Bernard Legras- French National Centre for Scientific Research
Bernard Legras
- French National Centre for Scientific Research
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Introduction
Publications
Publications (229)
The intense wildfires in Australia, during the 2019–2020 fire season, generated massive Pyro-cumulonimbus (pyro-Cb) clouds, and injected an unprecedented amount of smoke aerosols into the upper troposphere–lower stratosphere (UTLS). The smoke aerosols produced a self-sustaining confined anticyclonic vortex, that ascended up to 35 km altitude by Mar...
Plain Language Summary
Vertical wind is a key meteorological parameter. In the tropical Upper Troposphere Lower Stratosphere (UTLS, the atmospheric layer between 14 and 20 km altitude above sea level), it crucially affects the formation of clouds and the transport of trace gases, such as water vapor, ozone and radiatively active constituents. The e...
Plain Language Summary
The eruption of the submarine Hunga volcano in January 2022 polluted the global stratosphere with a large amount of water vapor and significantly perturbed the stratospheric aerosol layer. In this paper, we present a 1‐year long aftermath study of the stratospheric sulfur pollution from this volcanic eruption using observatio...
This study evaluates the observed non-linearity in the wind-precipitation relationship over India’s southwest coast and maps this non-linearity to monsoon intraseasonal oscillations. The wind-precipitation data is subjected to clustering, and five distinct regimes are identified. The large-scale dynamical and thermodynamical condition that leads to...
Gravity‐wave (GW) parameterizations from 12 general circulation models (GCMs) participating in the Quasi‐Biennial Oscillation initiative (QBOi) are compared with Strateole 2 balloon observations made in the tropical lower stratosphere from November 2019–February 2020 (phase 1) and from October 2021–January 2022 (phase 2). The parameterizations empl...
The Hunga volcano violently erupted on January 15th, 2022, and produced the largest stratospheric aerosol layer perturbation of the last 30 years. One notable effect of the Hunga eruption was the significant modification of the size distribution (SD) of the stratospheric aerosol layer with respect to background conditions and other recent moderate...
An enhanced aerosol layer, known as the Asian Tropopause Aerosol Layer (ATAL), has been observed within the seasonal Asian monsoon anticyclone (AMA) since the late 1990s. Given the apparently abrupt appearance of this layer based on observations, it has been speculated that it originates from increasing human made emissions in Asia. However, the AT...
A new class of vortices has been observed in the stratosphere following extreme wildfires (Canada 2017, Australia 2020) and volcanic eruptions (Raikoke 2019). These vortices are long‐lived mesoscale anticyclones (hundreds to 1,000 km in diameter) trapping plumes of aerosols and combustion/volcanic compounds. Owing to their unusual composition, thes...
Record-breaking wildfires ravaged south-eastern Australia during the fire season 2019–2020. The intensity of the fires reached its paroxysmal phase at the turn of the year 2019–2020, when large pyro-cumulonimbi developed. Pyro-convective activity injected biomass burning aerosols and gases in the upper-troposphere–lower-stratosphere (UTLS), produci...
A new class of vortices has been observed in the stratosphere after several extreme wildfires (Canada 2017, Australia 2020) and volcanic eruptions (Raikoke 2019). They are long-lived coherent plumes of aerosols and combustion/volcanic compounds confined within mesoscale (100s to 1000 km diameter) anticyclones. Due to their anomalous composition, th...
Plain Language Summary
We study the stratospheric aerosol plume produced by the Hunga Tonga–Hunga Ha'apai eruption on 15 January 2022 based on the high quality solar occultation measurements of the instrument SAGE III (Stratospheric Aerosol and Gas Experiment) onboard the International Space Station. These data reveal that the aerosol sizes are abo...
An enhanced aerosol layer, known as the Asian Tropopause Aerosol Layer (ATAL), has been observed within the seasonal Asian monsoon anticyclone (AMA) since the late 1990s. Given the apparently abrupt appearance of this layer based on observations, it has been speculated that it originates from increasing human made emissions in Asia. However, the AT...
