scholarly journals A sensitivity study on the retrieval of aerosol vertical profiles using the oxygen A-band

2015 ◽  
Vol 8 (11) ◽  
pp. 11853-11891
Author(s):  
S. F. Colosimo ◽  
V. Natraj ◽  
S. P. Sander ◽  
J. Stutz
Keyword(s):  
High Resolution ◽  
Information Content ◽  
Spectral Resolution ◽  
Surface Albedo ◽  
Dynamic Range ◽  
The Arctic ◽  
Transfer Model ◽  
Aerosol Extinction ◽  
Low Resolution ◽  
Tropospheric Aerosol

Abstract. Atmospheric absorption in the O2 A-band (12 950–13 200 cm−1) offers a unique opportunity to retrieve aerosol extinction profiles from space-borne measurements due to the large dynamic range of optical thickness in that spectral region. Absorptions in strong O2 lines are saturated; therefore, any radiance measured in these lines originates from scattering in the upper part of the atmosphere. Outside of O2 lines, or in weak lines, the atmospheric column absorption is small, and light penetrates to lower atmospheric layers, allowing for the quantification of aerosols and other scatterers near the surface. While the principle of aerosol profile retrieval using O2 A-band absorption from space is well known, a thorough quantification of the information content, i.e., the amount of vertical profile information that can be obtained, and the dependence of the information content on the spectral resolution of the measurements, has not been thoroughly conducted. Here, we use the linearized vector radiative transfer model VLIDORT to perform spectrally resolved simulations of atmospheric radiation in the O2 A-band in the presence of aerosol for four different generic scenarios: Urban, Highly polluted, Elevated layer, and Marine–Arctic. The high-resolution radiances emerging from the top of the atmosphere are degraded to different spectral resolutions, simulating spectrometers with different resolving powers. We use optimal estimation theory to quantify the information content in the aerosol profile retrieval with respect to different aerosol parameters and instrument spectral resolutions. The simulations show that better spectral resolution generally leads to an increase in the total amount of information that can be retrieved, with the number of degrees of freedom (DoF) varying between 0.34–2.11 at low resolution (5 cm−1) to 3.43–5.92 at high resolution (0.05 cm−1) for the four different cases. A particularly strong improvement was found in the retrieval of tropospheric aerosol extinction profiles in the lowest 5 km of the atmosphere. At high spectral resolutions (0.05 cm−1), 1.18–1.7 and 1.31–2.34 DoF can be obtained in the lower (0–2 km) and middle (2–5 km) troposphere, respectively, for the different cases. Consequently a separation of lower and mid tropospheric aerosols is possible, implying the feasibility of identification of elevated biomass burning aerosol plumes (Elevated layer scenario). We find that higher single scattering albedo (SSA) allows for the retrieval of more aerosol information. However, the dependence on SSA is weaker at higher spectral resolutions. The Marine (surface albedo 0.05) and Arctic (surface albedo 0.9) cases show that the dependence of DoF on the surface albedo decreases with higher resolution. While at low resolution (5 cm−1) the DoF is 1 for the Marine case and 0.34 for the Arctic case, the DoF considerably increase at 0.05 cm−1 resolution to 3.8 and 3.4, respectively. In the Arctic case this is an improvement of a factor of 10. The simulations also reveal a moderate dependence of information content on the integration time of the measurements, i.e., the noise of the spectra. However, our results indicate that a larger increase in DoF is obtained by an increase in spectral resolution despite lower signal-to-noise ratios.

scholarly journals A sensitivity study on the retrieval of aerosol vertical profiles using the oxygen A-band

2016 ◽  
Vol 9 (4) ◽  
pp. 1889-1905 ◽  
Author(s):  
Santo Fedele Colosimo ◽  
Vijay Natraj ◽  
Stanley P. Sander ◽  
Jochen Stutz
Keyword(s):  
High Resolution ◽  
Information Content ◽  
Biomass Burning ◽  
Spectral Resolution ◽  
Surface Albedo ◽  
The Arctic ◽  
Transfer Model ◽  
Aerosol Extinction ◽  
Low Resolution ◽  
Tropospheric Aerosol

