Chiral Perturbation Theory

An introduction to the methods and ideas of Chiral Perturbation Theory is presented in this talk. The discussion is illustrated with some phenomenological predictions that can be compared with available experimental results.Comment: 16 pages, 4 Postscript figures, uses epsf.sty. Talk presented at the International Conference on Particle Physics and Astrophysics in The Standard Model and Beyond, Bystra (Poland). Full Postscript file available at http://deneb.ugr.es/papers/ugft57.ps.g

A variational approach for retrieving ice cloud properties from infrared measurements: application in the context of two IIR validation campaigns

Cirrus are cloud types that are recognized to have a strong impact on the Earth-atmosphere radiation balance. This impact is however still poorly understood, due to the difficulties in describing the large variability of their properties in global climate models. Consequently, numerous airborne and space borne missions have been dedicated to their study in the last decades. The satellite constellation A-Train has proven to be particularly helpful to study cirrus on global scale due to such instruments as the Infrared Imaging Radiometer (IIR), which shows great sensitivity to the radiative and microphysical properties of these clouds. This study presents an algorithm that uses thermal infrared measurements to retrieve the optical thickness of cirrus and the effective size of their ice crystals. This algorithm is based on an optimal estimation scheme, which possesses the advantage of attributing precise uncertainties to the retrieved parameters. Two IIR airborne validation campaigns have been chosen as case studies. It is observed that optical thicknesses could be accurately retrieved but that large uncertainties may occur on the effective diameters. Strong agreements have been found between the products of our algorithm when separately applied to the measurements of IIR and of the airborne radiometer CLIMAT-AV, which comforts the results of previous validations of IIR level-1 measurements. Comparisons with in situ observations and with operational products of IIR also show confidence in our results. However, we have found that the quality of our retrievals can be strongly impacted by uncertainties related to the choice of a pristine crystal model and by poor constraints on the properties of possible liquid cloud layers underneath cirrus. Simultaneous retrievals of liquid clouds radiative and microphysical properties or the use of different ice crystal models should therefore be considered to improve the quality of the results

Comparison of PARASOL Observations with Polarized Reflectances Simulated Using Different Ice Habit Mixtures

Insufficient knowledge of the habit distribution and the degree of surface roughness of ice crystals within ice clouds is a source of uncertainty in the forward light scattering and radiative transfer simulations required in downstream applications involving these clouds. The widely used MODerate Resolution Imaging Spectroradiometer (MODIS) Collection 5 ice microphysical model assumes a mixture of various ice crystal shapes with smooth-facets except aggregates of columns for which a moderately rough condition is assumed. When compared with PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) polarized reflection data, simulations of polarized reflectance using smooth particles show a poor fit to the measurements, whereas very rough-faceted particles provide an improved fit to the polarized reflectance. In this study a new microphysical model based on a mixture of 9 different ice crystal habits with severely roughened facets is developed. Simulated polarized reflectance using the new ice habit distribution is calculated using a vector adding-doubling radiative transfer model, and the simulations closely agree with the polarized reflectance observed by PARASOL. The new general habit mixture is also tested using a spherical albedo differences analysis, and surface roughening is found to improve the consistency of multi-angular observations. It is suggested that an ice model incorporating an ensemble of different habits with severely roughened surfaces would potentially be an adequate choice for global ice cloud retrievals

Towards IASI-New Generation (IASI-NG): impact of improved spectral resolution and radiometric noise on the retrieval of thermodynamic, chemistry and climate variables