The Hunga Tonga-Hunga Ha’apai volcano violently erupted on 15 January 2022, producing the largest perturbation of the stratospheric aerosol layer since Pinatubo 1991, despite the estimated modest injection of SO2. Here we present novel SO2 and sulphate aerosol (SA) co-retrievals from the Infrared Atmospheric Sounding Instrument, and use them to stu...
The Tonga eruption of 15 January 2022 has released a long-lived stratospheric plume of sulfate aerosols. More than 15 months after, we focus on the high quality data series of SAGE III/ISS to determine the mean radius and size distribution of the aerosols and their total mass. We show that the persisting aerosols – with a mode width of 1.25 and an...
Record-breaking wildfires ravaged south-eastern Australia during the fire season 2019–2020. The intensity of the fires reached its paroxysmal phase at the turn of the year 2019–2020, when large pyro-cumulonimbi developed. Pyro-convective activity injected biomass burning aerosols and gases in the upper-troposphere—lower-stratosphere (UTLS), produci...
The eruption of the Hunga Tonga–Hunga Ha’apai (HTHH) volcano on 15 January 2022 injected large amounts of water vapor (H2O) directly into the stratosphere. While normal background levels of stratospheric H2O are not detectable in radio occultation (RO) measurements, effects of the HTHH eruption are clearly observed as anomalous refractivity profile...
During the extended activity of Mount Etna volcano in February–April 2021, three distinct paroxysmal events took place from February 21 to 26, which were associated with a very uncommon transport of the injected upper‐tropospheric plumes toward the north. Using a synergy of observations and modeling, we characterized the emissions and three‐dimensi...
The eruption of the submarine Hunga volcano in January 2022 was associated with a powerful blast that injected volcanic material to altitudes up to 58 km. From a combination of various types of satellite and ground-based observations supported by transport modeling, we show evidence for an unprecedented increase in the global stratospheric water ma...
We use a combination of spaceborne instruments to study the unprecedented stratospheric plume after the Tonga eruption of 15 January 2022. The aerosol plume was initially formed of two clouds at 30 and 28 km, mostly composed of submicron-sized sulfate particles, without ash, which is washed out within the first day following the eruption. The large...
The underwater Hunga Tonga-Hunga Ha-apai volcano erupted in the early hours of 15th January 2022, and injected volcanic gases and aerosols to over 50 km altitude. Here we synthesise satellite, ground-based, in situ and radiosonde observations of the eruption to investigate the strength of the stratospheric aerosol and water vapour perturbations in...
Following the Hunga Tonga eruption (20.6°S, 175.4°W, mid‐January 2022), we present a balloon‐borne characterization of the stratospheric aerosol plume one week after its injection (on 23 and 26 January 2022, La Réunion island at 21.1°S, 55.3°E). Satellite observations show that flight (a) took place during the overpass of a denser plume of sulfate...
The eruption of the submarine Hunga volcano in January 2022 was associated with a powerful blast that injected volcanic material to altitudes up to 58 km. From a combination of various types of satellite and ground-based observations supported by transport modeling, we show evidence for an unprecedented increase in the global stratospheric water ma...
As a consequence of extreme heat and drought, record-breaking wildfires developed and ravaged south-eastern Australia during the fire season 2019–2020. The fire strength reached its paroxysmal phase at the turn of the year 2019–2020. During this phase, pyrocumulonimbus clouds (pyroCb) developed and injected biomass burning aerosols and gases into t...
The eruption of the submarine Hunga volcano in January 2022 was associated with a powerful blast that injected volcanic material to altitudes up to 58 km. From a combination of various types of satellite and ground-based observations supported by transport modeling, we show evidence for an unprecedented increase in the global stratospheric water ma...
The underwater Hunga Tonga-Hunga Ha-apai (HT) volcano violently erupted on January 15th, 2022, injecting volcanic gases and aerosols at over 50 km altitude. Here we show the stratospheric aerosol and water vapour perturbations due to the HT eruption, the plume evolution during the first month dispersion and we estimate its short-term radiative impa...
