scholarly journals Polarimetric remote sensing in O<sub>2</sub> A and B bands: Sensitivity study and information content analysis for vertical profile of aerosols

2016 ◽  
Author(s):  
Shouguo Ding ◽  
Jun Wang ◽  
Xiaoguang Xu
Keyword(s):  
Information Content ◽  
Vertical Profile ◽  
Sensitivity Study ◽  
Peak Height ◽  
Gas Absorption ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Aerosol Layer ◽  
Gaussian Shape ◽  
Wide Range

Abstract. Theoretical analysis is conducted to reveal the information content of aerosol vertical profile in space-borne measurements of the backscattered radiance and degree of linear polarization (DOLP) in the O2 A and B bands. Assuming a quasi-Gaussian shape for aerosol vertical profile characterized by peak height H and half width γ (at half maximum), the Unified Linearized Vector Radiative Transfer Model (UNL-VRTM) is used to simulate the Stokes 4-vector elements of upwelling radiation at the top of atmosphere (TOA) and their Jacobians with respect to H and γ. Calculations for different aerosol types and different combinations of H and γ values show that the wide range of gas absorption optical depth in O2 A and B band enables the sensitivity of backscattered DOLP and radiance at TOA to the aerosol layer at different altitudes. Quantitatively, DOLP in O2 A and B bands is found to be more sensitive to H and γ than radiance, especially over the bright surfaces (with large visible reflectance). In many O2 wavelengths, Degree of Freedom for Signal (DFS) for retrieving H (or γ) generally increases with H (and γ) and can be close to unity in many cases, assuming that the composite uncertainty from surface and aerosol scattering properties as well as measurements is less than 5%. Further analysis demonstrates that DFS needed for simultaneous retrieval of H and γ for high-lofted aerosol profiles (H > 2 km) can be obtained from a combined use of DOLP measurements at ~10 O2 absorption A and B absorption wavelengths. However, challenges still remain for resolving aerosol profiles with H less than 2 km. Future hyperspectral measurements of DOPL in O2 A and B bands are needed to continue studying their potential and their combination with radiance and DOPL in atmospheric window channels for retrieving the vertical profiles of aerosols, especially highly scattering aerosols, over land.

scholarly journals Polarimetric remote sensing in oxygen A and B bands: sensitivity study and information content analysis for vertical profile of aerosols

2016 ◽  
Vol 9 (5) ◽  
pp. 2077-2092 ◽  
Author(s):  
Shouguo Ding ◽  
Jun Wang ◽  
Xiaoguang Xu
Keyword(s):  
Information Content ◽  
Vertical Profile ◽  
Sensitivity Study ◽  
Peak Height ◽  
Gas Absorption ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Aerosol Layer ◽  
Gaussian Shape ◽  
Wide Range

Abstract. Theoretical analysis is conducted to reveal the information content of aerosol vertical profile in space-borne measurements of the backscattered radiance and degree of linear polarization (DOLP) in oxygen (O2) A and B bands. Assuming a quasi-Gaussian shape for aerosol vertical profile characterized by peak height H and half width γ (at half maximum), the Unified Linearized Vector Radiative Transfer Model (UNL-VRTM) is used to simulate the Stokes four-vector elements of upwelling radiation at the top of atmosphere (TOA) and their Jacobians with respect to H and γ. Calculations for different aerosol types and different combinations of H and γ values show that the wide range of gas absorption optical depth in O2 A and B band enables the sensitivity of backscattered DOLP and radiance at TOA to the aerosol layer at different altitudes. Quantitatively, DOLP in O2 A and B bands is found to be more sensitive to H and γ than radiance, especially over the bright surfaces (with large visible reflectance). In many O2 absorption wavelengths, the degree of freedom of signal (DFS) for retrieving H (or γ) generally increases with H (and γ) and can be close to unity in many cases, assuming that the composite uncertainty from surface and aerosol scattering properties as well as measurements is less than 5 %. Further analysis demonstrates that DFS needed for simultaneous retrieval of H and γ can be obtained from a combined use of DOLP measurements at  ∼ 10–100 O2 A and B absorption wavelengths (or channels), depending on the specific values of H. The higher the aerosol layer, the fewer number of channels for DOLP measurements in O2 A and B bands are needed for characterizing H and γ. Future hyperspectral measurements of DOLP in O2 A and B bands are needed to continue studying their potential and their combination with radiance and DOLP in atmospheric window channels for retrieving the vertical profiles of aerosols, especially highly scattering aerosols, over land.

