Evaluation of linear ozone photochemistry parametrizations in a stratosphere-troposphere data assimilation system

This paper evaluates the performance of various linear ozone photochemistry parametrizations using the stratosphere-troposphere data assimilation system of the Met Office. A set of experiments were run for the period 23 September 2003 to 5 November 2003 using the Cariolle (v1.0 and v2.1), LINOZ and Chem2D-OPP (v0.1 and v2.1) parametrizations. All operational meteorological observations were assimilated, together with ozone retrievals from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). Experiments were validated against independent data from the Halogen Occultation Experiment (HALOE) and ozonesondes. Additionally, a simple offline method for comparing the parametrizations is introduced. <br><br> It is shown that in the upper stratosphere and mesosphere, outside the polar night, ozone analyses are controlled by the photochemistry parametrizations and not by the assimilated observations. The most important factor in getting good results at these levels is to pay attention to the ozone and temperature climatologies in the parametrizations. There should be no discrepancies between the climatologies and the assimilated observations or the model, but there is also a competing demand that the climatologies be objectively accurate in themselves. Conversely, in the lower stratosphere outside regions of heterogeneous ozone depletion, the ozone analyses are dominated by observational increments and the photochemistry parametrizations have little influence. <br><br> We investigate a number of known problems in LINOZ and Cariolle v1.0 in more detail than previously, and we find discrepancies in Cariolle v2.1 and Chem2D-OPP v2.1, which are demonstrated to have been removed in the latest available versions (v2.8 and v2.6 respectively). In general, however, all the parametrizations work well through much of the stratosphere, helped by the presence of good quality assimilated MIPAS observations

Concept of a laser-plasma based electron source for sub-10 fs electron diffraction

We propose a new concept of an electron source for ultrafast electron diffraction with sub-10~fs temporal resolution. Electrons are generated in a laser-plasma accelerator, able to deliver femtosecond electron bunches at 5 MeV energy with kHz repetition rate. The possibility of producing this electron source is demonstrated using Particle-In-Cell simulations. We then use particle tracking simulations to show that this electron beam can be transported and manipulated in a realistic beamline, in order to reach parameters suitable for electron diffraction. The beamline consists of realistic static magnetic optics and introduces no temporal jitter. We demonstrate numerically that electron bunches with 5~fs duration and containing 1.5~fC per bunch can be produced, with a transverse coherence length exceeding 2~nm, as required for electron diffraction

Estimation of Relative Abundance of Recreationally Important Finfish in the Virginia Portion of Chesapeake Bay: Annual Progress Report 1990-1991

A recent analysis of the Virginia portion of the National Marine Fisheries Service Marine Recreational Fisheries Statistics Survey (VMRC 1985) showed that Virginia marine recreational catches were dominated by six species (spot, croaker, weakfish, black sea bass, summer flounder, and bluefish) which constituted over 85% of the total estimated catch by both numbers caught and weight landed. All of these species except bluefish heavily utilize the lower Chesapeake Bay as a nursery area for early juveniles which are highly vulnerable to bottom trawls

A New Limit on the Antiproton Lifetime

Measurements of the cosmic ray pbar/p ratio are compared to predictions from an inhomogeneous disk-diffusion model of pbar production and propagation within the Galaxy, combined with a calculation of the modulation of the interstellar cosmic ray spectra as the particles propagate through the heliosphere to the Earth. The predictions agree with the observed pbar/p spectrum. Adding a finite pbar lifetime to the model, we obtain the limit tau_pbar > 0.8 Myr (90 % C.L.).Comment: 13 pages, 3 encapsulated Postscript figures, uses AASTeX; accepted by Astrophysical Journal; minor change

Performance of the MIND detector at a Neutrino Factory using realistic muon reconstruction

A Neutrino Factory producing an intense beam composed of nu_e(nubar_e) and nubar_mu(nu_mu) from muon decays has been shown to have the greatest sensitivity to the two currently unmeasured neutrino mixing parameters, theta_13 and delta_CP . Using the `wrong-sign muon' signal to measure nu_e to nu_mu(nubar_e to nubar_mu) oscillations in a 50 ktonne Magnetised Iron Neutrino Detector (MIND) sensitivity to delta_CP could be maintained down to small values of theta_13. However, the detector efficiencies used in previous studies were calculated assuming perfect pattern recognition. In this paper, MIND is re-assessed taking into account, for the first time, a realistic pattern recognition for the muon candidate. Reoptimisation of the analysis utilises a combination of methods, including a multivariate analysis similar to the one used in MINOS, to maintain high efficiency while suppressing backgrounds, ensuring that the signal selection efficiency and the background levels are comparable or better than the ones in previous analyses

Juvenile Fish and Blue Crab Stock Assessment Program Bottom Trawl Survey Annual Data Summary Report Volume 1999

This report summarizes data collected by the Virginia Institute of Marine Science (VIMS) monthly trawl survey cruises for January to December 1999. The trawl survey is a long-term, broad scope monitoring program. Its primary goal is to monitor juvenile abundance for marine and estuarine finfish and invertebrates. A major objective is to provide annual indices of juvenile abundance for recreationally, commercially, and ecologically important species of sufficient accuracy and precision for both immediate resource management needs and long-term understanding of environmental influences on fishery resources. A second important product of this effort is the documentation and monitoring of habitat utilization by juveniles and small adults of these species. The program also provides a sound framework for the procurement of biological samples for life history studies and other investigations relevant to fisheries resource management