![Climatology of Montgomery potential (m2s-2\documentclass[12pt]{minimal}...](publication/358769580/figure/fig3/AS:11431281087411194@1664589267234/Climatology-of-Montgomery-potential-m2s-2documentclass12ptminimal_Q320.jpg)
The Indian summer monsoon rainfall shows intraseasonal oscillations manifested as
active and break phases, and depending on the phase, the water vapor
concentration in the tropical tropopause layer (TTL) varies. Using dedicated
Lagrangian backward trajectory analysis and circulation dynamics within the Asian monsoon anticyclone, this study inves...
As a consequence of extreme heat and drought, record-breaking wildfires developed and ravaged south-eastern Australia during the fire season 2019–2020. The fire strength reached its paroxysmal phase at the turn of the year 2019–2020. During this phase, pyro-Cb developed and injected biomass burning aerosols and gases into the upper-troposphere–lowe...
The Asian monsoon anticyclone (AMA) represents one of the wettest regions in the lower stratosphere (LS) and is a key contributor to the global annual maximum in LS water vapour. While the AMA wet pool is linked with persistent convection in the region and horizontal confinement of the anticyclone, there remain ambiguities regarding the role of tro...
Triana will be the first Earth-observing mission to L-1. From this stable
vantage point, the satellite will have a continuous view of the entire sunlit face of the rotating Earth 1.5 million km away. Named for the sailor on Columbus’s voyage who first spotted the New World, Triana is an exploratory mission to investigate the scientific and technolo...
The Asian Monsoon Anticyclone (AMA) represents the wettest region in the lower stratosphere (LS) and is the key contributor to the global annual maximum in LS water vapour. While the AMA wet pool is linked with persistent convection in the region and horizontal confinement of the anticyclone, there remain ambiguities regarding the role of tropopaus...
During the monsoon season of the year 2017 the airborne StratoClim mission took place in Kathmandu, Nepal, with eight mission flights of the M-55 Geophysica in the upper troposphere–lower stratosphere (UTLS) of the Asian monsoon anticyclone (AMA) over northern India, Nepal, and Bangladesh. More than 100 events of new particle formation (NPF) were o...
The historically large and severe wildfires in Australia from September 2019 to March 2020 are known to have injected a smoke plume into the stratosphere around New Year, due to pyro-cumulonimbus (pyro-Cb) activity, that was subsequently distributed throughout the Southern Hemisphere (SH). We show with satellite, ground based remote sensing, and in...
This paper investigates the global stratospheric Brewer–Dobson circulation (BDC) in the ERA5 meteorological reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF). The analysis is based on simulations of stratospheric mean age of air, including the full age spectrum, with the Lagrangian transport model CLaMS (Chemical Lagran...
A polarization diversity elastic backscatter lidar was deployed on the equatorial island of Palau in February and March 2016 in the framework of the EU StratoClim project. The system operated unattended in the Palau Atmosferic Observatory from 15 February to 25 March 2016 during the nighttime. Each lidar profile extends from the ground to 30 km hei...
The two most intense wildfires of the last decade that took place in Canada in 2017 and Australia in 2019–2020 were followed by large injections of smoke into the stratosphere due to pyro-convection. After the Australian event, and discovered that part of this smoke self-organized as anticyclonic confined vortices that rose in the mid-latitude stra...
We developed a new retrieval algorithm based on the Infrared Atmospheric Sounding Interferometer (IASI) observations, called AEROIASI-H2SO4, to measure the extinction and mass concentration of sulphate aerosols (binary solution droplets of sulphuric acid and water), with moderate random uncertainties (typically ∼35% total uncertainty for column mas...
The StratoClim airborne campaign took place in Nepal from 27 July to 10 August 2017 to document the physical and chemical properties of the South Asian upper troposphere–lower stratosphere (UTLS) during the Asian summer monsoon (ASM). In the present paper, simulations with the Meso-NH cloud-chemistry model at a horizontal resolution of 15 km are pe...
