LATMOS IPSL

Guyancourt, France

LATMOS IPSL

Guyancourt, France

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Reverdin G.,LOCEAN Institute Pierre Simon Laplace IPSL | Morisset S.,LOCEAN IPSL | Bourras D.,LATMOS IPSL | Martin N.,LOCEAN IPSL | And 5 more authors.
Oceanography | Year: 2013

A new small wave rider called Surpact was developed for air-sea investigations. It was designed to attach to a drifter or a mooring and to float upon the surface waves in order to measure sea state and atmospheric sea level pressure as well as temperature and salinity at a small fixed depth from the surface. Wind speed is derived from Surpact sea state measurements, and the data are calibrated with co-located Special Sensor Microwave Imager Sounder (SSMIS) wind retrievals during a four-month deployment in the North Atlantic subtropics. Individual 15-minute wind estimates present a root mean square difference on the order of 15% with the SSMIS wind retrievals for wind speeds less than 12 m s-1. The wind retrievals might lag the actual wind changes for moderate to strong winds by an hour. This article discusses the accuracy of these wind retrievals based on in situ data collected during the Strasse cruise in August and September 2012. Temperature and salinity data are also examined. The authors find, under some sunny conditions, radiative warming of the temperature probe reduces the accuracy of some of the daytime temperature data and also affects corresponding salinity estimates. Nonetheless, small realistic daily cycles of near-surface salinity (0.01 psu amplitude) were observed. Also, examples of wind time series collected during salinity drops caused by rainfall during late 2012 in the North Atlantic subtropics indicate no intensification of wind during these rain events. © 2013 by The Oceanography Society.


Schneider N.M.,University of Colorado at Boulder | Deighan J.I.,University of Colorado at Boulder | Stewart A.I.F.,University of Colorado at Boulder | McClintock W.E.,University of Colorado at Boulder | And 13 more authors.
Geophysical Research Letters | Year: 2015

We report the detection of intense emission from magnesium and iron in Mars' atmosphere caused by a meteor shower following Comet Siding Spring's close encounter with Mars. The observations were made with the Imaging Ultraviolet Spectrograph, a remote sensing instrument on the Mars Atmosphere and Volatile EvolutioN spacecraft orbiting Mars. Ionized magnesium caused the brightest emission from the planet's atmosphere for many hours, resulting from resonant scattering of solar ultraviolet light. Modeling suggests a substantial fluence of low-density dust particles 1-100 μm in size, with the large amount and small size contrary to predictions. The event created a temporary planet-wide ionospheric layer below Mars' main dayside ionosphere. The dramatic meteor shower response at Mars is starkly different from the case at Earth, where a steady state metal layer is always observable but perturbations caused by even the strongest meteor showers are challenging to detect. © 2015. American Geophysical Union. All Rights Reserved.


Chepfer H.,University Pierre and Marie Curie | Noel V.,French National Center for Scientific Research | Winker D.,NASA | Chiriaco M.,LATMOS IPSL
Geophysical Research Letters | Year: 2014

Climate models predict that the geographic distribution of clouds will change in response to anthropogenic warming, though uncertainties in the existing satellite record are larger than the magnitude of the predicted effects. Here we argue that cloud vertical distribution, observable by active spaceborne sensors, is a more robust signature of climate change. Comparison of Atmospheric Model Intercomparison Project present day and +4 K runs from Coupled Model Intercomparison Project Phase 5 shows that cloud radiative effect and total cloud cover do not represent robust signatures of climate change, as predicted changes fall within the range of variability in the current observational record. However, the predicted forced changes in cloud vertical distribution (directly measurable by spaceborne active sensors) are much larger than the currently observed variability and are expected to first appear at a statistically significant level in the upper troposphere, at all latitudes. © 2014. American Geophysical Union. All Rights Reserved.


Chaffin M.S.,University of Colorado at Boulder | Chaufray J.-Y.,LATMOS IPSL | Stewart I.,University of Colorado at Boulder | Montmessin F.,LATMOS IPSL | And 2 more authors.
Geophysical Research Letters | Year: 2014

Mars today is much drier than the Earth, though they likely began with similar relative amounts of water. One potential cause for this discrepancy is hydrogen loss to space, which may have removed a large fraction of Mars' initial water. Here we demonstrate an order-of-magnitude change in the Martian hydrogen escape rate in 2007, inconsistent with established models for the source of escaping hydrogen. We analyze 121.6 nm (hydrogen Lyman-α) airglow observations made by the ultraviolet spectrometer on the Mars Express spacecraft over the second half of 2007. The enhanced escape rates we observe may be due to lower atmospheric heating and overturn during the 2007 (Mars Year 28) global dust storm, suggesting that hydrogen escape from Mars during dust storms may dominate loss of the planet's water inventory. This scenario has major implications for reconstructing the total amount of water lost to space over Martian history. ©2013. The Authors.


