Investigating the Halogen Chemistry From High-Latitude Nighttime Stratospheric Measurements of OClO and NO2

Two cases of simultaneous nighttime measurements of NO₂ and OClO in the winter polar stratosphere are analyzed in order to test our present knowledge of halogen chemistry in the presence of high amount of NO₂ at low temperature. Comparisons with Lagrangian model calculations using several hypotheses are performed. First simulations, using the admitted constant rates of chemical reaction, strongly underestimate the measured OClO while the NO₂ profiles are correctly reproduced. If uncertainties in actinic fluxes calculations are taken into account, simulation results do not show a significant reduction of the underestimation. A better agreement can be achieved if the formation of unstable isomers of ClONO₂ and of BrONO₂ occurs in the cold conditions of the polar stratosphere. An approximate value of the branching ratios of the channels leading to ClONO₂ and ClOONO, and to BrONO₂ and BrOONO, necessary to reproduce both OClO and NO₂ is given and discussed.     

ENSO anomalies over the Western United States: present and future patterns in regional climate simulations

Surface temperature, precipitation, specific humidity and wind anomalies associated with the warm and cold phases of ENSO simulated by WRF and HadRM are examined for the present and future decades. WRF is driven by ECHAM5 and CCSM3, respectively, and HadRM is driven by HadCM3. For the current decades, all simulations show some capability in resolving the observed warm-dry and cool-wet teleconnection patterns over the PNW and the Southwest U.S. for warm and cold ENSO. Differences in the regional simulations originate primarily from the respective driving fields. For the future decades, the warm-dry and cool-wet teleconnection patterns in association with ENSO are still represented in ECHAM5-WRF and HadRM. However, there are indications of changes in the ENSO teleconnection patterns for CCSM3-WRF in the future, with wet anomalies dominating in the PNW and the Southwest U.S. for both warm and cold ENSO, in contrast to the canonical patterns of precipitation anomalies. Interaction of anomalous wind flow with local terrain plays a critical role in the generation of anomalous precipitation over the western U.S. Anomalous dry conditions are always associated with anomalous airflow that runs parallel to local mountains and wet conditions with airflow that runs perpendicular to local mountains. Future changes in temperature and precipitation associated with the ENSO events in the regional simulations indicate varying responses depending on the variables examined as well as depending on the phase of ENSO.     

EIT: Extreme-ultraviolet Imaging Telescope for the SOHO mission

The Extreme-ultraviolet Imaging Telescope (EIT) will provide wide-field images of the corona and transition region on the solar disc and up to 1.5 R above the solar limb. Its normal incidence multilayer-coated optics will select spectral emission lines from Fe IX (171 ), Fe XII (195 ), Fe XV (284 ), and He II (304 ) to provide sensitive temperature diagnostics in the range from 6 × 10⁴ K to 3 × 10⁶ K. The telescope has a 45 x 45 arcmin field of view and 2.6 arcsec pixels which will provide approximately 5-arcsec spatial resolution. The EIT will probe the coronal plasma on a global scale, as well as the underlying cooler and turbulent atmosphere, providing the basis for comparative analyses with observations from both the ground and other SOHO instruments. This paper presents details of the EIT instrumentation, its performance and operating modes.     

Laboratory simulations of Titan's atmosphere: organic gases and aerosols

Titan, the main satellite of Saturn, has been observed by remote sensing for many years, both from interplanetary probes (Pioneer and Voyager's flybys) and from the Earth. Its N2 atmosphere, containing a small fraction of CH4 (approximately 2%), with T approximately 90 K and P approximately 1.5 bar at the ground level, is irradiated by solar UV photons and deeply bombarded by energetic particles, i.e. Saturn mangetospheric electrons and protons, interplanetary electrons and cosmic rays. The resulting energy deposition, which takes place mainly below 1000 km, initiates chemical reactions which yield gaseous hydrocarbons and nitriles and, through polymerisation processes, solid aerosol particles which grow by coagulation and settle down to the ground. At the present time, photochemical models strongly require the results of specific laboratory studies. Chemical rate constants are not well known at low temperatures, charged-particle-induced reactions are difficult to model and laboratory simulations of atmospheric processes are therefore of great interest. Moreover, the synthesis of organic compounds which have not been detected to date provides valuable information for future observations. The origin and chemical composition of aerosols depend on the nature of chemical and energy sources. Their production from gaseous species may be monitored in laboratory chambers and their optical or microphysical properties compared to those deduced from the observations of Titan's atmosphere. The development of simulation chambers of Titan's extreme conditions is necessary for a better understanding of past and future observations. Space probes will sound Titan's atmosphere by remote sensing and in situ analysis in the near future (Cassini-Huygens mission). It appears necessary, as a preliminary step to test on-board experiments in such chambers, and as a final step, when new space data have been acquired, to use them for more general scientific purposes.     