The Asian summer monsoon (ASM) traps convectively lifted boundary layer pollutants inside its upper-tropospheric lower-stratospheric Asian monsoon anticyclone (AMA). It is associated with a seasonal and spatially confined enhanced aerosol layer, called the Asian Tropopause Aerosol Layer (ATAL). Due to the dynamical variability of the AMA, the deart...
In June 2019 a stratospheric eruption occurred at Raikoke (48∘ N, 153∘ E). Satellite observations show the injection of ash and SO2 into the lower stratosphere and an early entrainment of the plume into a cyclone. Following the Raikoke eruption, stratospheric aerosol optical depth (sAOD) values increased in the whole Northern Hemisphere and tropics...
This paper investigates the global stratospheric Brewer–Dobson circulation (BDC) in the ERA5 meteorological reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF). The analysis is based on simulations of stratospheric mean age of air, including the full age spectrum, with the Lagrangian transport model CLaMS, driven by winds...
The scaling exponents of the distributions of cluster rain amount, R, and cluster size, A, for oceanic rain clusters over the Indian and Pacific warm pools, and the intertropical convergence zones over the eastern Pacific and the tropical Atlantic, were obtained from a set of regional climate model downscaling products. The main aim of the investig...
During the monsoon season of the year 2017 the airborne StratoClim mission took place in Kathmandu, Nepal with eight mission flights of the M-55 Geophysica in the upper troposphere/lower stratosphere (UT/LS) of the Asian Monsoon Anticyclone (AMA) over northern India, Nepal and Bangladesh. More than hundred events of New Particle Formation (NPF) wer...
We present the first high-resolution measurements of pollutant trace gases in the Asian summer monsoon upper troposphere and lowermost stratosphere (UTLS) from the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) during the StratoClim (Stratospheric and upper tropospheric processes for better climate predictions) campaign bas...
Clouds in the tropics have an important role in the energy budget, atmospheric circulation, humidity, and composition of the tropical-to-global upper-troposphere–lower-stratosphere. Due to its non-sun-synchronous orbit, the Cloud–Aerosol Transport System (CATS) onboard the International Space Station (ISS) provided novel information on clouds from...
The two most intense wildfires of the last decade that took place in Canada in 2017 and Australia in 2019-2020 were followed by large injections of smoke in the stratosphere due to pyroconvection. It was discovered by Khaykin et al. (2020, doi:10.1038/s43247-020-00022-5) and Kablick et al. (2020, doi:10.1029/2020GL088101) that, after the Australian...
The StratoClim stratospheric aircraft campaign took place in summer 2017 in Nepal (27 July–10 August) and provided for the first time a wide dataset of observations of air composition inside the Asian monsoon anticyclone (AMA). In the framework of this project, with the purpose of modelling the injection of pollutants and natural compounds into the...
A polarization diversity elastic backscatter lidar has been deployed in the equatorial island of Palau in February and March 2016, in the framework of the EU Stratoclim project. The system operated unattended in the Atmospheric Observatory of Palau Island from 15 February to 25 March 2016, during nighttime. Each lidar profile extends from the groun...
We study the transport pathways from the top of convective clouds to the lower tropical stratosphere during the Asian monsoon, using a dense cover of Lagrangian trajectories driven by observed clouds and the two reanalyses ERA-Interim and ERA5 with diabatic and kinematic vertical motions. We find that the upward propagation of convective impact is...
The Australian bushfires around the turn of the year 2020 generated an unprecedented perturbation of stratospheric composition, dynamical circulation and radiative balance. Here we show from satellite observations that the resulting planetary-scale blocking of solar radiation by the smoke is larger than any previously documented wildfires and of th...
The Asian Summer Monsoon (ASM) traps convectively-lifted boundary layer pollutants inside its upper-tropospheric lower-stratospheric Asian monsoon anticyclone (AMA). It is associated with a seasonal and spatially-confined enhanced aerosol layer, called the Asian Tropopause Aerosol Layer (ATAL). The knowledge of the ATAL properties in terms of aeros...