scholarly journals On the improvement of NO<sub>2</sub> satellite retrievals – aerosol impact on the airmass factors

2009 ◽  
Vol 2 (6) ◽  
pp. 3221-3264
Author(s):  
J. Leitão ◽  
A. Richter ◽  
M. Vrekoussis ◽  
A. Kokhanovsky ◽  
Q. J. Zhang ◽  
...  
Keyword(s):  
Optical Depth ◽  
Accurate Determination ◽  
Single Scattering ◽  
Sensitivity Study ◽  
Trace Gas ◽  
Radiative Transfer Model ◽  
Satellite Measurement ◽  
Transfer Model ◽  
Aerosol Layer ◽  
The Impact

Abstract. The accurate determination of nitrogen dioxide (NO2) tropospheric vertical columns from satellite measurements depends, partly, on the airmass factor (AMF) used. A sensitivity study was performed with the radiative transfer model SCIATRAN to better understand the impact of aerosols in the calculation of NO2 AMFs. This influence was studied by varying the NO2 and aerosol vertical distributions, as well as physical and optical properties of the particles. The key factors for these calculations were identified as the relation between trace gas and aerosol vertical profiles, the optical depth of the aerosol layer, and single scattering albedo. Overall it was found that aerosol mixed with the trace gas increases the measurements' sensitivity. The largest change, a factor of ~2 relative to the situation without aerosols, was found when a low layer of aerosol (600 m) was combined with a homogenous NO2 layer of 1.0 km. A layer of aerosol above the NO2 will usually reduce the sensitivity of the satellite measurement, a situation found mostly for runs with discrete elevated aerosol layers representative for long-range transport of aerosols that can generate a decrease of the AMF values of up to 70%. The use of measured aerosol profiles and modelled NO2 resulted, generally, in a much smaller changes of AMF relative to the pure Rayleigh case. Exceptions are some events of elevated layers with high aerosol optical depth that lead to a strong decrease of the AMF values. These results highlight the importance of aerosols in the retrieval of tropospheric NO2 columns from space and indicate the need for detailed information on aerosol properties and vertical distribution.

scholarly journals On the improvement of NO<sub>2</sub> satellite retrievals – aerosol impact on the airmass factors

2010 ◽  
Vol 3 (2) ◽  
pp. 475-493 ◽  
Author(s):  
J. Leitão ◽  
A. Richter ◽  
M. Vrekoussis ◽  
A. Kokhanovsky ◽  
Q. J. Zhang ◽  
...  
Keyword(s):  
Optical Depth ◽  
Accurate Determination ◽  
Single Scattering ◽  
Sensitivity Study ◽  
Trace Gas ◽  
Radiative Transfer Model ◽  
Satellite Measurement ◽  
Transfer Model ◽  
Aerosol Layer ◽  
The Impact

Abstract. The accurate determination of nitrogen dioxide (NO2) tropospheric vertical columns from satellite measurements depends strongly on the airmass factor (AMF) used. A sensitivity study was performed with the radiative transfer model SCIATRAN to better understand the impact of aerosols on the calculation of NO2 AMFs. This influence was studied by varying the NO2 and aerosol vertical distributions, as well as physical and optical properties of the particles. In terms of aerosol definitions, the key factors for these calculations were identified as the relation between trace gas and aerosol vertical profiles, the optical depth of the aerosol layer, and single scattering albedo. In addition, surface albedo also has a large impact on the calculations. Overall it was found that particles mixed with the trace gas increases the measurements' sensitivity, but only when the aerosol is not very absorbing. The largest change, a factor of ~2 relative to the situation without aerosols, was found when a low layer of aerosol (600 m) was combined with a homogenous NO2 layer of 1.0 km. A layer of aerosol above the NO2 usually reduces the sensitivity of the satellite measurement. This situation is found mostly for runs with discrete elevated aerosol layers (representative for long-range transport) that can generate a decrease of the AMF values of up to 70%. The use of measured aerosol profiles and modelled NO2 resulted, generally, in much smaller changes of AMF relative to the pure Rayleigh case. Exceptions are some events of elevated layers with high aerosol optical depth that lead to a strong decrease of the AMF values. These results highlight the importance of aerosols in the retrieval of tropospheric NO2 columns from space and indicate the need for detailed information on aerosol properties and vertical distribution.

