Fast radiative transfer using monochromatic look-up tables

Vincent, R. Anthony; Dudhia, A.

doi:10.1016/j.jqsrt.2016.04.011

Cited by 11 publications

(10 citation statements)

References 23 publications

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“…The 4A model is the official code selected by CNES for calibration and validation activities of the IASI, Merlin (https://merlin.cnes.fr), and Mi-croCarb (https://microcarb.cnes.fr) missions. A detailed description of the protocol and of the results of the interactive validation of GEISA and 4A/OP may be found in Armante et al (2016).…”

Section: The Forward Radiative Transfer Model: 4amentioning

confidence: 99%

Long-term assessment of the CALIPSO Imaging Infrared Radiometer (IIR) calibration and stability through simulated and observed comparisons with MODIS/Aqua and SEVIRI/Meteosat

et al. 2017

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International audienceThe quality of the calibrated radiances of the medium-resolution Imaging Infrared Radiometer (IIR) on-board the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) satellite is quantitatively evaluated from the beginning of the mission in June 2006. Two complementary "relative" and "stand-alone" approaches are used, which are related to comparisons of measured brightness temperatures and to model-to-observations comparisons, respectively. In both cases, IIR channels 1 (8.65 µm), 2 (10.6 µm), and 3 (12.05 µm) are paired with the Moderate Resolution Imaging Spectroradiometer (MODIS)/Aqua Collection 5 "companion" channels 29, 31, and 32, respectively, as well as with the Spinning Enhanced Visible and Infrared Imager (SEVIRI)/Meteosat companion channels IR8.7, IR10.8, and IR12, respectively. These pairs were selected before launch to meet radiometric, geometric, and space-time constraints. The prelaunch studies were based on simulations and sensitivity studies using the 4A/OP radiative transfer model and the more than 2300 atmospheres of the climatological Thermodynamic Initial Guess Retrieval (TIGR) input dataset further sorted into five air mass types. Using data from over 9.5 years of on-orbit operation, and following the relative approach technique, collocated measurements of IIR and of its companion channels have been compared at all latitudes over ocean, during day and night, and for all types of scenes in a wide range of brightness temperatures. The relative approach shows an excellent stability of IIR2–MODIS31 and IIR3–MODIS32 brightness temperature differences (BTDs) since launch. A slight trend within the IIR1–MODIS29 BTD, that equals −0.02 K yr⁻¹ on average over 9.5 years, is detected when using the relative approach at all latitudes and all scene temperatures. For very cold scene temperatures (190–200 K) in the tropics, each IIR channel is warmer than its MODIS companion channel by 1.6 K on average. For the stand-alone approach, clear sky measurements only are considered, which are directly compared with simulations using 4A/OP and collocated ERA-Interim (ERA-I) reanalyses. The clear sky mask is derived from collocated observations from IIR and the CALIPSO lidar. Simulations for clear sky pixels in the tropics reproduce the differences between IIR1 and MODIS29 within 0.02 K and between IIR2 and MODIS31 within 0.04 K, whereas IIR3–MODIS32 is larger than simulated by 0.26 K. The stand-alone approach indicates that the trend identified from the relative approach originates from MODIS29, whereas no trend (less than ±0.004 K yr⁻¹) is identified for any of the IIR channels. Finally, using the relative approach, a year-by-year seasonal bias between nighttime and daytime IIR–MODIS BTD was found at mid-latitude in the Northern Hemisphere. It is due to a nighttime IIR bias as determined by the stand-alone approach, which originates from a calibration drift during day-to-night transitions. The largest bias is in June and July when IIR2 and IIR3 are ...

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Section: The Forward Radiative Transfer Model: 4amentioning

confidence: 99%

Long-term assessment of the CALIPSO Imaging Infrared Radiometer (IIR) calibration and stability through simulated and observed comparisons with MODIS/Aqua and SEVIRI/Meteosat

et al. 2017

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“…kCARTA includes a computationally intensive line-by-line nonlocal thermodynamic equilibrium (NLTE) model to calculate the effects for this CO 2 band. The model requires the kinetic temperature profile and NLTE vibrational temperatures of the strong bands in this region to compute the optical depths and Planck modifiers for the strong NLTE bands and the weaker LTE bands (Edwards et al, 1993(Edwards et al, , 1998Lopez-Puertas and Taylor, 2001;Zorn et al, 2002), which are then used to compute a monochromatic top-of-atmosphere nadir radiance.…”

