The impact of the OSIRIS grating efficiency on radiance and trace-gas retrievals

2002 ◽  
Vol 80 (4) ◽  
pp. 469-481 ◽  
Author(s):  
C A McLinden ◽  
J C McConnell ◽  
K Strong ◽  
I C McDade ◽  
R L Gattinger ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Diffraction Grating ◽  
Infrared Imaging ◽  
Imaging System ◽  
Trace Gas ◽  
Radiative Transfer Model ◽  
Optical Absorption Spectroscopy ◽  
Transfer Model ◽  
Efficiency Coefficient ◽  
The Impact

The optical spectrograph and infrared imaging system (OSIRIS), launched in 2001, is a UV–visible diffraction-grating instrument designed to measure light scattered from the Earth's limb. Laboratory measurements of the OSIRIS diffraction-grating efficiency reveal a sensitivity to polarization including an anomalous structure of width 20–30 nm introduced into light polarized in a direction perpendicular to the grooves of the grating. A vector radiative-transfer model was used to generate synthetic OSIRIS spectra in an effort to examine the effect of this on radiances and trace-gas retrievals. Radiances that included grating effects were found to deviate by nearly 10% from those that did not and also contained the anomalous structure. Performing differential optical absorption spectroscopy (DOAS) on these spectra revealed errors in ozone apparent column densities of up to 80 DU. The size of the error was controlled mainly by the difference in polarization between the two DOAS spectra. Two possible correction methods were investigated. The first was to remove the grating effects by applying a correction factor to the raw radiances calculated using the vector radiative-transfer model. The second was to include the efficiency coefficient spectra in the DOAS fit. PACS Nos.: 42.68Mj, 98.55Qf

Impact of 3D cloud structures on tropospheric NO2 column measurements from UV-VIS sounders

2020 ◽  
Author(s):  
Huan Yu ◽  
Arve Kylling ◽  
Claudia Emde ◽  
Bernhard Mayer ◽  
Kerstin Stebel ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Mitigation Strategies ◽  
Trace Gas ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Vertical Column ◽  
Ice Clouds ◽  
Cloud Data ◽  
One Step ◽  
The Impact

<p>Operational retrievals of tropospheric trace gases from space-borne spectrometers are made using 1D radiative transfer models. To minimize cloud effects generally only partially cloudy pixels are analysed using simplified cloud contamination treatments based on radiometric cloud fraction estimates and photon path length corrections based on oxygen collision pair (O<sub>2</sub>-O<sub>2</sub>) or O<sub>2</sub>A-absorption band measurements. In reality, however, the impact of clouds can be much more complex, involving scattering of clouds in neighbouring pixels and cloud shadow effects. Therefore, to go one step further, other correction methods may be envisaged that use sub-pixel cloud information from co-located imagers. Such methods require an understanding of the impact of clouds on the real 3D radiative transfer. We quantify this impact using the MYSTIC 3D radiative transfer model. The generation of realistic 3D input cloud fields, needed by MYSTIC (or any other 3D radiative transfer model), is non-trivial. We use cloud data generated by the ICOsahedral Non-hydrostatic (ICON) atmosphere model for a region including Germany, the Netherlands and parts of other surrounding countries. The model simulates realistic liquid and ice clouds with a horizontal spatial resolution of 156 m and it has been validated against ground-based and satellite-based observational data.</p><p>As a trace gas example, we study NO<sub>2</sub>, a key tropospheric trace gas measured by the atmospheric Sentinels. The MYSTIC 3D model simulates visible spectra, which are ingested in standard DOAS retrieval algorithms to retrieve the NO<sub>2</sub> column amount. Spectra are simulated for a number of realistic cloud scenarios, snow free surface albedos, and solar and satellite geometries typical of low-earth and geostationary orbits. The retrieved NO<sub>2</sub> vertical column densities (VCD) are compared with the true values to identify conditions where 3D cloud effects lead to significant biases on the NO<sub>2</sub> VCDs. A variety of possible mitigation strategies for such pixels are then explored.</p>

Impact of 3D cloud structures on tropospheric NO2 column measurements from UV-VIS sounders

