FORLI radiative transfer and retrieval code for IASI
01 Jul 2012-Journal of Quantitative Spectroscopy & Radiative Transfer (Pergamon)-Vol. 113, Iss: 11, pp 1391-1408
TL;DR: In this article, the authors lay down the theoretical bases and the methods used in the Fast Optimal Retrievals on Layers for IASI (FORLI) software, which is developed and maintained at the Universite Libre de Bruxelles (ULB) with the support of the "Laboratoire Atmospheres, Milieux, Observations Spatiales" (LATMOS) to process radiance spectra from the Infrared Atmospheric Sounding Interferometer (IASI) in the perspective of local to global chemistry applications.
Abstract: This paper lays down the theoretical bases and the methods used in the Fast Optimal Retrievals on Layers for IASI (FORLI) software, which is developed and maintained at the "Universite Libre de Bruxelles" (ULB) with the support of the "Laboratoire Atmospheres, Milieux, Observations Spatiales" (LATMOS) to process radiance spectra from the Infrared Atmospheric Sounding Interferometer (IASI) in the perspective of local to global chemistry applications. The forward radiative transfer model (RTM) and the retrieval approaches are formulated and numerical approximations are described. The aim of FORLI is near-real-time provision of global scale concentrations of trace gases from IASI, either integrated over the altitude range of the atmosphere (total columns) or vertically resolved. To this end, FORLI uses precalculated table of absorbances. At the time of writing three gas-specific versions of this algorithm have been set up: FORLI-CO, FORLI-O3 and FORLI-HNO3. The performances of each are reviewed and illustrations of results and early validations are provided, making the link to recent scientific publications. In this paper we stress the challenges raised by near-real-time processing of IASI, shortly describe the processing chain set up at ULB and draw perspectives for future developments and applications.
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Cooperative Institute for Research in Environmental Sciences1, Centre national de la recherche scientifique2, University of Toulouse3, University of Bremen4, Université libre de Bruxelles5, Paris Diderot University6, University of the Littoral Opal Coast7, Agencia Estatal de Meteorología8, Polytechnic University of Catalonia9, National Center for Atmospheric Research10, Karlsruhe Institute of Technology11, Harvard University12, University of Washington13, University of Wollongong14, Academy of Athens15, Rutherford Appleton Laboratory16, California Institute of Technology17, China Meteorological Administration18, University of Toronto19, University of Liège20, Cooperative Institute for Mesoscale Meteorological Studies21, National Institute of Water and Atmospheric Research22, Forschungszentrum Jülich23, State University of New York System24, Swiss Federal Laboratories for Materials Science and Technology25, National Institute for Environmental Studies26, Goddard Space Flight Center27, Belgian Institute for Space Aeronomy28, Morgan State University29
TL;DR: The Tropospheric Ozone Assessment Report (TOAR) is an activity of the International Global Atmospheric Chemistry Project as mentioned in this paper, which provides a detailed view of ozone in the lower troposphere across East Asia and Europe.
Abstract: The Tropospheric Ozone Assessment Report (TOAR) is an activity of the International Global Atmospheric Chemistry Project. This paper is a component of the report, focusing on the present-day distribution and trends of tropospheric ozone relevant to climate and global atmospheric chemistry model evaluation. Utilizing the TOAR surface ozone database, several figures present the global distribution and trends of daytime average ozone at 2702 non-urban monitoring sites, highlighting the regions and seasons of the world with the greatest ozone levels. Similarly, ozonesonde and commercial aircraft observations reveal ozone’s distribution throughout the depth of the free troposphere. Long-term surface observations are limited in their global spatial coverage, but data from remote locations indicate that ozone in the 21st century is greater than during the 1970s and 1980s. While some remote sites and many sites in the heavily polluted regions of East Asia show ozone increases since 2000, many others show decreases and there is no clear global pattern for surface ozone changes since 2000. Two new satellite products provide detailed views of ozone in the lower troposphere across East Asia and Europe, revealing the full spatial extent of the spring and summer ozone enhancements across eastern China that cannot be assessed from limited surface observations. Sufficient data are now available (ozonesondes, satellite, aircraft) across the tropics from South America eastwards to the western Pacific Ocean, to indicate a likely tropospheric column ozone increase since the 1990s. The 2014–2016 mean tropospheric ozone burden (TOB) between 60˚N–60˚S from five satellite products is 300 Tg ± 4%. While this agreement is excellent, the products differ in their quantification of TOB trends and further work is required to reconcile the differences. Satellites can now estimate ozone’s global long-wave radiative effect, but evaluation is difficult due to limited in situ observations where the radiative effect is greatest.