Larroza E.G.,Brazilian National Nuclear Energy Commission | Nakaema W.M.,Brazilian National Nuclear Energy Commission | Bourayou R.,Brazilian National Nuclear Energy Commission | Hoareau C.,Ecole Polytechnique - Palaiseau | And 2 more authors.
Atmospheric Measurement Techniques | Year: 2013

This paper presents a methodology to calculate lidar ratios for distinct cirrus clouds that has been developed and implemented for a site located in the Southern Hemisphere. The cirrus cloud lidar data processing aims to consider a large cloud variability and cirrus cloud monitoring through a robust retrieval process. Among cirrus features estimates for complex scenes that lidar systems can provide, we highlight cloud geometrical information and extinction-to- backscatter ratio (known as lidar ratio or LR). In general, direct information on cirrus cloud microphysics is difficult to derive because LR depends on the presence of ice crystals and their properties such as shape, size, composition and orientation of particles. An iterative process to derive a stable LR value has been proposed. One of the keys is to restrict the analysis to conditions allowing accurate multilayer events. This method uses nonparametric statistical approaches to identify stationary periods according to cloud features and variability. Measurements performed in the region of the metropolitan city of São Paulo (MSP) have been used to implement and test the methodology developed for cirrus cloud characterization. Good results are represented by examining specific cases with multilayer cirrus cloud occurrence. In addition to the geometrical parameters obtained, cirrus LR values were calculated for a single day ranging from 19 ± 01 sr to 74 ± 13 sr for 2 observed layers. This large difference in LR can indicate a mixture of ice crystal particles with different sizes and shapes in both layers of the cirrus clouds. Trajectory analyses indicate that both of these cloud layers can be associated with different air mass and should be considered as 2 distinct clouds in climatology. © 2013 Author(s).f 0.


Reverdy M.,Ecole Polytechnique - Palaiseau | Chepfer H.,University Pierre and Marie Curie | Donovan D.,KNMI | Noel V.,Ecole Polytechnique - Palaiseau | And 4 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2015

Clouds still remain the largest source of uncertainty in model-based predictions of future climate; thus, the description of the clouds in climate models needs to be evaluated. In particular, the cloud detailed vertical distribution that impacts directly the cloud radiative effect needs to be evaluated. Active satellite sensors directly measure the cloud vertical distribution with high accuracy; their observations should be used for model evaluation together with a satellite simulator in order to allow fair comparison between models and observations. The next cloud lidar in space, EarthCARE/ATmospheric LIDar (ATLID), is planned for launch in 2018, while the current spaceborne cloud lidar CALIPSO/CALIOP is expected to stop collecting data within the next coming years. Here we describe the characteristics of the ATLID on board the EarthCARE satellite (spatial resolution, signal-to-noise ratio, wavelength, field of view, pulse repetition frequency, orbit, and high-spectral resolution lidar) that need to be taken into account to build a Cloud Feedback Model Intercomparison Project Observation Simulator Package (COSP)/ATLID simulator. We then present the COSP/ATLID simulator, and the low-, middle-, high-level cloud covers it produces, as well as the zonal mean cloud fraction profiles and the height-intensity histograms that are simulated by COSP/ATLID when overflying an atmosphere predicted by LMDZ5 global circulation model. Finally, we compare the clouds simulated by COSP/ATLID with those simulated by COSP/CALIPSO when overflying the same atmosphere. As the main differences between ATLID and CALIOP are taken into account in the simulators, the differences between COSP/ATLID and COSP/CALIPSO cloud covers are less than 1% in nighttime conditions Key Point EarthCARE simulator to evaluate cloud in climate models. © 2015. American Geophysical Union. All Rights Reserved.


Crismani M.M.J.,University of Colorado at Boulder | Schneider N.M.,University of Colorado at Boulder | Deighan J.I.,University of Colorado at Boulder | Stewart A.I.F.,University of Colorado at Boulder | And 11 more authors.
Geophysical Research Letters | Year: 2015

We used the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiting spacecraft to construct images of the hydrogen coma of comet C/2013 A1 (Siding Spring) days before its close encounter with Mars. We obtain a water production rate of 1.1 ± 0.5 × 1028 molecules/s and determine the total impacting fluence of atoms and molecules corresponding to the photodissociation of water and its daughter species to be 2.4 ± 1.2 × 104 kg. We use these observations to confirm predictions that the mass of delivered hydrogen is comparable to the existing reservoir above 150 km. Furthermore, we reconcile disparity between observations and predictions about the detectability of the hydrogen perturbation and thermospheric response. © 2015. American Geophysical Union. All Rights Reserved.


