Search

The mid-infrared lightweight tunable diode laser hygrometer, “Pico-Light H2O”, the successor to Pico-SDLA H2O, is presented and its performances are evaluated during the AsA 2022 balloon-borne intercomparison campaign conducted at the CNES Aire-sur-l'Adour (AsA, 43.70° N; 0.25° W) balloon launch facility and the Aeroclub d'Aire-sur-l'Adour in France. The Pico-Light instrument has primarily been developed for sounding of the upper troposphere and stratosphere, although during the AsA 2022 campaign we expand the range of comparison to include additionally the lower troposphere. Three different types of hygrometer and two models of radiosonde were flown, operated by the French Space Agency (CNES) and the NOAA Global Monitoring Laboratory (GML) scientific teams: Pico-Light H2O, the NOAA Frost Point Hygrometer (FPH), the micro-hygrometer (in an early phase of development), and M20 and iMet-4 sondes. Within this framework, we intend to validate measurements of Pico-Light H2O through a first intercomparison with the NOAA FPH instrument. The in situ monitoring of water vapour in the upper troposphere–lower stratosphere continues to be very challenging from an instrumental point of view because of the very small amounts of water vapour to be measured in these regions of the atmosphere. Between the lapse rate tropopause (11–12.3 km) and 20 km, the mean relative difference between water vapour mixing ratio measurements by Pico-Light H2O and NOAA FPH was 4.2 % ± 7.7 %, and the mean tropospheric difference was 3.84 % ± 23.64 %, with differences depending on the altitude range considered. In the troposphere, relative humidity (RH) over water comparisons led to agreement between Pico-Light and NOAA FPH of −0.2 % on average, with excursions of about 30 % RH due to moisture variability. Expanding the comparison to meteorological sondes, the iMet-4 sondes agree well with both Pico-Light and FPH between the ground and 7.5 km (within ± 3 % RH), as do the M20 sondes, up to 13 km, which are wet-biased by 3 % RH and dry-biased by 20 % in cases of saturation.

High-resolution in situ balloon measurements of water vapour, aerosol, methane and temperature in the upper tropical tropopause layer (TTL) and lower stratosphere are used to evaluate the processes affecting the stratospheric water budget: horizontal transport (in-mixing) and hydration by cross-tropopause overshooting updrafts. The obtained in situ evidence of these phenomena are analysed using satellite observations by Aura MLS (Microwave Limb Sounder) and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) together with trajectory and transport modelling performed using CLaMS (Chemical Lagrangian Model of the Stratosphere) and HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model. Balloon soundings were conducted during March 2012 in Bauru, Brazil (22.3° S) in the frame of the TRO-Pico campaign for studying the impact of convective overshooting on the stratospheric water budget. The balloon payloads included two stratospheric hygrometers: FLASH-B (Fluorescence Lyman-Alpha Stratospheric Hygrometer for Balloon) and Pico-SDLA instrument as well as COBALD (Compact Optical Backscatter Aerosol Detector) sondes, complemented by Vaisala RS92 radiosondes. Water vapour vertical profiles obtained independently by the two stratospheric hygrometers are in excellent agreement, ensuring credibility of the vertical structures observed. A signature of in-mixing is inferred from a series of vertical profiles, showing coincident enhancements in water vapour (of up to 0.5 ppmv) and aerosol at the 425 K (18.5 km) level. Trajectory analysis unambiguously links these features to intrusions from the Southern Hemisphere extratropical stratosphere, containing more water and aerosol, as demonstrated by MLS and CALIPSO global observations. The in-mixing is successfully reproduced by CLaMS simulations, showing a relatively moist filament extending to 20° S. A signature of local cross-tropopause transport of water is observed in a particular sounding, performed on a convective day and revealing water vapour enhancements of up to 0.6 ppmv as high as the 404 K (17.8 km) level. These are shown to originate from convective overshoots upwind detected by an S-band weather radar operating locally in Bauru. The accurate in situ observations uncover two independent moisture pathways into the tropical lower stratosphere, which are hardly detectable by space-borne sounders. We argue that the moistening by horizontal transport is limited by the weak meridional gradients of water, whereas the fast convective cross-tropopause transport, largely missed by global models, can have a substantial effect, at least at a regional scale.

In this paper we compare water vapor mixing ratio measurements from two quasi-parallel flights of the Pico-SDLA H2O and FLASH-B hygrometers. The measurements were made on 10 February 2013 and 13 March 2012, respectively, in the tropics near Bauru, São Paulo state, Brazil during an intense convective period. Both flights were performed as part of a French scientific project, TRO-Pico, to study the impact of the deep-convection overshoot on the water budget. Only a few instruments that permit the frequent sounding of stratospheric water vapor can be flown within small-volume weather balloons. Technical difficulties preclude the accurate measurement of stratospheric water vapor with conventional in situ techniques. The instruments described here are simple and lightweight, which permits their low-cost deployment by non-specialists aboard a small weather balloon. We obtain mixing ratio retrievals which agree above the cold-point tropopause to within 1.9 and 0.5 % for the first and second flights, respectively. This level of agreement for balloon-borne measured stratospheric water mixing ratio constitutes one of the best agreement reported in the literature. Because both instruments show similar profiles within their combined uncertainties, we conclude that the Pico-SDLA H2O and FLASH-B data sets are mutually consistent.