274 citations
Cites methods from "FORLI radiative transfer and retrie..."
...IASI-FORLI: Ozone vertical profiles are retrieved on the global scale in near real time with the FORLI-O3 (for IASI– v20151001) processing chain set up by the Université Libre de Bruxelles (U.L.B.) and LATMOS teams (Hurtmans et al., 2012)....
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TL;DR: The authors used in situ observations from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, the Midwest Ammonia Monitoring Project, 11 surface site campaigns as well as Infrared Atmospheric Sounding Interferometer (IASI) satellite measurements with the GEOS-Chem model to investigate inorganic aerosol loading and atmospheric ammonia concentrations over the United States.
Abstract: We use in situ observations from the Interagency Monitoring of PROtected Visual Environments (IMPROVE) network, the Midwest Ammonia Monitoring Project, 11 surface site campaigns as well as Infrared Atmospheric Sounding Interferometer (IASI) satellite measurements with the GEOS-Chem model to investigate inorganic aerosol loading and atmospheric ammonia concentrations over the United States IASI observations suggest that current ammonia emissions are underestimated in California and in the springtime in the Midwest In California this underestimate likely drives the underestimate in nitrate formation in the GEOS-Chem model However in the remaining continental United States we find that the nitrate simulation is biased high (normalized mean bias > = 10) year-round, except in Spring (due to the underestimate in ammonia in this season) None of the uncertainties in precursor emissions, the uptake efficiency of N2O5 on aerosols, OH concentrations, the reaction rate for the formation of nitric acid, or the dry deposition velocity of nitric acid are able to explain this bias We find that reducing nitric acid concentrations to 75% of their simulated values corrects the bias in nitrate (as well as ammonium) in the US However the mechanism for this potential reduction is unclear and may be a combination of errors in chemistry, deposition and sub-grid near-surface gradients This "updated" simulation reproduces PM and ammonia loading and captures the strong seasonal and spatial gradients in gas-particle partitioning across the United States We estimate that nitrogen makes up 15−35% of inorganic fine PM mass over the US, and that this fraction is likely to increase in the coming decade, both with decreases in sulfur emissions and increases in ammonia emissions
233 citations
Cites methods from "FORLI radiative transfer and retrie..."
...The retrievals are performed in near real time using the fast radiative transfer model FORLI (Hurtmans et al., 2012)....
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TL;DR: In this article, an improved retrieval scheme of NH3 total columns from the measurements of the Infrared Atmospheric Sounding Interferometer (IASI) is described. But this scheme consists of the calculation of a dimensionless spectral index from the IASI level 1C radiances, which is subsequently converted to a total NH3 column using look-up tables built from forward radiative transfer model simulations.
Abstract: . Ammonia (NH3) emissions in the atmosphere have increased substantially over the past decades, largely because of intensive livestock production and use of fertilizers. As a short-lived species, NH3 is highly variable in the atmosphere and its concentration is generally small, except near local sources. While ground-based measurements are possible, they are challenging and sparse. Advanced infrared sounders in orbit have recently demonstrated their capability to measure NH3, offering a new tool to refine global and regional budgets. In this paper we describe an improved retrieval scheme of NH3 total columns from the measurements of the Infrared Atmospheric Sounding Interferometer (IASI). It exploits the hyperspectral character of this instrument by using an extended spectral range (800–1200 cm−1) where NH3 is optically active. This scheme consists of the calculation of a dimensionless spectral index from the IASI level1C radiances, which is subsequently converted to a total NH3 column using look-up tables built from forward radiative transfer model simulations. We show how to retrieve the NH3 total columns from IASI quasi-globally and twice daily above both land and sea without large computational resources and with an improved detection limit. The retrieval also includes error characterization of the retrieved columns. Five years of IASI measurements (1 November 2007 to 31 October 2012) have been processed to acquire the first global and multiple-year data set of NH3 total columns, which are evaluated and compared to similar products from other retrieval methods. Spatial distributions from the five years data set are provided and analyzed at global and regional scales. In particular, we show the ability of this method to identify smaller emission sources than those previously reported, as well as transport patterns over the ocean. The five-year time series is further examined in terms of seasonality and interannual variability (in particular as a function of fire activity) separately for the Northern and Southern Hemispheres.