2021 ◽  
Author(s):  
Huan Yu ◽  
Arve Kylling ◽  
Claudia Emde ◽  
Bernhard Mayer ◽  
Michel Van Roozendael ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Synthetic Data ◽  
Sensitivity Study ◽  
Trace Gas ◽  
Radiative Transfer Model ◽  
Retrieval Algorithm ◽  
Transfer Model ◽  
Boundary Layer Clouds ◽  
Cloud Parameters ◽  
The Impact

<p>Operational retrievals of tropospheric trace gases from space-borne spectrometers are made using 1D radiative transfer models. To minimize cloud effects generally only partially cloudy pixels are analysed using simplified cloud contamination treatments based on radiometric cloud fraction estimates and photon path length corrections based on oxygen collision pair (O2-O2) or O2A-absorption band measurements. In reality, however, the impact of clouds can be much more complex, involving unresolved sub-pixel clouds, scattering of clouds in neighbouring pixels, and cloud shadow effects, such that 3D radiation scattering from unresolved boundary layer clouds may give significant biases in the trace gas retrievals. In order to quantify this impact, we use the MYSTIC 3D radiative transfer model to generate synthetic data. The realistic 3D cloud fields, needed for MYSTIC input, are generated by the ICOsahedral Non-hydrostatic (ICON) atmosphere model for a region including Germany, the Netherlands and parts of other surrounding countries. The retrieval algorithm is applied to the synthetic data and comparison to the known input trace gas concentrations yields the retrieval error due to 3D cloud effects. <br>In this study, we study NO2, which is a key tropospheric trace gas measured by TROPOMI and the future atmospheric Sentinels (S4 and S5). The work starts with a sensitivity study for the simulations with a simple 2D box cloud. The influence of cloud parameters (e.g., cloud top height, cloud optical thickness), observation geometry, and spatial resolution are studied, and the most significant dependences of retrieval biases are identified and investigated. Several approaches to correct the NO2 retrieval in the cloud shadow are explored and ultimately applied to both synthetic data with realistic 3D clouds and real observations.</p>

A vector radiative-transfer model for the Odin/OSIRIS project

2002 ◽  
Vol 80 (4) ◽  
pp. 375-393 ◽  
Author(s):  
C A McLinden ◽  
J C McConnell ◽  
E Griffioen ◽  
C T McElroy
Keyword(s):  
Radiative Transfer ◽  
Infrared Imaging ◽  
Radiative Transfer Equation ◽  
Imaging System ◽  
Scattered Light ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Weighting Functions ◽  
Uv Visible ◽  
Solution Parameters

A vector radiative-transfer code has been developed that is able to accurately and efficiently calculate radiance and polarization scattered from Earth's limb. A primary application of this code will be towards generating weighting functions, based on calculated limb radiances, for the retrieval of trace gases (O3, NO2, BrO, OClO, and O4) from the optical spectrograph and infrared imaging system (OSIRIS). OSIRIS is a UV–visible instrument on board the Odin satellite that measures limb-scattered light. This model solves the vector radiative-transfer equation using an iterative technique simultaneously in both plane-parallel and spherical-shell atmospheres. OSIRIS simulated limb radiance and polarization and OSIRIS weighting functions are presented along with a discussion of the numerical solution parameters, model intercomparisons and timings, and necessary model improvements. Overall agreement with other models was found to be very good and model speed is comparable to a fast finite-difference code. A set of OSIRIS reference atmospheres have been compiled for use with radiative-transfer models. Each of the 216 atmospheres (18 latitudes × 12 months) include profiles of air, pressure, temperature, ozone, NO2, BrO, and stratospheric aerosols.PACS Nos.: 42.68-w, 94.10Gb

The impact of sea-glint upon limb radiance

2007 ◽  
Vol 85 (11) ◽  
pp. 1159-1176
Author(s):  
D A Degenstein ◽  
A E Bourassa ◽  
E J Llewellyn ◽  
N D Lloyd
Keyword(s):  
Radiative Transfer ◽  
Zenith Angle ◽  
Arabian Sea ◽  
Solar Zenith Angle ◽  
Imaging System ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Test Case ◽  
Infra Red ◽  
The Impact