The 8 o'clock Arc: A Serendipitous Discovery of a Strongly Lensed Lyman Break Galaxy in the SDSS DR4 Imaging Data

We report on the serendipitous discovery of the brightest Lyman Break Galaxy (LBG) currently known, a galaxy at z=2.73 that is being strongly lensed by the z=0.38 Luminous Red Galaxy (LRG) SDSS J002240.91+143110.4. The arc of this gravitational lens system, which we have dubbed the "8 o'clock arc" due to its time of discovery, was initially identified in the imaging data of the Sloan Digital Sky Survey Data Release 4 (SDSS DR4); followup observations on the Astrophysical Research Consortium (ARC) 3.5m telescope at Apache Point Observatory confirmed the lensing nature of this system and led to the identification of the arc's spectrum as that of an LBG. The arc has a spectrum and a redshift remarkably similar to those of the previous record-holder for brightest LBG (MS 1512-cB58, a.k.a "cB58"), but, with an estimated total magnitude of (g,r,i) = (20.0,19.2,19.0) and surface brightness of (mu_g,mu_r,mu_i) = (23.3, 22.5, 22.3) mag/arcsec^2, the 8 o'clock arc is thrice as bright. The 8 o'clock arc, which consists of three lensed images of the LBG, is 162deg (9.6arcsec) long and has a length-to-width ratio of 6:1. A fourth image of the LBG -- a counter-image -- can also be identified in the ARC 3.5m g-band images. A simple lens model for the system assuming a singular isothermal ellipsoid potential yields an Einstein radius of 2.91+/-0.14 arcsec, a total mass for the lensing LRG (within the (10.6+/-0.5)/h kpc enclosed by the lensed images) of 1.04x10^12/h Msun, and a magnification factor for the LBG of 12.3(+15/-3.6). The LBG itself is intrinsically quite luminous (approximately 6L*) and shows indications of massive recent star formation, perhaps as high as 160/h Msun/year.Comment: 4 pages 5 figures, submitted to ApJ Letter

Estimation of Relative Abundance of Recreationally Important Finfish in the Virginia Portion of Chesapeake Bay: Annual Progress Report 1991-1992

Provisional annual indices of juvenile abundance have been generated from trawl survey data for five species of key recreational importance in the Virginia portion of Chesapeake Bay (spot, croaker, weakfish, summer flounder and black sea bass) and one species of secondary importance (scup) for the period 1988-1991. Only summer flounder catches resulted in an index that showed a consistent (upward) trend over the four years sampled, but the maximal value recorded for 1991 (2.8) was not statistically significantly higher than the prior year, in contrast to the previous increases observed. Atlantic croaker showed the greatest variability between years, with the 1989 index of 65 being 5 to 7 times higher than that seen in the other three years. The spot and weakfish indices both exhibited minimal values in 1991 (17 and 4 respectively) and suggested a declining trend, but there was considerable overlap of confidence intervals between years and the pattern was not definitive. Black sea bass and scup juvenile recruitment to lower Chesapeake Bay showed no evidence of a trend over the four year period

Evaluating the recruitment of American eel, Anguilla rostrata, to the Potomac - Spring 2000 : March 2000 - June 2000

Measures of juvenile recruitment success have long been recognized as a valuable fisheries management tool. In the Chesapeake Bay, these measures have provided reliable indicators for future year class strength for blue crabs (Lipcius and van Engel, 1990), striped bass (Goodyear, 1985), and several other recreationally important fishes (Geer and Austin, 1999). The American eel, Anguilla rostrata, is a valuable commercial species along the entire Atlantic coast from New Brunswick to Florida. Landings along the U.S. Atlantic coast have varied from 290 MT in 1962 to a high of 1600 MT in 1975 (NMFS, 1999). In recent years there seems to be declining harvest, with similar pattems seen in the Canadian maritime providences. The Mid-Atlantic states (New York, New Jersey, Delaware, Maryland, and Virginia) have comprised the largest portion of the East Coast catch (88% of the reported landings) since 1988 (NMFS 1999). The Chesapeake Bay jurisdictions ofVirginia, Maryland, and Potomac River Fisheries Commission (PRFC) alone represent 30, 15, and 18% respectively, of the annual United States (Gulf and Atlantic coast states) commercial harvest for the years 1987-1996 (ASMFC, 1999). Some fishery -independent indices have shown a decline in abundance in recent years (Richkus and Whalens 1999). Hypotheses for the decline include shifts in the Gulf Stream, pollution, over- fishing, parasites, and barriers to passage (Castonguay et al. 1994 ). Many fisheries management teclmiques have not been applied to American eels because little basic biological infom1ation is known. Variation in growth rates, length at age, and other biological parameters has complicated stock assessment methodologies and management efforts. Additionally, few studies have addressed the recruitment of glass eels to the estuaries from the spawning grounds in the Sargasso Sea