Abstract. Atmospheric absorption in the O2 A-band (12 950–13 200 cm−1) offers a unique opportunity to retrieve aerosol extinction profiles from space-borne measurements due to the large dynamic range of optical thickness in that spectral region. Absorptions in strong O2 lines are saturated; therefore, any radiance measured in these lines originates from scattering in the upper part of the atmosphere. Outside of O2 lines, or in weak lines, the atmospheric column absorption is small, and light penetrates to lower atmospheric layers, allowing for the quantification of aerosols and other scatterers near the surface.While the principle of aerosol profile retrieval using O2 A-band absorption from space is well-known, a thorough quantification of the information content, i.e., the amount of vertical profile information that can be obtained, and the dependence of the information content on the spectral resolution of the measurements, has not been thoroughly conducted. Here, we use the linearized vector radiative transfer model VLIDORT to perform spectrally resolved simulations of atmospheric radiation in the O2 A-band for four different aerosol extinction profile scenarios: urban (urban–rural areas), highly polluted (megacity areas with large aerosol extinction), elevated layer (identifying elevated plumes, for example for biomass burning) and low extinction (representative of small aerosol extinction, such as vegetated, marine and arctic areas). The high-resolution radiances emerging from the top of the atmosphere measurements are degraded to different spectral resolutions, simulating spectrometers with different resolving powers. We use optimal estimation theory to quantify the information content in the aerosol profile retrieval with respect to different aerosol parameters and instrument spectral resolutions. The simulations show that better spectral resolution generally leads to an increase in the total amount of information that can be retrieved, with the number of degrees of freedom (DoF) varying between 0.34–2.01 at low resolution (5 cm−1) to 3.43–5.38 at high resolution (0.05 cm−1) among all the different cases. A particularly strong improvement was found in the retrieval of tropospheric aerosol extinction profiles in the lowest 5 km of the atmosphere. At high spectral resolutions (0.05 cm−1), 1.18–1.48 and 1.31–1.96 DoF can be obtained in the lower (0–2 km) and middle (2–5 km) troposphere, respectively, for the different cases. Consequently, a separation of lower and mid tropospheric aerosols is possible, implying the feasibility of identification of elevated biomass burning aerosol plumes (elevated layer scenario). We find that a higher single scattering albedo (SSA) allows for the retrieval of more aerosol information. However, the dependence on SSA is weaker at higher spectral resolutions. The vegetation (surface albedo 0.3), marine (surface albedo 0.05) and arctic (surface albedo 0.9) cases show that the dependence of DoF on the surface albedo decreases with higher resolution. At low resolution (5 cm−1), the DoF are 1.19 for the marine case, 0.73 for the vegetation case and 0.34 for the arctic case, but increase considerably at 0.05 cm−1 resolution to 3.84 (marine) and 3.43 (both vegetation and arctic), showing an improvement of a factor of 10 for the arctic case. Vegetation and arctic case also show the same DoF at higher resolution, showing that an increase of albedo beyond a certain value, i.e., 0.3 in our case, does not lead to a larger information content. The simulations also reveal a moderate dependence of information content on the integration time of the measurements, i.e., the noise of the spectra. However, our results indicate that a larger increase in DoF is obtained by an increase in spectral resolution despite lower signal-to-noise ratios.

scholarly journals Estimate of the D/H ratio in the Martian upper atmosphere from the low spectral resolution mode of MAVEN/IUVS

2020 ◽  
Author(s):  
Jean-Yves Chaufray ◽  
Majd Mayyasi ◽  
Michael Chaffin ◽  
Justin Deighan ◽  
Dolon Bhattacharyya ◽  
...  
Keyword(s):  
High Resolution ◽  
Spectral Resolution ◽  
Quantitative Information ◽  
Upper Atmosphere ◽  
Vertical Profiles ◽  
Low Resolution ◽  
Mars Atmosphere

