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Boulder City, Colorado, United States

Manney G.L.,NorthWest Research Assoc | Manney G.L.,New Mexico Institute of Mining and Technology | Lawrence Z.D.,New Mexico Institute of Mining and Technology | Santee M.L.,Jet Propulsion Laboratory | And 3 more authors.
Atmospheric Chemistry and Physics | Year: 2015

A sudden stratospheric warming (SSW) in early January 2013 caused the Arctic polar vortex to split and temperatures to rapidly rise above the threshold for chlorine activation. However, ozone in the lower stratospheric polar vortex from late December 2012 through early February 2013 reached the lowest values on record for that time of year. Analysis of Aura Microwave Limb Sounder (MLS) trace gas measurements and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) polar stratospheric cloud (PSC) data shows that exceptional chemical ozone loss early in the 2012/13 Arctic winter resulted from a unique combination of meteorological conditions associated with the early-January 2013 SSW: unusually low temperatures in December 2012, offspring vortices within which air remained well isolated for nearly 1 month after the vortex split, and greater-than-usual vortex sunlight exposure throughout December 2012 and January 2013. Conditions in the two offspring vortices differed substantially, with the one overlying Canada having lower temperatures, lower nitric acid (HNO3), lower hydrogen chloride, more sunlight exposure/higher ClO in late January, and a later onset of chlorine deactivation than the one overlying Siberia. MLS HNO3 and CALIPSO data indicate that PSC activity in December 2012 was more extensive and persistent than at that time in any other Arctic winter in the past decade. Chlorine monoxide (ClO, measured by MLS) rose earlier than previously observed and was the largest on record through mid-January 2013. Enhanced vortex ClO persisted until mid-February despite the cessation of PSC activity when the SSW started. Vortex HNO3 remained depressed after PSCs had disappeared; passive transport calculations indicate vortex-averaged denitrification of about 4 parts per billion by volume. The estimated vortex-averaged chemical ozone loss, ∼ 0.7-0.8 parts per million by volume near 500 K (∼21 km), was the largest December/January loss in the MLS record from 2004/05 to 2014/15. © Author(s) 2015. CC Attribution 3.0 License. Source

Cole S.T.,Woods Hole Oceanographic Institution | Wortham C.,University of Washington | Kunze E.,NorthWest Research Assoc | Owens W.B.,Woods Hole Oceanographic Institution
Geophysical Research Letters | Year: 2015

Stirring along isopycnals is a significant factor in determining the distribution of tracers within the ocean. Salinity anomalies on density surfaces from Argo float profiles are used to investigate horizontal stirring and estimate eddy mixing lengths. Eddy mixing length and velocity fluctuations from the ECCO2 global state estimate are used to estimate horizontal diffusivity at a 300 km scale in the upper 2000 m with near-global coverage. Diffusivity varies by over two orders of magnitude with latitude, longitude, and depth. In all basins, diffusivity is elevated in zonal bands corresponding to strong current regions, including western boundary current extension regions, the Antarctic Circumpolar Current, and equatorial current systems. The estimated mixing lengths and diffusivities provide an observationally based data set that can be used to test and constrain predictions and parameterizations of eddy stirring. ©2015. American Geophysical Union. All Rights Reserved. Source

Fontenla J.M.,NorthWest Research Assoc | Stancil P.C.,University of Georgia | Landi E.,University of Michigan
Astrophysical Journal | Year: 2015

The previous calculations of the Solar Spectral Irradiance (SSI) by the Solar Radiation Physical Modeling, version 2 system, are updated in this work by including new molecular photodissociation cross-sections of important species, and many more levels and lines in its treatment of non-LTE radiative transfer. The current calculations including the new molecular photodissociation opacities produce a reduced over-ionizaton of heavy elements in the lower chromosphere and solve the problems with prior studies of the UV SSI in the wavelength range 160-400 nm and now reproduce the available observations with much greater accuracy. Calculations and observations of the near-UV at 0.1 nm resolution and higher are compared. The current set of physical models includes four quiet-Sun and five active-region components, from which radiance is computed for ten observing angles. These radiances are combined with images of the solar disk to obtain the SSI and Total Solar Irradiance and their variations. The computed SSI is compared with measurements from space at several nm resolution and agreement is found within the accuracy level of these measurements. An important result is that the near-UV SSI increase with solar activity is significant for the photodissociation of ozone in the terrestrial atmosphere because a number of highly variable upper chromospheric lines overlap the ozone Hartley band. © 2015. The American Astronomical Society. All rights reserved.. Source

Braun D.C.,NorthWest Research Assoc
Astrophysical Journal | Year: 2016

We use helioseismic holography to study the association of shallow flows with solar flare activity in about 250 large sunspot groups observed between 2010 and 2014 with the Helioseismic and Magnetic Imager on the Solar Dynamics Observatory. Four basic flow parameters: horizontal speed, horizontal component of divergence, vertical component of vorticity, and a vertical kinetic helicity proxy, are mapped for each active region (AR) during its passage across the solar disk. Flow indices are derived representing the mean and standard deviation of these parameters over magnetic masks and compared with contemporary measures of flare X-ray flux. A correlation exists for several of the flow indices, especially those based on the speed and the standard deviation of all flow parameters. However, their correlation with X-ray flux is similar to that observed with the mean unsigned magnetic flux density over the same masks. The temporal variation of the flow indices are studied, and a superposed epoch analysis with respect to the occurrence to 70 M and X-class flares is made. While flows evolve with the passage of the ARs across the disk, no discernible precursors or other temporal changes specifically associated with flares are detected. © 2016. The American Astronomical Society. All rights reserved.. Source

Masci F.,Italian National Institute of Geophysics and Volcanology | Thomas J.N.,NorthWest Research Assoc | Thomas J.N.,DigiPen Institute of Technology | Thomas J.N.,University of Washington
Radio Science | Year: 2015

The scientific literature includes many reports of ionospheric phenomena that are retrospectively identified prior to seismic events. These disturbances of the Earth's ionosphere are considered to be possible precursors of the impending earthquakes. However, a causal relationship between ionospheric phenomena and earthquakes has never been definitively demonstrated, and attempts at identifying precursory effects in the ionosphere have been called into question by several studies. Among the candidate indicators of ionospheric precursors there is the Spatial Scintillation Index (SSI) proposed by Pulinets et al. (2007). The usefulness of this index in the search for precursory effects of earthquakes has been criticized by Thomas et al. (2012) and Masci (2013). In a recent report, Pulinets and Davidenko (2014) attempt to briefly respond to the remarks of these researchers. Here we cast doubt that Pulinets and Davidenko (2014) have shown that SSI is a reliable indicator of precursory effects of earthquakes in the ionosphere. © 2015. American Geophysical Union. All Rights Reserved. Source

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