Atmospheric radiative transfer modeling: a summary of the AER codes

Abstract

• Retrievals of far infrared surface emissivity are reported for the first time, exploiting aircraft observations taken over Greenland. • The retrieved emissivity reaches values as low as 0.89 over the range 360-535 cm-1 , where the associated uncertainties are smallest. • Simulations of the surface emissivity are unable to simultaneously match retrievals in the far and mid infrared.

ARTS, the Atmospheric Radiative Transfer Simulator – version 2.2, the planetary toolbox edition

“…This particularly covers models for the micro-and millimeter-wave region (e.g., Liebe et al, 1993;Rosenkranz, 1993Rosenkranz, , 1998 but also several editions of the Clough-Kneizys-Davies continuum model (CKD; Clough et al, 1989Clough et al, , 2005, later enhanced by Mlawer and Tobin (MT_CKD;Mlawer et al, 2012), models that cover the entire millimeter to infrared spectral range. However, all of these continua have been developed with a focus on Earth observations.…”

“…From the early days onwards, high-level computer codes for energy flux computation and remote-sensing simulations developed somewhat independently, and not many complex codes can be used for both applications. Notable exceptions are libRadtran (Emde et al, 2016), which can be used for sensor simulation and flux calculation in the shortwave, and the family of models by AER (Atmospheric and Environmental Research; Clough et al, 2005). The tendency for models to specialize is often not driven by physics (for example, low-level solvers like DISORT (Stamnes et al, 1988) are suitable for both applications); it rather seems to be driven by practical constraints, resulting from the requirements of the two communities.…”

“…Out of an appreciation of this, a few RT codes have been developed that are fairly broad in scope, agnostic of a particular sensor, and used for a wide range of applications. Besides the already mentioned AER model family (Clough et al, 2005) and libRadtran (Emde et al, 2016), Dudhia (2017), and Schreier et al (2014) could be named here as general-purpose models for the infrared spectral range, as well as, of course, the Atmospheric Radiative Transfer Simulator (ARTS), the subject of this article.…”

Simulated retrievals for the remote sensing of CO<sub>2</sub>, CH<sub>4</sub>, CO, and H<sub>2</sub>O from geostationary orbit

“…We use realistic atmospheric profiles from the GEOS-CHEM global 3-D chemical transport model (Bey et al, 2001), with line positions and strengths obtained from the HITRAN 2008 molecular spectroscopic database. These are then input to a line-by-line radiative transfer model (LBLRTM) (Clough et al, 2005) to generate the optical depths (ODs). The state-of-the-art vector linearized discrete ordinate radiative transfer (VLIDORT) model (Spurr, 2006) generates the synthetic radiance data after its model output is convolved with the instrument line VLIDORT, a state-of-the-art radiative transfer model, generates the synthetic data after its model output is convolved with the instrument line shape (ILS) and random measurement noise is added.…”

A NIR spectrum of a hot Jupiter from the ground: Preliminary results

“…These analysis techniques were previously used to detect new molecular emission features from warm gas in circumstellar disks (Mandell et al 2008), reaching line-continuum contrast sensitivities of better than 1/2000 at L-band wavelengths. To correct for changing atmospheric conditions and airmass, we utilize terrestrial spectral transmittance models synthesized with the LBLRTM atmospheric modeling code (Clough et al 2005) based on line parameters from the HITRAN 2008 molecular database updated with the latest spectroscopic parameters (Rothman et al 2009). We fit models for every AB image set, enabling us to compensate for changes over the night and between stellar targets, and we perform the same telluric removal routine on both the science target and the calibration star.…”