Poseidon-2 Radar Altimeter Design and Results of In-Flight Performances

Poseidon-2 is the dual frequency, solid-state radar altimeter embarked on the CNES/NASA oceanographic satellite Jason-1. This article gives a brief summary of the instrument design and some in-flight performances. Flight results have confirmed the very good results of the altimeter transfer function, which is very stable, and that the range noise at instrument level is less than 2 cm for a Significant Wave Height of 2 m.     

Biomarkers in flounder (Platichthys flesus): an evaluation of their use in pollution monitoring

Flounder (Platichthys flesus) is among the most common fish-species in Norwegian and European estuaries. It lives in or on sediments from which it also finds most of its food. The aim of the present work was to evaluate biomarkers in flounder for possible future use in monitoring programmes. There were clear biomarker responses in flounder following injection of model contaminants benzo[a]pyrene (B[a]P), PCB #156 and Cd, singly or in sequence. Cytochrome P4501A responded following injection of the organic contaminants and metallothionein (MT) following Cd injection. All groups receiving B[a]P, either singly or in combination with other contaminants, accumulated high levels of B[a]P-metabolites in bile. There was little change in glutathione-S-transferase activity (measured using CDNB as substrate) following the treatments. Starvation appeared to affect the response of hepatic MT to Cd, but none of the other biomarkers. PAH in sediments elicited strong biomarker responses in caged flounder, whereas sediment-associated metals appeared to be largely unavailable to flounder in this study.     

On lipid surface films on the sea. I. A simple method for sampling and studies of composition

A method for collection of surface films on the sea has been developed and tested at various places along the Swedish West Coast. Considerable amounts of lipids on the sea surface were found even when no seaslicks were observed. Triglycerides, free fatty acids, and wax esters are the dominating constituents, and there are characteristic deviations in the fatty-acid patterns compared to the corresponding lipids dissolved in the sub-surface water. Organochlorine residues, phthalic acid esters and heavy metals also occur in considerable amounts.     

Hydrochemical and sedimentary responses of paired High Arctic watersheds to unusual climate and permafrost disturbance,Cape Bounty,Melville Island,Canada

High Arctic river responses to changing hydroclimatic and landscape processes are poorly understood. In non‐glacierized basins, snowmelt and rainfall generate river discharge, which provides first order control over fluxes. Further factors include the seasonality of precipitation, seasonal active layer development, and permafrost disturbance. These controls were evaluated in terms of sedimentary and biogeochemical fluxes from paired catchments at Cape Bounty, Melville Island, Nunavut during 2006–2009. Results indicate that the source of runoff can be more important than the amount of runoff for sediment, solutes, and organic yields. Although the snowmelt period is typically the most important time for these yields, heavy late summer precipitation events can create disproportionately large yields. Rainfall increases yields because it hydrologically connects areas otherwise isolated. Inorganic solute yields from late summer rainfall are higher because the thick active layer maximizes hydrologic interactions with mineral soils and generates high solute concentrations. Results also indicate that while the catchments are broadly similar, subtle topographic differences result in important inter‐catchment differences in runoff and suspended and dissolved loads. The East watershed, which had less extensive permafrost disturbance, consistently had higher concentrations of dissolved solids. These higher dissolved fluxes cannot therefore be explained by thermokarst features, but rather by deeper active layer development, due to a greater proportion of south‐facing slopes. Although warm temperatures in 2007 led to extensive active layer disturbance in the West watershed, because the disturbances were largely hydrologically disconnected, the total disturbed area was small, and inter‐annual variability in discharge was high, there was no detectable response in dissolved loads to disturbances. Sediment availability increased after 2007, but yields have largely returned to pre‐disturbance levels. Results indicate that seasonality and frequency‐magnitude characteristics of projected increases in precipitation must be considered along with active layer changes to predict the fluvial sedimentary and biogeochemical response to regional climate change. Copyright © 2011 John Wiley & Sons, Ltd.