Section: Nonlocal Thermodynamic Equilibrium Computationsmentioning

confidence: 99%

kCARTA: a fast pseudo line-by-line radiative transfer algorithm with analytic Jacobians, fluxes, nonlocal thermodynamic equilibrium, and scattering for the infrared

et al. 2020

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A fast pseudo-monochromatic radiative transfer package using a singular value decomposition (SVD) compressed atmospheric optical depth database has been developed, primarily for simulating radiances from hyperspectral sounding instruments (resolution ≥ 0.1 cm −1 ). The package has been tested extensively for clear-sky radiative transfer cases, using field campaign data and satellite instrument data. The current database uses HITRAN 2016 line parameters and is primed for use in the spectral region spanning 605 to 2830 cm −1 . Optical depths for other spectral regions (15-605 and 2830-45 000 cm −1 ) can also be generated for use by kCARTA. The clear-sky radiative transfer model computes the background thermal radiation quickly and accurately using a layer-varying diffusivity angle at each spectral point; it takes less than 30 s (on a 2.8 GHz core using four threads) to complete a radiance calculation spanning the infrared. The code can also compute non-local thermodynamic equilibrium effects for the 4 µm CO 2 region, as well as analytic temperature, gas and surface Jacobians. The package also includes flux and heating rate calculations and an interface to an infrared scattering model.

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“…In this case, F models how electromagnetic radiation propagates through an atmospheric state (x) to yield the radiance observed by IASI (y) with m number of spectral channels. The work presented in this paper uses the reference forward model (RFM) to simulate such spectral radi-ances (Dudhia, 2017). When the radiative transfer function is sufficiently linear about a reference state vector (x 0 ) of length n, F can be linearized according to…”

Section: Linear Retrieval Frameworkmentioning

confidence: 99%

“…The proposed method is linear in the sense that an estimate for each pixel is made only once, thus bypassing the iterative steps. By precalculating the RTM, the retrieval operates roughly 10 4 times faster than an iterative method using a line-by-line RTM, even when performance is sped up using monochromatic look-up tables (Vincent and Dudhia, 2017). Improving retrieval speed this dramatically comes at the cost of reduced accuracy compared to more robust iterative methods.…”

Section: Introductionmentioning

confidence: 99%

“…Second, all physical parameters affecting the spectral signal above instrument noise are jointly estimated to account for their influence upon the desired quantity (OCS total columns in this case). One popular alternative, as first described by von Clarmann et al (2001), is to create an effective measurement covariance that treats the components of the signal due to variations in parameters not explicitly retrieved as noise (Walker et al, 2011;Van Damme et al, 2014). The two methods (joint retrievals versus effective noise) produce identical results under idealized conditions.…”

Section: Introductionmentioning

confidence: 99%

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Fast retrievals of tropospheric carbonyl sulfide with IASI

Vincent

Dudhia

2017

Atmos. Chem. Phys.

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Abstract. Iterative retrievals of trace gases, such as carbonyl sulfide (OCS), from satellites can be exceedingly slow. The algorithm may even fail to keep pace with data acquisition such that analysis is limited to local events of special interest and short time spans. With this in mind, a linear retrieval scheme was developed to estimate total column amounts of OCS at a rate roughly 10 4 times faster than a typical iterative retrieval. This scheme incorporates two concepts not utilized in previously published linear estimates. First, all physical parameters affecting the signal are included in the state vector and accounted for jointly, rather than treated as effective noise. Second, the initialization point is determined from an ensemble of atmospheres based on comparing the model spectra to the observations, thus improving the linearity of the problem. All of the 2014 data from the Infrared Atmospheric Sounding Interferometer (IASI), instruments A and B, were analysed and showed spatial features of OCS total columns, including depletions over tropical rainforests, seasonal enhancements over the oceans, and distinct OCS features over land. Error due to assuming linearity was found to be on the order of 11 % globally for OCS. However, systematic errors from effects such as varying surface emissivity and extinction due to aerosols have yet to be robustly characterized. Comparisons to surface volume mixing ratio in situ samples taken by NOAA show seasonal correlations greater than 0.7 for five out of seven sites across the globe. Furthermore, this linear scheme was applied to OCS, but may also be used as a rapid estimator of any detectable trace gas using IASI or similar nadir-viewing instruments.

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Fast radiative transfer using monochromatic look-up tables

Cited by 11 publications

References 23 publications

Long-term assessment of the CALIPSO Imaging Infrared Radiometer (IIR) calibration and stability through simulated and observed comparisons with MODIS/Aqua and SEVIRI/Meteosat

Long-term assessment of the CALIPSO Imaging Infrared Radiometer (IIR) calibration and stability through simulated and observed comparisons with MODIS/Aqua and SEVIRI/Meteosat

kCARTA: a fast pseudo line-by-line radiative transfer algorithm with analytic Jacobians, fluxes, nonlocal thermodynamic equilibrium, and scattering for the infrared

Fast retrievals of tropospheric carbonyl sulfide with IASI

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