<p>The recent observations performed with the high-resolution “echelle mode” by the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission indicated large deuterium brightness near Ls=270°. The deuterium brightness observed at the beginning of the mission, when Mars was close to its perihelion show brightness ~ 1 kR much larger than the first deuterium detection from Earth ~ 20-50R in 20-21 January 1997 (Ls = 67°). This low brightness of the deuterium emission is consistent with the lack of deuterium observation with the echelle mode of IUVS at solar longitudes around aphelion (Ls = 71°). During southern summer (Ls = 270°), especially near the terminator, the Lyman-α emission observed at 121.6 nm with the “low resolution mode” presents some vertical profiles that were not reproducible with models including only the emission from the thermal hydrogen population. In this study, we investigate the possibility to derive quantitative information on the D/H ratio at Mars from the vertical Lyman-α profiles observed with the “low resolution mode”, and the main limits of the method.</p>

Radiative forcing over the Arctic of aerosols from the August 2017 Canadian and Greenlandic wildfires

2021 ◽  
Author(s):  
Filippo Calì Quaglia ◽  
Daniela Meloni ◽  
Alcide Giorgio di Sarra ◽  
Tatiana Di Iorio ◽  
Virginia Ciardini ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Radiative Forcing ◽  
Solar Zenith Angle ◽  
Surface Albedo ◽  
High Arctic ◽  
The Arctic ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Aerosol Layer ◽  
Radiative Effect

<p>Extended and intense wildfires occurred in Northern Canada and, unexpectedly, on the Greenlandic West coast during summer 2017. The thick smoke plume emitted into the atmosphere was transported to the high Arctic, producing one of the largest impacts ever observed in the region. Evidence of Canadian and Greenlandic wildfires was recorded at the Thule High Arctic Atmospheric Observatory (THAAO, 76.5°N, 68.8°W, www.thuleatmos-it.it) by a suite of instruments managed by ENEA, INGV, Univ. of Florence, and NCAR. Ground-based observations of the radiation budget have allowed quantification of the surface radiative forcing at THAAO. </p><p>Excess biomass burning chemical tracers such as CO, HCN, H2CO, C2H6, and NH3 were  measured in the air column above Thule starting from August 19 until August 23. The aerosol optical depth (AOD) reached a peak value of about 0.9 on August 21, while an enhancement of wildfire compounds was  detected in PM10. The measured shortwave radiative forcing was -36.7 W/m2 at 78° solar zenith angle (SZA) for AOD=0.626.</p><p>MODTRAN6.0 radiative transfer model (Berk et al., 2014) was used to estimate the aerosol radiative effect and the heating rate profiles at 78° SZA. Measured temperature profiles, integrated water vapour, surface albedo, spectral AOD and aerosol extinction profiles from CALIOP onboard CALIPSO were used as model input. The peak  aerosol heating rate (+0.5 K/day) was  reached within the aerosol layer between 8 and 12 km, while the maximum radiative effect (-45.4 W/m2) is found at 3 km, below the largest aerosol layer.</p><p>The regional impact of the event that occurred on August 21 was investigated using a combination of atmospheric radiative transfer modelling with measurements of AOD and ground surface albedo from MODIS. The aerosol properties used in the radiative transfer model were constrained by in situ measurements from THAAO. Albedo data over the ocean have been obtained from Jin et al. (2004). Backward trajectories produced through HYSPLIT simulations (Stein et al., 2015) were also employed to trace biomass burning plumes.</p><p>The radiative forcing efficiency (RFE) over land and ocean was derived, finding values spanning from -3 W/m2 to -132 W/m2, depending on surface albedo and solar zenith angle. The fire plume covered a vast portion of the Arctic, with large values of the daily shortwave RF (< -50 W/m2) lasting for a few days. This large amount of aerosol is expected to influence cloud properties in the Arctic, producing significant indirect radiative effects.</p>

scholarly journals Lunar Image Fusion using Wavelet Transform

2013 ◽  
pp. 211-215
Author(s):  
Dr.Vani. K ◽  
Anto. A. Micheal
Keyword(s):  
High Resolution ◽  
Image Fusion ◽  
Spatial Resolution ◽  
Spectral Resolution ◽  
Lunar Surface ◽  
High Spatial Resolution ◽  
Multispectral Image ◽  
High Spectral Resolution ◽  
Low Resolution ◽  
Mineral Mapping