Besides their strong contribution to weather forecast improvement through data assimilation, thermal infrared sounders onboard polar-orbiting platforms are now playing a key role for monitoring atmospheric composition changes. The Infrared Atmospheric Sounding Interferometer (IASI) instrument developed by the French space agency (CNES) and launched by Eumetsat onboard the Metop satellite series is providing essential inputs for weather forecasting and pollution/climate monitoring owing to its smart combination of large horizontal swath, good spectral resolution and high radiometric performance. EUMETSAT is currently preparing the next polar-orbiting program (EPS-SG) with the Metop-SG satellite series that should be launched around 2020. In this framework, CNES is studying the concept of a new instrument, the IASI-New Generation (IASI-NG), characterized by an improvement of both spectral and radiometric characteristics as compared to IASI, with three objectives: (i) continuity of the IASI/Metop series; (ii) improvement of vertical resolution; (iii) improvement of the accuracy and detection threshold for atmospheric and surface components. In this paper, we show that an improvement of spectral resolution and radiometric noise fulfill these objectives by leading to (i) a better vertical coverage in the lower part of the troposphere, thanks to the increase in spectral resolution; (ii) an increase in the accuracy of the retrieval of several thermodynamic, climate and chemistry variables, thanks to the improved signal-to-noise ratio as well as less interferences between the signatures of the absorbing species in the measured radiances. The detection limit of several atmospheric species is also improved. We conclude that IASI-NG has the potential for strongly benefiting the numerical weather prediction, chemistry and climate communities now connected through the European GMES/Copernicus initiative

Towards IASI-New Generation (IASI-NG): impact of improved spectral resolution and radiometric noise on the retrieval of thermodynamic, chemistry and climate variables

Besides their strong contribution to weather forecast improvement through data assimilation, thermal infrared sounders onboard polar-orbiting platforms are now playing a key role for monitoring atmospheric composition changes. The Infrared Atmospheric Sounding Interferometer (IASI) instrument developed by the French space agency (CNES) and launched by Eumetsat onboard the Metop satellite series is providing essential inputs for weather forecasting and pollution/climate monitoring owing to its smart combination of large horizontal swath, good spectral resolution and high radiometric performance. EUMETSAT is currently preparing the next polar-orbiting program (EPS-SG) with the Metop-SG satellite series that should be launched around 2020. In this framework, CNES is studying the concept of a new instrument, the IASI-New Generation (IASI-NG), characterized by an improvement of both spectral and radiometric characteristics as compared to IASI, with three objectives: (i) continuity of the IASI/Metop series; (ii) improvement of vertical resolution; (iii) improvement of the accuracy and detection threshold for atmospheric and surface components. In this paper, we show that an improvement of spectral resolution and radiometric noise fulfill these objectives by leading to (i) a better vertical coverage in the lower part of the troposphere, thanks to the increase in spectral resolution; (ii) an increase in the accuracy of the retrieval of several thermodynamic, climate and chemistry variables, thanks to the improved signal-to-noise ratio as well as less interferences between the signatures of the absorbing species in the measured radiances. The detection limit of several atmospheric species is also improved. We conclude that IASI-NG has the potential for strongly benefiting the numerical weather prediction, chemistry and climate communities now connected through the European GMES/Copernicus initiative

FORUM Earth Explorer 9: Characteristics of Level 2 Products and Synergies with IASI-NG

open10siFunding: The work presented was supported by the ESA–ESTEC Contract No. 4000124803/18/NL/CT, FORUM: consolidation of requirements and reference scenariosFORUM (Far-infrared Outgoing Radiation Understanding and Monitoring) has been approved to be the ninth Earth Explorer mission of the European Space Agency. The mission is scheduled for launch on a Polar satellite in the 2025–2026 time frame. The core FORUM instrument is a Fourier Transform Spectrometer measuring, with very high accuracy, the upwelling spectral radiance, from 100 to 1600 cm^-1 (from 100 to 6.25 microns in wavelength), thus covering the Far-Infrared (FIR), and a Mid-Infrared (MIR) portion of the spectrum emitted by the Earth. FORUM will fly in loose formation with the MetOp-SG-1A satellite, hosting the Infrared Atmospheric Sounding Interferometer – New Generation (IASI-NG). IASI-NG will measure only the MIR part of the upwelling atmospheric spectrum, from 645 to 2760 cm^-1 (from 15.5 to 3.62 microns in wavelength), thus, the matching FORUM measurements will supply the missing FIR complement. Together, the two missions will provide, for the first time, a spectrally resolved measurement of the full Earth emitted thermal spectrum. The calibrated spectral radiance will be, on its own, the main product of the FORUM mission, however, the radiances will also be processed up to Level 2, to determine the vertical profile of water vapour, surface spectral emissivity and cloud parameters in the case of cloudy atmospheres. In this paper we assess the performance of the FORUM Level 2 products based on clear-sky simulated retrievals and we study how the FORUM and IASI-NG matching measurements can be fused in a synergistic retrieval scheme, to provide improved Level 2 products. Considering only the measurement noise and the systematic calibration error components, we find the following figures for the synergistic FORUM and IASI-NG retrieval products. In the upper troposphere/lower stratosphere region, individual water vapour profiles can be retrieved with 1 km vertical sampling and an error ranging from 10% to 15%. In the range from 300 to 600 cm^-1 , surface spectral emissivity can be retrieved with an absolute error as small as 0.001 in dry Polar atmospheres. Ice cloud parameters such as ice water path and cloud top height can be retrieved with errors smaller than 10% and 1 km, respectively, for ice water path values ranging from 0.2 to 60 g/m^2openRidolfi, Marco; Del Bianco, Samuele; Di Roma, Alessio; Castelli, Elisa; Belotti, Claudio; Dandini, Paolo; Di Natale, Gianluca; Dinelli, Bianca Maria; C.-Labonnote, Laurent; Palchetti, LucaRidolfi, Marco; Del Bianco, Samuele; Di Roma, Alessio; Castelli, Elisa; Belotti, Claudio; Dandini, Paolo; Di Natale, Gianluca; Dinelli, Bianca Maria; C.-Labonnote, Laurent; Palchetti, Luc