184 citations
Cites methods from "FORLI radiative transfer and retrie..."
...The comparison between Figs.2 (FORLI optimal estimation scheme) and6 (our new HRI-based retrieval scheme) reveal a significant additional number of daily retrieved NH3 column values....
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...3, the retrieval method is thoroughly described and its advantages are discussed against other existing retrieval schemes, especially the Fast Optimal Retrieval on Layers for IASI (FORLI) (Hurtmans et al., 2012)....
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...A quantitative comparison between the NH3 total columns retrieved from FORLI and the HRI scheme presented here is provided in Fig.9....
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...FORLI retrievals are, however, only performed on the IASI spectra from the morning orbit and for which the NH3 signal is clearly detected www.atmos-chem-phys.net/14/2905/2014/ Atmos....
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...A detailed comparison with the retrieval results from the FORLI software, which uses a full radiative transfer model, showed good agreement overall (correlation coefficient of 0.81, with FORLI biased high by 35 %)....
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National Center for Atmospheric Research1, California Institute of Technology2, Centre national de la recherche scientifique3, University of Toronto4, Netherlands Institute for Space Research5, Université libre de Bruxelles6, Royal Netherlands Meteorological Institute7, Dalhousie University8, University of Maryland, College Park9
TL;DR: In this article, the authors present a comprehensive record of satellite observations from 2000 through 2011 of total column CO using the available measurements from nadir-viewing thermal infrared instruments: MOPITT, AIRS, TES and IASI.
Abstract: . Atmospheric carbon monoxide (CO) distributions are controlled by anthropogenic emissions, biomass burning, transport and oxidation by reaction with the hydroxyl radical (OH). Quantifying trends in CO is therefore important for understanding changes related to all of these contributions. Here we present a comprehensive record of satellite observations from 2000 through 2011 of total column CO using the available measurements from nadir-viewing thermal infrared instruments: MOPITT, AIRS, TES and IASI. We examine trends for CO in the Northern and Southern Hemispheres along with regional trends for Eastern China, Eastern USA, Europe and India. We find that all the satellite observations are consistent with a modest decreasing trend ~ −1 % yr −1 in total column CO over the Northern Hemisphere for this time period and a less significant, but still decreasing trend in the Southern Hemisphere. Although decreasing trends in the United States and Europe have been observed from surface CO measurements, we also find a decrease in CO over E. China that, to our knowledge, has not been reported previously. Some of the interannual variability in the observations can be explained by global fire emissions, but the overall decrease needs further study to understand the implications for changes in anthropogenic emissions.
170 citations
01 Apr 2013
153 citations
Cites methods from "FORLI radiative transfer and retrie..."
...Standard filtering as recommended in Hurtmans et al. (2012) was applied to residual radiances (in W(cm2 srcm−1)−1): −0.15×109 ≤ bias ≤ 0.25×10−9 and RMS ≤ 2.7×10−9.10...
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...For carbon monoxide, profiles are retrieved using an optimal estimation approach, implemented in the Fast Optimal Retrievals on Layers for IASI (FORLI) software (Hurtmans et al., 2012)....