scholarly journals A new gas absorption optical depth parameterisation for RTTOV version 13

2021 ◽  
Vol 14 (5) ◽  
pp. 2899-2915
Author(s):  
James Hocking ◽  
Jérôme Vidot ◽  
Pascal Brunel ◽  
Pascale Roquet ◽  
Bruna Silveira ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Radiative Transfer ◽  
Optical Depth ◽  
Weather Prediction ◽  
Current Approach ◽  
Gas Absorption ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Wide Range ◽  
Microwave Radiances

Abstract. This paper describes a new gas optical depth parameterisation implemented in the most recent release, version 13, of the radiative transfer model RTTOV (Radiative Transfer for TOVS). RTTOV is a fast, one-dimensional radiative transfer model for simulating top-of-atmosphere visible, infrared, and microwave radiances observed by downward-viewing space-borne passive sensors. A key component of the model is the fast parameterisation of absorption by the various gases in the atmosphere. The existing parameterisation in RTTOV has been extended over many years to allow for additional variable gases in RTTOV simulations and to account for solar radiation and better support geostationary sensors by extending the validity to higher zenith angles. However, there are limitations inherent in the current approach which make it difficult to develop it further, for example by adding new variable gases. We describe a new parameterisation that can be applied across the whole spectrum, that allows for a wide range of zenith angles in support of solar radiation and geostationary sensors, and for which it will be easier to add new variable gases in support of user requirements. Comparisons against line-by-line radiative transfer simulations and against observations in the ECMWF operational system yield promising results, suggesting that the new parameterisation generally compares well with the old one in terms of accuracy. Further validation is planned, including testing in operational numerical weather prediction data assimilation systems.

scholarly journals Vertical profile of tropospheric ozone derived from synergetic retrieval using three different wavelength ranges, UV, IR, and microwave: sensitivity study for satellite observation

2018 ◽  
Vol 11 (3) ◽  
pp. 1653-1668 ◽  
Author(s):  
Tomohiro O. Sato ◽  
Takao M. Sato ◽  
Hideo Sagawa ◽  
Katsuyuki Noguchi ◽  
Naoko Saitoh ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Tropospheric Ozone ◽  
Vertical Profile ◽  
Reduction Rate ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Sensitivity Study ◽  
Maximum Sensitivity ◽  
Radiative Transfer Model ◽  
Transfer Model

Abstract. We performed a feasibility study of constraining the vertical profile of the tropospheric ozone by using a synergetic retrieval method on multiple spectra, i.e., ultraviolet (UV), thermal infrared (TIR), and microwave (MW) ranges, measured from space. This work provides, for the first time, a quantitative evaluation of the retrieval sensitivity of the tropospheric ozone by adding the MW measurement to the UV and TIR measurements. Two observation points in East Asia (one in an urban area and one in an ocean area) and two observation times (one during summer and one during winter) were assumed. Geometry of line of sight was nadir down-looking for the UV and TIR measurements, and limb sounding for the MW measurement. The retrieval sensitivities of the ozone profiles in the upper troposphere (UT), middle troposphere (MT), and lowermost troposphere (LMT) were estimated using the degree of freedom for signal (DFS), the pressure of maximum sensitivity, reduction rate of error from the a priori error, and the averaging kernel matrix, derived based on the optimal estimation method. The measurement noise levels were assumed to be the same as those for currently available instruments. The weighting functions for the UV, TIR, and MW ranges were calculated using the SCIATRAN radiative transfer model, the Line-By-Line Radiative Transfer Model (LBLRTM), and the Advanced Model for Atmospheric Terahertz Radiation Analysis and Simulation (AMATERASU), respectively. The DFS value was increased by approximately 96, 23, and 30 % by adding the MW measurements to the combination of UV and TIR measurements in the UT, MT, and LMT regions, respectively. The MW measurement increased the DFS value of the LMT ozone; nevertheless, the MW measurement alone has no sensitivity to the LMT ozone. The pressure of maximum sensitivity value for the LMT ozone was also increased by adding the MW measurement. These findings indicate that better information on LMT ozone can be obtained by adding constraints on the UT and MT ozone from the MW measurement. The results of this study are applicable to the upcoming air-quality monitoring missions, APOLLO, GMAP-Asia, and uvSCOPE.