This paper is an attempt to combine high resolution panchromatic lunar image with low resolution multispectral lunar image to produce a composite image using wavelet approach. There are many sensors that provide us image data about the lunar surface. The spatial resolution and spectral resolution is unique for each sensor, thereby resulting in limitation in extraction of information about the lunar surface. The high resolution panchromatic lunar image has high spatial resolution but low spectral resolution; the low resolution multispectral image has low spatial resolution but high spectral resolution. Extracting features such as craters, crater morphology, rilles and regolith surfaces with a low spatial resolution in multispectral image may not yield satisfactory results. A sensor which has high spatial resolution can provide better information when fused with the high spectral resolution. These fused image results pertain to enhanced crater mapping and mineral mapping in lunar surface. Since fusion using wavelet preserve spectral content needed for mineral mapping, image fusion has been done using wavelet approach.

3. LYMAN Technical Description

1988 ◽  
Vol 7 (3) ◽  
pp. 290-334
Keyword(s):  
High Resolution ◽  
Spectral Range ◽  
Spectral Resolution ◽  
Grazing Incidence ◽  
Field Of View ◽  
Type Ii ◽  
Low Resolution ◽  
Service Module ◽  
Technical Description ◽  
Extreme Uv

The LYMAN Observatory payload is mounted on a service module which which offers pointing, power and telemetry and which has substantial commonality with the SOHO concept. The payload consists of a Wolter-Schwartzschild Type II Grazing Incidence telescope with monolithic primary and secondary elements feeding far-UV and extreme-UV spectrographs. It is designed to offer an effective collecting area of greater than 10 cm2 over a limited field of view with a spectral resolution on astronomical targets of 30000 in the prime ( λ900 - 1250 Å ) spectral range. This will allow high-resolution observations on sources as faint as 15 mag. LYMAN will also be capable of high resolution observations up to 1800Å, and will offer low-resolution spectroscopy in the extreme-UV down to about 100Å.

scholarly journals Global stratospheric aerosol extinction profile retrievals from SCIAMACHY limb-scatter observations

2012 ◽  
Vol 5 (4) ◽  
pp. 5993-6035 ◽  
Author(s):  
F. Ernst ◽  
C. von Savigny ◽  
A. Rozanov ◽  
V. Rozanov ◽  
K.-U. Eichmann ◽  
...  
Keyword(s):  
Surface Albedo ◽  
Optimal Estimation ◽  
Stratospheric Aerosol ◽  
Visible Spectral Range ◽  
Radiative Transfer Model ◽  
Retrieval Algorithm ◽  
Transfer Model ◽  
Aerosol Extinction ◽  
Index Approach ◽  
The Impact

Abstract. Stratospheric aerosol extinction profiles are retrieved from SCIAMACHY/Envisat limb-scatter observations in the visible spectral range. The retrieval algorithm is based on a colour-index approach using the normalized limb-radiance profiles at 470 nm and 750 nm wavelength. The optimal estimation approach in combination with the radiative transfer model SCIATRAN is employed for the retrievals. This study presents a detailed description of the retrieval algorithm, and a sensitivity analysis investigating the impact of the most important parameters that affect the aerosol extinction profile retrieval accuracy. It is found that the parameter with the largest impact is surface albedo, particularly for SCIAMACHY observations in the Southern Hemisphere where the error in stratospheric aerosol extinction can be up to 50% if the surface albedo is not well known. The effect of errors in the assumed ozone and neutral density profiles on the aerosol profile retrievals is with generally less than 6% relatively small. The aerosol extinction profiles retrieved from SCIAMACHY are compared with co-located SAGE II solar occultation measurements of stratospheric aerosol extinction during the period 2003–2005. The mean aerosol extinction profiles averaged over all co-locations agree to within 20% between 15 and 35 km altitude. However, larger differences are observed at specific latitudes.