A simple radiative transfer model is developed to calculate the contribution of sea-glint to limb radiance. It is shown that the absolute sea-glint signal peaks between 70° and 80° solar zenith angle. Sea-glint can contribute 10–15% of the total limb radiance at wavelengths greater than 600 nm, which is several times brighter than an equivalent 5% reflecting Lambertian ocean surface. A test case was identified over the Arabian Sea in October 2002 and the model results compared to limb observations from the Optical Spectrograph and Infra-Red Imaging System (OSIRIS) on-board the Odin satellite. PACS Nos.: 94.10.Gb, 93.85.+q, 42.68.Ay, 42.68.Mj

3D Remote Sensing of Trace Gas Distributions with HAIDI (Heidelberg Airborne Imaging DOAS Instrument) - Power Plant and Ship Emissions observed during the EMeRGe Campaigns

2021 ◽  
Author(s):  
Katja Bigge ◽  
Udo Frieß ◽  
Denis Pöhler ◽  
Ulrich Platt
Keyword(s):  
Remote Sensing ◽  
Radiative Transfer ◽  
Power Plants ◽  
Trace Gases ◽  
Trace Gas ◽  
Radiative Transfer Model ◽  
Optical Absorption Spectroscopy ◽  
Transfer Model ◽  
Flight Altitude ◽  
Airborne Imaging

<p><span>Compared to ground-based or satellite measurements, atmospheric observations based on aircraft missions have many advantages, such as the potential to observe a large atmospheric volume using remote sensing measurements, among which Differential Optical Absorption Spectroscopy (DOAS) is a well established method for the observation of integrated trace gas concentrations along the light path. However, the interpretation of remote spectroscopic measurements using scattered sunlight is complicated due to the lack of prior knowledge on the light paths between sun and detector, and thus on the observed air volume. Using radiative transfer calculations, quantities commonly derived from DOAS measurements are integrated vertical columns of various trace gases, providing no information about their vertical distribution.</span></p><p><span>On the ground, tomographic approaches have been used to reconstruct the spatial distribution of trace gases by using multiple viewing directions and detectors. <!-- Bislang eigentlich höchstens 2D (Pöhler et al) oder 1D (MAX-DOAS Profil-retrieval) -->HAIDI, the Heidelberg Airborne Imaging DOAS Instrument, was designed to transfer this concept to the air. In addition to its excellent temporal and spatial resolution (40 m x 40 m at 1.5 km flight altitude, 266 m x 266 m at 10 km flight altitude, at 10 ms temporal resolution), HAIDI uses three separate scanning telescopes aimed at +/-45° forward- and backward looking angles and the nadir direction. In combination with a 3D radiative transfer model, this allows a reconstruction of the 3D distribution of the detected trace gases in the vicinity of the flight track.</span></p><p><span>HAIDI joined the EMerGe (Effect of Megacities on the Transport and transformation of Pollutants on the Regional to Global Scales) missions on HALO, the High Altitude and LOng range research aircraft based at DLR (German Aerospace Center) in Oberpfaffenhofen, Germany. The EMerGe missions targeted the emission outflows of megacities to investigate their compositions and the atmospheric impact of urban pollution in Europe (July 2017) and Asia (March 2018). HAIDI observed a number of trace gases such as NO<sub>2,</sub> SO<sub>2</sub> and HCHO. For NO<sub>2</sub> and SO<sub>2</sub> in particular, strong plumes originating from power plants and ships were found, which were then used for inversion of the 3D distribution of the plume and emission estimation. Here we present the method and results of the HAIDI measurements during the EMeRGe missions.</span></p>

scholarly journals Performance of the line-by-line radiative transfer model (LBLRTM) for temperature and species retrievals: IASI case studies from JAIVEx