The AquaVIT-1 intercomparison of atmospheric water vapor measurement techniques was conducted at the aerosol and cloud simulation chamber AIDA (Aerosol Interaction and Dynamics in the Atmosphere) at the Karlsruhe Institute of Technology, Germany, in October 2007. The overall objective was to intercompare state-of-the-art and prototype atmospheric hygrometers with each other and with independent humidity standards under controlled conditions. This activity was conducted as a blind intercomparison with coordination by selected referees. The effort was motivated by persistent discrepancies found in atmospheric measurements involving multiple instruments operating on research aircraft and balloon platforms, particularly in the upper troposphere and lower stratosphere, where water vapor reaches its lowest atmospheric values (less than 10 ppm). With the AIDA chamber volume of 84 m3, multiple instruments analyzed air with a common water vapor mixing ratio, by extracting air into instrument flow systems, by locating instruments inside the chamber, or by sampling the chamber volume optically. The intercomparison was successfully conducted over 10 days during which pressure, temperature, and mixing ratio were systematically varied (50 to 500 hPa, 185 to 243 K, and 0.3 to 152 ppm). In the absence of an accepted reference instrument, the absolute accuracy of the instruments was not established. To evaluate the intercomparison, the reference value was taken to be the ensemble mean of a core subset of the measurements. For these core instruments, the agreement between 10 and 150 ppm of water vapor is considered good with variation about the reference value of about ±10% (±1σ). In the region of most interest between 1 and 10 ppm, the core subset agreement is fair with variation about the reference value of ±20% (±1σ). The upper limit of precision was also derived for each instrument from the reported data. The implication for atmospheric measurements is that the substantially larger differences observed during in-flight intercomparisons stem from other factors associated with the moving platforms or the non-laboratory environment. The success of AquaVIT-1 provides a template for future intercomparison efforts with water vapor or other species that are focused on improving the analytical quality of atmospheric measurements on moving platforms.

The MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation) experiment took place in July 2009. The aim of this campaign was to study the aging and reactions of aerosol and gas-phase emissions in the city of Paris. Three ground-based measurement sites and several mobile platforms including instrument equipped vehicles and the ATR-42 aircraft were involved. We present here the variations in particle- and gas-phase species over the city of Paris, using a combination of high-time resolution measurements aboard the ATR-42 aircraft. Particle chemical composition was measured using a compact time-of-flight aerosol mass spectrometer (C-ToF-AMS), giving detailed information on the non-refractory submicron aerosol species. The mass concentration of black carbon (BC), measured by a particle absorption soot photometer (PSAP), was used as a marker to identify the urban pollution plume boundaries. Aerosol mass concentrations and composition were affected by air-mass history, with air masses that spent longest time over land having highest fractions of organic aerosol and higher total mass concentrations. The Paris plume is mainly composed of organic aerosol (OA), BC, and nitrate aerosol, as well as high concentrations of anthropogenic gas-phase species such as toluene, benzene, and NOx. Using BC and CO as tracers for air-mass dilution, we observe the ratio of ΔOA / ΔBC and ΔOA / ΔCO increase with increasing photochemical age (−log(NOx / NOy)). Plotting the equivalent ratios of different organic aerosol species (LV-OOA, SV-OOA, and HOA) illustrate that the increase in OA is a result of secondary organic aerosol (SOA) formation. Within Paris the changes in the ΔOA / ΔCO are similar to those observed during other studies in London, Mexico City, and in New England, USA. Using the measured SOA volatile organic compounds (VOCs) species together with organic aerosol formation yields, we were able to predict ~50% of the measured organics. These airborne measurements during the MEGAPOLI experiment show that urban emissions contribute to the formation of OA and have an impact on aerosol composition on a regional scale.