scholarly journals Self-Dictionary Regression for Hyperspectral Image Super-Resolution

2018 ◽  
Vol 10 (10) ◽  
pp. 1574 ◽  
Author(s):  
Dongsheng Gao ◽  
Zhentao Hu ◽  
Renzhen Ye
Keyword(s):  
High Resolution ◽  
Spatial Resolution ◽  
Spectral Resolution ◽  
Cross Correlation ◽  
Hyperspectral Image ◽  
High Spatial Resolution ◽  
Super Resolution ◽  
High Spectral Resolution ◽  
Low Resolution ◽  
Image Super Resolution

Due to sensor limitations, hyperspectral images (HSIs) are acquired by hyperspectral sensors with high-spectral-resolution but low-spatial-resolution. It is difficult for sensors to acquire images with high-spatial-resolution and high-spectral-resolution simultaneously. Hyperspectral image super-resolution tries to enhance the spatial resolution of HSI by software techniques. In recent years, various methods have been proposed to fuse HSI and multispectral image (MSI) from an unmixing or a spectral dictionary perspective. However, these methods extract the spectral information from each image individually, and therefore ignore the cross-correlation between the observed HSI and MSI. It is difficult to achieve high-spatial-resolution while preserving the spatial-spectral consistency between low-resolution HSI and high-resolution HSI. In this paper, a self-dictionary regression based method is proposed to utilize cross-correlation between the observed HSI and MSI. Both the observed low-resolution HSI and MSI are simultaneously considered to estimate the endmember dictionary and the abundance code. To preserve the spectral consistency, the endmember dictionary is extracted by performing a common sparse basis selection on the concatenation of observed HSI and MSI. Then, a consistent constraint is exploited to ensure the spatial consistency between the abundance code of low-resolution HSI and the abundance code of high-resolution HSI. Extensive experiments on three datasets demonstrate that the proposed method outperforms the state-of-the-art methods.

scholarly journals A synthetic data set of high-spectral resolution infrared spectra for the Arctic atmosphere

2016 ◽  
Author(s):  
C. J. Cox ◽  
P. M. Rowe ◽  
S. P. Neshyba ◽  
V. P. Walden
Keyword(s):  
Remote Sensing ◽  
Radiative Transfer ◽  
Infrared Spectra ◽  
Spectral Resolution ◽  
High Spectral Resolution ◽  
The Arctic ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Data Set ◽  
Atmospheric State

Abstract. Retrievals of cloud microphysical and macrophysical properties from ground-based and satellite-based infrared remote sensing instruments are critical for understanding clouds. However, retrieval uncertainties are difficult to quantify without a standard for comparison. This is particularly true over the polar regions where surface-based data for a cloud climatology are sparse, yet clouds represent a major source of uncertainty in weather and climate models. We describe a synthetic high-spectral resolution infrared data set that is designed to facilitate validation and development of cloud retrieval algorithms for surface- and satellite-based remote sensing instruments. Since the data set is calculated using pre-defined cloudy atmospheres, the properties of the cloud and atmospheric state are known a priori. The atmospheric state used for the simulations is drawn from radiosonde measurements made at the North Slope of Alaska (NSA) Atmospheric Radiation Measurement (ARM) site at Barrow, Alaska (71.325° N, 156.615° W), a location that is generally representative of the western Arctic. The cloud properties for each simulation are selected from statistical distributions derived from past field measurements. Upwelling (at 60 km) and downwelling (at the surface) infrared spectra are simulated for 222 cloudy cases from 50–3000 cm−1 (3.3 to 200 μm) at monochromatic (line-by-line) resolution at a spacing of ~ 0.01 cm−1 using the Line-by-line Radiative Transfer Model (LBLRTM) and the discrete-ordinate-method radiative transfer code (DISORT). These spectra are freely available for interested researchers from the ACADIS data repository (doi:10.5065/D61J97TT).