Polarized light scattering by inhomogeneous hexagonal monocrystals. Validation with ADEOS-POLDER measurements

Various in situ measurements of the light-scattering diagram in ice clouds were performed with a new nephelometer during several airborne campaigns. These measurements were favorably compared with a theoretical scattering model called Inhomogeneous Hexagonal Monocrystal (IHM) model. This model consists in computing the scattering of light by an ensemble of randomly oriented hexagonal ice crystals containing spherical impurities of soot and air bubbles. It is achieved by using a combination of ray tracing, Mie theory, and Monte Carlo techniques and enables to retrieve the six independent elements of the scattering matrix. This good agreement between nephelometer measurements and IHM model provides an opportunity to use this model in order to analyze ADEOS-POLDER total and polarized reflectance measurements over ice clouds. POLDER uses an original concept to observe ice cloud properties, enabling to measure reflectances and polarized reflectances, for a given scene, under several (up to 14) viewing directions. A first analysis of ice cloud spherical albedoes over the terrestrial globe for November 10, 1996, and April 23, 1997, shows a rather good agreement between measurements and modeling. Moreover, polarized reflectances are also calculated and show a satisfactory agreement with measurements

Etude des propriétés optiques et radiatives des cirrus à l'aide de modèles microphysiques élaborés (analyse de mesures in situ (Néphélomètre) et satellitaire (POLDER))