This paper presents a first demonstration of range-resolved differential absorption LIDAR (DIAL) measurements of the water vapor main isotopologue H 2 16 O and the less abundant semi-heavy water isotopologue HD 16 O with the aim of determining the isotopic ratio. The presented Water Vapor and Isotope Lidar (WaVIL) instrument is based on a parametric laser source emitting nanosecond pulses at 1.98 µm and a direct-detection receiver utilizing a commercial InGaAs PIN photodiode. Vertical profiles of H 2 16 O and HD 16 O were acquired in the planetary boundary layer in the suburban Paris region up to a range of 1.5 km. For time averaging over 25 min, the achieved precision in the retrieved water vapor mixing ratio is 0.1 g kg -1 (2.5% relative error) at 0.4 km above ground level (a.g.l.) and 0.6 g kg -1 (20%) at 1 km a.g.l. for 150 m range bins along the LIDAR line of sight. For HD 16 O, weaker absorption has to be balanced with coarser vertical resolution (600 m range bins) in order to achieve similar relative precision. From the DIAL measurements of H 2 16 O and HD 16 O, the isotopic abundance δD was estimated as -51‰ at 0.4 km above the ground and -119‰ in the upper part of the boundary layer at 1.3 km a.g.l. Random and systematic errors are discussed in the form of an error budget, which shows that further instrumental improvements are required on the challenging path towards DIAL-profiling of the isotopic abundance with range resolution and precision suitable for water cycle studies.

The in situ tests of first ever autonomous aerosol and cloud backscatter LIDAR (light detection and ranging) systems implemented on buoys for Arctic observations has been achieved in 2015 within the French EQUIPEX IAOOS project. The environmental and operational constraints were met by adopting a concept of a fibered microjoule lidar system using a laser diode. Two systems have been developed with and without polarization analysis capability. A specific optical design was used for polarization discrimination. These systems were integrated in buoys and tested in the Arctic in 2014 and 2015 at latitudes higher than 80°N. Data were transmitted through an Iridium space link. Measurements have been obtained 90% of the time from the non-polarized system in 2014 over 8 months as the first fully equipped buoy drifted from the Barneo Russian camp close to the North Pole toward Svalbard. A polarized system was then tested over a short period in winter 2015 north of Svalbard during the Norwegian campaign N-ICE. In April and May 2014, the unattended lidar measurements showed a large occurrence of aerosols and haze. The average attenuated scattering ratio for non-cloudy profiles during this period was about 2.2. Aerosols could reach an altitude of 5km on average, whereas over the rest of the period low level clouds (below 1000 m) were prevailing with an average attenuated scattering ratio of about 10 3 . The main features of the developed lidar instruments and first results are presented here.

A high spectral resolution (HSR) measurement capability in the ultraviolet has been added to the 3-wavelength-2-polarization-backscatter lidar LNG (lidar aerosols nouvelle génération) and tested during several flights. The system includes a Mach-Zehnder interferometer (MZI) as a spectral discriminator and does not require any frequency locking between the emitter and the interferometer. Results obtained during test flights show that the backscatter and extinction coefficients at 355 nm can be measured with a relative precision of 10% for 60 m and 240 m vertical resolution, respectively, in aerosol layers of 10 -6   m -1  sr -1 backscatter coefficient with a 30-km horizontal resolution. The same relative precision is obtained in cirrus clouds of a 2×10 -5   m -1  sr -1 backscatter coefficient for the same vertical resolution and a horizontal resolution reduced to 5 km. The capacity of the system to perform wind velocity measurements is also demonstrated with precisions in the range of 1 to 2  ms -1 . Particle-to-total backscatter ratio and line-of-sight speed measurements have been performed on ground echoes; averaged data show biases less than 1% and 0.15  ms -1 , respectively.

A new type 1 ternary biphasic system composed of cyclopentyl methyl ether, dimethylformamide and water was developed, characterized and successfully used for the purification of a lipophilic, protected peptide by pH-zone refining centrifugal partition chromatography. The protected peptide is an 8-mer, key intermediate in bivalirudin (Angiomax®) synthesis and shows a very low solubility in the solvents usually used in liquid chromatography. All ionic groups, except the N-terminal end of the peptide, are protected by a benzyl group. The purification of this peptide was achieved with a purity of about 99.04% and a recovery of 94% using the new ternary biphasic system cyclopentyl methyl ether/dimethylformamide/water (49:40:11, v/v) in the descending pH-zone refining mode with triethylamine (28 mM) as the retainer and methanesulfonic acid (18 mM) as the eluter., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Protected synthetic peptide intermediates are often hydrophobic and not soluble in most common solvents. They are thus difficult to purify by preparative reversed-phase high-performance liquid chromatography (RP-HPLC), usually used for industrial production. It is then challenging to develop alternative chromatographic purification processes. Support-free liquid-liquid chromatographic techniques, including both hydrostatic (centrifugal partition chromatography or CPC) and hydrodynamic (counter-current chromatography or CCC) devices, are mainly involved in phytochemical studies but have also been applied to synthetic peptide purification. In this framework, two new biphasic solvent system compositions covering a wide range of polarity were developed to overcome solubility problems mentioned above. The new systems composed of heptane/tetrahydrofuran/acetonitrile/dimethylsulfoxide/water and heptane/methyl-tetrahydrofuran/N-methylpyrrolidone/water were efficiently used for the CPC purification of a 39-mer protected exenatide (Byetta®) and a 8-mer protected peptide intermediate of bivalirudin (Angiox®) synthesis. Phase compositions of the different biphasic solvent systems were determined by (1)H nuclear magnetic resonance. Physico-chemical properties including viscosity, density and interfacial tension of these biphasic systems are also described., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Synthetic hydrophobic non-ionizable peptides are not soluble in most common solvents and are thus difficult to purify by preparative reversed-phase HPLC, normally used for industrial production. The challenge exists to develop alternative purification chromatographic processes using suitable solvents and providing good yields, high purity and sufficient productivity. A 11mer hydrophobic synthetic modified cyclosporine, showing an anti-HIV activity, was successfully purified by centrifugal partition chromatography using the biphasic solvent system heptane/ethyl acetate/acetone/methanol/water (1:2:2:1:2, v/v). A 5% co-current elution - made possible by the liquid nature of the two phases - has been used in order to avoid hydrodynamic instabilities mainly due to the physico-chemical properties of the target peptide. This original solution was developed after the study of the effect of the peptide on the hydrodynamic behavior of the two phases during the separation, and the visualization of the flow patterns using the Visual-CPC device. Critical impurities were efficiently eliminated and the peptide was recovered in high yield and high productivity achieving the specifications requirements., (Copyright © 2013 Elsevier B.V. All rights reserved.)