scholarly journals Vertical profile of tropospheric ozone derived from synergetic retrieval using three different wavelength ranges, UV, IR, and Microwave: sensitivity study for satellite observation

2017 ◽  
Author(s):  
Yasuko Kasai ◽  
Tomohiro O. Sato ◽  
Takao M. Sato ◽  
Hideo Sagawa ◽  
Katsuyuki Noguchi ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Vertical Profile ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Satellite Observation ◽  
Sensitivity Study ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Retrieval Method ◽  
Advanced Model

Abstract. We performed a quantitative feasibility study of constraining the vertical profile of the amount of ozone in the troposphere by using a synergetic retrieval method on multiple spectra, i.e., ultraviolet (UV), thermal infrared (TIR) and microwave (MW) ranges, measured from space. Twenty atmospheric scenarios for East Asia in summer and winter seasons were assumed in this study. Geometry of line-of-sight was nadir down-looking for UV and TIR measurements, and limb-sounding for MW measurement. The sensitivities of retrieved ozone in the upper troposphere (UT), middle troposphere (MT) and lowermost troposphere (LMT) were estimated using values of the degree of freedom for signal (DFS), partial column error, and averaging kernel matrix, derived based on the optimal estimation method. The measurement noises were assumed at the same level as the currently available instruments. The weighting functions for the UV, TIR and MW ranges were calculated using the SCIATRAN radiative transfer model, the Line-By-Line Radiative Transfer Model, and the Advanced Model for Atmospheric Terahertz Radiation Analysis and Simulation, respectively. In the UT region, the DFS value was enhanced by about 200 % by adding the MW measurements to the combination of UV and TIR measurements. We found that the DFS value of the LMT ozone was increased by approximately 40 % by adding the MW measurements to the combination of UV and TIR measurements; nevertheless, the MW measurement alone has no sensitivity for the LMT ozone. Better information of the LMT ozone can be educed by adding constraints on the UT and MT ozone from the MW measurement. The results of this study will be implemented in the Japanese air-quality monitoring missions, APOLLO, GMAP-Asia and uvSCOPE.

scholarly journals A new gas absorption optical depth parameterisation for RTTOV v13

2021 ◽  
Author(s):  
James Hocking ◽  
Jérôme Vidot ◽  
Pascal Brunel ◽  
Pascale Roquet ◽  
Bruna Silveira ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Radiative Transfer ◽  
Optical Depth ◽  
Weather Prediction ◽  
Current Approach ◽  
Gas Absorption ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Wide Range ◽  
Microwave Radiances

Abstract. This paper describes a new gas optical depth parameterisation implemented in the most recent release, version 13, of the radiative transfer model RTTOV (Radiative Transfer for TOVS). RTTOV is a fast, one-dimensional radiative transfer model for simulating top-of-atmosphere visible, infrared and microwave radiances observed by downward-viewing space-borne passive sensors. A key component of the model is the fast parameterisation of absorption by the various gases in the atmosphere. The existing parameterisation in RTTOV has been extended over many years to allow for additional variable gases in RTTOV simulations and to account for solar radiation and better support geostationary sensors by extending the validity to higher zenith angles. However, there are limitations inherent in the current approach which make it difficult to develop it further, for example by adding new variable gases. We describe a new parameterisation that can be applied across the whole spectrum, allows for a wide range of zenith angles in support of solar radiation and geostationary sensors, and for which it will be easier to add new variable gases in support of user requirements. Comparisons against line-by-line radiative transfer simulations, and against observations in the ECMWF operational system yield promising results, suggesting that the new parameterisation generally compares well with the old one in terms of accuracy. Further validation is planned, including testing in operational numerical weather prediction data assimilation systems.