2009 ◽  
Vol 9 (19) ◽  
pp. 7397-7417 ◽  
Author(s):  
M. W. Shephard ◽  
S. A. Clough ◽  
V. H. Payne ◽  
W. L. Smith ◽  
S. Kireev ◽  
...  
Keyword(s):  
Water Vapor ◽  
Radiative Transfer ◽  
Trace Gas ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Line Intensities ◽  
Remote Sounding ◽  
Instrument Noise ◽  
Large Peak ◽  
Line Coupling

Abstract. Presented here are comparisons between the Infrared Atmospheric Sounding instrument (IASI) and the "Line-By-Line Radiative Transfer Model" (LBLRTM). Spectral residuals from radiance closure studies during the IASI JAIVEx validation campaign provide insight into a number of spectroscopy issues relevant to remote sounding of temperature, water vapor and trace gases from IASI. In order to perform quality IASI trace gas retrievals, the temperature and water vapor fields must be retrieved as accurately as possible. In general, the residuals in the CO2 ν2 region are of the order of the IASI instrument noise. However, outstanding issues with the CO2 spectral regions remain. There is a large residual ~−1.7 K in the 667 cm−1 Q-branch, and residuals in the CO2 ν2 and N2O/CO2 ν3 spectral regions that sample the troposphere are inconsistent, with the N2O/CO2 ν3 region being too negative (warmer) by ~0.7 K. Residuals on this lower wavenumber side of the CO2 ν3 band will be improved by line parameter updates, while future efforts to reduce the residuals reaching ~−0.5 K on the higher wavenumber side of the CO2 ν3 band will focus on addressing limitations in the modeling of the CO2 line shape (line coupling and duration of collision) effects. Brightness temperature residuals from the radiance closure studies in the ν2 water vapor band have standard deviations of ~0.2–0.3 K with some large peak residuals reaching ±0.5–1.0 K. These are larger than the instrument noise indicating that systematic errors still remain. New H2O line intensities and positions have a significant impact on the retrieved water vapor, particularly in the upper troposphere where the water vapor retrievals are 10% drier when using line intensities compared with HITRAN 2004. In addition to O3, CH4, and CO, of the IASI instrument combined with an accurate forward model allows for the detection of minor species with weak atmospheric signatures in the nadir radiances, such as HNO3 and OCS.

Polar  Stratospheric Clouds detection at Belgrano II Antarctic station from DOAS measurements

2021 ◽  
Author(s):  
Laura Gómez Martín ◽  
Daniel Toledo ◽  
Margarita Yela ◽  
Cristina Prados-Román ◽  
José Antonio Adame ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Color Index ◽  
Radiative Transfer Model ◽  
Optical Absorption Spectroscopy ◽  
Transfer Model ◽  
Meteorological Model ◽  
Weather Forecasts ◽  
Stratospheric Temperature ◽  
Stratospheric Clouds

<p><span>Ground-based zenith DOAS (Differential Optical Absorption Spectroscopy) measurements have been used to detect and estimate the altitude of PSCs over Belgrano II Antarctic station during the polar sunrise seasons of 2018 and 2019. The method used in this work studies the evolution of the color index (CI) during twilights. The CI has been defined here as the ratio of the recorded signal at 520 and 420 nm. In the presence of PSCs, the CI shows a maximum at a given solar zenith angle (SZA). The value of such SZA depends on the altitude of the PSC. By using a spherical Monte Carlo radiative transfer model (RTM), the method has been validated and a function relating the SZA of the CI maximum and the PSC altitude has been calculated. Model simulations also show that PSCs can be detected and their altitude can be estimated even in presence of optically thin tropospheric clouds or aerosols. Our results are in good agreement with the stratospheric temperature evolution obtained through the ERA5 data reanalysis from the global meteorological model ECMWF (European Centre for Medium Range Weather Forecasts) and the PSCs observations from CALIPSO (Cloud-Aerosol-Lidar and Infrared Pathfinder Satellite Observations).</span></p><p><span>The methodology used in this work could also be applied to foreseen and/or historical measurements obtained with ground-based spectrometers such e. g. the DOAS instruments dedicated to trace gas observation in Arctic and Antarctic sites. This would also allow to investigate the presence and long-term evolution of PSCs.</span></p><p><span><strong>Keywords: </strong>Polar stratospheric clouds; color index; radiative transfer model; visible spectroscopy.</span></p>