By using a tunable diode laser absorption spectrometer in conjunction with a cryogenically cooled multipath cell, we have revisited the air-induced pressure-broadening coefficients and the narrowing coefficients related to the Dicke effect, as well as the temperature dependences, for the R(18) and R(20) lines of the (10°1)I←(00°0) vibrational band at 2.68 μm of carbon dioxide. The selected transitions are used to probe in situ CO2 in the troposphere and the lower stratosphere by using balloon-borne laser sensors. The achieved measurements are thoroughly compared to existing former determinations. The impact of processing the in situ atmospheric CO2 spectra with this new set of molecular data is reported., (Copyright © 2013 Elsevier B.V. All rights reserved.)

This article presents the scope and optimization strategies employed in ion-exchange centrifugal partition chromatography (IXCPC). Both the weak and the strong modes were used to separate the constituents of a model mixture of dipeptides. Thus, the combined use of the quaternary biphasic solvent system, methyl-tert-butylether/acetonitrile/n-butanol/water (2:1:2:5, v/v) in the descending mode, of the lipophilic di(2-ethylhexyl)phosphoric acid (DEHPA) cation-exchanger, and of two displacers: calcium chloride and hydrochloric acid, has proven to be efficient for the preparative separation of the model mixture of five dipeptides (GG, GY, AY, LV and LY, in the order they were collected). The separation was optimized by splitting the stationary phase into two sections that differed by their triethylamine concentration. Moreover, the chemical nature of the exchanger/analyte entities that were involved in the chromatographic process was determined by (31)P and (1)H DOSY NMR experiments., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Since 1997, two near-infrared laser diode sensors have been developed with the support of the CNES, the French space agency, to provide in situ data of H(2)O, CH(4) and CO(2) in the middle atmosphere. The realized instruments were flown from stratospheric balloons within the framework of European campaigns for the study of stratospheric ozone and water vapor and were involved in the validation of the ODIN and ENVISAT satellites. In this paper, we describe the developed laser probing technique, we report atmospheric measurements and finally we discuss future perspectives, particularly the in situ laser sensing of the lower atmosphere of Mars and the implication of the laser hygrometers in balloon campaigns at mid-latitudes and tropical regions to investigate the sources and sinks of stratospheric H(2)O.

A dual-beam detector is used to measure atmospheric trace species by differential absorption spectroscopy with commercial near-infrared InGaAs laser diodes. It is implemented on the Spectromètre à Diodes Laser Accordables, a balloonborne tunable diode laser spectrometer devoted to the in situ monitoring of CH4 and H2O. The dual-beam detector is made of simple analogical subtractor circuits combined with InGaAs photodiodes. The detection strategy consists in taking the balanced analogical difference between the reference and the sample signals detected at the input and the output of an open optical multipass cell to apply the full dynamic range of the measurements (16 digits) to the weak molecular absorption information. The obtained sensitivity approaches the shot-noise limit. With a 56-m optical cell, the detection limit obtained when the spectra is recorded within 8 ms is approximately 10(-4) (expressed in absorbance units). The design and performances of both a simple subtractor and an upgraded feedback subtractor circuit are discussed with regard to atmospheric in situ CH4 absorption spectra measured in the 1.653-microm region. Mixing ratios are obtained from the absorption spectra by application of a nonlinear least-squares fit to the full molecular line shape in conjunction with in situ P and T measurements.