scholarly journals PRELIMINARY SENSITIVITY STUDY OF AEROSOL LAYER HEIGHT FROM SYNTHETIC MULTIANGLE POLARIMETRIC REMOTE SENSING MEASUREMENTS

2019 ◽  
Vol XLII-3/W9 ◽  
pp. 63-69
Author(s):  
W. Z. Hou ◽  
H. F. Wang ◽  
Z. Q. Li ◽  
L. L. Qie ◽  
B. Y. Ge ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Information Content ◽  
Sensitivity Study ◽  
Transfer Model ◽  
Aerosol Layer ◽  
Layer Height ◽  
Polarization Measurements ◽  
Near Ultraviolet ◽  
Study Results ◽  
Model Aerosol

Abstract. Many previous studies have shown that multiangle, multispectral polarimetric remote sensing can provide valuable information on aerosol microphysical and optical properties, in which the aerosol layer height (ALH) is an important parameter but with less studies, especially in the near-ultraviolet (near-UV) and visible (VIS) wavelength bands. Based on the optimal estimation (OE) theory and information content analysis method, we focus on the sensitivity study of ALH with the synthetic data in the near-UV and VIS wavelength in the range of 410–865 nm, and further to assess the capability of multiangle intensity and polarization measurements for the retrieval of ALH. Unified Linearized Vector Radiative Transfer Model (UNL-VRTM) has been used as the forward model to simulate the intensity and polarized radiance at the top of atmosphere (TOA), as well as the Jacobians of TOA results with respective to corresponding parameters. The degree of freedom for signal (DFS) and a posteriori error are introduced to quantity the information content of ALH from the intensity and polarization measurements, respectively. By assuming the surface type, aerosol model, aerosol loads, prior errors and observation geometries, the sensitivity of ALH has been preliminarily investigated. The sensitivity study results show that the near-UV and polarization measurements are the important source of information content for the aerosol height retrieval in satellite remote sensing.

scholarly journals Extensive reduction of surface UV radiation since 1750 in world's populated regions

2009 ◽  
Vol 9 (20) ◽  
pp. 7737-7751 ◽  
Author(s):  
M. M. Kvalev&amp;aring;g ◽  
G. Myhre ◽  
C. E. Lund Myhre
Keyword(s):  
Uv Radiation ◽  
Correlation Coefficients ◽  
Ultra Violet ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Polar Regions ◽  
Ultra Violet Radiation ◽  
Wide Range ◽  
Extensive Surface ◽  
Year 2000

Abstract. Human activity influences a wide range of components that affect the surface UV radiation levels, among them ozone at high latitudes. We calculate the effect of human-induced changes in the surface erythemally weighted ultra-violet radiation (UV-E) since 1750. We compare results from a radiative transfer model to surface UV-E radiation for year 2000 derived by satellite observations (from Total Ozone Mapping Spectroradiometer) and to ground based measurements at 14 sites. The model correlates well with the observations; the correlation coefficients are 0.97 and 0.98 for satellite and ground based measurements, respectively. In addition to the effect of changes in ozone, we also investigate the effect of changes in SO2, NO2, the direct and indirect effects of aerosols, albedo changes and aviation-induced contrails and cirrus. The results show an increase of surface UV-E in polar regions, most strongly in the Southern Hemisphere. Furthermore, our study also shows an extensive surface UV-E reduction over most land areas; a reduction up to 20% since 1750 is found in some industrialized regions. This reduction in UV-E over the industrial period is particularly large in highly populated regions.

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

&lt;p&gt;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&amp;#176;N, 68.8&amp;#176;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.&amp;#160;&lt;/p&gt;&lt;p&gt;Excess biomass burning chemical tracers such as CO, HCN, H2CO, C2H6, and NH3 were&amp;#160; 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&amp;#160; detected in PM10. The measured shortwave radiative forcing was -36.7 W/m2 at 78&amp;#176; solar zenith angle (SZA) for AOD=0.626.&lt;/p&gt;&lt;p&gt;MODTRAN6.0 radiative transfer model (Berk et al., 2014) was used to estimate the aerosol radiative effect and the heating rate profiles at 78&amp;#176; 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&amp;#160; aerosol heating rate (+0.5 K/day) was&amp;#160; 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.&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;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 (&lt; -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.&lt;/p&gt;

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