Molecular composition of clouds: a comparison between samples collected at tropical (Réunion Island, France) and mid-north (Puy de Dôme, France) latitudes

The composition of dissolved organic matter of cloud water has been investigated through non-targeted high-resolution mass spectrometry on only a few samples that were mostly collected in the Northern Hemisphere in the USA, Europe and China. There remains, therefore, a lack of measurements for clouds located in the Southern Hemisphere, under tropical conditions and influenced by forest emissions. As a matter of fact, the comparison of the composition of clouds collected in different locations is challenging since the methodology for the analysis and data treatment is not standardized. In this work, the chemical composition of three samples collected at Réunion Island (REU) during the BIO-MAÏDO field campaign, in the Indian Ocean, with influences from marine, anthropogenic and biogenic (tropical) emissions, is investigated and compared to the chemical composition of samples collected at the Puy de Dôme (PUY) observatory in France. The same methodology of analysis and data treatment was employed, producing a unique dataset for the investigation of the molecular composition of organic matter in cloud water. Besides the analysis of elemental composition, we investigated the carbon oxidation state (OSC) of dissolved organic matter, finding that overall samples collected at PUY are more oxidized than those collected at REU. Molecular formulas were also classified based on stoichiometric elemental ratios, showing the high frequency and abundance of reduced organic compounds, classified as lipids (LipidC), in this matrix, which led to a search for terpene oxidation products in cloud water samples. To better discriminate between samples collected at PUY and REU, statistical analysis (principal component analysis and agglomerative hierarchical clustering) was performed on the ensemble of molecular formulas and their intensities. Samples collected at REU have a different composition from samples collected at PUY, which is mainly linked to different primary sources, the processing of organic matter in cloud water and the influence of different primary emissions at the two locations.</p

The immune system as a foundation for immunologic therapy and hematologic malignancies: a historical perspective.

In this review we aim to provide a historical overview of the immunotherapeutic approaches which have been developed for the treatment of hematological malignancies. After briefly summarizing the development of the theory of cancer immune surveillance, we describe how initial studies discovering the efficacy of the immune-mediated graft-versus-tumor effects after allogeneic hematopoietic cell transplantation led to new transplantation approaches (termed non-myeloablative transplantation) relying almost exclusively on graft-versus-tumor effects for tumor eradication. We then summarize important steps in the development of tumor vaccines and autologous adoptive immunotherapy in patients with hematological malignancies. Finally, we describe historical discoveries leading to the recent success with monoclonal antibodies as treatment for lymphomas, chronic lymphocytic leukemia, and acute myeloid leukemia

The onset of precipitation in warm cumulus clouds: An observational case-study.

International audienceData collected with a ground radar and an instrumented aircraft during the Small Cumulus Microphysics Study (SCMS) are analysed to examine the physical processes that control the onset of precipitation. On 10 August 1995, the Météo-France Merlin-IV successively sampled the core of the top cell in three convective clouds, following the cells from their initial stage of young vigorous ascending turrets up to their decaying stage. Simultaneous range-height indicator (RHI) scans were also performed by the National Center for Atmospheric Research CP2 radar. Although the three clouds showed similar values of the droplet number concentrations and were able to generate precipitation embryos, the first two collapsed after reaching an altitude of 3 km above sea level, without producing any precipitation, while the third one reached a higher level of 4 km and produced significant precipitation. This case-study illustrates how sensitive the onset of precipitation is to cloud dynamics, revealing that in a conditionally unstable atmosphere hardly noticeable changes in cloud thermodynamics and microphysics may lead to major changes in cloud vertical development and precipitation. Copyright © 2010 Royal Meteorological Societ

Experimental study on the evolution of droplet size distribution during the fog life cycle

International audienceThe evolution of the droplet size distribution (DSD) during the fog life cycle remains poorly understood and progress is required to reduce the uncertainty of fog forecasts. To gain insights into the physical processes driving the microphysical properties, intensive field campaigns were conducted during the winters of 2010-2013 at the Instrumented Site for Atmospheric Remote Sensing Research (SIRTA) in a semi-urban environment southwest of Paris city center to monitor the simultaneous variations in droplet microphysical properties and their potential interactions at the different evolutionary stages of the fog events. Liquid water content (LWC), fog droplet number concentration (N d) and effective diameter (D eff) show large variations among the 42 fog events observed during the campaign and for individual events. Our findings indicate that the variability of these parameters results from the interaction between microphysical, dynamical and radiative processes. During the formation and development phases, activation of aerosols into fog droplets and condensational growth were the dominant processes. When vertical development of radiation fog occurred under the influence of increasing wind speed and subsequent turbulent motion, additional condensational growth of fog droplets was observed. The DSDs with single mode (around 11 µm) and double mode (around 11 and 22 µm) were observed during the field campaign. During the development phase of fog with two droplet size modes, a mass transfer occurred from the smaller droplets into the larger ones through collision-coalescence or Ostwald ripening processes. During the mature phase, evaporation due to surface warming induced by infrared radiation emitted by fog was the dominant process. Additional droplet removal through sedimentation is observed during this phase for fog with two droplet size modes. Because of differences in the physical processes involved, the relationship between LWC and N d is largely driven by the DSD. Although a positive relationship is found in most of the events due to continuous activation of aerosol into fog droplets, LWC varies at a constant N d in fog with large D eff (> 17 µm) due to additional collision-coalescence and Ostwald ripening processes. This work illustrates the need to accurately estimate the supersaturation for simulating the continuous activation of aerosols into droplets during the fog life cycle and to include advanced parameterizations of relevant microphysical processes such as collision-coalescence and Ostwald ripening processes, among others, in numerical models