Due to their increasing spatial resolution, numerical weather prediction (NWP) models and the associated analyses resolve a growing fraction of the gravity wave (GW) spectrum. However, it is unclear how well this “resolved” part of the spectrum truly compares to the actual atmospheric variability. In particular, the Lagrangian variability, relevant...
In June 2019 a stratospheric moderate eruption occurred at Raikoke (48° N, 153° E). Satellite observations show the injection of ash and SO2 into the lower stratosphere and an early entrainment of the plume into a cyclone. Following the Raikoke eruption stratospheric Aerosol Optical Depth (sAOD) values increased in the whole northern hemisphere and...
We examine differences among reanalysis high-cloud products in the tropics, assess the impacts of these differences on radiation budgets at the top of the atmosphere and within the tropical upper troposphere and lower stratosphere (UTLS), and discuss their possible origins in the context of the reanalysis models. We focus on the ERA5 (fifth-generat...
During an extended volcanic unrest starting in 2017, two main moderate stratospheric eruptions occurred at the Ambae volcano (15°S and 167°E), Vanuatu, in April and July 2018. Observations from a geostationary orbit show that the April and July eruptions injected a volcanic plume into the lower stratosphere. While aerosol enhancements from the Apri...
The StratoClim airborne campaign took place in Nepal from 27 July to 10 August 2017 to document the physical and chemical properties of the South Asian Upper Troposphere Lower Stratosphere (UTLS) during the Asian Summer Monsoon (ASM). In the present paper, simulations with the Meso-NH cloud-chemistry model at a horizontal resolution of 15 km are pe...
We present the first high resolution measurements of pollutant trace gases in the Asian Summer Monsoon Upper Troposphere and Lowermost Stratosphere (UTLS) from the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) during the StratoClim (Stratospheric and upper tropospheric processes for better climate predictions) campaign wit...
Wildfire-driven pyro-convection is capable of lifting combustion products into the stratosphere, polluting it with smoke at hemispheric and monthly scales and producing an impact comparable to that of infrequent moderate volcanic eruptions. The Australian bushfires that raged around the turn of the year 2020 have put a new benchmark on the magnitud...
In this paper, we study the tracking of deformable shapes in sequences of images. Our target application is the tracking of clouds in satellite images. We propose to use a recent state-of-the-art method for off-the-grid sparse analysis to describe clouds in image as mixtures of 2D atoms. Then, we introduce a method to handle the tracking with its s...
Abstract. Due to their increasing spatial resolution, numerical weather prediction (NWP) models and the associated analyses resolve a growing fraction of the gravity wave (GW) spectrum. However, it is unclear how well this resolved part of the spectrum actually compares to the actual atmospheric variability. In particular, the Lagrangian variabilit...
The tropical tropopause layer (TTL) is the transition region between the well-mixed convective troposphere and the radiatively controlled stratosphere with air masses showing chemical and dynamical properties of both regions. The representation of the TTL in meteorological reanalysis data sets is important for studying the complex interactions of c...
Abstract. The StratoClim stratospheric aircraft campaign took place in summer 2017 in Nepal (the 27th of July–10th of August) and provided a wide dataset of observations of air composition inside the Asian Monsoon Anticyclone. In the framework of this project, with the purpose of modelling the injection of pollutants and natural compounds into the...
Abstract. We study the transport pathways from the top of convective clouds to the lower
tropical stratosphere during the Asian monsoon, using massive Lagrangian trajectories driven by observed clouds and the two reanalysis ERA-Interim and ERA5 with diabatic and kinematic vertical motions. We find that the upward propagation of convective impact i...
We show that a fire plume injected into the lower stratosphere at high northern latitudes during the Canadian wildfire event in August 2017 partly reached the tropics. The transport to the tropics was mediated by the anticyclonic flow of the Asian monsoon circulation. The fire plume reached the Asian monsoon area in late August/early September, whe...
