exceptionally warm temperatures (−1.5°C) are now well documented. Less well understood are active ice nuclei (−2 to −5°C) found in sea water, marine fog and the marine atmosphere in general. Recently, the authors have isolated an ice nucleation-active (INA) bacterial strain (FB 1032) from cultures of the marine dinoflagellate, Heterocapsa niei. FB 1032 is halotolerant and phenotypically similar to Pseudomonas fluorescens biotype G, although it differs from biotype G strains in its bacteriophage sensitivity and expression of the INA phenotype. A search for the INA pseudomonad in sea water at La Jolla, California was unsuccessful, but several INA Erwinia sp. were isolated. The possible terrestrial origin of these INA bacteria is suggested

Metapopulation capacity with self-colonization: Finding the best patches in fragmented habitats

Habitat fragmentation continues to be a leading threat for our global future. Methods to quantify fragmentation of habitat landscapes, particularly for endangered species, would be especially useful in conservation planning. Using the principles of metapopulation theory, we updated and devised two methods for analyzing fragmented landscapes: metapopulation capacity and abandonment rate. Our version of metapopulation capacity includes a self-colonization component to counteract the issue metapopulation theory experiences with single large patches. We then tested these methods on satellite image range maps of endemic birds in the highland forests of northern Central America.

The metapopulation capacity method proved to be a better measure in that it highlighted which patches would be the most successful habitat in the landscape, based on size and connectivity to surrounding patches, thus allowing for species persistence. Unexpectedly, the abandonment rate method proved useful in providing a way of measuring each individual patch’s support to the rest of the landscape system. This could then be used to rank the remaining patches in order of their greatest contribution. Finally, by using a historical satellite map that showed previously forested habitat in the now deforested landscape, we were able to generate optimal restoration sequences by ranking each 1 km squares’ potential contribution

Suppression of combustion oscillations with mechanical devices Interim report

Static rocket thrust chamber simulator for cylindrical cold flow-type apparatus desig

Airborne measurements of tropospheric ozone destruction and particulate bromide formation in the Arctic

Aircraft profiles of O3 concentrations over the Arctic ice pack in spring exhibit a depletion of O3 beneath the surface temperature inversion. One such profile from the NOAA WP-3D Arctic Gas and Aerosol Sampling Program (AGASP) flights in April, 1986 north of Alert, NWT (YLT, 82.5 N) is shown. The gradient of O3 across the temperature inversion, which is essentially a step function from tropospheric values (35 to 40 ppbv) to 0, is somewhat masked by a 1-min running mean applied to the data. Evidence is presented that O3 destruction beneath the Arctic temperature inversion is the result of a photochemical reaction between gaseous Br compounds and O3 to produce particulate Br aerosol. It is noted that in springtime, O3 at the Alert Baseline Station regularly decreases from 30 to 40 ppbv to near 0 over the period of a few hours to a day. At the same time, there is a production of particulate Br with a near 1.0 anti-correlation to O3 concentration. Surface concentrations of bromoform in the Arctic exhibit a rapid decrease following polar sunrise. AGASP aircraft measurements of filterable bromine particulates in the Arctic (March-April, 1983 and 1986) are shown. The greatest concentrations of Br aerosol (shown as enrichment factors relative to to Na in seawater, EFBR (Na)) were observed in samples collected beneath the surface temperature inversion over ice. Samples collected at the same altitude over open ocean (off Spitzbergen) labeled Marine did not exhibit similar Br enrichments. A second region of particulate Br enrichment was observed in the lower stratosphere, which regularly descends to below 500 mb (5.5 km) in the high Arctic. The NOAA WP-3D flew in the stratosphere on all AGASP flights and occasionally measured O3 concentrations in excess of 300 ppbv

Springtime surface ozone fluctuations at high Arctic latitudes and their possible relationship to atmospheric bromine

At high Arctic stations such as Barrow, Alaska, springtime near-surface ozone amounts fluctuate between the highest and lowest values seen during the course of the year. Episodes when the surface ozone concentration is essentially zero last up to several days during this time of year. In the Arctic Gas and Aerosol Sampling Program (AGASP-I and AGASP-II) in 1983 and 1986, it was found that ozone concentrations often showed a very steep gradient in altitude with very low values near the surface. The cold temperatures, and snow-covered ground make it unlikely that the surface itself would rapidly destroy significant amounts of ozone. The AGASP aircraft measurements that found low ozone concentrations in the lowest layers of the troposphere also found that filterable excess bromine (the amount of bromine in excess of the sea salt component) in samples collected wholly or partially beneath the temperature inversion had higher bromine concentrations than other tropospheric samples. Of the four lowest ozone minimum concentrations, three of them were associated with the highest bromine enrichments. Surface measurements of excess filterable bromine at Barrow show a strong seasonal dependence with values rising dramatically early in March, then declining in May. The concentration of organic bromine gases such as bromoform rise sharply during the winter and then begin to decline after March with winter and early spring values at least three times greater than the summer minimum

Reduction of Martian Sample Return Mission Launch Mass with Solar Sail Propulsion

Solar sails have the potential to provide mass and cost savings for spacecraft traveling within the innter solar system. Companies like L'Garde have demonstrated sail manufacturability and various i-space development methods. The purpose of this study was to evaluate a current Mars sample return architecture and to determine how cost and mass would be reduced by incorporating a solar sail propulsion system. The team validated the design proposed by L'Garde, and scaled the design based on a trajectory analysis. Using the solar sail design reduced the required mass, eliminating one of the three launches required in the original architecture

