Balloon-borne radiometer measurement of Northern Hemisphere mid-latitude stratospheric HNO3 profiles spanning 12 years

Low-resolution atmospheric thermal emission spectra collected by balloon-borne radiometers over the time span of 1990–2002 are used to retrieve vertical profiles of HNO3, CFC-11 and CFC-12 volume mixing ratios between approximately 10 and 35 km altitude. All of the data analyzed have been collected from launches from a Northern Hemisphere mid-latitude site, during late summer, when stratospheric dynamic variability is at a minimum. The retrieval technique incorporates detailed forward modeling of the instrument and the radiative properties of the atmosphere, and obtains a best fit between modeled and measured spectra through a combination of onion-peeling and global optimization steps. The retrieved HNO3 profiles are consistent over the 12-year period, and are consistent with recent measurements by the Atmospheric Chemistry Experiment-Fourier transform spectrometer satellite instrument. This suggests that, to within the errors of the 1990 measurements, there has been no significant change in the HNO3 summer mid-latitude profile

First space-borne measurements of methanol inside aged southern tropical to mid-latitude biomass burning plumes using the ACE-FTS instrument

International audienceFirst measurements from space of upper tropospheric and lower stratospheric methanol profiles within aged fire plumes are reported. Elevated levels of methanol at 0–45° S from 30 September to 3 November 2004 have been measured by the high resolution infrared spectrometer ACE-FTS onboard the SCISAT satellite. Methanol volume mixing ratios higher than 4000 pptv are detected and are strongly correlated with other fire products such as CO, C2H6, and HCN. A sensitivity study of the methanol retrieval, accounting for random and systematic contributions, shows that the retrieved methanol profile for a single occultation exceeds 100% error above 16.5 km, with an accuracy of about 20% for measurements inside polluted air masses. The upper tropospheric enhancement ratio of methanol with respect to CO is estimated from the correlation plot between methanol and CO for aged tropical biomass burning plumes. This ratio is in good agreement with the ratio measured in the free troposphere (up to 12 km) by recent aircraft studies and does not suggest any secondary production of methanol by oxidation in aged biomass burning plumes

First space-borne measurements of methanol inside aged tropical biomass burning plumes using the ACE-FTS instrument

International audienceFirst measurements from space of upper tropospheric and lower stratospheric methanol profiles within aged fire plumes are reported. Elevated levels of methanol at 0–45° S from 30 September to 3 November 2004 have been measured by the high resolution infrared spectrometer ACE-FTS onboard the SCISAT satellite. Methanol volume mixing ratios higher than 4000 pptv are detected and are strongly correlated with other fire products such as CO, C2H6, and HCN. A sensitivity study of the methanol retrieval, accounting for random and systematic contributions, shows that the retrieved methanol profile is reliable from 8.5 to 16.5 km, with an accuracy of about 20% for measurements inside polluted air masses. The upper tropospheric enhancement ratio of methanol with respect to CO is estimated from the correlation plot between methanol and CO for aged tropical biomass burning plumes. This ratio is in good agreement with the ratio measured in the free troposphere (up to 12 km) by recent aircraft studies and does not suggest any secondary production of methanol by oxidation in aged biomass burning plumes

Secondary HIV Infection and Mitigation in Cure-Related HIV Trials During Analytical Treatment Interruptions

To the Editor—We are writing to express concerns regarding facts reported in 2 recent Journal of Infectious Diseases articles pertaining to the ANRSLIGHT study, conducted in 18 clinical sites in France between September 2013 and May 2015. Initially, we were delighted to see the authors implemented several inclusion criteria that we believe were likely to ensure safety of participants during the analytical treatment interruption (ATI) that occurred during the trial, for example a nadir of CD4+ T-cell count of ≥300 cells/mm3 and an initial CD4+ T-cell count of ≥600/mm3. However, other aspects are dismaying, including the detailed identifying information about the index participant and partner. We fear it is possible to identify both persons from the elaborate medical and nonmedical history provided. After contacting the study Principal Investigator, Dr Lelièvre, through a European colleague, it appears there were no consents to disclose this information. Thus, we feel strongly that it was inappropriate to include such comprehensive, potentially identifying details

Derivation of tropospheric methane from TCCON CH₄ and HF total column observations