We developed a new retrieval algorithm based on the Infrared Atmospheric Sounding Interferometer (IASI) observations, called AEROIASI-Sulphates, to measure vertically-resolved sulphate aerosols (SA) extinction and mass concentration profiles, with limited theoretical uncertainties (typically ~25 % total uncertainty for SA mass column estimations)....
The rise of ammonia emissions in Asia is predicted to increase radiative cooling and air pollution by forming ammonium nitrate particles in the lower troposphere. There is, however, a severe lack of knowledge about ammonia and ammoniated aerosol particles in the upper troposphere and their possible effects on the formation of clouds. Here we employ...
The tropical tropopause layer (TTL) is the transition region between the well mixed, convective troposphere and the radiatively controlled stratosphere with air masses showing chemical and dynamical properties of both regions. The representation of the TTL in meteorological reanalysis data sets is important for studying the complex interactions of...
An accelerating Brewer–Dobson circulation (BDC) is a robust signal of climate change in model predictions but has been questioned by trace gas observations. We analyse the stratospheric mean age of air and the full age spectrum as measures for the BDC and its trend. Age of air is calculated using the Chemical Lagrangian Model of the Stratosphere (C...
An accelerating Brewer–Dobson circulation (BDC) is a robust signal of climate change in model predictions but has been questioned by trace gas observations. We analyse the stratospheric mean age of air and the full age spectrum as measures for the BDC and its trend. Age of air is calculated using the Chemical Lagrangian Model of the Stratosphere (C...
1.Reported on the measurements of HNO3 and HCN from two Geophysica flights in the Asian Summer Monsoon Anticyclone
2. Discussed the impact of convective events on HNO3 and HCN with Lagrangian models TRACZILLA and CLaMS
3. Showed the air mass origins of sampled HNO3 and HCN along flights based on backward trajectory calculations from the two Lagrang...
We show that a fire plume originating at high northern latitudes during the Canadian wildfire event in July/August 2017 reached the tropics, and subsequently the tropical stratosphere via the ascending branch of the Brewer-Dobson Circulation (BDC). The transport from high to low latitudes in the upper troposphere and lowermost stratosphere was medi...
An accelerating Brewer-Dobson circulation (BDC) is a robust signal of climate change in model predictions but has been questioned by trace gas observations. We analyze stratospheric mean age of air and the full age spectrum as measures for the BDC and its trend. Age of air is calculated with the Chemical Lagrangian Model of the Stratosphere (CLaMS)...
The stratospheric Brewer–Dobson circulation (BDC) determines the transport and atmospheric lifetime of key radiatively active trace gases and further impacts surface climate through downward coupling. Here, we quantify the variability in the lower stratospheric BDC induced by the El Niño–Southern Oscillation (ENSO), using satellite trace gas measur...
The reanalysis from the major weather centers are aiming at
providing a detailed historical description of the state of the
atmosphere that is often used as a reference in climate
studies.
While the reanalysis are in good or very agreements
regarding the variables which are directly constrained by the
assimilated observations, they usually differ...
The stratospheric circulation determines the transport and lifetime of key greenhouse gases, including water vapor and ozone, which radiatively impact surface climate. The unusually warm El Niño Southern Oscillation (ENSO) event aligned with a disrupted Quasi-Biennial Oscillation (QBO) caused an unprecedented perturbation to this circulation in 201...
The stratospheric circulation determines the transport and lifetime of key trace gases in a changing climate, including water vapor and ozone, which radiatively impact surface climate. The unusually warm El Niño–Southern Oscillation (ENSO) event aligned with a disrupted Quasi-Biennial Oscillation (QBO) caused an unprecedented perturbation to this c...
High-resolution backward and forward trajectory calculations are used to study the transport of convective air in and around the Asian Monsoon Anticyclone (AMA). We focus on the 2017 summer season which is the first one during which MSG (Meteosat Second Generation) data and products are available over the Asian Monsoon region and during which the S...