Instrumental Resolution Considerations for Fourier Transform Infrared Gas-Phase Spectroscopy

1997 ◽  
Vol 51 (8) ◽  
pp. 1159-1169 ◽  
Author(s):  
P. Jaakkola ◽  
J. D. Tate ◽  
M. Paakkunainen ◽  
J. Kauppinen ◽  
P. Saarinen
Keyword(s):  
Fourier Transform ◽  
High Resolution ◽  
Gas Phase ◽  
Dynamic Range ◽  
Fourier Transform Infrared ◽  
High Signal ◽  
Low Resolution ◽  
Instrumental Resolution ◽  
Ft Ir ◽  
Gas Phase Spectroscopy

Instrumental resolution has a significant effect on the performance of Fourier transform infrared (FT-IR) spectrometers used for gasphase analysis. Low-resolution FT-IR spectroscopy offers some valuable advantages compared with the traditional high-resolution FT-IR gas-phase spectroscopy, especially in nonlaboratory environments. First, high signal-to-noise ratio (SNR) spectra can be acquired in field conditions without the use of traditional liquid nitrogen-cooled detectors. Second, the dynamic range for quantitative analysis is larger for low-resolution spectroscopy than for high-resolution due to the lower absorbance values and lower noise levels. Third, spectral analysis speed is increased and data storage requirements are substantially reduced. The purpose of this study was to investigate the effect of instrumental resolution on FT-IR gas-phase analysis. The effects of spectral resolution on sensitivity, selectivity, accuracy, precision, spectral overlap, dynamic range, and nonlinearity are separately discussed.

scholarly journals A synthetic data set of high-spectral-resolution infrared spectra for the Arctic atmosphere

2016 ◽  
Vol 8 (1) ◽  
pp. 199-211 ◽  
Author(s):  
Christopher J. Cox ◽  
Penny M. Rowe ◽  
Steven P. Neshyba ◽  
Von P. Walden
Keyword(s):  
Remote Sensing ◽  
Radiative Transfer ◽  
Infrared Spectra ◽  
Spectral Resolution ◽  
High Spectral Resolution ◽  
The Arctic ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Data Set ◽  
Atmospheric State

Abstract. Cloud microphysical and macrophysical properties are critical for understanding the role of clouds in climate. These properties are commonly retrieved from ground-based and satellite-based infrared remote sensing instruments. However, retrieval uncertainties are difficult to quantify without a standard for comparison. This is particularly true over the polar regions, where surface-based data for a cloud climatology are sparse, yet clouds represent a major source of uncertainty in weather and climate models. We describe a synthetic high-spectral-resolution infrared data set that is designed to facilitate validation and development of cloud retrieval algorithms for surface- and satellite-based remote sensing instruments. Since the data set is calculated using pre-defined cloudy atmospheres, the properties of the cloud and atmospheric state are known a priori. The atmospheric state used for the simulations is drawn from radiosonde measurements made at the North Slope of Alaska (NSA) Atmospheric Radiation Measurement (ARM) site at Barrow, Alaska (71.325° N, 156.615° W), a location that is generally representative of the western Arctic. The cloud properties for each simulation are selected from statistical distributions derived from past field measurements. Upwelling (at 60 km) and downwelling (at the surface) infrared spectra are simulated for 260 cloudy cases from 50 to 3000 cm−1 (3.3 to 200 µm) at monochromatic (line-by-line) resolution at a spacing of  ∼  0.01 cm−1 using the Line-by-line Radiative Transfer Model (LBLRTM) and the discrete-ordinate-method radiative transfer code (DISORT). These spectra are freely available for interested researchers from the NSF Arctic Data Center data repository (doi:10.5065/D61J97TT).

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