LILLE1-BU (590092102) / SudocSudocFranceF

Study of ice cloud properties from infrared satellite measurements

&amp;lt;p class=&amp;quot;AbstractText&amp;quot;&amp;gt;&amp;lt;span lang=&amp;quot;EN-US&amp;quot;&amp;gt;This study aims to explore and quantify the added value of the far-infrared for the restitution of ice cloud optical properties with the future instrument from the Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM, Palchetti et al. (2020)) mission from the European Space Agency (ESA). FORUM&amp;lt;/span&amp;gt; &amp;lt;span lang=&amp;quot;EN-US&amp;quot;&amp;gt;will provide new insight into the far infra-red Earth&amp;amp;#8217;s radiation budget and its climate feedbacks, such as those related to the water vapor and ice clouds. FORUM will measure the infrared (IR) emission spectrum of the Earth at the top of the atmosphere between 100-1600 cm&amp;lt;sup&amp;gt; -1&amp;lt;/sup&amp;gt;, with a spectral resolution around 0.5 cm&amp;lt;sup&amp;gt; -1&amp;lt;/sup&amp;gt;. This work aims at preparing and exploiting future FORUM observations in synergy with observations from the Infrared Atmospheric Sounding Interferometer - New Generation (IASI-NG, Crevoisier et al., 2014).&amp;lt;/span&amp;gt;&amp;lt;/p&amp;gt; &amp;lt;p class=&amp;quot;AbstractText&amp;quot;&amp;gt;&amp;lt;span lang=&amp;quot;EN-US&amp;quot;&amp;gt;This study applies the algorithm recently developed by Leonarski et al. (2021) to retrieve ice cloud properties from IASI and IASI-NG instruments using the Radiative Transfer for TOVS (RTTOV) model (Saunders et al., 2018). This algorithm was here adapted for use of the FORUM instrument, as well as the instrumental synergy between FORUM and IASI-NG. The algorithm was tested on synthetic FORUM measurements derived from atmospheric vertical profiles coming from a global operational short-range forecasts database from the Center for Medium-range Weather Forecasts (ECMWF). The first results of this study show that the far- and mid- infrared measurements can be successfully used to inverse ice cloud properties (such as the water path (IWP), and the cloud top and bottom heights). Results from the comparison between FORUM and IASI-NG performances will be shown, as well as the added value of using the instrumental synergy between FORUM and IASI-NG for the study of ice cloud properties. Finally, the sensitivity of the retrieved properties to the microphysical model used in the forward model will also discussed.&amp;lt;/span&amp;gt;&amp;lt;/p&amp;gt; &amp;lt;p class=&amp;quot;AbstractText&amp;quot;&amp;gt;&amp;lt;span lang=&amp;quot;EN-US&amp;quot;&amp;gt;&amp;amp;#160;&amp;lt;/span&amp;gt;&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;References&amp;lt;/p&amp;gt; &amp;lt;p class=&amp;quot;RefText&amp;quot;&amp;gt;Crevoisier, C., Clerbaux, C., Guidard, V., Phulpin, T., Armante, R., Barret, B., ... &amp;lt;span lang=&amp;quot;EN-US&amp;quot;&amp;gt;&amp;amp; Stubenrauch, C. (2014). Towards IASI-New Generation (IASI-NG): impact of improved spectral resolution and radiometric noise on the retrieval of thermodynamic, chemistry and climate variables. &amp;lt;em&amp;gt;Atmospheric Measurement Techniques&amp;lt;/em&amp;gt;, &amp;lt;em&amp;gt;7&amp;lt;/em&amp;gt;(12), 4367-4385.&amp;lt;/span&amp;gt;&amp;lt;/p&amp;gt; &amp;lt;p class=&amp;quot;RefText&amp;quot;&amp;gt;&amp;lt;span lang=&amp;quot;EN-US&amp;quot;&amp;gt;Leonarski, L., C-Labonnote, L., Compi&amp;amp;#232;gne, M., Vidot, J., Baran, A. J., &amp;amp; Dubuisson, P. (2021). Potential of Hyperspectral Thermal Infrared Spaceborne Measurements to Retrieve Ice Cloud Physical Properties: Case Study of IASI and IASI-NG. &amp;lt;em&amp;gt;Remote Sensing&amp;lt;/em&amp;gt;, &amp;lt;em&amp;gt;13&amp;lt;/em&amp;gt;(1), 116.&amp;lt;/span&amp;gt;&amp;lt;/p&amp;gt; &amp;lt;p class=&amp;quot;RefText&amp;quot;&amp;gt;&amp;lt;span lang=&amp;quot;EL&amp;quot;&amp;gt;Palchetti, L., Brindley, H., Bantges, R., Buehler, S. A., Camy-Peyret, C., Carli, B., ... &amp;amp; Serio, C. (2020). unique far-infrared satellite observations to better understand how Earth radiates energy to space.&amp;amp;#160;&amp;lt;em&amp;gt;Bulletin of the American Meteorological Society&amp;lt;/em&amp;gt;,&amp;amp;#160;&amp;lt;em&amp;gt;101&amp;lt;/em&amp;gt;(12), E2030-E2046.&amp;lt;/span&amp;gt;&amp;lt;/p&amp;gt; &amp;lt;p class=&amp;quot;RefText&amp;quot;&amp;gt;&amp;lt;span lang=&amp;quot;EN-US&amp;quot;&amp;gt;Saunders, R., Hocking, J., Turner, E., Rayer, P., Rundle, D., Brunel, P., ... &amp;amp; Lupu, C. (2018). An update on the RTTOV fast radiative transfer model (currently at version 12). Geoscientific Model Development, 11(7), 2717-2737.&amp;lt;/span&amp;gt;&amp;lt;/p&amp;gt;</jats:p