Mangano V.,National institute for astrophysics | Massetti S.,National institute for astrophysics | Milillo A.,National institute for astrophysics | Plainaki C.,National institute for astrophysics | And 3 more authors.
Planetary and Space Science | Year: 2015

The Na exosphere of Mercury is being studied since its discovery in mid '80s from Earth-based telescopes, and it has revealed a high dynamics and variability. Although the processes and their relationships characterising the Hermean exosphere generation and dynamics are still not exhaustively understood, there are no doubts on a tight interconnection among the planet's surface, exosphere, intrinsic magnetic field, the solar wind and the Interplanetary Magnetic Field (IMF). In this paper we analyze an extended dataset of images of the exospheric Na emission, collected from 2009 to 2013, by means of the THEMIS ground-based telescope, in order to perform a comprehensive statistical study of the recurrent Na emission patterns, and also their potential relationship with the IMF variability. For this purpose, we take advantage of a subset (years 2011-2013) of contemporary in-situ measurements of the IMF obtained by the MAG instrument on-board the MESSENGER spacecraft. We found that the high latitude double peak is the most common Na emission pattern, supporting the view that the solar wind ion precipitation through the polar cusps has an important role in the generation of the observed Na exospheric configuration. Moreover, the lack of a statistically significant North-South asymmetry seems to disfavor the existence of an asymmetric and/or shifted intrinsic magnetic dipole. By analyzing a subset of quasi-full disk images, we found that the double peak Na emission is typically aligned along the meridian, mostly occurring in the pre-noon sector (53%), about 1/3 close to the noon meridian (36%), whereas only 11% takes place in the post-noon sector. Finally, the comparison with the IMF data seems to indicate that the contribution of the IMF B X component to the magnetic reconnection is generally weak, even if we found a noticeable correlation between positive IMF B X and symmetric double peak pattern. Negative IMF B Z values are usually connected to double peak emission, whereas positive IMF B Z values are more frequently associated to single peaked equatorial Na emission. © 2015 Elsevier Ltd.


Keckhut P.,LATMOS IPSL | Hauchecorne A.,LATMOS IPSL | Funatsu B.,University of Rennes 2 – Upper Brittany | Khaykin S.,LATMOS IPSL | And 3 more authors.
EPJ Web of Conferences | Year: 2016

Rayleigh lidar in synergy with satellite observations (SSU and AMSU) allow insuring an efficient monitoring and showing that cooling has continued. New approach for trend detection has been developed allowing a better estimate of changes due to radiative forcing. Stratospheric Warmings and gravity waves contribute to insure a dynamical feedback of the long-term changes. © 2016 Owned by the authors, published by EDP Sciences.


Josset D.,NRC Research Associate | Hou W.,U.S. Navy | Pelon J.,LATMOS IPSL | Hu Y.,NASA | And 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

In the past few years, we have demonstrated how the surface return measured by the active instruments onboard CloudSat and CALIPSO could be used to retrieve the optical depth and backscatter phase function (lidar ratio) of aerosols and ice clouds. This methodology lead to the development of a data fusion product publicly available at the ICARE archive center using the Synergized Optical Depth of Aerosols and Ice Clouds (SODA & ICE) algorithm1. This algorithm, also allowing to derive ocean surface wind speed, has been extended to include dense cloud surface return to analyze aerosol and cloud properties above such clouds. This low level data fusion of CALIPSO and CloudSat ocean surface echoes has been used by several researchers to explore different research paths. Among them, we can cite: A new characterization of the lidar ratio of cirrus clouds2 The analysis of the precipitable water and development of a new Millimeter-Wave Propagation Model for the W-Band observations (EMPIRIMA3) The analysis of the lidar ratio of sea-spray aerosols4, and of Aerosol multilayer lidar ratio and extinction5 A contribution to the retrieval of the subsurface particulate backscatter coefficients of phytoplankton particles6 In this paper, we present the main features of SODA & ICE, summarizing some of the results obtained. This low level data fusion of CALIPSO and CloudSat ocean surface echoes has been used by several researchers to explore different research paths. Among them, we can cite: A new characterization of the lidar ratio of cirrus clouds2 The analysis of the precipitable water and development of a new Millimeter-Wave Propagation Model for the W-Band observations (EMPIRIMA3) The analysis of the lidar ratio of sea-spray aerosols4, and of Aerosol multilayer lidar ratio and extinction5 A contribution to the retrieval of the subsurface particulate backscatter coefficients of phytoplankton particles6 In this paper, we present the main features of SODA & ICE, summarizing some of the results obtained. © 2015 SPIE.

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