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Deep convection overshooting the lowermost stratosphere is well known for its role in the local stratospheric water vapour (WV) budget. While it is seldom the case, local enhancements of WV associated with stratospheric overshoots are often published. Nevertheless, one debatable topic prevails on the global impact of this event with respect to the temperature-driven dehydration of air parcels entering the stratosphere. As a first step, it is crucial to quantify their role at a local scale before assessing their impact at a large-scale in a meteorological model. It would lead to a forcing scheme for overshoots in the global models. This paper reports on the local enhancements of WV linked to stratospheric overshoots, observed during the TRO-Pico campaign conducted in March 2012 in Bauru, Brazil, using the BRAMS (Brazilian version of RAMS) mesoscale model. Since numerical simulation depends on the choice of several preferred parameters, each having its uncertainties, we vary the microphysics or the vertical resolution while simulating the overshoots. Thus, we produce a set of simulations illustrating the possible variations in representing the stratospheric overshoots. To resolve better the stratospheric hydration, we opt for simulations with the 800-m-horizontal-grid-point presentation. Next, we validate these simulations against the Bauru S-band radar echo tops and the TRO-Pico balloon-borne observations of WV and particles. Two of the three simulations' setups yield results compatible with the TRO-Pico observations. From these two simulations, we determine approximately 333 t to 2000 t of WV mass prevailing in the stratosphere due to an overshooting plume depending on the simulation setup. About 70 % of the ice mass remains between the 380 K to 385 K isentropic levels. The overshooting top comprises pristine ice and snow, while aggregates only play a role just above the tropopause. Interestingly, the horizontal cross-section of the overshooting top is about 450 km2 at 380 K isentrope, which is similar to the horizontal-grid-point resolution of a simulation that cannot compute overshoots explicitly. These results could establish a forcing scheme of overshooting hydration or dehydration in a large-scale simulation.

The relationship between global temperature and greenhouse gases (GHGs) content of the atmosphere has been documented in prehistorical records. Due to human activity, the actual concentration of GHGs is higher than in the past 800,000 years, and today's rate of increase is worrying. In a near future, the increase of GHGs in the atmosphere will have serious consequences on the radiative and chemical balance of our atmosphere, leading to serious damages on the biodiversity and human health. Then, climate change has become a fundamental issue. To understand the processes driving our atmosphere, scientists have been probing our atmosphere since 1783 when first temperature and pressure measurements were performed onboard hydrogen-filled balloon. Stratospheric balloons are unique platforms to probe the atmosphere, particularly at the interface between the troposphere and the stratosphere, where major processes occur. Numerous open questions remain about our climate future. The atmosphere is a complex environment where various interaction processes occur which are not well understood to date. Further observations are required to improve climate models and therefore predictions to help taking action to limit anthropogenic contribution to climate change. To probe the atmosphere, scientists have been developing more and more precise and accurate instruments. In this chapter, we focused on in situ diode laser spectrometers which are high-resolution sensors allowing for continuous measurements of GHGs in the atmosphere. This chapter describes also some important atmospheric processes driving our climate and actual capabilities offered by stratospheric balloons to probe our atmosphere. Examples of results obtained from past balloon campaigns are also shown, demonstrating the actual state of the art in atmospheric sciences and particularly on open questions related to climate change.

Newly developed mid-infrared lightweight hygrometer, Pico-Light H2O has been tested in-flight on February 19, 2019 and October 16, 2019. It has been flown under a 1200 g rubber balloon operated by CNES from the Aire-sur-l'Adour facility (France) within the E.U. funded HEMERA WP11. During these two flights, we were able to obtain coincident MLS v4 and v5 water vapor and temperature profiles, leading to an inter-comparison between Pico-Light and Aura-MLS water vapor and temperature retrievals. Results from the comparison are in line with previous reported studies . Here, differences in the mid-latitude stratosphere and upper troposphere (20–316 hPa) are within 7 % and 64 % respectively. Largest differences with MLS v4 occurring within the upper troposphere nearby the cold point tropopause. The v5 MLS data have been corrected for observed dry bias nearby the tropopause, allowing to partially solve the observed discrepancies. Additionally, on February 19, the hygrometer has flown within an air filament from polar latitudes most of the flight for which a signature is observed on the water vapor profile and confirmed with ozone reanalysis from ERA 5and potential vorticity from MIMOSA advection model.