The Total Carbon Column Observing Network (TCCON) is a global ground-based network of Fourier transform spectrometers that produce precise measurements of column-averaged dry-air mole fractions of atmospheric methane (CH₄). Temporal variability in the total column of CH₄ due to stratospheric dynamics obscures fluctuations and trends driven by tropospheric transport and local surface fluxes that are critical for understanding CH₄ sources and sinks. We reduce the contribution of stratospheric variability from the total column average by subtracting an estimate of the stratospheric CH₄ derived from simultaneous measurements of hydrogen fluoride (HF). HF provides a proxy for stratospheric CH₄ because it is strongly correlated to CH₄ in the stratosphere, has an accurately known tropospheric abundance (of zero), and is measured at most TCCON stations. The stratospheric partial column of CH₄ is calculated as a function of the zonal and annual trends in the relationship between CH₄ and HF in the stratosphere, which we determine from ACE-FTS satellite data. We also explicitly take into account the CH₄ column averaging kernel to estimate the contribution of stratospheric CH₄ to the total column. The resulting tropospheric CH₄ columns are consistent with in situ aircraft measurements and augment existing observations in the troposphere

Observation of Sulfate Aerosols and SO₂ From the Sarychev Volcanic Eruption Using Data From the Atmospheric Chemistry Experiment (ACE)

[1] Infrared spectra measured by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) on the SCISAT satellite were used to analyze the Sarychev volcanic aerosol after the eruption in June 2009. Evidence of the Sarychev eruptions was first detected in July 2009 from enhanced SO2 concentrations and atmospheric extinction. By February 2010, the atmosphere had returned to pre-Sarychev conditions. In July 2009, the volcanic plume was found between 8.5 km and 17.5 km in altitude at mid- and high latitudes (55°N–70°N). The first SO2 and sulfate aerosol retrievals carried out using the infrared solar occultation spectra recorded with the ACE-FTS are presented here. The size distribution parameters, the aerosol volume slant column and the composition of the sulfate aerosol were obtained by using a least squares algorithm. The maximum volume slant column of the aerosols was found to be 850 μm3 cm−3 km, which results in an approximate aerosol loading of 3 μm3 cm−3. One month after the eruption, the composition of the aerosols providing the best-fit is a 75% sulfuric acid-water solution with an effective radius (Reff) of 0.1–0.3 μm

Technical design

To convert Bergenmeersen from a flood control area (FCA) to a flood control area with controlled reduced tide (FCA-CRT), the existing dykes were modified and a new inlet and outlet construction was built. This chapter outlines the hydraulic and geotechnical design. This encompasses raising the existing ring dyke around the area, the new stability calculations and the modified dyke revetment along the water and land side. The inlet and outlet structure is also described. The hydraulic boundary conditions are extremely important to the design

Stratospheric Lifetimes of CFC-12, CCl4, CH4, CH3CL and N20 from Measurements Made By The Atmospheric Chemistry Experiment-Fourier Transform Spectrometer

Long lived halogen-containing compounds are important atmospheric constituents since they can act both as a source of chlorine radicals, which go on to catalyse ozone loss, and as powerful greenhouse gases. The long-term impact of these species on the ozone layer is dependent on their stratospheric lifetimes. Using observations from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) we present calculations of the stratospheric lifetimes of CFC-12, CCl4, CH4, CH3Cl and N2O. The lifetimes were calculated using the slope of the tracer-tracer correlation of these species with CFC-11 at the tropopause. The correlation slopes were corrected for the changing atmospheric concentrations of each species based on age of air and CFC-11 measurements from samples taken aboard the Geophysica aircraft - along with the effective linear trend of the volume mixing ratio (VMR) from tropical ground based AGAGE (Advanced Global Atmospheric Gases Experiment) sites. Stratospheric lifetimes were calculated using a CFC-11 lifetime of 45 yr. These calculations produced values of 113 + (-) 26 (18) yr (CFC-12), 35 + (-) 11 (7) yr (CCl4), 69 + (-) 65 (23) yr (CH3Cl), 123 + (-) 53 (28) yr (N2O) and 195 + (-) 75 (42) yr (CH4). The errors on these values are the weighted 1 sigma non-systematic errors. Systematic errors were estimated by recalculating lifetimes using VMRs which had been modified to reflect differences between ACE-FTS retrieved VMRs and those from other instruments. The results of these calculations, including systematic errors, were as follows: 113 + (-) 32 (20) for CFC-12, 123 + (-) 83 (35) for N2O, 195 + (-) 139 (57) for CH4, 35 + (-) 14 (8) for CCl4 and 69 + (-) 2119 (34) yr for CH3Cl. For CH3Cl & CH4 this represents the first calculation of the stratospheric lifetime using data from a space based instrument