Volcanic eruptions are a major natural source of gases and aerosols, which perturbs the atmospheric chemistry (Graf et al. in Chem Geol 147:131–45, 1998) and the Earth’s radiative transfer (Robock and Oppenheimer in Volcanism and the Earth’s atmosphere. Washington, DC, USA: American Geophysical Union, pp. 187–236, 2003).
The stratospheric circulation is an important element of climate as it determines the concentration of radiatively active species like water vapor and aerosol above the tropopause. Climate models predict that increasing greenhouse gas levels speed up the stratospheric circulation. However, these results have been challenged by observational estimat...
Monitoring gaseous and particulate volcanic emissions with remote observations is of particular importance for climate studies, air quality and natural risk assessment. The concurrent impact of the simultaneous presence of sulphur dioxide (SO2) emissions and the subsequently formed secondary sulphate aerosols (SSA) on the thermal infraRed (TIR) sat...
Using multi-year satellite rainfall estimates, the distributions of the area and the total rain rate of rain clusters over the equatorial Indian, Pacific and Atlantic oceans were found to exhibit a power law , in which S represents either the cluster area or the cluster total rain rate and fS(s) denotes the probability density function of finding a...
Using multiyear satellite rainfall estimates, the distributions of the area, and the total rain rate of rain clusters over the equatorial Indian, Pacific, and Atlantic Oceans was found to exhibit a power law f[subscript s](s)~s[superscript -ζ[subscript s]], in which S represents either the cluster area or the cluster total rain rate and f[subscript...
In this study, we construct a new monthly zonal mean carbon dioxide (CO2) distribution from the upper troposphere to the stratosphere over the 2000–2010 time period. This reconstructed CO2 product is based on a Lagrangian backward trajectory model driven by ERA-Interim reanalysis meteorology and tropospheric CO2 measurements. Comparisons of our CO2...
The influence of deep convection on water vapor in the Tropical Tropopause Layer (TTL), the region just below the high ($\sim$18 km), cold tropical tropopause, remains an outstanding question in atmospheric science. Moisture transport to this region is important for climate projections because it drives the formation of local cirrus (ice) clouds, w...
The emission of gases and aerosols due to volcanic activity may impact significantly atmospheric composition, cloud occurrence and properties, and the regional and global climate. While the effects of strong explosive (stratospheric) eruptions are relatively well known, limited information on the impacts of small to moderate volcanic activities, in...
In this study, we aim to reconstruct a relevant and new database of monthly zonal mean distribution of carbon dioxide (CO2) at global scale extending from the upper-troposphere (UT) to stratosphere (S). This product can be used for model and satellite validation in the UT/S, as a prior for inversion modelling and mainly to analyse a plausible featu...
In this paper we combine SO2 and ash plume dispersion modelling with satellite and surface remote sensing observations to study the regional influence of a relatively weak volcanic eruption from Mount Etna on the optical and micro-physical properties of Mediterranean aerosols. We analyse the Mount Etna eruption episode of 25–27 October 2013. The ev...
Transit properties across the tropical tropopause layer are studied using extensive forward and backward Lagrangian diabatic trajectories between cloud tops and the reference surface 380 K. After dividing the tropical domain into 11 subregions according to the distribution of land and convection, we estimate the contribution of each region to the u...
Wave-induced lagrangian fluctuations of temperature and vertical velocity in the lower stratosphere are quantified using measurements from superpressure balloons (SPBs). Observations recorded every minute along SPB flights allow the whole gravity-wave spectrum to be described, and provide unprecedented information on both the intrinsic-frequency sp...
We use the Weather Research and Forecast (WRF) model to simulate
a large-scale tropical tropopause layer (TTL) cirrus in order to understand
the formation and life cycle of the cloud. This cirrus event has been
previously described through satellite observations by Taylor et al. (2011).
Comparisons of the simulated and observed cirrus show a fair a...
The effective diffusivity based on passive tracer advection is used to evaluate the long-term mixing properties for the period 1980–2012 in the lower stratosphere and upper troposphere (UTLS) using data from the ERA-Interim reanalysis. The regions of strongest interannual variability in effective diffusivity coincide with the regions of strong clim...