Made available in DSpace on 2018-11-26T17:48:49Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-03-16 Agence Nationale de la Recherche (ANR) region Champagne-Ardenne in France Direction Generale de l'Armement (PRECIP-CLOUD project) European Union's Framework Program MUSIC project LEFE project Overshoots a grande echelle Centre National d'Etudes Spatiales (CNES) Centre de Calcul ROMEO In order to better understand the water vapor (WV) intrusion into the tropical stratosphere, a mesoscale simulation of the tropical tropopause layer using the BRAMS (Brazilian version of Regional Atmospheric Modeling System (RAMS)) model is evaluated for a wet season. This simulation with a horizontal grid point resolution of 20kmx20km cannot resolve the stratospheric overshooting convection (SOC). Its ability to reproduce other key parameters playing a role in the stratospheric WV abundance is investigated using the balloon-borne TRO-Pico campaign measurements, the upper-air soundings over Brazil, and the satellite observations by Aura Microwave Limb Sounder, Microwave Humidity Sounder, and Geostationary Operational Environmental Satellite 12. The BRAMS exhibits a good ability in simulating temperature, cold-point, WV variability around the tropopause. However, the simulation is typically observed to be warmer by approximate to 2.0 degrees C and wetter by approximate to 0.4 ppmv at the hygropause, which can be partly affiliated with the grid boundary nudging of the model by European Centre for Medium-Range Weather Forecasts operational analyses. The modeled cloud tops show a good correlation (maximum cross-correlation of approximate to 0.7) with Geostationary Operational Environmental Satellite 12. Furthermore, the overshooting cells detected by Microwave Humidity Sounder are observed at the locations, where 75% of the modeled cloud tops are higher than 11km. Finally, the modeled inertia-gravity wave periodicity and wavelength are comparable with those deduced from the radio sounding measurements during TRO-Pico campaign. The good behavior of BRAMS confirms the SOC contribution in the WV abundance, and variability is of lesser importance than the large-scale processes. This simulation can be used as a reference run for upscaling the impact of SOC at a continental scale for future studies. UFR Sci Exactes & Naturelles, GSMA, CNRS, UMR 7331, Reims, France CNRS, CNRM, Meteo France, UMR3589, Toulouse, France UPMC Univ Paris 06, Sorbonne Univ, PSL Res Univ,ENS, LMD,IPSL,CNRS,UMR 8539,Ecole Polytech,Univ Paris, Palaiseau, France Ecole Polytech, ENS, CNRS, LMD,IPSL,UPMC, Paris, France INSU, Div Tech, Pl Aristide Briand, Meudon, France UPMC Univ Paris 06, UVSQ Univ Paris Saclay, CNRS, LATMOS,IPSL, Guyancourt, France Univ Estadual Paulista, Inst Pesquisas Meteorol, Bauru, Brazil Univ Estadual Paulista, Inst Pesquisas Meteorol, Bauru, Brazil Agence Nationale de la Recherche (ANR): ANR-2010-BLAN-609-01 European Union's Framework Program: 603608 MUSIC project: ANR-14-CE01-0014 Centre de Calcul ROMEO: 669

In this work, we have revisited the spectroscopy of the R(6) manifold of the ν3 band of methane which is particularly suitable for in situ laser monitoring of CH4. For that purpose, a home-made Difference Frequency Generation (DFG) laser emitting at 3.24 µm has been coupled to a cryogenically-cooled optical cell to investigate the temperature dependences of the air-broadening, the air-narrowing and the air-mixing coefficients of these ν3 R(6) manifold transitions. The temperatures of the measurements range from 213.5 K to room temperature. These are typically the temperatures found in the troposphere and the lower stratosphere. Finally, the measured spectroscopic parameters have been used to process the in-situ methane absorption spectra recorded by a balloon-borne laser diode spectrometer.

Made available in DSpace on 2018-12-11T17:06:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-09-29 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°ĝ€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 0.5ĝ€ppmv) and aerosol at the 425ĝ€K (18.5ĝ€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°ĝ€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 0.6ĝ€ppmv as high as the 404ĝ€K (17.8ĝ€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. LATMOS CNRS Université de Versailles St Quentin GSMA Université de Reims Champagne Ardenne and CNRS Instituto de Pesquisas Meteorológicas (IPMet) UNESP Forschungszentrum Jülich Division Technique de l'Insu CNRS Science Systems and Applications Inc NASA Langley Research Center ETH Zurich Institute for Atmospheric and Climate Science St. Petersburg State University National Institute of Standards and Technology Instituto de Pesquisas Meteorológicas (IPMet) UNESP

We report the development of a laser sonde operated under stratospheric balloons and devoted to the in-situ measurement of carbon dioxide in the upper troposphere and the lower stratosphere. In the 2.68 micron region, strong CO2 transitions are suitable for the in-situ monitoring of carbon dioxide, which gives ∼10% absorption depth and, moreover, antimonide laser diodes are nowadays available that show relevant spectral properties for absorption spectroscopy. The light-weight sensor is based on 50-cm single path configuration and is operated open to the atmosphere. We provide details of the design of the instrument and data processing. The performance and the stability of the instrument were evaluated with the Allan variance technique. The spectrometer was test-flown in the Arctic stratosphere from Kiruna, Sweden and we report preliminary flight results.

International audience; The 3.25 micron spectral region is very suitable for the in situ sensing of CH4 in the troposphere and the lower stratosphere with light-weight laser sensors. Several transitions of the strong fundamental ν 3 band of CH4 are revisited in this spectral region using an ultra-compact Difference-Frequency Generation (DFG) laser. Accurate intensities as well as self-broadening coefficients are reported for several manifolds that are particularly relevant to the monitoring of CH4. The study is extended to over hundred transitions reachable over the tunability range of the laser. Moreover, this DFG laser is the light source of a new, highly-compact CH4 laser spectrometer to be operated from weather balloon. The CH4 laser sensor is described and preliminary flight results are reported.