Marine and terrestrial influences on ice nucleating particles during continuous springtime measurements in an Arctic oilfield location

Aerosols that serve as ice nucleating particles (INPs) have the potential to modulate cloud microphysical properties and can therefore impact cloud radiative forcing (CRF) and precipitation formation processes. In remote regions such as the Arctic, aerosol–cloud interactions are severely understudied yet may have significant implications for the surface energy budget and its impact on sea ice and snow surfaces. Further, uncertainties in model representations of heterogeneous ice nucleation are a significant hindrance to simulating Arctic mixed-phase cloud processes. We present results from a campaign called INPOP (Ice Nucleating Particles at Oliktok Point), which took place at a US Department of Energy Atmospheric Radiation Measurement (DOE ARM) facility in the northern Alaskan Arctic. Three time- and size-resolved aerosol impactors were deployed from 1 March to 31 May 2017 for offline ice nucleation and chemical analyses and were co-located with routine measurements of aerosol number and size. The largest particles (i.e., ≥ 3 µm or “coarse mode”) were the most efficient INPs by inducing freezing at the warmest temperatures. During periods with snow- and ice-covered surfaces, coarse mode INP concentrations were very low (maximum of 6 × 10−4 L−1 at −15 ∘C), but higher concentrations of warm-temperature INPs were observed during late May (maximum of 2 × 10−2 L−1 at −15 ∘C). These higher concentrations were attributed to air masses originating from over open Arctic Ocean water and tundra surfaces. To our knowledge, these results represent the first INP characterization measurements in an Arctic oilfield location and demonstrate strong influences from mineral and marine sources despite the relatively high springtime pollution levels. Ultimately, these results can be used to evaluate the anthropogenic and natural influences on aerosol composition and Arctic cloud properties

HOVERCAT: a novel aerial system for evaluation of aerosol-cloud interactions

Aerosols have a profound impact on cloud microphysics through their ability to serve as ice nucleating particles (INPs). As a result, cloud radiative properties and precipitation processes can be modulated by such aerosol&ndash;cloud interactions. However, one of the largest uncertainties associated with atmospheric processes is the indirect effect of aerosols on clouds. The need for more advanced observations of INPs in the atmospheric vertical profile is apparent, yet most ice nucleation measurements are conducted on the ground or during infrequent and intensive airborne field campaigns. Here, we describe a novel measurement platform that is less expensive and smaller (&lt;&thinsp;5&thinsp;kg) when compared to traditional aircraft and tethered balloon platforms and that can be used for evaluating two modes of ice nucleation (i.e., immersion and deposition). HOVERCAT (Honing On VERtical Cloud and Aerosol properTies) flew during a pilot study in Colorado, USA, up to 2.6&thinsp;km above mean sea level (1.1&thinsp;km above ground level) and consists of an aerosol module that includes an optical particle counter for size distributions (0.38&ndash;17&thinsp; &micro;m in diameter) and a new sampler that collects up to 10 filter samples for offline ice nucleation and aerosol analyses on a launched balloon platform. During the May 2017 test flight, total particle concentrations were highest closest to the ground (up to 50&thinsp;cm&minus;3 at &lt;&thinsp;50&thinsp;m above ground level) and up to 2 in 10 2 particles were ice nucleation active in the immersion mode (at &minus;23&thinsp;∘C). The warmest temperature immersion and deposition mode INPs (observed up to &minus;6 and &minus;40.4&thinsp;∘C, respectively) were observed closest to the ground, but overall INP concentrations did not exhibit an inverse correlation with increasing altitude. HOVERCAT is a prototype that can be further modified for other airborne platforms, including tethered balloon and unmanned aircraft systems. The versatility of HOVERCAT affords future opportunities to profile the atmospheric column for more comprehensive evaluations of aerosol&ndash;cloud interactions. Based on our test flight experiences, we provide a set of recommendations for future deployments of similar measurement systems and platforms.</p

Influence of Oil and Gas Emissions on Summertime Ozone in the Colorado Northern Front Range

Tropospheric O 3 has been decreasing across much of the eastern U.S. but has remained steady or even increased in some western regions. Recent increases in VOC and NO x emissions associated with the production of oil and natural gas (O&NG) may contribute to this trend in some areas. The Northern Front Range of Colorado has regularly exceeded O 3 air quality standards during summertime in recent years. This region has VOC emissions from a rapidly developing O&NG basin and low concentrations of biogenic VOC in close proximity to urban-Denver NO x emissions. Here VOC OH reactivity (OHR), O 3 production efficiency (OPE), and an observationally constrained box model are used to quantify the influence of O&NG emissions on regional summertime O 3 production. Analyses are based on measurements acquired over two summers at a central location within the Northern Front Range that lies between major regional O&NG and urban emission sectors. Observational analyses suggest that mixing obscures any OPE differences in air primarily influenced by O&NG or urban emission sector. The box model confirms relatively modest OPE differences that are within the uncertainties of the field observations. Box model results also indicate that maximum O 3 at the measurement location is sensitive to changes in NO x mixing ratio but also responsive to O&NGVOC reductions. Combined, these analyses show that O&tp://esrl. noaa.gov/csd, FRAPPNG alkanes contribute over 80% to the observed carbon mixing ratio, roughly 50% to the regional VOC OHR, and approximately 20% to regional photochemical O 3 production