Parametric representation of the cloud droplet spectra for LES warm bulk microphysical schemes

International audienceParametric functions are currently used to represent droplet spectra in clouds and to develop bulk parameterizations of the microphysical processes and of their interactions with radiation. The most frequently used parametric functions are the Lognormal and the Generalized Gamma which have three and four independent parameters, respectively. In a bulk parameterization, two parameters are constrained by the total droplet number concentration and the liquid water content. In the Generalized Gamma function, one parameter is specified a priori, and the fourth one, like the third parameter of the Lognormal function, shall be tuned, for the parametric function to statistically best fit observed droplet spectra. These parametric functions are evaluated here using droplet spectra collected in non-or slightly precipitating stratocumulus and shallow cumulus. Optimum values of the tuning parameters are derived by minimizing either the absolute or the relative error for successively the first, second, fifth, and sixth moments of the droplet size distribution. A trade-off value is also proposed that minimizes both absolute and relative errors for the four moments concomitantly. Finally, a parameterization is proposed in which the tuning parameter depends on the liquid water content. This approach significantly improves the fit for the smallest and largest values of the moments

3D in-situ measurements of entrainment-related cumulus clouds properties using a swarm of unmanned aerial vehicles

International audienceEntrainment-related shallow cumulus clouds properties have largely been studied using large-eddy simulation. These previousstudies have led to various cumulus clouds parameterizations. On the other hand, simultaneous in-situ 3D sampling ofindividual cloud at spatial and temporal resolutions comparable to Large Eddy Simulation (LES) is still lacking. The need to fill inthis 3D observational data insufficiency and to validate previous LES findings has propelled the Skyscanner project; using theconcept of a multi-UAV-based adaptive sampling strategy. This project is a joint collaboration with institutes specializing inaviation, robotics, and atmospheric science. In order to capture 3D cloud properties simultaneously, the multi-UAVs pathplanning relies on a cumulus cloud conceptual model. This model that relates the evolution of geometrical and microphysicalproperties of individual clouds has been derived from LES numerical experiments using MesoNH-LES and potentially WRFLESmodels. In addition to the interaction with individual cloud properties, the multi-UAVs path planning is sensitive to theevolution of the convective boundary layer and the cloud spatial extent. The synchronized swarm of unmanned aerial vehicles(UAVs) focuses mainly on locating and quantifying the evolution of the entrainment-related cloud properties including thesubsiding shell around individual shallow cumulus clouds

Un drone au-dessus des océans : le projet Miriad

Le Centre National de Recherches Météorologiques (CNRM) de Météo-France est porteur d'un projet dédié à l'étude de la couche limite marine de l'atmosphère à l'aide de drones instrumentés : MIRIAD (Système de Mesures scIentifiques de flux de suRface en mIlieu mAritime embarqué sur Drone).International audienc

Évaluation d'une configuration améliorée d'AROME pour les prévisions de brouillard pendant la campagne SOFOG3D

International audienceThis paper evaluates fog forecasts of a new AROME configuration dedicated to fog thanks to observations of the recent field campaign SOuth westFOGs 3Dimensions (SOFOG3D). This new configuration takes advantage of an upgraded horizontal and vertical resolution, of a 2-moment microphysical scheme (LIMA) and of the inclusion of a parametrization of the droplets deposition onto vegetation. A statistical study conducted over the 6 months of the SOFOG3D field campaign allowed the evaluation of the quality of fog forecasts produced by this new configuration to compare it to the current operational configuration of AROME. The main findings are as follows: the new configuration forecast more fog events, with a few more false alarms, but improved the amount of fogs with low top height and with a low water content, underestimated by the reference configuration. The importance of the first level height for a good representation of the first few meters above the ground is crucial to improve the fog formation forecast. A delay of fog dissipation in the morning was highlighted in operational simulations and slightly reduced thanks to LIMA. This two-moment scheme produced thinner fogs, with less water content. These are more realistic, compared with observations, and thinner fog is also easier for solar radiation to dissipate