Modelling understory light availability in a heterogeneous landscape using drone-derived structural parameters and a 3D radiative transfer model

2020 ◽  
Author(s):  
Dominic Fawcett ◽  
Jonathan Bennie ◽  
Karen Anderson
Keyword(s):  
Radiative Transfer ◽  
Vegetation Index ◽  
Structural Parameters ◽  
Point Clouds ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Area Index ◽  
Vegetation Height ◽  
Plant Area Index ◽  
The Impact

<p>The light environment within vegetated landscapes is a key driver of microclimate, creating varied habitats over small spatial extents and controls the distribution of understory plant species. Modelling spatial variations of light at these scales requires finely resolved (< 1 m) information on topography and canopy properties. We demonstrate an approach to modelling spatial distributions and temporal progression of understory photosynthetically active radiation (PAR) utilising a three dimensional radiative transfer model (discrete anisotropic radiative transfer model: DART) where the scene is parameterised by drone-based data.</p><p>The study site, located in west Cornwall, UK, includes a small mixed woodland as well as isolated free-standing trees. Data were acquired from March to August 2019. Vegetation height and distribution were derived from point clouds generated from drone image data using structure-from-motion (SfM) photogrammetry. These data were supplemented by multi-temporal multispectral imagery (Parrot Sequoia camera) which were used to generate an empirical model by relating a vegetation index to plant area index derived from hemispherical photography taken over the same time period. Simulations of the 3D radiative budget were performed for the PAR wavelength interval (400 – 700 nm) using DART.</p><p>Besides maps of instantaneous above and below canopy irradiance, we provide models of daily light integrals (DLI) which are assessed against field validation measurements with PAR quantum sensors. We find relatively good agreement for simulated PAR in the woodland. The impact of simplifying assumptions regarding leaf angular distributions and optical properties are discussed. Finally, further opportunities which fine-grained drone data can provide in a radiative transfer context are highlighted.</p>

scholarly journals Parameterizing radiative transfer to convert MAX-DOAS dSCDs into near-surface box averaged mixing ratios and vertical profiles

2012 ◽  
Vol 5 (5) ◽  
pp. 7641-7673 ◽  
Author(s):  
R. Sinreich ◽  
A. Merten ◽  
L. Molina ◽  
R. Volkamer
Keyword(s):  
Boundary Layer ◽  
Radiative Transfer ◽  
Mexico City ◽  
Vertical Gradient ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Transfer Model ◽  
Model Calculations ◽  
Near Surface ◽  
Mixing Ratios

Abstract. We present a novel parameterization method to convert Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) differential Slant Column Densities (dSCDs) into near-surface box averaged volume mixing ratios. The approach is applicable inside the planetary boundary layer under conditions with significant aerosol load, does not require a-priori assumptions about the trace gas vertical distribution and builds on the increased sensitivity of MAX-DOAS near the instrument altitude. It parameterizes radiative transfer model calculations and significantly reduces the computational effort. The biggest benefit of this method is that the retrieval of an aerosol profile, which usually is necessary for deriving a trace gas concentration from MAX-DOAS dSCDs, is not needed. The method is applied to NO2 MAX-DOAS dSCDs recorded during the Mexico City Metropolitan Area 2006 (MCMA-2006) measurement campaign. The retrieved volume mixing ratios of two elevation angles (1° and 3°) are compared to volume mixing ratios measured by two long-path (LP)-DOAS instruments located at the same site. Measurements are found to agree well during times when vertical mixing is expected to be strong. However, inhomogeneities in the air mass above Mexico City can be detected by exploiting the different horizontal and vertical dimensions probed by MAX-DOAS measurements at different elevation angles, and by LP-DOAS. In particular, a vertical gradient in NO2 close to the ground can be observed in the afternoon, and is attributed to reduced mixing coupled with near surface emission. The existence of a vertical gradient in the lower 250 m during parts of the day shows the general challenge of sampling the boundary layer in a representative way and emphasizes the need of vertically resolved measurements.

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