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References
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Harvard University1, University of Reims Champagne-Ardenne2, College of William & Mary3, Old Dominion University4, University of Lisbon5, University of Burgundy6, California Institute of Technology7, Centre national de la recherche scientifique8, Université catholique de Louvain9, University of York10, University College London11, National Institute of Standards and Technology12, University of Waterloo13, National Center for Atmospheric Research14, University of Cologne15, Karlsruhe Institute of Technology16, Langley Research Center17
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Abstract: This paper describes the contents of the 2016 edition of the HITRAN molecular spectroscopic compilation. The new edition replaces the previous HITRAN edition of 2012 and its updates during the intervening years. The HITRAN molecular absorption compilation is composed of five major components: the traditional line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, infrared absorption cross-sections for molecules not yet amenable to representation in a line-by-line form, collision-induced absorption data, aerosol indices of refraction, and general tables such as partition sums that apply globally to the data. The new HITRAN is greatly extended in terms of accuracy, spectral coverage, additional absorption phenomena, added line-shape formalisms, and validity. Moreover, molecules, isotopologues, and perturbing gases have been added that address the issues of atmospheres beyond the Earth. Of considerable note, experimental IR cross-sections for almost 300 additional molecules important in different areas of atmospheric science have been added to the database. The compilation can be accessed through www.hitran.org. Most of the HITRAN data have now been cast into an underlying relational database structure that offers many advantages over the long-standing sequential text-based structure. The new structure empowers the user in many ways. It enables the incorporation of an extended set of fundamental parameters per transition, sophisticated line-shape formalisms, easy user-defined output formats, and very convenient searching, filtering, and plotting of data. A powerful application programming interface making use of structured query language (SQL) features for higher-level applications of HITRAN is also provided.
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Abstract: The radiative transfer models developed at AER are being used extensively for a wide range of applications in the atmospheric sciences. This communication is intended to provide a coherent summary of the various radiative transfer models and associated databases publicly available from AER ( http://www.rtweb.aer.com ). Among the communities using the models are the remote sensing community (e.g. TES, IASI), the numerical weather prediction community (e.g. ECMWF, NCEP GFS, WRF, MM5), and the climate community (e.g. ECHAM5). Included in this communication is a description of the central features and recent updates for the following models: the line-by-line radiative transfer model (LBLRTM); the line file creation program (LNFL); the longwave and shortwave rapid radiative transfer models, RRTM_LW and RRTM_SW; the Monochromatic Radiative Transfer Model (MonoRTM); the MT_CKD Continuum; and the Kurucz Solar Source Function. LBLRTM and the associated line parameter database (e.g. HITRAN 2000 with 2001 updates) play a central role in the suite of models. The physics adopted for LBLRTM has been extensively analyzed in the context of closure experiments involving the evaluation of the model inputs (e.g. atmospheric state), spectral radiative measurements and the spectral model output. The rapid radiative transfer models are then developed and evaluated using the validated LBLRTM model.
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University of Waterloo1, Meteorological Service of Canada2, University of Paris3, Université libre de Bruxelles4, NASA Headquarters5, Belgian Institute for Space Aeronomy6, University of Toronto7, Trent University8, University of Western Ontario9, Goddard Space Flight Center10, University of Saskatchewan11, York University12, Canadian Space Agency13, Langley Research Center14, Laval University15, At Bristol16
TL;DR: The Atmospheric Chemistry Experiment (ACE) is a Canadian satellite mission for remote sensing of the Earth's atmosphere that was launched into low Earth circular orbit (altitude 650 km, inclination 74°) on 12 Aug. 2003.
Abstract: SCISAT-1, also known as the Atmospheric Chemistry Experiment (ACE), is a Canadian satellite mission for remote sensing of the Earth's atmosphere. It was launched into low Earth circular orbit (altitude 650 km, inclination 74°) on 12 Aug. 2003. The primary ACE instrument is a high spectral resolution (0.02 cm-1) Fourier Transform Spectrometer (FTS) operating from 2.2 to 13.3 μm (750-4400 cm-1). The satellite also features a dual spectrophotometer known as MAESTRO with wavelength coverage of 285-1030 nm and spectral resolution of 1-2 nm. A pair of filtered CMOS detector arrays records images of the Sun at 0.525 and 1.02 μm. Working primarily in solar occultation, the satellite provides altitude profile information (typically 10-100 km) for temperature, pressure, and the volume mixing ratios for several dozen molecules of atmospheric interest, as well as atmospheric extinction profiles over the latitudes 85°N to 85°S. This paper presents a mission overview and some of the first scientific results. Copyright 2005 by the American Geophysical Union.
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TL;DR: The IASI nadir looking thermal infrared sounder onboard MetOp will provide 15 years of global scale observations for a series of key atmospheric species, with unprecedented spatial sampling and coverage as discussed by the authors.
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566 citations